draft sctp phase 5b engineering report v10...investments to the salmon creek treatment plant (sctp)...

D I S C O V E R Y C L E A N W A T E R A L L I A N C E

Final Draft Engineering Report for the

Phase 5B Project—Salmon Creek

Treatment Plant Improvements

Phase 5 Expansion Program

An Alliance Capital Project delivered by Clark Regional Wastewater District as

Administrative Lead for the Discovery Clean Water Alliance

Prepared for

Washington State Department of Ecology

August 2018

2020 SW Fourth Avenue, 3rd Floor

Portland, Oregon 97201

iii

Contents Section Page

Acronyms and Abbreviations ............................................................................................................... ix

Executive Summary ......................................................................................................................... ES‐1 Introduction ................................................................................................................................ ES‐1 Background Information ............................................................................................................. ES‐1 Future Conditions ....................................................................................................................... ES‐2 Recommended Improvements ................................................................................................... ES‐3 Air Quality and Odor Control ...................................................................................................... ES‐3 Financial Considerations, Staffing, and Schedule ....................................................................... ES‐4 Compliance with Regulatory Requirements ............................................................................... ES‐5

1 Introduction ......................................................................................................................... 1‐1 1.1 Discovery Clean Water Alliance ....................................................................................... 1‐1 1.2 Project Purpose ................................................................................................................ 1‐1 1.3 Project Need .................................................................................................................... 1‐1 1.4 Engineering Report Organization ..................................................................................... 1‐3 1.5 Owner and Authorized Representative ........................................................................... 1‐5

2 Background Information ....................................................................................................... 2‐1 2.1 Historical Regulatory and Planning Framework .............................................................. 2‐1

2.1.1 Existing Permit Requirements ............................................................................ 2‐1 2.1.2 Recent Salmon Creek Treatment Plant Performance ......................................... 2‐2

2.2 Current Treatment Processes .......................................................................................... 2‐2 2.2.1 Existing Design Capacity and Wastewater Flow and Character ......................... 2‐2 2.2.2 Basis of Treatment Capacity ............................................................................... 2‐4

2.3 Emerging Regulatory Considerations ............................................................................. 2‐10 2.3.1 Relevant Regulatory Developments Since Previous Planning Approvals ......... 2‐11

3 Future Conditions ................................................................................................................. 3‐1 3.1 Projected Flows and Loads .............................................................................................. 3‐1 3.2 Additional Flows............................................................................................................... 3‐2

3.2.1 Imported Waste Activated Sludge Flow ............................................................. 3‐2 3.3 Phase 5B Improvements Program Approach to Discharge Standards ............................ 3‐2

3.3.1 Alliance Actions to Address Columbia River Discharge Issues ............................ 3‐2 3.3.2 Phase 5B Engineering Report Approach to Possible Future Regulatory

Outcomes ............................................................................................................ 3‐5 3.3.3 Treatment Plant Process Design Criteria and Estimated Performance .............. 3‐7

4 Recommended Improvements .............................................................................................. 4‐1 4.1 Preliminary Treatment ..................................................................................................... 4‐1

4.1.1 Design Parameters .............................................................................................. 4‐1 4.1.2 Proposed Improvements .................................................................................... 4‐2 4.1.3 Projected Performance ....................................................................................... 4‐3 4.1.4 Redundancy Requirements ................................................................................. 4‐3

4.2 Primary Treatment ........................................................................................................... 4‐3 4.2.1 Design Parameters .............................................................................................. 4‐3 4.2.2 Proposed Improvements .................................................................................... 4‐4 4.2.3 Projected Performance ....................................................................................... 4‐4

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4.2.4 Redundancy Requirements ................................................................................. 4‐4 4.3 Aeration Basins ................................................................................................................ 4‐4

4.3.1 Design Parameters .............................................................................................. 4‐4 4.3.2 Proposed Improvements .................................................................................... 4‐6 4.3.3 Projected Performance ....................................................................................... 4‐6 4.3.4 Redundancy Requirements ............................................................................... 4‐12

4.4 Secondary Clarifiers & Return Activated Sludge Pumping System ................................ 4‐12 4.4.1 Design Criteria ................................................................................................... 4‐12 4.4.2 Proposed Improvements .................................................................................. 4‐13 4.4.3 Projected Performance ..................................................................................... 4‐13 4.4.4 Redundancy Requirements ............................................................................... 4‐14 4.4.5 Return Activated Sludge System ....................................................................... 4‐14 4.4.6 Hypochlorite Dosing Station for Return Activated Sludge Chlorination ........... 4‐15

4.5 Disinfection .................................................................................................................... 4‐17 4.5.1 Design Criteria ................................................................................................... 4‐17 4.5.2 Proposed Improvements .................................................................................. 4‐17 4.5.3 Projected Performance ..................................................................................... 4‐17 4.5.4 Redundancy Requirements ............................................................................... 4‐17

4.6 Effluent Pump Station .................................................................................................... 4‐18 4.6.1 Design Criteria ................................................................................................... 4‐18 4.6.2 Proposed Improvements .................................................................................. 4‐18 4.6.3 Projected Performance ..................................................................................... 4‐19 4.6.4 Redundancy Requirements ............................................................................... 4‐21

4.7 Waste Activated Sludge Thickening ............................................................................... 4‐21 4.7.1 Design Criteria ................................................................................................... 4‐21 4.7.2 Proposed Improvements .................................................................................. 4‐21 4.7.3 Projected Performance ..................................................................................... 4‐21 4.7.4 Redundancy Requirements ............................................................................... 4‐21

4.8 Anaerobic Digestion ....................................................................................................... 4‐21 4.8.1 Design Criteria ................................................................................................... 4‐21 4.8.2 Proposed Improvements .................................................................................. 4‐22 4.8.3 Projected Performance ..................................................................................... 4‐22 4.8.4 Redundancy Requirements ............................................................................... 4‐22

4.9 Digested Biosolids Dewatering ...................................................................................... 4‐22 4.9.1 Design Criteria ................................................................................................... 4‐22 4.9.2 Proposed Improvements .................................................................................. 4‐23 4.9.3 Projected Performance ..................................................................................... 4‐23 4.9.4 Redundancy Requirements ............................................................................... 4‐23

4.10 Plant Hydraulics ............................................................................................................. 4‐23 4.11 Selected Alternative Description ................................................................................... 4‐24

5 Air Quality and Odor Control ................................................................................................ 5‐1 5.1 Regulatory Context and Requirements............................................................................ 5‐1

5.1.1 Nuisance Odors ................................................................................................... 5‐1 5.1.2 Toxic Air Pollutants ............................................................................................. 5‐1 5.1.3 Odor Criteria Requirements ................................................................................ 5‐1

5.2 Odor Control .................................................................................................................... 5‐1 5.2.1 Overview and Current Performance ................................................................... 5‐1 5.2.2 Alternative Analysis and Projected Performance ............................................... 5‐2 5.2.3 Recommended Alternative ................................................................................. 5‐6

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6 Financial Considerations, Staffing, and Schedule ................................................................... 6‐1 6.1 Preliminary Cost Estimate ................................................................................................ 6‐1 6.2 Project Funding ................................................................................................................ 6‐2 6.3 Staffing Requirements ..................................................................................................... 6‐2 6.4 Project Schedule .............................................................................................................. 6‐2

7 Compliance with Regulatory Requirements .......................................................................... 7‐1 7.1 Permitting and Regulations ............................................................................................. 7‐1 7.2 Environmental Impacts .................................................................................................... 7‐1 7.3 Compliance with Water Quality Standards ..................................................................... 7‐4

8 Engineering Report Requirements Checklist .......................................................................... 8‐1

9 References ............................................................................................................................ 9‐1

Appendixes

A Process Calculations

B Salmon Creek Treatment Plant Phase 4 Odor Control Update

C Water Quality Compliance Evaluation

Tables

ES‐1 Projected Flows and Loads ......................................................................................................... ES‐2

9BES‐2 Summary of Proposed Improvements ........................................................................................ ES‐3

ES‐3 Summary of Total Phase 5B Project Costs .................................................................................. ES‐4

2‐1 Current NPDES Effluent Permit Limits .......................................................................................... 2‐1

2‐2 Annual Influent Flows and Loads .................................................................................................. 2‐3

2‐3 Maximum Month to Annual Average Flow and Load Peaking Factors ......................................... 2‐3

9B2‐4 Aeration Basin Dimensions ........................................................................................................... 2‐6

9B2‐5 Existing Aeration System Capacity ................................................................................................ 2‐7

9B2‐6 Secondary Clarifier Dimensions .................................................................................................... 2‐9

3‐1 Projected Flows and Loads ........................................................................................................... 3‐1

3‐2 Regulatory Pathways for SCTP Improvements Depending on Disposition of 303(d) Listing for Dissolved Oxygen .................................................................................................................... 3‐6

9B4‐1 Design Parameters for Preliminary Treatment ............................................................................. 4‐1

9B4‐2 Design Parameters for Primary Treatment ................................................................................... 4‐3

4‐3 Design Parameters for Aeration Basins ........................................................................................ 4‐5

4‐4 Summary of Aeration Basin Performance .................................................................................... 4‐9

9B4‐5 Design Parameters of Anoxic Selectors ...................................................................................... 4‐10

9B4‐6 Operational Parameters for the Blower System at 17.5 mgd ADMM ........................................ 4‐10

9B4‐7 Summary of Aeration Capacity (CH2M [2009] Methodology) .................................................... 4‐11

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9B4‐8 Design Parameters for Secondary Clarifiers ............................................................................... 4‐13

9B4‐9 RAS Pump Design Criteria ........................................................................................................... 4‐15

4‐10 Return Activated Sludge Chlorination Design Criteria ................................................................ 4‐16

4‐11 Peak‐hour Flow Data ................................................................................................................... 4‐18

4‐12 Design Peak‐hour Influent Flow by Phase .................................................................................. 4‐19

9B4‐13 Effluent Pump Design Criteria ..................................................................................................... 4‐20

9B4‐14 Design Criteria for WAS Thickening ............................................................................................ 4‐21

9B4‐15 Operational Parameters for the Anaerobic Digestion System at 17.5 mgd ADMM ................... 4‐22

9B4‐16 Operational Parameters for the Digested Biosolids Dewatering System at 17.5 mgd ADMM ......................................................................................................................... 4‐22

4‐17 Projected Effluent Values of Oxygen‐Demanding Substances ................................................... 4‐24

4‐18 Water Quality Compliance Evaluation Results ........................................................................... 4‐25

9B4‐19 Summary of Proposed Improvements ........................................................................................ 4‐26

4‐20 Mass Balance of SCTP Flows and Loads at Design ADMM Conditions ....................................... 4‐29

5‐1 Bio‐trickling Filter Approach, 1‐Hour Peak Average H2S Concentrations at Sensitive Receptors ...................................................................................................................................... 5‐5

5‐2 Bio‐trickling Filter Design Criteria ................................................................................................. 5‐6

6‐1 Project Costs ................................................................................................................................. 6‐1

8‐1 Requirements for Engineering Reports ........................................................................................ 8‐1

Figures

1‐1 Salmon Creek Treatment Plant Design Capacity versus Projected Demand for Influent Flow ................................................................................................................................. 1‐2

1‐2 Salmon Creek Treatment Plant Design Capacity versus Projected Demand for Influent Loading ............................................................................................................................ 1‐3

2‐1 Monthly Plant Effluent Concentration Data – BOD5, TSS & NH3‐N (mg/L) ................................... 2‐2

2‐2 2014–2017 BOD5 Percentage Removal versus Primary Clarifier SOR ........................................... 2‐5

2‐3 2014–2017 TSS Percentage Removal versus Primary Clarifier SOR .............................................. 2‐5

2‐4 Schematic Diagram of Linked Aeration Basins 1 and 3 in Series (Typical also to Aeration Basins 2 and 4) ............................................................................................................... 2‐6

2‐5 Schematic Diagram of Aeration Basins 5 and 6 ............................................................................ 2‐7

2‐6 MLSS Concentration and SVI Over Time ....................................................................................... 2‐8

2‐7 2014–2017 Effluent TSS versus SVI ............................................................................................... 2‐9

3‐1 Section View of Salmon Creek Treatment Plant Outfall and Diffuser .......................................... 3‐4

4‐1 Screens Rebuilt in 2017 ................................................................................................................. 4‐2

4‐2 Schematic Diagram of Aeration Basins 1 through 7 as CMAS Reactors ....................................... 4‐7

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4‐3 Process Flow Diagram of Aeration Basins 1 and 3 in Reactor‐in‐series Configuration (Typical to Aeration Basins 2 and 4) ............................................................................................. 4‐8

4‐4 Process Flow Diagram of Aeration Basin 5 (Typical to 6 and 7) in Reactor‐in‐series Configuration ................................................................................................................................ 4‐8

4‐5 Blower Systems ........................................................................................................................... 4‐11

4‐6 Return Activated Sludge Pumping .............................................................................................. 4‐15

4‐7 Skid‐mounted Hypochlorite Pump System, from ProMinent Fluid Controls LTD ....................... 4‐17

4‐8 Pump Curve and System Curve for the Peak Hour Condition ..................................................... 4‐20

4‐9 Hydraulic Profile .......................................................................................................................... 4‐27

4‐10 Unit Process Capacity Assessment Summary ............................................................................. 4‐30

4‐11 Schematic Process Flow Diagram of the Salmon Creek Treatment Plant with Proposed Imrovements ............................................................................................................................... 4‐31

4‐12 Salmon Creek Treatment Plant Phase 5B Improvements for 17.5 mgd ..................................... 4‐33

5‐1 Simplified Schematic Diagram of a Bio‐trickling filter System ...................................................... 5‐3

5‐2 Isopleths Showing Lines of Constant H2S Concentration in mg/m3 —1‐Hour Annual Peak, Bio‐trickling Filter Approach ................................................................................................ 5‐4

5‐3 Isopleths Showing Lines of Constant Odor Concentration in D/T—1‐Hour Annual Peak, Bio‐trickling Filter Approach ................................................................................... 5‐5

5‐4 Covered Primary Clarifier .............................................................................................................. 5‐6

5‐5 Preliminary Layout of Odor Control System ................................................................................. 5‐9

6‐1 Project Schedule ........................................................................................................................... 6‐3

ix

Acronyms and Abbreviations °C degrees Celsius

AA annual average

AAF average‐annual flow

ADMM average‐day maximum month

Alliance Discovery Clean Water Alliance

ASIL Acceptable Source Impact Level

BFP belt filter press

BOD biochemical oxygen demand

BOD5 5‐day biochemical oxygen demand

CMAS complete‐mix activated sludge

CSTR continuously‐stirred tank reactor

DNS determination of non‐significance

D/T dilutions‐to‐threshold

Ecology State of Washington Department of Ecology

EPA U.S. Environmental Protection Agency

F/M food to microorganisms

fpm feet per minute

GBT gravity belt thickener

gpd/ft2 gallons per day per square foot

gpm gallons per minute

gpm/m gallons per minute per meter

H2S hydrogen sulfide

hp horsepower

lb pound

lb/ft3 pound per cubic foot

lb/hr/m pounds per hour per meter

IWA International Water Association

M&E Metcalf & Eddy

MG million gallons

mgd million gallons per day

mg/L milligrams per liter

mg/m3 milligrams per cubic meter

mg/m3/ppbV milligrams per cubic meter per parts per billion volume

ACRONYMS AND ABBREVIATIONS

x

mL/g milliliter per gram

MLSS mixed liquor suspended solids

MLVSS mixed liquor volatile suspended solids

MMF maximum‐month flow

MMWW maximum month wet weather

NA not applicable

NH3‐N ammonia‐nitrogen

NPDES National Pollutant Discharge Elimination System

O&M operations and maintenance

ORS organic reduced sulfur

P.E. Professional Engineer

PHF peak‐hour flow

ppd pounds per day

ppd‐ft2 pounds per day per square foot

R&R repair and replacement

RAS return activated sludge

RCW Revised Code of Washington

ROI Return of the Investment Analysis

rpm revolutions per minute

scfm standard cubic feet per minute

SCTP Salmon Creek Treatment Plant

SEPA State Environmental Policy Act

SOR surface overflow rate

SRT solids retention time

SVI sludge volume index

SWCAA Southwest Washington Clean Air Agency

TSS total suspended solids

UV ultraviolet

VS volatile solids

WAC Washington Administrative Code

WAS waste activated sludge

WEF Water Environment Federation

WWTP wastewater treatment plant

ES‐1

Executive Summary

Introduction The Phase 5B Project—Salmon Creek Treatment Plant Improvements consists of several important investments to the Salmon Creek Treatment Plant (SCTP) that will increase capacity and continue to maintain a consistent high level of effluent quality. The project proposes to construct a new aeration basin with new aeration equipment as well as a new, larger secondary clarifier. The return activated sludge (RAS) and effluent pumping capacity will be increased, the primary clarifiers will be covered, and a new odor control facility will be constructed to ventilate the headworks and the primary clarifiers. The project is expected to increase treatment capacity of the SCTP from 14.95 million gallons per day (mgd) of maximum month flow up to 17.5 mgd, which will allow the plant to meet projected wastewater flows and loads until 2030 according to current estimates. In addition, the construction of odor control facilities will help to mitigate potential odorous air emissions from the SCTP.

The Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan Amendment (2013 Facilities Plan Update) (CH2M, 2013), approved by the State of Washington Department of Ecology (Ecology) in a letter dated September 4, 2013, describes the need for the capital improvements of the Phase 5B Project, which is one of several planned SCTP expansion phases. The plant endeavors to protect public health and the environment by maintaining a high degree of treatment and capacity in the face of future growth of the population within the service area.

Ecology requires the Discovery Clean Water Alliance (Alliance) to submit a plan and schedule maintaining adequate capacity in its treatment facilities when one of the following two conditions is met:

Actual flow or actual waste load reaches 85 percent of the rated capacity of the facility for 3 consecutive months, or

Projected flow or projected waste load will reach the design capacity of the facility within 5 years

Recent analysis of the projected waste flow and loading to the plant as well as current plant performance suggests that treatment capacity could be reached within several years. The ongoing assessments of flow and load have identified the need for the Alliance to initiate planning for the improvements described in this Engineering Report.

The Alliance prepared this Engineering Report in conformance with the Washington Administrative Code (WAC) 173‐240‐060 and the Washington State Department of Ecology’s Criteria for Sewage Works Design (2008).

Background Information The SCTP is located at 15100 NW McCann Road, Vancouver, Washington, 98685. The SCTP serves approximately 100,000 Clark County residents living inside the Clark Regional Wastewater District and the cities of Battle Ground and Ridgefield. In June 2014, the Board of County Commissioners agreed to transfer the plant to the Alliance, a regional sewer entity with four Member agencies: Clark County, Clark Regional Wastewater District, and the cities of Battle Ground and Ridgefield. The transfer took place at the start of 2015 and Clark County staff operate SCTP through an operator’s agreement with the Alliance.

The SCTP provides secondary treatment of municipal wastewater, which consists of screening, grit removal, primary clarification, aeration, secondary clarification, and ultraviolet disinfection. The primary

EXECUTIVE SUMMARY

ES-2

and waste activated solids are digested in anaerobic digesters, mechanically dewatered, and stored for

subsequent beneficial reuse. All unit processes are being operated as designed. A more detailed

description of each process and an evaluation of its current capacity are provided as part of this report.

Future Conditions The Alliance has developed projections for wastewater flows and loads that indicate that the SCTP could

approach its treatment capacity within several years and that the Phase 5B Project proposed in this

Engineering Report will extend SCTP’s treatment capacity until approximately 2030.

Table ES-1 presents a summary of the projected flow and loads to the plant.

The SCTP discharge to the Columbia River is located near RM 96, which is approximately midway

between the confluence of the Willamette River (RM 101) and the Lewis River (RM 88) confluence with

the Columbia River. Ecology’s 2014 303(d) list includes an Assessment Unit (AU) that consists of this 13-

mile reach of the Columbia River, which is currently included as a Category 5 listing that is impaired for

temperature, DO, and bacteria. Based on the Category 5 listing status, a TMDL study is expected to be

developed for these parameters at some time in the future, unless additional data support

reclassification or removal of the Category 5 listings through the ongoing biennial update process. The

Alliance evaluation of and actions to address these three listings are summarized below:

• Bacteria: The Alliance near-term capital projects propose to continue the high level of disinfection

required by the NPDES permit using UV light disinfection of wastewater, which will address the

bacteria listing by not causing or contributing to the impairment.

• Temperature: The Alliance will continue to monitor legal and regulatory developments in this area

and understands Ecology will most likely implement the results of these processes through the

ongoing NPDES permit renewal processes. The Alliance’s Phase 5B Engineering Report includes a

Water Quality Compliance Evaluation (included as Appendix C) in the event that the improvements

were considered expanded action under the Clean Water Act. The Water Quality Compliance

Evaluation documents that the SCTP discharge associated with the proposed improvements and the

Table ES-1. Projected Flows and Loads

Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

(Unit processes capacity evaluation projected flows and loads* at ADMM = 17.5 mgd)

Item Value

Projected Influent Flow

Annual Average, mgd 13.3

ADMM, mgd 17.5

Peak Day, mgd 26.6

Peak Hour, mgd 33.1

Maximum Month Projected Loads

5-day Biochemical Oxygen Demand, ppd 30,520

Total Suspended Solids, ppd 35,770

% Volatile Solids 92%

Ammonia-Nitrogen (NH3-N), ppd 4,006

Alkalinity (CaCO3), ppd 29,938

*The projected loads were calculated using SCTP historical data from January 2011 to December

2017.

ADMM = average-day maximum month; mgd = million gallons per day; ppd = pounds per day.

EXECUTIVE SUMMARY

ES‐3

current Columbia River diffuser does not result in a measurable change in Columbia River water temperature (as defined in WAC 173‐201A‐200 and WAC 173‐201A‐320), and it complies with Ecology’s requirements.

Dissolved Oxygen: The DO listing is more recent and further study and investigations are ongoing with regard to the listing. As described in more detail in Section 3.3, the Alliance is working with Ecology to provide an accurate assessment of existing data and also to provide Ecology with additional data and information so that informed regulatory determinations can be made with respect to the listing.

Recommended Improvements The major improvements required for the increase of plant capacity are a new aeration basin and equipment, a new secondary clarifier, a new RAS chlorination system, and new RAS and effluent pumps. Ancillary improvements include covering the primary clarifiers and ventilating the headworks and primary clarifiers to a new odor control facility. Together, these recommended improvements are estimated to increase the plant’s treatment capacity to 17.5 mgd on a maximum month basis.

A summary of the recommended improvements to the plant is provided in Table ES‐2.

9BTable ES‐2. Summary of Proposed Improvements Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Proposed Improvement

Preliminary Treatment Odor Control

Primary Treatment Covers + Odor Control

Aeration Basins New Aeration Basin 7

Blowers New Blower No. 8

Secondary Clarifiers Demolish Secondary Clarifier 2 (90 ft diameter)

New Secondary Clarifier 5 (120 ft diameter)

RAS/WAS New RAS pumps and RAS chlorination

Disinfection ‐‐

Effluent Pump Station New Effluent Pumps

WAS Thickening ‐‐

Anaerobic Digestion ‐‐

Digested Biosolids Dewatering Solids Conditioning System

Air Quality and Odor Control CH2M conducted an alternatives analysis of odor control technologies that would be appropriate to implement at SCTP to mitigate the potential for odorous air emissions. In March 2007, odor sampling and odor dispersion modeling activities were performed to characterize the odor footprint at the SCTP. CH2M’s recommendation from the 2007 analysis was to cover the primary clarifiers and preliminary treatment channels and ventilate these areas to a new odor control system. Additional odor sampling was performed during late summer and fall 2017 to provide current data for basis of design of the proposed systems.

EXECUTIVE SUMMARY

ES‐4

This recommendation was carried forward into the updated analysis performed in 2017. In addition, two odor control technologies were evaluated in this context: (1) vapor‐phase odor control system (bio‐trickling filter), and (2) high rate engineered media biofilter. Because of air quality criteria, the bio‐trickling filter system is recommended for installation.

Financial Considerations, Staffing, and Schedule A preliminary estimate of the total project costs for the proposed project based on the Engineering Report recommendations is presented in Table ES‐3. The estimate assumes costs for all elements expected to be part of the final design.

The cost estimate is considered to be consistent with Class 5 estimates, as defined by the Estimate Classification system of the Association for the Advancement of Cost Engineering International (formerly known as the American Association of Cost Engineers). The estimate was developed without detailed engineering data and is considered approximate. Class 5 estimates are normally expected to be accurate within minus 50 percent to plus 100 percent. This range implies that there is a high probability that the final project cost will fall within the range.

Table ES‐3. Summary of Total Phase 5B Project Costs Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Item Cost Estimate

Delivery:

Planning $350,000

Engineering & Survey $2,500,000

Environmental & Other Permitting $480,000

Stakeholder Engagement & Outreach $120,000

Project Management $250,000

Construction Management $2,500,000

Total Delivery Cost $6,200,000

Construction:

Preliminary and Primary Treatment (Covers and Odor Control) $3,800,000

Aeration Basin 7 $2,800,000

Blower Addition $365,000

Demolish Secondary Clarifier 2 $300,000

Secondary Clarifier 5 $1,770,000

Demolish Building 87 $200,000

Secondary Treatment (RAS Chlorination Improvements) $250,000

RAS Pumps (Replacement and New) $750,000

Effluent Pump Station Modifications $735,000

Solids Dewatering (Allowance for Orège SLG® implementation) $250,000

Yard Piping $840,000

Contingency $5,740,000

Total Construction Cost $17,800,000

Total Project Cost $24,000,000

EXECUTIVE SUMMARY

ES-5

The capital expenditures portion of the proposed project will be funded as an Alliance Capital Project.

The Alliance Capital Project work is funded by a combination of Regional Service Charges and debt

proceeds to fund larger capital projects. The Alliance costs are then allocated to the Alliance Member

agencies, based on the amount of capacity allocation purchased with the project.

The allocation of costs for the project is summarized as follows:

• City of Battle Ground 19.2% of project cost $4,600,000

• Clark Regional Wastewater District 80.8% of project cost $19,400,000

• Total 100% of project cost $24,000,000

Compliance with Regulatory Requirements All proposed improvements to the SCTP will occur within the existing plant site. In accordance with

Revised Code of Washington (RCW) 90.48.110, all engineering reports, plans, and specifications for new

construction or improvements to existing sewage treatment systems shall be submitted to and

approved by Ecology before construction may begin. RCW 90.48.110 also allows delegation of this

authority to local authorities that meet Ecology’s criteria. The Clark Regional Wastewater District meets

Ecology’s criteria and has entered into a formal delegation agreement with Ecology. As a result, the

District will perform as the delegated authority for certain review and approval responsibilities. The

Alliance will serve as State Environmental Policy Act (SEPA) lead agency under its adopted SEPA rules.

The Alliance will obtain all necessary permits and approvals as discussed in Section 7.1.

Development of this Engineering Report requires the Alliance to consider environmental values under

the SEPA. Consequently, the Alliance will conduct a SEPA environmental review as lead agency per SEPA

rules adopted under WAC 197-11. Please refer to Section 7.2 and to SEPA DNS 001-2018 for all

documentation related to the SEPA review for this project.

A Water Quality Compliance Evaluation is provided as Appendix C of this report. This report provides an

evaluation of the Salmon Creek Treatment Plant (SCTP) Phase 5B plant capacity expansion with regard

to water quality in the Columbia River and Washington water quality standards (Washington

Administrative Code [WAC] 173-201A). The Phase 5B effluent flows will be discharged into the Columbia

River through the existing SCTP outfall and multi-port diffuser until the replacement outfall and diffuser

are completed under the Phase 5A project in 2023. This evaluation has been prepared to be consistent

with WAC 173-201A, and to align with the Washington State Department of Ecology (Ecology) Water

Quality Program Permit Writer's Manual (Permit Writer’s Manual) (2015) and Water Quality Program

Guidance Manual: Supplemental Guidance on Implementing the Tier II Antidegradation (Ecology, 2011).

After evaluating all unit processes at the SCTP, it is concluded that with the proposed improvements, the

treatment processes can treat up to a maximum monthly flow of 17.5 mgd and the associated flows and

loads without affecting the ability of the SCTP to reliably and consistently produce a high-quality effluent

with very low concentrations for oxygen-depleting substances, if that is determined to be required. The

improvements as proposed are protective of the Columbia River water resources and can be useful and

value added in any future process configuration and therefore are a reasonable investment of public

resources over the long term.

SECTION 1

1‐1

Introduction

1.1 Discovery Clean Water Alliance The Discovery Clean Water Alliance (Alliance) legally formed on January 4, 2013, representing the culmination of several years of evaluation to determine the optimum long‐term framework for delivery of regional wastewater transmission and treatment services to the urban growth areas in the central portion of Clark County, Washington. The Alliance serves four Member agencies: City of Battle Ground, Clark County, Clark Regional Wastewater District, and the City of Ridgefield. The Members jointly own and jointly manage regional wastewater assets under Alliance ownership through an interlocal framework established under the State of Washington Joint Municipal Utility Services Act (Revised Code of Washington [RCW] Chapter 39.106).

The Alliance is responsible for managing the capacity of its assets. The Salmon Creek Treatment Plant (SCTP) is the Alliance’s primary regional asset and is located at 15100 Northwest McCann Road in Vancouver, Washington.

1.2 Project Purpose This report documents the existing conditions and system capacity at SCTP and identifies the improvements necessary to provide additional capacity in the wastewater infrastructure system at SCTP. Long‐range planning was performed and described in the August 2013 Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan Amendment (2013 Facilities Plan Update), approved by the State of Washington Department of Ecology (Ecology) in a letter dated September 4, 2013. The 2013 Facilities Plan Update provided an update to the July 2004 Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan (2004 Facilities Plan), which defined the Phase 5 Expansion Program intended to provide sufficient capacity to meet projected demand to 2028. Due to fluctuations in the growth rate of the service area, this Phase 5 expansion capacity is now projected to support the community until 2030. The 2013 Facilities Plan Update defined the Phase 5 expansion as the addition of Aeration Basin 7, construction of a new outfall, and other site improvements. This Engineering Report describes the proposed alternative to maintain conservative treatment capacity, consistent with the framework established in the approved 2013 Facilities Plan Update.

1.3 Project Need The NPDES permit limits provide the basis for the phasing of SCTP improvements as described in the 2004 Wastewater Facilities Plan/General Sewer Plan (2004 Facilities Plan) and the 2013 Wastewater Facilities Plan/General Sewer Plan (2013 Facility Plan Update), with the exception of the ammonia limit which was developed as part of the 2005 NPDES permit renewal and reflected in the 2013 Facility Plan Update. The Phase 5 Expansion described in the 2013 Facility Plan Update includes one new aeration basin and construction of a replacement outfall and diffuser that would expand the plant to a capacity of 18 million gallons per day (mgd) on a maximum monthly flow basis. This baseline project would represent the continuation of the engineering design basis and operational performance meeting the current NPDES permit limits.

The State of Washington Department of Ecology (Ecology) requires the Discovery Clean Water Alliance (Alliance) to submit a plan and schedule maintaining adequate capacity in its treatment facilities when one of the following two conditions is met:

SECTION 1 – INTRODUCTION

1‐2

Actual flow or actual waste load reaches 85 percent of the rated capacity of the facility for 3 consecutive months, or

Projected flow or projected waste load will reach the design capacity of the facility within 5 years

Recent analysis of the projected waste flow and loading to the plant, as well as current plant performance, suggests that treatment capacity could be reached within the next several years, depending on growth patterns in the service area for the facility. The ongoing assessments of flow and load have identified the need for the Alliance to initiate the Phase 5 Expansion Program in order to meet the permit requirements summarized above to maintain adequate capacity in the treatment facilities. Figures 1‐1 and 1‐2 present the flow and loading trends for the plant as well as the phasing of the expansion projects.

Figure 1‐1. Salmon Creek Treatment Plant Design Capacity versus Projected Demand for Influent Flow Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

(mgd = million gallons per day)


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Figure 1‐2. Salmon Creek Treatment Plant Design Capacity versus Projected Demand for Influent Loading Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

(BOD = 5‐day biochemical oxygen demand; ppd = pounds per day; TSS = total suspended solids)

The Phase 5 Expansion Program is consistent with the currently‐adopted planning basis and is being implemented in the following two separate projects:

Phase 5A Project—Columbia River Outfall and Effluent Pipeline to design and construct a replacement effluent pipeline and replacement Columbia River outfall to address long‐term system hydraulic capacity, shoreline stability and improved diffuser location and dilution performance. This project has independent utility and is required to support future (Phase 6 and later) expansion phases of SCTP. While the project does not directly increase discharge capacity for the system, it is moving forward at this time consistent with the approved planning framework and in order to coordinate with other near‐term planned private property improvements in the affected area.

Phase 5B Project—Salmon Creek Treatment Plant Improvements to address facility loading and treatment capacity with an updated process and hydraulic analysis, and facility improvements. This project is required to address shorter‐term capacity needs related to flow and organic loading to the facility. Consistent with the approved planning framework, this project does result in an increased facility and discharge capacity by addressing the secondary treatment process as the limiting capacity element within the facility.

While both occur under the overall Phase 5 Expansion Program, the Phase 5A Project is distinctly separate from Phase 5B Project. The Phase 5B Project results in an increased treatment and discharge capacity while the Phase 5A Project supports future phases of expansion. The projects are functionally independent. A separate engineering report has been developed for the Phase 5A Project.

1.4 Engineering Report Organization This report is organized and prepared to meet specific Ecology requirements for a wastewater Engineering Report per Washington Administrative Code (WAC) 173‐240‐060. The following is an outline of the information provided in subsequent sections.


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Section 2, Background Information. A discussion of current wastewater flow and loading characteristics as well as existing facility equipment and performance is included to provide a context and framework for evaluating the proposed project.

Section 3, Future Conditions. This section includes projections for future waste flows and loads expected at SCTP.

Section 4, Recommended Improvements. Technical details of the recommended improvements are provided in this section.

Section 5, Air Quality and Odor Control. Technical details of the analysis and recommended alternative for odor control are provided in this section.

Section 6, Financial Considerations, Staffing, and Schedule. Financial information that needs to be considered to implement the proposed project, such as costs of the selected alternative and user charges and funding sources, are reviewed. Staffing impacts at the facility are reviewed.

Section 7, Compliance with Regulatory Requirements. This section contains additional miscellaneous information, such as environmental compliances and implementation issues that were not addressed in previous sections.

Section 8, Engineering Report Requirements Checklist. Requirements for Engineering Reports as defined in Criteria for Sewage Works Design (2008) are listed and information is provided about how they are handled in this Engineering Report.

Section 9, References. Listing of references cited in text.


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1.5 Owner and Authorized Representative The Owner of the SCTP is the Alliance. The District is responsible for engineering and capital planning, as well as the overall financial and administrative functions of the Alliance. The Owner's authorized representative for this facility is Dale Lough. His contact information is as follows:

Dale W. Lough, P.E. Capital Program Manager Clark Regional Wastewater District (Administrative Lead for Discovery Clean Water Alliance) 8000 NE 52nd Court P.O. Box 8979 Vancouver, Washington 98668 Telephone: 360‐993‐8856

[email protected]

SECTION 2

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Background Information This section presents a summary of the regulatory and planning framework to date, historical performance of the Salmon Creek Treatment Plant, the current wastewater flows and loading to SCTP as well as a description of the existing capacities of the treatment systems in operation at the plant. This section also presents discussion on emerging regulatory considerations as they relate to the Salmon Creek Treatment Plant.

2.1 Historical Regulatory and Planning Framework

2.1.1 Existing Permit Requirements The Salmon Creek Treatment Plant (SCTP) has been operating under its current National Pollutant Discharge Elimination System (NPDES) permit since March 2012. Table 2‐1 below summarizes the effluent limits contained in the current permit.

Table 2‐1. Current NPDES Permit Effluent Limitsa Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Parameter Average Monthly Average Weekly Maximum Dailyb

Biochemical Oxygen Demand (5 Day)

30 mg/L 3,741 ppd 45 mg/L 5,612 ppd __

Total Suspended Solids 30 mg/L 3,741 ppd 45 mg/L 5,612 ppd _

Fecal Coliform Bacteria 200 / 100 mL 400 / 100 mL _

pH Daily minimum is equal to or greater than 6.0 and the daily maximum is less than or equal to 9.0.

Acute Whole Effluent Toxicity

No acute toxicity detected in a test concentration representing the acute critical effluent concentration (ACEC).

Total Ammonia (as NH3‐N)

18.7 mg/L __ 37.5 mg/L

a The average monthly and weekly effluent limitations are based on the arithmetic mean of the samples taken with the exception of fecal coliform, which is based on the geometric mean.

b The maximum daily effluent limitation is defined as the highest allowable daily discharge. The daily discharge means the discharge of a pollutant measured during a calendar day. For pollutants with limitations expressed in unites of mass, the daily discharge is calculated as the total mass of the pollutant discharged over the day. For other units of measurement, the daily discharge is the average measurement of the pollutant over the day.

The 5‐day Biochemical Oxygen Demand (BOD5) and Total Suspended Solids (TSS) effluent limits are based on the state regulation for secondary treatment standards (WAC 173‐221‐040). The permit further requires 85 percent removal of influent concentrations of BOD5 and TSS. The ammonia limits are based on water quality criteria for the protection of aquatic life from ammonia toxicity, which were first implemented programmatically in the NPDES permit issued in June 2005. The ammonia limits were required when the Phase 4 Expansion construction project was completed and the resulting increase in discharge capacity was formally recognized, which occurred in 2009. The facility has been operating under these effluent requirements for approximately the last ten years.

SECTION 2 – BACKGROUND INFORMATION

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2.1.2 Recent Salmon Creek Treatment Plant Performance The SCTP has maintained a high‐quality effluent that is well within the NPDES permit limits. While minor variations in these effluent data have occurred that are attributable to short‐duration process conditions, no excursion has resulted in a violation of the monthly effluent limits. Figure 2‐1 shows 8 years of effluent concentration data for total ammonia (NH3‐N), BOD5, and TSS ‐ as compared to NPDES permit limits. SCTP has demonstrated reliable treatment performance, producing high‐quality effluent that is well within effluent limits prior to discharge to the Columbia River via its outfall diffuser. This outcome is a success representing both the appropriateness of the original treatment plant process planning basis and engineering design as well as the ongoing efforts of the facility operations and maintenance staff.

Figure 2‐1. Monthly Plant Effluent Concentration Data – BOD5, TSS & NH3‐N (mg/L) Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

2.2 Current Treatment Processes

2.2.1 Existing Design Capacity and Wastewater Flow and Character Currently, per National Pollutant Discharge Elimination System (NPDES) Permit No. WA0023639, the SCTP has a rated capacity of 14.95 million gallons per day (mgd) maximum month flow. The current rating for 5‐day biochemical oxygen demand (BOD5) maximum month average daily loading is 25,400 pounds per day (ppd). The current rating for total suspended solids (TSS) maximum month average daily loading is 28,200 ppd.

A review of historical flows and loads was conducted to provide an accurate characterization of the flow and loading for the facility. Historical plant data from January 2011 to December 2017 are summarized below in Table 2‐2 in terms of the annual average influent flows and loads.


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Table 2‐2. Annual Influent Flows and Loads Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Year Flow (mgd)

BOD5 (ppd)

TSS (ppd)

NH3‐N* (ppd)

Minimum 7‐day Average

Temperature (°C)

2011 7.30 15,092 15,303 2,031 13.6

2012 7.55 15,703 17,093 2,191 13.6

2013 7.03 16,210 16,724 2,087 13.9

2014 7.33 16,849 18,988 2,206 13.4

2015 7.29 16,897 19,179 2,220 15.2

2016 7.84 17,336 19,358 2,282 13.4

2017 8.43 18,838 20,860 2,255 13.4

Average 7.58 16,441 18,599 2,184 13.8

*NH3‐N loads represent loads to the primary clarifier and include projected recycle loads.

BOD5 = 5‐day biochemical oxygen demand; mgd = million gallons per day; NH3‐N = ammonia‐nitrogen; ppd = pounds per day; TSS = total suspended solids.

Maximum month to annual average flow and load peaking factors from 2011 through 2017 are presented in Table 2‐3. The average of the peaking factors from the 2011 through 2017 period is a representative measure to project plant flows. For mass‐based loads (BOD5, TSS, and NH3‐N), the 95th percentile of the peaking factors was chosen as a conservative estimate based on guidance from Section 5.5.4 of the U.S. Environmental Protection Agency’s (EPA) Technical Support Document for Water Quality‐Based Toxics Control (1991), which states that the average monthly limit (i.e., maximum month) for mass‐based contaminant loads should be based on the 95th percentile level rather than the average value.

Table 2‐3. Maximum Month to Annual Average Flow and Load Peaking Factors Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Year Flow (mgd)

BOD5 (ppd)

TSS (ppd)

NH3‐N* (ppd)

2011 1.29 1.11 1.21 1.24

2012 1.26 1.13 1.15 1.26

2013 1.32 1.09 1.11 1.13

2014 1.24 1.12 1.24 1.11

2015 1.49 1.13 1.20 1.12

2016 1.41 1.20 1.24 1.13

2017 1.18 1.11 1.13 1.10

Average 1.32 NA NA NA

95th Percentile NA 1.18 1.24 1.26

*NH3‐N loads represent loads to the primary clarifier and include projected recycle loads.

BOD5 = 5‐day biochemical oxygen demand; mgd = million gallons per day; NA = not applicable; NH3‐N = ammonia‐nitrogen; ppd = pounds per day; TSS = total suspended solids.


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In addition, the 2.5 peaking factor recommended by in Criteria for Sewage Works Design was used to

calculate the peak-hour flow.

2.2.2 Basis of Treatment Capacity

Components of Existing Treatment Facility

Preliminary Treatment

The SCTP has two 6-millimeter mechanically cleaned bar screens, a bypass channel equipped with a

manual bar screen, and two 20-foot diameter vortex grit units as part of preliminary treatment. The

total capacities for the existing raw screening and grit removal processes are 34 mgd and 50 mgd on a

peak-hour basis, respectively.

The washer function of the washer/compactor at the headworks has been decommissioned at the plant

due to maintenance difficulties with the equipment. The preliminary treatment process performs

acceptably with the washer function decommissioned.

Primary Treatment

Primary treatment consists of four identical rectangular clarifiers. The primary clarifiers are 20 feet by

160 feet with a side water depth of 11 feet. SCTP data from January 2014 to December 2017 show that

the SCTP usually operates with one to three of the primary clarifiers online. These data also show that

the minimum 30-day average BOD5 and TSS removals are 40 and 69 percent, respectively. Figures 2-2

and 2-3 show that even operating at high surface overflow rates (SORs) and with only one primary

clarifier online, the BOD5 removal is more than 40 percent and the TSS removal is more than 69 percent

most of the time.

Criteria for Sewage Works Design states that:

…A well-designed and properly operated primary clarifier, providing primary solids removal or co-settling,

should remove 30 to 35 percent of the BOD5 and 50 to 60 percent of the suspended solids from raw

domestic wastewater.

The historical data presented in Figures 2-2 and 2-3 demonstrate that the primary clarifiers at SCTP

generally perform more effectively than the typical range indicated in the Criteria for Sewage Design.

For design purposes, however, the more conservative values of 35 percent BOD removal and 60 percent

TSS removal indicated in the Criteria for Sewage Design will be used.


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Figure 2‐2. 2014‐2017 BOD5 Percentage Removal versus Primary Clarifier SOR Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

(gpd/ft2 = gallons per day per square foot; PC = primary clarifier)

Figure 2‐3. 2014‐2017 TSS Percentage Removal versus Primary Clarifier SOR Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

(gpd/ft2 = gallons per day per square foot; PC = primary clarifier)

The Phase 3 and 4 projects included scum removal mechanisms at the primary clarifiers, which have been decommissioned and removed by plant staff due to limited amounts of scum being realized and the maintenance needs of the equipment. Scum is conveyed to the secondary process with the primary

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

0 500 1,000 1,500 2,000 2,500 3,000 3,500BOD5percentage Rem

oval, %

SOR, gpd/ft2

1 PC Online 2 PC Online 3 PC Online 4 PC Online

35% Removal

0.0

10.0

20.0

30.0

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oval, %

SOR, gpd/ft2

1 PC Online 2 PC Online 3 PC Online 4 PC Online

60% Removal


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effluent and is removed in the secondary clarifiers. This scum removal approach has worked reliably for several years and is therefore planned to continue.

Aeration Basins

The SCTP currently has six aeration basins. The dimensions of the basins are listed in Table 2‐4. Aeration Basins 1 and 2 have been retrofitted to operate in series with Aeration Basins 3 and 4 as parallel trains (e.g., the anoxic volume in Aeration Basin 1 is used together with the aerobic volume in the remainder of Aeration Basin 1 and the complete aerobic volume in Aeration Basin 3 to act as a complete bioreactor). Aeration Basins 5 and 6 are long, narrow, plug‐flow basins that feature baffled anoxic zones followed by plug flow aerobic zones. The SCTP has two independent blower systems. One system provides air for Aeration Basins 1 through 4, and the other system provides air to Aeration Basins 5 and 6.

9BTable 2‐4. Aeration Basin Dimensions Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Aeration Basins Dimensions

(feet) Side Water Depth

(feet) Anoxic Volume (Each), MG

Aerobic Volume (Each), MG

Aeration Basins 1 and 2 94 x 41 14 0.20 0.20

Aeration Basins 3 and 4 94 x 49 15.5 0 0.53

Aeration Basins 5 and 6 323 x 18 20 0.22 0.65

Figure 2‐4 presents a process flow diagram of Aeration Basins 1 and 3, illustrating how they are linked to operate in series. Note that Aeration Basins 1 and 3 are each further subdivided into two cells by baffle walls, creating a total of four reactor chambers, with one functioning as an anoxic reactor and the others as aerobic reactors. Aeration Basins 2 and 4 are linked together in series using the same configuration.

Figure 2‐4. Schematic Diagram of Linked Aeration Basins 1 and 3 in Series (Typical also to Aeration Basins 2 and 4) Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

The newer aeration basins, Aeration Basins 5 and 6, have been designed as plug‐flow reactors, featuring narrow, long channels with baffled anoxic and aerobic zones to eliminate short‐circuiting and increase treatment efficiency. Figure 2‐5 presents a schematic diagram of the newer basins.


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Figure 2-5. Schematic Diagram of Aeration Basins 5 and 6


Aeration System

The blower system that provides air for Aeration Basins 1 through 4 has four 3,300-standard-cubic-foot-

per-minute (scfm) positive displacement blowers, while the blower system for Aeration Basins 5 and 6

has two 4,500-scfm single stage blowers and one 2,500-scfm single stage blower. The aeration basins

are equipped with 12-inch, fine-bubble ceramic diffusers. Table 2-5 summarizes the overall capacity of

each system.

9BTable 2-5. Existing Aeration System Capacity


Item Value

Aeration Basins 1 through 4

Number of Blowers (Identical) 4

Blower Type Positive Displacement, Rotary

Lobe

Blower Capacity (each), scfm 3,300

Blower Power, hp 150

Aeration Basins 5 and 6

Number of Blowers 3

Blower Type Single-Stage Centrifugal

Blower Capacity (each), scfm Two 4,500

One 2,500

Blower Power, hp Two 250

One 150

Current Performance – Secondary Treatment

The SCTP achieves monthly average ammonia-nitrogen effluent concentrations between 0.3 and 11.3

mg-N/L. The ammonia-nitrogen effluent concentrations are well within the effluent ammonia-nitrogen

permit limit of 18.7 mg-N/L average monthly.

Historical data from January 2014 to December 2017 show that the mixed liquor suspended solids

(MLSS) concentration at the basins is maintained between 1,700 and 3,700 milligrams per liter (mg/L).

Figure 2-6 shows the MLSS concentrations during this period. The data also show a high variability on

the sludge volume index (SVI). During this period, the average SVI was 125 milliliters per gram (mL/g),


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but SVI values as high as 350 mL/g were observed. The SVI is less than 195 mL/g 90 percent of the time

and lower than 229 mL/g 95 percent of the time. Figure 2-6 shows that the variability of the SVI is not

related to the MLSS concentration.

Figure 2-6. MLSS Concentration and SVI Over Time


During the last episode of relatively high SVI values (April 2017), the SCTP staff implemented the

temporary chlorination of RAS, which brought the SVI down in a matter of days. At the time, SCTP staff

members were allowing the growth of filamentous bacteria in order to help trap and settle pin-floc in an

effort to produce very high-quality effluent. When SVI exceeded 250 mL/g, SCTP staff utilized totes of

12.5 percent hypochlorite to chlorinate the RAS. The initial dose was set at 0.5 pound (lb) Cl2 per 1,000

lb MLSS on April 26, 2017. This dose was maintained for 2 days and on April 28, 2017, the dose was

decreased to 0.25 lb Cl2 per 1,000 lb MLSS. This dose was maintained until the SVI had dropped to 150

mL/g, and on May 10, 2017, staff ended hypochlorite dosing.

RAS chlorination is recommended as a part of the facility improvements to prevent high-SVI conditions,

as discussed in more detail in Section 4.4.6.

Secondary Clarifiers

Four secondary clarifiers are currently in place at SCTP: two 90-foot-diameter (Secondary Clarifiers 1 and

2) and two 105-foot-diameter clarifiers (Secondary Clarifiers 3 and 4). Secondary Clarifiers 3 and 4 are

typically online. Secondary Clarifiers 1 and 2 are brought online as needed. Table 2-6 summarizes the

dimensions of each clarifier.

0

50

100

150

200

250

300

350

400

-

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

8/14/2013 3/2/2014 9/18/2014 4/6/2015 10/23/2015 5/10/2016 11/26/2016 6/14/2017 12/31/2017

SVI,

mL/

g

MLS

S, m

g/L

MLSS SVI


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9BTable 2‐6. Secondary Clarifier Dimensions Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Aeration Basins Diameter (feet)

Side Water Depth (feet)

Clarifier 1 90 12.5

Clarifier 2 90 14.85

Clarifiers 3 and 4 105 16

Historical data from January 2014 to December 2017 show that the monthly average TSS secondary effluent concentration is between 3.6 and 13.2 mg/L, which is well within the effluent TSS permit limit of 30 mg/L. Figure 2‐7 shows that the effluent TSS is generally below 30 mg/L even at high SVI values.

Figure 2‐7. 2014‐2017 Effluent TSS versus SVI Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Return Activated Sludge System

Six identical pumps are currently in place in the RAS pump station. Each pump is rated at 3.3 mgd. Pump 1 serves Clarifier 1, Pump 2 serves Clarifier 2, and Pump 5 serves as a swing pump for Clarifiers 1 and 2. Similarly, Pump 3 serves Clarifier 3, Pump 4 serves Clarifier 4, and Pump 6 serves as a swing pump for Clarifiers 3 and 4. The total RAS flow capacity is 13.2 mgd with each swing pump out of service. Historical data from January 2014 to December 2017 show that the RAS rate is maintained between 45 to 60 percent of the plant ADMM influent flow.

Disinfection

SCTP utilizes a medium pressure, high intensity UV system for disinfection. The facility consists of 1 channel, 2 banks, and 20 modules. The system is currently rated to treat up to 34 mgd at peak‐hour conditions.

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SVI, mL/g


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Effluent Pump Station

The existing effluent pump station is rated to meet the Phase 4 peak‐hour flow of 28.3 mgd. With the largest pump out of service, the remaining pumps have the capacity to handle peak‐hour flow conditions, so redundancy requirements are met. The existing vertical, mixed flow, open line shaft effluent pumping system consists of Pumps 1 and 3 (14‐inch pumps) and Pumps 2 and 4 (18‐inch pumps).

Waste Activated Sludge Thickening

Two 2‐meter gravity belt thickeners (GBTs) are used to thicken waste activated sludge (WAS) at the plant. Currently, SCTP operates one of the GBTs continuously. Wasting sludge continually can be beneficial for the stability of secondary treatment. For this reason, it is a common practice in the industry to run the WAS thickening facilities continuously.

The SCTP is currently sending the filtrate and washwater generated by the dewatering process to the WAS line to reduce the solids recirculated to the front of the plant. To improve reliability, the SCTP implemented additional control features such as interlocking the GBT thickening process and the belt filter press (BFP) dewatering process so that if a GBT drive fails, the BFPs, dewatering feed pumps, washwater, and dewatering polymer feed will also stop. The plant staff has also installed zero‐speed switches on GBT drive rolls that trigger an additional alarm when the drive roll zero speed is detected. Adequate upstream holding time is available to accommodate the duration of any such stoppages.

Anaerobic Digestion

Two 825,000‐gallon mesophilic anaerobic digesters are used to treat the primary sludge and WAS generated at the SCTP and a small fraction of imported WAS from the City of Ridgefield. Primary sludge and WAS are blended together in a 72,000‐gallon blending tank before being sent to the digesters.

Existing digester gas is combusted in hot water boilers to heat the digestion process, with excess gas combusted in a waste gas incinerator.

The scum concentrator equipment installed during Phase 3 was decommissioned before the Phase 4 project and subsequently demolished. The process benefits (reduction of water to the digester) were outweighed by the maintenance needs, energy use, and degrading condition of equipment. The plant operates acceptably in this configuration and has done so for over 10 years.

The SCTP currently produces Class B biosolids.

Digested Biosolids Dewatering

The SCTP uses two 2‐meter BFPs to dewater the digested sludge. Currently, SCTP operates one of the BFPs continuously. As mentioned before, the filtrate generated by the BFP operation is discharged to the feed line to the GBT equipment as described above.

The SCTP has four 1,300‐cubic‐yard storage bunkers to store the dewatered sludge cake. According to the 2013 Facilities Plan Update (CH2M, 2013), dewatered sludge cake in excess of that capacity will be hauled both locally and to eastern Washington as needed so that the combination of bunker storage and hauling is sufficient to manage dewatered sludge cake at the SCTP. A truck scale onsite is used to confirm truck loading before hauling from the site.

2.3 Emerging Regulatory Considerations Planning to ensure reliable and predicable wastewater service is one of several core values of the Alliance and these core values are used to shape Alliance investments and decision making. As regulatory requirements change, the Alliance’s ongoing capital and operational planning responds to new information, regulatory requirements, and customer needs in order to deliver service according to


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the Alliance’s core values. In this context, it is appropriate to review emerging regulatory topics that may provide additional context for the Phase 5B project.

2.3.1 Relevant Regulatory Developments Since Previous Planning Approvals In the time since Ecology approved the 2013 Facilities Plan Amendment, the following two key developments have occurred, which could affect current and future capital and operational planning at SCTP.

Ecology’s 2016 Water Quality Standards Update of Human Health Criteria (WAC 173‐201A‐240) and revisions to the NPDES Permit Implementation Tools

Ecology’s Clean Water Act 303(d) Water Quality Assessment and 2014 303(d) listings

2.3.1.1 2016 Water Quality Standards Update of Human Health Criteria

Ecology published updated water quality criteria for the protection of human health or human health criteria (HHC) in Washington State’s water quality standards on August 1, 2016, which was reviewed by the U.S. Environmental Protection Agency (EPA) with a decision on November 15, 2016. The EPA decision became effective December 28, 2016, in accordance with the Clean Water Act (CWA). After comparing available SCTP effluent water chemistry within the new HHC, there are two compounds of interest for the Alliance: arsenic and phthalates.

Background arsenic levels in the Columbia River currently exceed the 2016 HHC by a substantial margin and the de minimis input of arsenic in the SCTP effluent discharge is overshadowed by background arsenic concentrations in the river. EPA rejected Ecology’s proposed arsenic criteria and instead imposed the current federal arsenic water quality criteria in the state water quality standards. The Alliance understands that this circumstance has prompted Ecology to reassess arsenic HHC criteria in water, which could provide the basis to develop a Columbia River basin variance or intake credit for arsenic for municipal dischargers.

A second chemical of concern is the category of phthalates, which are commonly used as plasticizers to increase flexibility and longevity of polyvinyl chloride (PVC) and other plastics. Phthalates are commonly found in the wastewater of most urban areas, due to the ubiquitous use of products made from PVC, including common water and wastewater pipeline materials. The 2016 HHC for bis(2‐ethylhexyl) phthalate will likely require Ecology to develop a statewide programmatic management approach for phthalates monitoring that will be implemented through the regular and ongoing NPDES permit renewal framework and non‐point‐source reductions.

Because neither arsenic or phthalates can be responsibly managed in the context of end‐of‐pipe treatment for the near‐term (Phase 5) capital projects, the Alliance understands these items will be addressed programmatically in future efforts associated with NPDES permit renewals or future facility planning efforts, as additional guidance is available from Ecology and/or EPA at the time of planning.

The updated water quality standards include tools that could potentially be applicable to the SCTP in the future, such as compliance schedules, intake credits and variances.

2.3.1.2 CWA 303(d) Listings

Under Section 303(d) of the CWA, Ecology has responsibility to identify, classify, and manage impaired waters. As part of this responsibility, Ecology is required to develop water quality assessments of freshwater and marine waters, review credible data to classify waterbodies (Categories 1 to 5, unimpaired to impaired), and to submit the water quality assessment and 303(d) list to EPA for review and approval. The current 303(d) listings for the Columbia River reach where the SCTP outfall is located (River Mile 96) are based on Ecology’s 2014 Water Quality Assessment, which was approved by EPA in July 2016.


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Ecology’s 2014 303(d) list includes an Assessment Unit (AU) that consists of approximately 13 miles of

the lower Columbia River from the confluence of the Willamette River (RM 101) to the confluence of the

Lewis River (RM 88). Within this large reach or AU, the Columbia River is currently listed as impaired for

temperature, dissolved oxygen (DO), and bacteria. These three Category 5 listings in the 2014 list are

identified as follows:

• Bacteria (Listing 6705)

• Temperature (Listing 7884)

• Dissolved Oxygen (Listing 49047)

These Category 5 water quality listings mean that a total maximum daily load (TMDL) study is expected

to be developed unless additional data collections result in reclassification or removal of the Category 5

listings. The bacteria listing is based on the 1998 Water Quality Assessment and no new bacteria data

have been incorporated into the assessment since the 1998 listing. Reaches of the lower Columbia River

have been listed for temperature for several decades, and EPA has taken the lead of developing a

temperature TMDL for the Columbia and Snake Rivers. The DO listing is of more recent origin and based

only on shallow shoreline measurements collected in 2006-2009 to assess impact of aquatic plant

growth areas on water quality along the river bank. Each of these listings is further considered in

Section 3.3 of this report with respect to the Phase 5 Expansion Program approach to discharge

standards.

SECTION 3

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Future Conditions This section presents the planning basis to date and analyzes projected SCTP influent flows and loads and discusses plant recycle and additional flows. These values incorporate updated planning values providing specific recommendations consistent with the general guidance from the 2013 Facilities Plan Update.

3.1 Projected Flows and Loads The average flows and loads presented in Table 3‐1 were used to calculate the BOD5, TSS, and NH3‐N annual average concentrations. The flow and load design peaking factors listed in Table 2‐2 were used to calculate the annual average flow associated with an average‐day maximum month (ADMM) flow of 17.5 mgd. The annual average concentrations and average flow were used to calculate the projected annual average BOD5, TSS, and NH3‐N loads. Then the projected annual average loads were multiplied by the design load peaking factors to calculate the projected ADMM loads used for this evaluation. Table 3‐1 presents the projected flows and loads associated with an ADMM of 17.5 mgd.

Table 3‐1. Projected Flows and Loads Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements (Unit processes capacity evaluation projected flows and loads* at ADMM = 17.5 mgd)

Item Value

Projected Influent Flow

Annual Average, mgd 13.3

ADMM, mgd 17.5

Peak Day, mgd 26.6

Peak Hour, mgd 33.1

Maximum Month Projected Loads

5‐day Biochemical Oxygen Demand, ppd 30,520

Total Suspended Solids, ppd 35,770

% Volatile Solids 92%

Ammonia‐Nitrogen (NH3‐N), ppd 4,006

Alkalinity (CaCO3), ppd 29,938

*The projected loads were calculated using SCTP historical data from January 2011 to December 2017.

The recommended development plan for SCTP has been divided into phases. The current phase presents the necessary improvements to meet an overall treatment capacity of 17.5 mgd, which corresponds to year 2030 loadings based on the current projections depicted in Figure 1‐2. However, while the phasing has been developed to match stated flow projections corresponding to specific years in the planning horizon, the intent has been to develop a phased capital improvement plan based on flow and load, rather than hard dates. This has allowed for appropriate investment in the facility that is consistent with the actual rate of economic and demographic growth in the service area.

The SCTP has realized slightly lower ADMM flows than projected in the 2004 Facilities Plan and the 2013 Facilities Plan Update likely due to domestic water conservation measures that are being broadly observed across many water and wastewater utility systems, but, importantly, the waste load (BOD5, TSS, and ammonia‐nitrogen) has generally followed the forecasted loadings as shown in Figure 1‐2.

SECTION 3 – FUTURE CONDITIONS

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The Alliance has closely monitored influent flows, loads, and process performance to ensure compliance with the 85 percent of rated capacity threshold notification requirement. With the proposed improvements, SCTP can treat up to an ADMM flow of 17.5 mgd and the associated flows and loads without affecting the ability of the SCTP to reliably and consistently comply with wastewater permit terms and conditions to produce a high‐quality effluent.

3.2 Additional Flows

3.2.1 Imported Waste Activated Sludge Flow Currently, the SCTP is treating additional WAS from the City of Ridgefield. The SCTP receives an average of 47,500 gallons per month at an average of 3.3 percent solids concentration (11,850 dry pounds per month) of thickened WAS that is digested at the SCTP. To assess the SCTP capacity at 17.5 mgd, it was assumed that the SCTP will continue treating WAS from the City of Ridgefield.

The Discovery Corridor Wastewater Transmission System connecting the City of Ridgefield to SCTP is now in place and flows from the majority of new development are being sent directly to SCTP rather than to the City of Ridgefield. This development has been factored into flow projections to SCTP.

3.3 Phase 5B Improvements Program Approach to Discharge Standards

3.3.1 Alliance Actions to Address Columbia River Discharge Issues The SCTP discharge to the Columbia River is located near RM 96, which is approximately midway between the confluence of the Willamette River (RM 101) and the Lewis River (RM 88) confluence with the Columbia River. As noted above, Ecology’s 2014 303(d) list includes an AU that consists of this 13‐mile reach of the Columbia River, which is currently included as a Category 5 listing that is impaired for temperature, DO, and bacteria. Based on the Category 5 listing status, a TMDL study is expected to be developed for these parameters at some time in the future, unless additional data support reclassification or removal of the Category 5 listings through the ongoing biennial update process. The Alliance evaluation of and actions to address these three listings are discussed below:

3.3.1.1 Bacteria

The Alliance near‐term capital projects propose to continue the high level of disinfection required by the NPDES permit using UV light disinfection of wastewater, which will address the bacteria listing by not causing or contributing to the impairment.

3.3.1.2 Temperature

To address the temperature listing, a broad multi‐state, regional approach will be required. Studies have indicated that the temperature issue is dominated largely by the effects of large pools of water stored behind dams on the Columbia River and Snake River systems. Municipal discharges are a small component of this larger temperature issue. The Draft Temperature TMDL for the Columbia and Snake Rivers was issued in 2003 and included an overall heat load allocation for municipal discharges that will be further apportioned when the TMDL is finalized and a managed implementation plan is developed. This topic is also currently the subject of federal court litigation. As a result, the temperature listing is beyond the scope of what near‐term Alliance capital project investments can directly anticipate or responsibly address. The Alliance will continue to monitor legal and regulatory developments in this area and understands Ecology will most likely implement the results of these processes through the ongoing NPDES permit renewal processes. The Alliance’s Phase 5B Engineering Report includes a Water


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Quality Compliance Evaluation (included as Appendix C) in the event that the improvements were considered expanded action under the Clean Water Act. The Water Quality Compliance Evaluation documents that the SCTP discharge associated with the proposed improvements and the current Columbia River diffuser does not result in a measurable change in Columbia River water temperature (as defined in WAC 173‐201A‐200 and WAC 173‐201A‐320), and it complies with Ecology’s requirements.

3.3.1.3 Dissolved Oxygen

The DO listing is more recent and further study and investigations are ongoing with regard to the listing. As described in more detail below, the Alliance is working with Ecology to provide an accurate assessment of existing data and also to provide Ecology with additional data and information so that informed regulatory determinations can be made with respect to the listing. Each of these efforts is explained below.

3.3.1.3.1 Review of Data Applied in Ecology’s 2014 Water Quality Assessment and 303(d) Listing. Based on information available through Ecology’s website, data utilized to inform the listing were provided by a volunteer group focused on shallow shoreline water quality conditions that could affect juvenile salmonids due to aquatic plant growth conditions. The intent of this study had a narrow focus and was not specifically designed to characterize the overall free‐flowing river water quality, especially with respect to the offshore location of discharges from municipal treatment facilities. Due to the volunteer nature of the data collection effort and Ecology resource limitations, the Alliance understands that a formal Quality Assurance Project Plan (QAPP) may not have been reviewed by Ecology prior to the sampling effort, and the relevant documentation to show compliance with the QAPP may not have been submitted to Ecology after the sampling effort.

In May 2018, the Alliance made a Public Records Request to Ecology for all available collected water quality data, instrument calibration records, and the program QAPP for these 2007‐2009 water quality monitoring data. In mid‐June 2018, Ecology provided records and data for this monitoring work. Recognizing Ecology’s staff time limitations, the Alliance has offered to have these data reviewed by qualified water quality scientists to understand the integrity of these data for use in the water quality assessment and 303(d) processes. This work is ongoing at this time. Preliminary review of these data recently provided by Ecology confirms the study focus area was shallow (wadable) areas at certain sites predisposed to algae and aquatic plant growth. The Alliance plans to share its findings once these relevant data have been completely reviewed and anticipates that this work will provide a scientific basis for changing the listing from a Category 5 (impaired) listing to a Category 2 or 3 (not known to be impaired) listing during the 2016 water quality assessment process, as is further explained below.

Further analysis of the information recently provided indicates that the current DO listing was not based on DO concentration measurements below the 1‐day minimum criteria during the summer season (6.5 milligrams per liter [mg/L]; June 14‐September 16) or 1‐day minimum criteria during the remainder of the year (8.0 mg/L; September 17‐June 13). Rather, this DO listing is based on calculated DO saturations below 90 percent saturation that were calculated by Ecology using historical DO data and historical local airfield barometric pressure data.

Figure 3‐1 shows a schematic cross section of the existing SCTP outfall diffuser location in the Columbia River. The existing SCTP outfall diffuser is located approximately 250 feet off the east river shoreline at low river stage on the slope into the deep river channel and within the free‐flowing river.


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Figure 3‐1. Section View of Salmon Creek Treatment Plant Outfall and Diffuser Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

3.3.1.3.2 2016 Water Quality Assessment – Alliance Data Provided to Ecology. In coordination with an Alliance design development of the replacement SCTP outfall at RM 96, the Alliance sponsored an extensive Columbia River water quality data collection effort during the dry season of August to October 2015. The data collection effort was intentionally conducted during the low flow river period and corresponding maximum seasonal ambient and river water temperatures. The water quality monitoring included DO, temperature, pH, and conductivity using water column profile measurements obtained from a boat in the free‐flowing river. In addition, a water quality instrument was deployed on an anchored cable array to record continuous measurements to compare with the water column profiles. These data complied with the applicable water quality standards for DO concentration and saturation in the river. The work was completed according to a QAPP, which was subject to three separate Ecology reviews. Comments from Ecology were incorporated into the final QAPP. All data and required documentation were submitted to Ecology during the “call for data” period in 2016.

These 2015 data are summarized in plots included in a separate technical memorandum titled “Water Quality Compliance Evaluation for the Phase 5B Project – Salmon Creek Treatment Plant Improvements” included as Appendix C. Importantly, these DO measurements were recorded in the flowing Columbia River between River Mile 95 and 96 and they do not show any exceedances of DO criteria during the critical low river flow period. The Alliance understands that this information will be formally considered as Ecology processes the 2016 Water Quality Assessment.

These 2015 data showing compliance with water quality standards in the flowing Columbia River, along with the additional information that the 2006‐2009 sampling was only performed in shallow shoreline areas “at sites predisposed to algae and aquatic plant growth” would provide Ecology with a scientific basis to change the current listing from Category 5 to Category 3 or 2 in the 2016 Water Quality Assessment.

3.3.1.3.3 2018 Columbia River Water Quality Monitoring Program. In June 2018, the Alliance and City of Vancouver prepared a QAPP to conduct the most extensive and comprehensive monitoring program of DO, temperature, conductivity, and pH conducted to date. The program is focused on in‐stream measurements between RM 110 and RM 95 during the critical period of July‐September. The QAPP was submitted to Ecology for review prior to starting monitoring. This QAPP was prepared for the 2018 Columbia River Water Quality Monitoring Program to be conducted during the 3‐month


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critical period (July – September) identified in Ecology’s Revised Draft Water Quality Policy 1‐11 for Dissolved Oxygen measurements. The Alliance and City of Vancouver have agreed to extend the sampling program downstream to the area of the SCTP outfall (RM 96), so it will provide in‐stream measurements between RM 110 and RM 95. As a result, the Alliance is sponsoring a portion of the work. This effort will be the most comprehensive to‐date in terms of defining the DO conditions in a broad section of the Columbia River as it traverses the boundary with Clark County. Vancouver staff has coordinated the sampling program protocols with relevant Ecology managers to align with Ecology’s Revised Draft Water Quality Policy 1‐11 for Dissolved Oxygen measurements and provide the most relevant data for understanding Columbia River DO conditions and informing subsequent regulatory decisions. These data will be submitted to Ecology in late 2018 or early 2019. Review of these data would need to happen in 2019, prior to the potential start of another season of water quality monitoring in July through September 2019. The cost to Vancouver and the Alliance for this study over the two‐year period is estimated to be approximately $250,000. Once these data have been provided to Ecology, an independent review of the 303(d) listing will likely be in order, given the size and importance of the Columbia River to Washington State, as well as the availability of a large amount of current and representative data.

In addition, the Alliance’s Phase 5B Engineering Report includes a Water Quality Compliance Evaluation (Appendix C). The Water Quality Compliance Evaluation documents that the SCTP discharge associated with the proposed improvements and the current Columbia River diffuser does not result in a measurable change in Columbia River water dissolved oxygen conditions (as defined in WAC 173‐201A‐200 and WAC 173‐201A‐320), and it complies with Ecology’s requirements.

In summary, the Alliance is engaged with multiple actions that require a substantial investment of time and resources to collect additional DO data, evaluate existing data, and research DO conditions in the Columbia River. These efforts will provide Ecology with substantial new information and data to support reassessment of the classification of the subject reach of the Columbia River for DO compliance with water quality standards and better inform the prospective 303(d) listing processes.

3.3.2 Phase 5B Engineering Report Approach to Possible Future Regulatory Outcomes

In Chapter 6 – Water Quality‐Based Effluent Limits for Surface Waters in Ecology’ Permit Writer’s Manual (Ecology, 2015), Section 3.3.11 includes guidance regarding permitting discharges to a 303(d) Listed waterbody with no TMDL developed. Per Figure 23 in Chapter 6 of Ecology’s Permit Writer’s Manual, several possible outcomes could result from Ecology’s review of river monitoring data and reevaluation of the basis of the 303(d) listing for DO impairment at the SCTP point of discharge (RM 96). Table 3‐2 provides a summary of possible regulatory pathways for the SCTP improvements and NPDES permitting depending on the disposition of the 303(d) Listing of dissolved oxygen in the river. In review of the possible regulatory pathways and associated proposed facilities in Phase 5B, each pathway leads either to additional focus on oxygen demanding substances in the Phase 5B project, or the process reverts to historical planning framework and effluent limits are developed normally through the NPDES permit renewal process.


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Table 3‐2. Regulatory Pathways for SCTP Improvements Depending on Disposition of 303(d) Listing for Dissolved Oxygen Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Regulatory Scenarios

Description of Possible Ecology Disposition and Water Quality

Determination Regulatory Implementation and Effect

on Phase 5B Project

Baseline Condition 2014 303(d) listing for DO, if it is considered relevant to the SCTP offshore “point of discharge” per Permit Writers Manual (Chapter 6)

Additional focus on oxygen demanding substances warranted in Phase 5 design.

Scenario A ‐ Review of data informing 2014 listing

Ecology reviews existing 2014 listing data (shoreline sampling data) and concludes it is not representative to the offshore “point of discharge” per Permit Writers Manual (Chapter 6)

Historical planning framework with respect to DO (same as the “Develop Effluent Limits Normally” option from the PWM Chapter 6, Figure 23).

Scenario B – Review of 2016 water quality assessment

2016 WQ Assessment considers 2014 listing data (shoreline sampling data) and 2015 Alliance data (offshore sites) showing no offshore impairment results in 303(d) listing change to Category 2 or 3 (“Segment is a Waters of Concern” or “Segment Lacks Sufficient Data”)

Historical planning framework with respect to DO (per PWM Chapter 6, Figure 23).

Scenario C1 – Review of 2018‐2019 Columbia River Water Quality Monitoring Program Study results

Data confirms Columbia River is not impaired resulting in 303(d) listing change to Category 1

Historical planning framework with respect to DO (per PWM Chapter 6, Figure 23).

Scenario C2 ‐ Review of 2018‐2019 Columbia River Water Quality Monitoring Program Study results

Data confirms Columbia River has some dry season DO impairments

Additional focus on oxygen demanding substances warranted in Phase 5 design, especially with respect to the dry season.

As indicated in Table 3‐2, there are multiple possible future regulatory outcomes with respect to the 303(d) listing for DO and how that listing would inform the design basis for the Phase 5B Improvements and future projects. In order to be flexible with respect to possible future regulatory outcomes, to be consistent with the current approved planning documents, and provide for public investments that are useful and necessary over time, the Alliance is recommending an approach that will advance elements of the Phase 6 Expansion Project secondary treatment process into the Phase 5 design in order to provide for increased secondary treatment process capacity. The Phase 6 components moved forward include additional secondary clarifier capacity and additional aeration blower capacity. In addition, RAS pumping improvements and a RAS chlorination system will complete the effort to improve all aspects of the secondary treatment process. This approach will provide for flexibility to address either of the possible future regulatory outcomes:

If a DO impairment is substantiated through the additional study and regulatory processes, this approach will significantly enhance the facility’s ability to treat the oxygen demanding substances to high levels and will be protective of the Columbia River resource. Specific plant performance is analyzed and depicted in this Engineering Report for the improvements recommended.

If a DO impairment is not substantiated through the additional study and regulatory processes, then the early delivery of the Phase 6 facilities will be still be useful and appropriate to the long term needs of the facility. Additional operational flexibility will be provided in the near term and the facility capacity can be further addressed in future planning work to inform the Phase 6 project.


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The Alliance has presented a proposed project approach that is protective of the water quality resource at the point of discharge. The substantial financial investments proposed are compatible with any future treatment alternative, as secondary treatment capacity and the related facilities will be required under either scenario outlined above.

3.3.3 Treatment Plant Process Design Criteria and Estimated Performance In the context of the ongoing water quality investigations and considering current growth trends, the Alliance proposes that it is most prudent to move forward with previously planned work for the SCTP at this time. Further, to account for the ongoing Columbia River water quality monitoring data collections and analyses, the Alliance proposes to employ a more conservative secondary treatment design for the treatment plant project as part of these capital investments. By putting the additional capacity in place in the near term and providing an enhanced secondary treatment process capable of materially oxidizing any potential influent waste load, the Alliance is being proactive and responsive to the potential concerns over DO in the Columbia River, while constructing facilities that have benefit under any future regulatory outcome.

The major improvements required for the increase of plant secondary process capacity are as follows:

Phase 5 Project Elements (as planned) – the addition of Aeration Basin 7 (similar to AB 5 and 6) with the attendant aeration equipment, instrumentation and controls will be provided.

Phase 6 Project Elements (as planned) – the addition of Secondary Clarifier 5 (a larger clarifier at 120‐foot diameter) with the removal of Secondary Clarifier 2 (a smaller clarifier at 90‐foot diameter), the addition of an aeration blower and RAS pumping capacity improvements will be advanced to the Phase 5 Project.

Moving the Phase 5B project forward now to ensure that adequate capacity is in place, provides assurance that the SCTP will remain in a stable condition and continue to provide reliable and high‐level treatment. With the improvements that are proposed, the facility will have capacity to further oxidize oxygen‐demanding substances well beyond the current permit limits, if the ongoing regulatory processes determine this is required. Conversely, if the ongoing regulatory processes determine that the historical planning basis is appropriate, then a portion of the Phase 6 project will have been delivered early providing additional operational flexibility in the near term. The proposed Phase 5B improvements will provide needed capacity for the next decade and provide a high level of treatment, reliability, and redundancy while the future facility configuration is assessed in future planning efforts.

As described in this Report, the proposed Phase 5B project is respectful of and compatible with any future regulatory outcome. The improvements as proposed are protective of the Columbia River water resources and can be useful and value added in any future process configuration and therefore are a reasonable investment of public resources over the long term.

SECTION 4

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Recommended Improvements This section documents the recommended improvements for the planning horizon, as well as the phasing of those improvements, by unit process. Modifications to the design criteria do not materially change the recommended treatment improvements for the SCTP for the planning horizon as presented in the 2004 Facilities Plan and the 2013 Facilities Plan Update.

The unit process evaluation presented in this report identifies current performance and potential limitations to confirm the recommendations from previous planning efforts. As part of the evaluation, it was also determined that the reliability/redundancy requirements for each unit process were satisfied while operating at 17.5 mgd ADMM. The SCTP is a Class 2 facility and the reliability/redundancy requirements are found in Ecology’s Criteria for Sewage Works Design (2008).

Appendix A to the Engineering Report provides unit process sizing calculations. The criteria used for this evaluation are based on the Criteria for Sewage Works Design, where applicable. In cases where specific guidance is not provided by the Criteria for Sewage Works Design, the following industry‐standard references have been consulted and utilized: Wastewater Engineering: Treatment and Resource Recovery (Metcalf & Eddy [M&E], 5th Ed.), Design of Municipal Wastewater Treatment Plant, WEF Manual of Practice 8 (MOP 8), and Operation of Nutrient Removal Facilities, WEF Manual of Practice 37 (MOP 37).

4.1 Preliminary Treatment

4.1.1 Design Parameters WAC 173‐308‐205 requires all biosolids (including septage) or sewage sludge to be treated by a process such as physical screening or another method to significantly remove manufactured inert substances prior to final deposition. Meeting this requirement may occur at any point in the wastewater treatment or biosolids manufacturing process. At SCTP this requirement is met at the preliminary treatment facility by screening raw sewage through a fine screen with maximum aperture of 6 millimeters (which is less than the maximum requirement of 3/8 inch [9.5 millimeters]).

Design criteria for raw sewage screening and grit removal are based on peak‐hour flow conditions and are not impacted by load considerations. As shown in Table 4‐1, the peak‐hour flow associated with an ADMM flow of 17.5 mgd is 33.1 mgd. Since both the screening and the grit removal are rated to treat peak‐hour flows of 34 mgd, both systems will be able to treat more than the peak‐hour flow associated with an ADMM flow of 17.5 mgd.

9BTable 4‐1. Design Parameters for Preliminary Treatment Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Capacity Source of Data Criteria for Sewage Works Design

MOP 8

M&E (5th Ed.)

MOP 37

Number of Screens 2 screens with backup bar screen

Existing Redundancy: A backup bar screen or bypass channel

‐‐ ‐‐ ‐‐

Screening Capacity, mgd

34 Existing ‐‐ ‐‐ ‐‐ ‐‐

Screening Capacity Required, mgd

33.1 Peak Hour Flow

‐‐ ‐‐ ‐‐ ‐‐

Number of Vortex Grit Units

2 Existing ‐‐ ‐‐ ‐‐ ‐‐

SECTION 4 – RECOMMENDED IMPROVEMENTS

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9BTable 4‐1. Design Parameters for Preliminary Treatment Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Capacity Source of Data Criteria for Sewage Works Design

MOP 8

M&E (5th Ed.)

MOP 37

Grit Removal Capacity, mgd

50 Existing design criteria

‐‐ ‐‐ ‐‐ ‐‐

4.1.2 Proposed Improvements The existing screens were fully rebuilt in 2017 as shown in Figure 4‐1. No modifications to the manual bypass screen, or provisions of additional biosolids screening are proposed as a part of this project. Headworks will be ventilated to the odor control system as part of the Phase 5B Improvements Program, and replacement of the washer/compactor equipment is planned as part of the Phase 6 Expansion Program.

Figure 4‐1. Screens Rebuilt in 2017 Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Ventilating the headworks for odor control will not result in any additional monitoring requirements. The headworks facility is currently equipped with a combustible gas detection unit.


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4.1.3 Projected Performance Since both screens were rebuilt very recently, they are expected to operate effectively for many years. Existing screening capacity exceeds the peak hour flow projections for Phase 5B, and the need for additional screening capacity will be evaluated as part of future expansion projects.

4.1.4 Redundancy Requirements The SCTP has a backup manually cleaned bar screen that provides the redundancy required by Criteria for Sewage Works Design. The manual bypass screen is used to protect the facility from damage during peak flows and simultaneous equipment failure. The high influent channel level and bypass gate function is tested annually, but anecdotal accounts from operations staff indicate that the manual screen is not known to have been required to operate in the last 10 years.

4.2 Primary Treatment

4.2.1 Design Parameters Primary clarification capacity is based on the specific SOR at average annual and peak‐hour flows. Criteria for Sewage Works Design recommends an average design SOR between 800 and 1,200 gallons per day per square foot (gpd/ft2) and a peak design SOR between 2,000 and 3,000 gpd/ft2. It also states that “at these loading rates, a well‐designed and properly operated primary clarifier, providing primary solids removal or co‐settling, should remove 30 to 35 percent of the BOD5 and 50 to 60 percent of the suspended solids from raw domestic wastewater.”

Historical results from SCTP demonstrate a minimum 30‐day average BOD5 removal through the primary treatment of 40 percent. However, using a lower BOD5 removal in planning calculations provides additional conservativism to the secondary treatment system design, providing additional capacity to treat higher loads passed from the primary clarifiers.

Table 4‐2 summarizes the major primary clarifier design parameters at the SCTP, together with the estimated performance at 17.5 mgd ADMM using Criteria for Sewage Works Design recommended values for 35 percent BOD5 removal and 60 percent TSS removal.

9BTable 4‐2. Design Parameters for Primary Treatment Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process

Performance at 17.5 mgd Source of Data Criteria for Sewage Works Design

MOP 8 a

M&E (5th Ed.) b

MOP 37

Number of Clarifiers

4 Existing Redundancy: with a single primary clarifier out of service, the remaining units need to treat 50% of the flow

‐‐ ‐‐ ‐‐

Number in Service

4 Basis of calculation

‐‐ ‐‐ ‐‐ ‐‐

Peak‐hour SOR, gpd/ft2

2,620

(1,762 w/ 1 unit out of

service at 50% design flow)

Calculated value 2,000 to 3,000 2,000 to 3,000

2,000 to 3,000

‐‐

AA SOR, gpd/ft2

1,067

(726 w/ 1 unit out of service at 50% design

flow)

Calculated value 800 to 1,200 800 to 1,200

800 to 1,200

‐‐


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9BTable 4-2. Design Parameters for Primary Treatment


Unit

Process

Performance

at 17.5 mgd Source of Data Criteria for Sewage Works Design

MOP

8 a

M&E

(5th Ed.) b

MOP

37

BOD

Removal,

%

35 Basis of

calculation

30 to 35 25 to 40 --

TSS

Removal,

%

60 Basis of

calculation

50 to 60 -- -- --

a Water Environment Federation, Manual of Practice No. 8, 6th Edition.

b M&E 5th Edition, Table 5-19.

4.2.2 Proposed Improvements

No new additional capacity is required to meet projected flows and loads for the Phase 5B Project.

However, the primary clarifiers will be covered and ventilated to an odor control system. Covering the

primary clarifiers is essential to capturing nuisance odors. Combustible gas detection equipment at each

primary clarifier will be provided after the primary clarifiers are covered and vented for odor control.

4.2.3 Projected Performance

At the average-annual flow rate and peak-hour flow rate associated with an ADMM flow of 17.5 mgd,

and operating all primary clarifiers, the average and peak design SORs are 1,061 gpd/ft2 and

2,614 gpd/ft2, respectively. The primary clarifier SORs under both scenarios are within the ranges

suggested by Criteria for Sewage Works Design.

Figures 2-2 and 2-3 in Section 2.2 illustrates the high-performance level of the primary clarifiers across a

wide range of influent loading conditions and demonstrates the conservatism inherent in their design.

These historical data confirm that the existing primary clarifiers will be able to treat an ADMM flow of

17.5 mgd and the associated flows and loads.

4.2.4 Redundancy Requirements

The EPA Reliability Classification for the SCTP is Class 2, which means that with a single primary clarifier

out of service, the remaining units need to treat 50 percent of the flow. With four existing equally sized

primary clarifiers, the effective result is that the redundancy requirements are not the governing

criterion.

4.3 Aeration Basins

4.3.1 Design Parameters

Evaluation and design of the secondary treatment system is based on the criteria presented in Criteria

for Sewage Works Design where available. Where necessary criteria have not been specified in the

Criteria for Sewage Works Design, the following references have been consulted and utilized:

Wastewater Engineering: Treatment and Resource Recovery (M&E), Design of Municipal Wastewater

Treatment Plant, WEF Manual of Practice 8 (MOP 8), and Operation of Nutrient Removal Facilities, WEF

Manual of Practice 37 (MOP 37). Table 4-3 presents a summary of the operational parameters of the

expanded secondary system as well as the recommended ranges provided in the references.


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Table 4‐3. Design Parameters for Aeration Basins Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Performance at 17.5 mgd

Criteria for Sewage Works and Design MOP 8 a M&E (5th Ed.) b MOP 37

Number of Basins c 7 ‐‐ ‐‐ ‐‐ ‐‐

Number in Service 7 ‐‐ ‐‐ ‐‐ ‐‐

Dissolved Oxygen, mg/L 2.0 ≥ 2.0 ≥ 2.0 ≥ 2.0 ≥ 2.0

MLSS, mg/L 3,400 1,500 to 3,500 2,000 to 3,500 1,000 to 3,000 ‐‐

SRT, days 7.3 Not listed for nitrification

8 to 20 days 3 to 15 days 4 to 6 days (typical range)

F/M, lb BOD Applied/lb MLVSS‐day

0.21 Not listed for nitrification

0.1 to 0.25 0.2 to 0.4 ‐‐

Water Temperature, °C

Annual Minimum 7‐day Average

13.4 ‐‐ ‐‐ ‐‐ Minimum 7‐day average

Annual Minimum Day

13.0 ‐‐ ‐‐ ‐‐ ‐‐

Dry Weather Minimum 7‐day Average

16.9 ‐‐ ‐‐ ‐‐ ‐‐

a WEF Manual of Practice No. 8, 6th Edition, Table 12.2 for single‐stage nitrification (adapted in part from M&E 4th Ed.); note that criteria for the Modified Ludzack‐Ettinger process not included in this table.

b M&E, 5th Edition, Table 8‐19, for Conventional Plug Flow; note that the criteria for the Modified Ludzack‐Ettinger process is not included in this table.

c Aeration Basins 1–4, Aeration Basins 5–7: 4.49 million gallons total.

4.3.1.1 Wet Weather Conditions

A major concern for the aeration basins during wet weather conditions is biological ammonia removal performance. Cold weather exerts a significant downward pressure on the growth rate of the nitrifying organisms that are responsible for ammonia removal. As such, it is important to identify an appropriate minimum design temperature at which to estimate the projected ammonia removal performance of the system.

It should be noted that although the Criteria for Sewage Works and Design does not specify a means for determining the appropriate water temperature to use as a design criterion, Ecology has suggested in verbal communications to use the minimum daily temperature rather than the conventional minimum 7‐day average temperature. The use of the minimum daily temperature however is conventionally avoided due to the potentially large impacts to facility design that can result from outliers in recorded data (due to measurement errors, equipment failure, or aberrant conditions).

Chapter 2.1 of MOP 37 notes the following:

“Use of daily values for wastewater temperature and SRTaerobic should be avoided. Instead, moving average values are recommended to dampen intermittent operations and sampling variability. Generally, a 7‐day moving average is satisfactory to minimize the effect of variability without creating a significant ‘lag’ effect on calculated values.”


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In the case of SCTP, since the SRT of the system will be 7.2 days, the average solids particle will by

definition spend 7.2 days within the aeration basins. As a result, over that 7.2-day SRT, nitrifiers will be

exposed to an average temperature roughly equal to the 7-day average. Because the 7-day minimum

average temperature anticipates the most stringent microbial growth environment to be expected while

limiting the inappropriate effect that outlier data can have on the sizing and design of the facility, it is a

properly conservative parameter to use for design of aeration basins.

Nonetheless, it is good practice to understand the sensitivity that aeration basin performance exhibits

when being subjected to the two different temperatures. In the case of SCTP, the minimum daily

temperature (13.0°C) differs from the minimum 7-day temperature (13.4°C) by only four-tenths of a

degree. This difference was estimated to result in a 0.3 mg/L variation in the effluent concentration of

ammonia, demonstrating that the secondary system is not overly sensitive to temperature variations in

this range and is sufficiently configured to effectively remove ammonia during minimum day

temperature conditions.

4.3.1.2 Dry Weather Conditions

During warmer weather, the growth rate of nitrifying organisms is significantly greater and exerts much

less effect on the performance of the system. However, since the Columbia River receiving water body is

currently listed as impaired with respect to dissolved oxygen in the warmer dry weather months, it is

important to scrutinize the biological performance during this season to ensure that oxygen demand

loading to the river is kept to a minimum. This study therefore includes a scenario for dry weather

performance that examines the performance of the aeration basins under minimum projected 7-day

temperatures during dry weather months (May through October) while treating maximum month dry

weather flows and ADMM loads. The projected performance of the aeration basins under this scenario

is presented in Section 4.3.3 below.


The Phase 5B Project proposes the construction of a new aeration basin (Aeration Basin 7) that will

match the configuration and size of the existing Aeration Basins 5 and 6. This new basin, along with the

existing basins, will be designed to have sufficient capacity to treat flows and projected loads up to a

maximum month average of 17.5 mgd.


Pollutant removal performance of the expanded secondary treatment system has been projected using

two distinct mathematical methodologies for three different operating scenarios (minimum week

temperature, minimum day temperature, and dry weather minimum week temperature). The first

approach (1), referred to either as the continuously-stirred tank reactor (CSTR) or as the complete-mix

activated sludge (CMAS) reactor method, assumes that each of the aeration basins function as single,

thoroughly-mixed tanks. The second approach (2), uses calculations of physical and kinetic

characteristics compliant with published CSTR-in-series analyses. Because Aeration Basins 1 through 4

are baffled with three complete-mix aerobic reactors-in-series and Aeration Basins 5 through 7 have

long, baffled plug-flow configurations that approximate four complete-mix aerobic reactors-in-series as

shown in Section 2.2.2, the CMAS method should be considered a simplified, conservative approach to

projecting their performance. The CMAS method is useful in demonstrating the minimum pollutant

removal for a single complete-mix basin of the same size as the secondary system at SCTP but will

underestimate the performance of a reactor-in-series configuration of the same volume. It is prudent to

evaluate the performance of the aeration basins using the two described approaches and to determine

how conservative the CMAS approach may be when compared to reasonable calculations of physical

and kinetic characteristics compliant with published CSTR-in-series analyses.


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4.3.3.1 Complete‐Mix Activated Sludge (CMAS) Method Setup

Figure 4‐2 presents a schematic diagram of Aeration Basins 1 through 7 depicted as CMAS reactors.

Figure 4‐2. Schematic Diagram of Aeration Basins 1 through 7 as CMAS Reactors Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Detailed calculations for the three scenarios using the CMAS method adapted from Ecology’s calculations are provided in Appendix A. Results of the calculations are summarized in Table 4‐4 in Section 4.3.3.3.

4.3.3.2 Continually‐Stirred Tank Reactors (CSTR) in Series Setup

The second approach to estimating the treatment performance of the secondary system is to use the CSTR‐in‐series method (2). The CSTR‐in‐series method is similar to the CMAS method and uses the same governing equations for microbial growth and decay to predict contaminant removal, but subdivides the reactor into sub‐volumes that are mathematically treated as individual complete‐mix reactors.

The secondary basins at SCTP are set up as two distinct families of reactors operating in parallel to one another. The older basins, Aeration Basins 1 – 4, are set up in series, such that flow travels either from Aeration Basin 1 to 3, or from 2 to 4, resulting in two trains, as shown in the process flow diagram in Figure 4‐3. Each individual basin (1 through 4) is further subdivided by baffle walls into two smaller reactors. The first subdivided zones of Aeration Basins 1 and 2 function as anoxic zones, while the other two subdivided zones function as aerobic reactors. Both subdivided zones of Aeration Basins 3 and 4 function as aerobic zones in series. The overall result is a secondary treatment process that features two trains each with four reactors‐in‐series (one anoxic zone followed by three aerobic zones). Figure 4‐3 presents a schematic diagram of Aeration Basins 1 and 3, visually indicating how the basins are linked to provide one train with four reactor‐in‐series. Aeration Basins 2 and 4 are linked together in the same formation and serve as the second train of four reactors.


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Figure 4‐3. Process Flow Diagram of Aeration Basins 1 and 3 in Reactor‐in‐series Configuration (Typical to Aeration Basins 2 and 4)


Aeration Basins 5, 6, and (New) 7 utilize long, narrow channels that create more of a plug‐flow environment than the older aeration basins described above. These basins also have a baffle wall separating the anoxic and aerobic zones followed by long aerobic reaches. Their plug‐flow environments are best represented using a reactor‐in‐series methodology as well. The EPA’s Design Manual: Fine Pore Aeration Systems (1989) presents an equation to determine the number of CSTRs‐in‐series that should be used to best approximate the treatment capacity of a plug‐flow reactor. The equation uses the basin geometry and the influent and recycle flows to arrive at an estimate of equivalent CMAS basins in series best representing the plug flow reactor. The equation is as follows:

N = 7.4 LQ(1 + rr) ÷ (WH) (4‐1)

Where,

N = equivalent number of basins in series L = aeration basin length, m Q = wastewater flow, m3/s rr = return activated sludge recycle ratio (dimensionless) W = aeration basin width, m H = water depth, m

Solving Equation 4‐1 for the number of reactors for Aeration Basins 5, 6, and 7 indicates that these basins can be conservatively described by five reactors operating in series, with one anoxic zone upfront followed by four aerobic zones, as presented schematically in Figure 4‐4.

Figure 4‐4. Process Flow Diagram of Aeration Basin 5 (Typical to 6 and 7) in Reactor‐in‐series Configuration Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements


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Detailed calculations for the three scenarios using the CSTR‐in‐series method as presented in M&E are provided in Appendix A. Results of the calculations are summarized in Table 4‐4 in Section 4.3.3.3 below.

4.3.3.3 Summary of Aeration Basin Performance

Under the conditions described above, the process calculations predict an MLSS concentration of 3,400 mg/L. This is based on carrying an SRT of 7.2 days, allowing the system to fully nitrify. As the results presented below in Table 4‐4 demonstrate, the system produces an effluent ammonia‐nitrogen concentration that is both well under the 18.7‐mg N/L limit established in the permit during all periods and would avoid increased degradation of the receiving water body during the dissolved‐oxygen‐impaired dry weather season.

The CSTR‐in‐series method predicts lower ammonia concentrations than the CMAS calculations, a finding that agrees with plant experience and industry standard guidance, as presented in M&E, which states that for a given volume, a bioreactor operating in the reactor‐in‐series configuration will have a higher treatment capacity than a bioreactor of the same volume operating in the CMAS configuration.

The SCTP has always been able to fully nitrify without experiencing any alkalinity limitation and maintaining a neutral effluent pH. Table 4‐4 presents the results of a sensitivity analysis to both temperature (at 13.0°C, 13.4°C, 16.9°C) and calculation method (between the simplified CMAS approach and the CSTR‐in‐series approach, which is more representative of plant configuration and performance.) The wet weather season temperature sensitivity analysis indicates that the aeration basins are not highly sensitive to temperature difference within the small range shown, between the minimum 7‐day value and the minimum day rounded value.

Table 4‐4. Summary of Aeration Basin Performance Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Scenario Calculation Method

Temperature (°C)

Influent NH3‐N (mg/L)

Effluent NH3‐N (mg/L)

Effluent BOD5 (mg/L)

Effluent TSS

(mg/L)

Overall SRT

(days) Yield (ppd)

Wet Weather Minimum Week Temperature

CMAS 13.4 31.0 2.7 7.6 8.0 7.2 0.85

CSTR‐in‐Series 13.4 31.0 1.5 7.6 8.0 7.2 0.85

Wet Weather Minimum Day Temperature

CMAS 13.0 31.0 3.0 7.6 8.0 7.2 0.85

CSTR‐in‐Series 13.0 31.0 1.8 7.6 8.0 7.2 0.85

Dry Weather Minimum Day Temperature

CMAS 16.9 34.8 0.7 5.7 6.9 9.3 0.82

CSTR‐in‐Series 16.9 34.8 0.2 5.7 6.9 9.3 0.82

4.3.3.4 Anoxic Selector Performance

Both existing systems of aeration basins at SCTP provide adequate conditions for denitrification under current flow and loading conditions, and the addition of a plug‐flow basin will increase anoxic capacity. The anoxic zone incorporated into the aeration basins, in addition to providing a level of denitrification, will act as a metabolic‐based selector. The anoxic environment favors the growth of floc‐forming bacteria, improving the sludge‐settling characteristics of the biomass. The typical references cited throughout the Engineering Report (i.e., Criteria for Sewage Works Design, WEF MOP 8, and M&E) do not include detailed information on the design of a metabolic‐based selector. The Manual on the Causes and Control of Activated Sludge Bulking, Foaming, and Other Separations Problems (IWA, 2003) recommends an SRT within the anoxic selector between 1 to 3 days and an F/M ratio of less than 1


4-10

pound of BOD applied per pound of MLVSS per day. With an additional selector, the expanded basins

will provide an SRT of 1.7 days with an F/M ratio of 2.07 pounds of BOD per pound of MLVSS per day at

17.5 mgd ADMM flows. The estimated contact time in the anoxic zones of the expanded system will be

33.4 minutes under these conditions, assuming a RAS rate equal to 65 percent of the influent flow and a

mixed liquor recirculation rate of 16.14 mgd.

The ammonia-nitrogen is oxidized into nitrate-nitrogen within the system through the nitrification

process. A portion of the nitrate-nitrogen is sent into the selector by recirculating mixed liquor at a rate

of approximately 92 percent of the influent flow (at 17.5 mgd). All the primary effluent is introduced

into the selectors, providing the BOD required for denitrification. Under the conditions described above,

the system will reduce nitrate-nitrogen concentrations across the anoxic selectors to an estimated

15 mg/L in the effluent.

Table 4-5. Design Parameters of Anoxic Selectors


Unit Process

Performance at

17.5 mgd Source of Data

Criteria for

Sewage

Works

Design

MOP

8

M&E

(5th Ed.)

MOP

37

Anoxic

Selectors:

kinetic and

metabolic

selection

-- Manual on the Causes and Control of

Activated Sludge Bulking, Foaming, and

Other Separations Problems, 2003, 3rd

Edition (IWA, 2003)

-- -- -- --

ADMM Contact

Time, minutes

33.4 Calculated value -- -- 20 to

60

--

ADMM SRT,

days

1.71 Calculated value

Typical range: 1 to 2 (IWA, 2003)

-- -- -- --

ADMM lb F/M,

BOD Appl./lb

MLVSS-day

2.07 Calculated value

-- -- -- --

Mixed-Liquor

Recycle Pumps

(Total), mgd

16.14 One pump in each Aeration Basin 3, 4, 5,

6, and 7

-- -- -- --

4.3.3.5 Blower System Performance

The major operational parameters for the blower system are summarized in Table 4-6. The configuration

and overall projected performance of the blower system is illustrated in Figure 4-5.

9BTable 4-6. Operational Parameters for the Blower System at 17.5 mgd ADMM


Item Predicted Value Recommended Value*

Aerated Zone Dissolved Oxygen, mg/L 2.0 1.5

lb O2/lb BOD Required, lb 1.2 1.25

lb O2/lb Total Kjeldahl Nitrogen, lb 4.6 4.6

lb O2/lb NO3 Recovered, lb 2.86 M&E (p. 812)

Primary Effluent Flow Split to Aeration Basins 1 to 4, % 42 NA

Primary Effluent Flow Split to Aeration Basins 5 to 7, % 58 NA


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9BTable 4‐6. Operational Parameters for the Blower System at 17.5 mgd ADMM Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Item Predicted Value Recommended Value*

Aeration Basin 1 through 4 Total Required Air Rate, scfm (Firm Capacity: 9,900 scfm)

8,241 (9,323 peak day) NA

Aeration Basin 5 through 7 Total Required Air Rate, scfm (Firm Capacity: 11,500 scfm)

8,176 (9,252 peak day) NA

*Criteria for Sewage Works Design.

Figure 4‐5. Blower Systems


Calculations based on industry‐standard methodologies and the previous capacity rating (CH2M, 2009) were performed to validate the oxygen demand of the system, assuming no denitrification on the system. The air demand was calculated based on peak day loads associated with an ADMM of 17.5 mgd. The results of the aeration capacity analysis are summarized in Table 4‐7. Appendix A includes calculations for the aeration system. This is a conservative approach as these results show that even if the oxygen credit for denitrification is not taken into account, the proposed blower system will be able to provide the air required to treat 17.5 mgd and associated peak day flows and loads.

9BTable 4‐7. Summary of Aeration Capacity (CH2M [2009] Methodology) Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Air Demand at Peak Day (scfm)

Proposed Installed Firm Capacity (scfm)

Proposed Installed Total Capacity (scfm)

Aeration Basins 1 – 4 9,323 9,900 13,200

Aeration Basins 5 – 7 9,252 11,500 16,000


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Criteria for Sewage Works Design requires that aeration systems be designed to provide capacity with the largest blower out of service (i.e., firm capacity). Based on the estimated air demands, the proposed blowers will be capable of providing enough oxygen during peak day conditions.

4.3.3.6 Aeration Basin 1 – 4 Blower Replacement Return of the Investment Analysis (ROI)

An ROI for replacing the existing positive displace blowers that serve Aeration Basins 1 – 4, with more efficient turbo blowers, was performed as part of this evaluation. The current air demands were calculated using the annual average flow and loads, and the annual average flow and associated loads were calculated using historical plant data from January 2011 to December 2017.

Historical plant data show that the SCTP only operates one or two aeration basins over 90 percent of the time. Consequently, for this analysis it was assumed that Aeration Basins 1– 4 are used to treat all the average flow and associated loads. Under these conditions, it is estimated that the plant will require approximately 7,994 scfm to treat the average loads at 60°F. Three new 150‐hp turbo blowers will require the equivalent of 360 hp to deliver the air needed under the conditions described above.

The cost to replace all four existing blowers and install four new 150‐hp turbo blowers is approximately $850,000. Turbo blowers are 25 to 28 percent more efficient than positive displace blowers (Leuven et al., undated). For this evaluation, it was assumed that turbo blowers are 26.5 percent more efficient than the existing positive displacement blowers. Assuming an electric cost of $0.049/kilowatt‐hour, an energy incentive of $0.32/kilowatt‐hour saved, new turbo blowers have a payback period of 22 years. This payback period does not meet the Alliance policy for a 5‐year ROI to fund the project in the near term. Based on this result, it was decided not to replace the blowers as part of this phase. However, the Alliance will continue to monitor trends in this area and plan to replace the existing blowers with more efficient technology at the end of the useful life of the existing blowers or when a more attractive ROI can be demonstrated.

4.3.4 Redundancy Requirements Ecology requires that there are at least two equal‐volume basins. The SCTP will have seven aeration basins after Phase 5B is constructed that provide the redundancy required by Ecology. The capacity of the plant was determined assuming that all the aeration basins were online because a backup basin is not required.

Ecology requires the SCTP to have a sufficient number of blowers to satisfy the design air demand with the largest‐capacity‐unit out of service. The SCTP has two independent blower systems. One system provides air for Aeration Basins 1 through 4 and the other system provides air to Aeration Basins 5 through 7. As shown in Table 4‐7, the air demands at an ADMM of 17.5 mgd for Aeration Basins 1 through 4 and Aeration Basins 5 through 7 are below the firm capacities of their respective blower systems.

4.4 Secondary Clarifiers & Return Activated Sludge Pumping System

4.4.1 Design Criteria The major design parameters for the secondary clarifiers are summarized in Table 4‐8. Treating 17.5 mgd with all the secondary clarifiers online will result in an SOR of 970 gpd/ft2 at peak hour flows (33.1 mgd), which meets the 1,200 gpd/ft2 maximum recommended value specified in Criteria for Sewage Works Design.


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9BTable 4‐8. Design Parameters for Secondary Clarifiers Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Performance at 17.5 mgd Source of Data

Criteria for Sewage Works Design

MOP 8 a

M&E (5th Ed.) b

MOP 37

Number of Clarifiers

4 Including proposed Phase 5B secondary clarifier

improvements

Redundancy: with a single secondary clarifier out of

service, the remaining units need to treat 50% of the flow

‐‐ ‐‐ ‐‐

Number in Service

4 Operational assumption ‐‐ ‐‐ ‐‐ ‐‐

SVI, mL/g 195 90th percentile value for the SVI based on

historical SCTP data from January 2014 to June

2017

< 150

RAS chlorination will achieve SVI < 150 mL/g; the system can operate at an SVI of 200 mL/g without losing solids

through the weirs

‐‐ ‐‐ ‐‐

AA SOR, gpd/ft2

390

(292 w/ largest clarifier out of service at 50% design flows)

Calculated value ‐‐ 400 to 700

600 to 800

‐‐

Peak‐hour SOR Rate, gpd/ft2

970

(725 w/ largest out of service at

50% design flows)

Calculated value < 1,200 1,000 to 1,600

1,200 to 1,600

‐‐

AA Solids Loading Rate, ppd‐ft2

17.7

(13.1 w/ largest out of service at

50% design flows)

Calculated value ‐‐ 20 to 30 24 to 36 ‐‐

Peak‐hour Solids Loading Rate, ppd‐ft2

43.4

(32.4 w/ largest out of service at

50% design flows)

Calculated value ‐‐ 40 to 50 48 ‐‐

a Water Environment Federation, Manual of Practice No. 8, 6th Edition, Table 12.30.

b M&E 5th Edition, Table 8‐34, Selectors, biological nutrient removal.

ppd‐ft2 = pounds per day per square foot.

4.4.2 Proposed Improvements The existing 90‐foot‐diameter Secondary Clarifier 2 will be demolished and replaced by a new Secondary Clarifier 5 with a 120‐foot‐diameter circular clarifier and a 15‐foot sidewater depth. The new clarifier will provide additional settling capacity, and the demolition of Secondary Clarifier 2 will provide space on the site for the construction of Aeration Basin 7.

4.4.3 Projected Performance The projected performance of the secondary clarifiers under a variety of conditions is presented above in Table 4‐8. These data indicate that the secondary clarifier overflow rates and solids loading rates are below Ecology and industry‐standard limits for optimal secondary clarifier performance.


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To check the current peak overflow rates experienced at the SCTP, the daily average flow data from each day during 2015 were multiplied by a peaking factor of 2.5 (as listed in the Facilities Plan) and divided by the sum of the area of all the secondary clarifiers in service each day. The daily average TSS effluent concentrations were significantly lower than the monthly average limit of 30 mg/L even during the days with high peak overflow rates.

The 90th percentile value for the SVI is used as part of this evaluation. This is noted within M&E that if data are available, typically the 90th to 95th percentile values are used by engineering firms. It is our recommendation that the 90th percentile value is appropriate for this evaluation given that a RAS chlorination system will be installed to minimize incidents of high SVIs occur. With a permanent RAS chlorination system installed, SCTP staff will be able to proactively manage the SVI levels in the system. It is proposed that when the SVI starts trending upward, the RAS chlorination system should be initiated when an SVI value of 150 mL/g is exceeded. This provides SCTP with a feature to maintain the SVI at low levels.

RAS chlorination is commonly used to control activated sludge bulking by selectively mitigating the growth of nuisance filaments, which are primarily located on the outer layer of the biomass flocs. See Section 4.4.6 for detailed recommendations.

This project will replace the existing RAS pumps with new RAS pumps, providing SCTP with a greater RAS capacity. See Section 4.4.5 for detailed recommendations.

4.4.4 Redundancy Requirements Ecology requires that with the largest‐flow‐capacity secondary clarifier out of service, the remaining secondary clarifiers shall treat 50 percent of the design flow to meet redundancy. The requirement is met by the existing secondary clarifiers at the SCTP.

4.4.5 Return Activated Sludge System The Phase 5B Project will replace the existing RAS pumps with new RAS pumps. For the Phase 5 flow evaluation, an average RAS rate of 65 percent has been assumed. New RAS pumps will have a wide range of turndown capability in order to meet a variety of conditions. Pump 2, serving Secondary Clarifier 2 will be demolished along with existing Secondary Clarifier 2. Pumps 1 and 5, which serve the smaller Secondary Clarifier 1, will be replaced with 2,500 gpm pumps. Pumps 3, 4, and 6, which serve the larger Secondary Clarifiers 3 and 4, will be replaced with 3,400‐gpm pumps. New RAS Pumps 7 and 8 serving new Secondary Clarifier 5 will be 4,500‐gpm pumps and will be installed in the existing RAS Pump Station. Operational configuration will be the same as the current RAS pumps with Pump 5 serving as a backup pump for Secondary Clarifier 1, Pump 6 serving as a swing pump for Secondary Clarifiers 3 and 4, and Pump 8 serving as backup for Pump 7. The current motor size of 50 hp will remain unchanged for Pumps 1 and 5. The motors for Pumps 3, 4, and 6 will increase to 75 hp. New RAS Pumps 7 and 8 will require 100 hp motors. The drives, conductors and conduit serving the RAS pumps will be replaced as part of the system upgrade. Existing discharge piping and appurtenances for each of Pumps 3, 4, and 6 will be replaced with larger pipe and appurtenances to accommodate higher flows. Pump design will account for pump turndown to provide operational flexibility at lower flows. Design criteria for the new RAS pumps are summarized in Table 4‐9. The RAS pump arrangement is depicted in Figure 4‐6. The new RAS pumps will allow for improved withdrawal from the secondary clarifiers, addressing the impacts on the design SVI on the system.


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9BTable 4‐9. RAS Pump Design Criteria Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Item Capacity (gpm/mgd) Anticipated Horsepower

Pumps 1, 5 2,500 / 3.6 50

Pumps 3, 4, 6 3,400 / 4.9 75

Pumps 7, 8 4,500 / 6.4 100

Return Activated Sludge (RAS)

RAS

Secondary Clarifier 1

(to Aeration Basins)

RASRAS

Secondary Clarifier 5 (New)

Secondary Clarifier 3 Secondary Clarifier 4

RAS Pump 1(New 2,500 gpm)






RAS Pump 5 (New 4,500 gpm)

Figure 4‐6. Return Activated Sludge Pumping Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

4.4.6 Hypochlorite Dosing Station for Return Activated Sludge Chlorination RAS chlorination is one common method to help control activated sludge bulking. Excessive growth of filamentous organisms in the activated sludge can be detrimental to sludge settling and impact secondary effluent quality. Temporary injection of chlorine solution into the RAS flowstream can be used to selectively control the growth of nuisance filaments, which are primarily located on the outer layer of the biomass flocs.

The SCTP previously had the capability to add chlorine solution at the RAS/WAS Pump Station using the former control building’s chlorine gas system. Chlorine solution entered the RAS/WAS Pump Station from the west side and was injected in the RAS piping from Secondary Clarifiers 3 and 4, upstream of RAS Pumps 3, 4, and 6. However, the chlorine gas system was abandoned during Phase 3 when the plant switched to ultraviolet (UV) disinfection.

Restoring RAS chlorination requires a small chemical system. Preliminary design criteria are summarized in Table 4‐10. Liquid sodium hypochlorite should be used to create the chlorine solution because it is a safe source of chlorine and readily available from chemical distributers. Chemical totes are the preferred storage method because they can be obtained with chemical containment, minimizing the need for

8


4-16

additional infrastructure. A portable, skid-mounted chemical metering pump system, illustrated in

Figure 4-7, can provide sufficient capacity using 120-volt power. The skid would include all

appurtenances to dilute the hypochlorite and measure flow. Jar testing will be conducted during

detailed design to determine the required dosing rate. Hypochlorite dosing data from the April 2017 SVI

event described in Section 2.2.2 will be used to set parameters for jar testing. SCTP achieved reduction

of SVI within days by administering low doses of 0.25 to 0.50 lb Cl2 per 1,000 lb MLSS.

The recommended location for this hypochlorite system is adjacent to the east side of RAS/WAS pump

station. The existing W3 system at the plant will provide dilution water. A 2 ½-inch chlorine solution pipe

will deliver hypochlorite solution directly to the RAS piping.

The following additional improvements to the RAS chlorination system are recommended as well:

(1) relocation of the RAS injection point within the RAS/WAS Pump Station to downstream of all four

secondary clarifiers, and (2) adding an injection quill for improved introduction of chlorine solution.

Table 4-10. Return Activated Sludge Chlorination Design Criteria


Parameter Units Value

Hypochlorite Dose pounds-chlorine/1000 pound-MLSS*day 2 – 8 *

Maximum Duration of Injection days 5

Biomass Inventory, maximum month pounds 106,000

Hypochlorite Solution 12.5%

Hypochlorite Solution Required, at maximum month gallons per day 200 to 800

Tote Volume, each gallons 275

Dilution Water gallons per minute 25

* Design hypochlorite dose for equipment sizing is per industry recommendations (M&E) and designer experience at 2 to 8

pounds-chlorine/1,000 pound-MLSS*day, and this is conservative, considering good dose response has been achieved at a

lower dose 0.25 to 0.50 lb Cl2 per 1,000 lb MLSS. This entire dose range is expected to be able to be provided by a single

system due to inherent turn-down capability of the dosing pumps.


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Figure 4‐7. Skid‐mounted Hypochlorite Pump System, from ProMinent Fluid Controls LTD


4.5 Disinfection

4.5.1 Design Criteria The current UV disinfection system consists of 20 modules and is sized to treat up to 34 mgd of flow.

4.5.2 Proposed Improvements There are no proposed improvements to the disinfection system within the scope of the current improvements project. The need for additional disinfection capacity should be reexamined during the next phase of expansion.

4.5.3 Projected Performance The current 34 mgd capacity of the system exceeds the 33.1 mgd peak hour influent flow expected at 17.5 mgd ADMM.

4.5.4 Redundancy Requirements Ecology requires that the remaining units treat at least 50 percent of the total design flow if the largest‐flow‐capacity unit is out of service. The existing two lamp banks meet the performance and redundancy requirements.


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4.6 Effluent Pump Station

4.6.1 Design Criteria Plant influent and effluent data indicate an 8 percent attenuation of flow across the plant. The effluent peak‐hour influent and effluent flows were monitored from 2003 through 2016, and the data support a reduction in the peak‐hour effluent flow as basis of design for the expanded facility. The annual data are presented in Table 4‐11. Phase 5 peak‐hour influent flow is 33.1 mgd. Accounting for attenuation across the plant, the design Phase 5 peak‐hour effluent flow for the effluent pump station is justified at 30.4 mgd.

Table 4‐11. Peak‐hour Flow Data Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements (Phase 5B Project basis of design, effluent peak‐hour flow: 33.1 x 91.9% = 30.4 mgd)

Year

Average‐ annual

Flow (AAF) (mgd)

Maximum‐ month Flow (MMF) (mgd)

Peak‐hour Flow (PHF) (mgd)

Peak‐hour Flow Date

Effluent Peak‐hour Flow (mgd)

Peaking Factor

(MMF/AAF) (mgd)

Peaking Factor

(PHF/AAF) (mgd)

Ratio: Peak

Effluent to Peak

Influent Flow

2003 a 6.51 7.34 13.50 01/31/03

1.13 2.07

2004 b 6.49 7.91 11.88 02/01/04 11.30 1.22 1.83 95.1%

2005 c 6.66 7.70 13.16 12/30/05 12.28 1.16 1.98 93.3

2006 7.30 9.52 13.63 11/06/06 13.78 1.30 1.87 101.1

2007 7.02 8.54 14.20 12/03/07 13.66 1.22 2.02 96.2%

2008 6.86 8.41 13.97 12/27/08 13.95 1.23 2.04 99.9%

2009 6.80 8.35 14.40 01/02/09 13.60 1.23 2.12 94.4%

2010 7.46 9.11 15.20 12/11/10 13.76 1.22 2.04 90.5%

2011 7.30 9.06 14.54 11/22/11 13.58 1.24 1.99 93.4%

2012 d 7.55 9.37 14.80 01/18/12 13.19 1.24 1.96 89.1%

2013 7.06 8.04 14.73 01/28/13 13.94 1.14 2.09 94.6%

2014 7.32 8.77 14.98 02/17/14 13.63 1.20 2.05 91.0%

2015 7.31 10.73 18.89 12/07/15 14.82 1.47 2.58 78.5%

2016 7.84 9.40 16.28 01/17/16 14.94 1.20 2.08 91.8%

Average 91.9%

a Plant database starts in November 2003. b 11.88167 for the hour ending at 12:50 p.m. c 13.16 is the peak instantaneous flow on 12/31/2005; 13.15 is the peak instantaneous flow on 12/30/2005. The highest 1‐hour average on 12/30/2005 was 12.8. The highest 1‐hour average for the year was 12/31/2005, 13.10 (13.09833). d 2012 MMF data were modified from 8.86 (March) to 9.37 (December).

4.6.2 Proposed Improvements The existing effluent pumps will be modified to meet Phase 5 peak‐hour effluent flows. Replacing two of the four existing pumps while continuing to pump through the existing effluent pipeline and outfall diffuser will meet the Phase 5 peak hour flow associated with Phase 5B Project flows and loads.


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4.6.3 Projected Performance Under low river stage and low to moderate flows, effluent is conveyed to the Columbia River by gravity. Under higher river stages and higher effluent flow rates, gravity flow to the river is not possible so the effluent pump station provides pressurized conveyance into the effluent pipelines. Currently, the effluent pump station is rated for the Phase 4 peak‐hour flow, which is 28.3 mgd. The SCTP capacity will continue to expand through Phases 5 through 9, and the effluent pump station will need to meet the final buildout peak‐hour flow, which is 72.0 mgd. See Table 4‐12 with peak‐hour design flows required by phase.

Table 4‐12. Design Peak‐hour Influent Flow by Phase Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Phase Peak‐hour Influent Flow (Effluent Flow*) (mgd)

Phase 4 28.3

Phase 5 33.1 (30.4*)

Phase 6 43.0

Phase 7 54.0

Phase 8 62.0

Phase 9 72.0

*8% reduction from peak influent flow due to attenuation across the plant. See Table 5‐10.

Current rated effluent pumping capacity with Pumps 1, 2, and 3 for Phase 4 peak‐hour flow is 28.3 mgd. The existing vertical turbine style effluent pumping system consists of Pumps 1 and 3 (125 hp pumps) and Pumps 2 and 4 (200 hp pumps). In order to meet the Phase 5B peak‐hour flow of 30.4 mgd, one existing small pump and one existing large pump must be replaced with larger 400 hp pumps. To meet the EPA redundancy requirements, the effluent pump station must be hydraulically designed to pass a peak‐hour flow with the largest effluent pump out of service at the 100‐year flood stage. Therefore, the effluent pump station must pass peak‐hour flow with either of the new larger pumps offline. The pump curve and system curve for the peak hour condition are shown in Figure 4‐8. Effluent pump design criteria are summarized in Table 4‐13.


4‐20

Figure 4‐8. Pump Curve and System Curve for the Peak Hour Condition Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

9BTable 4‐13. Effluent Pump Design Criteria Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Item Capacity (gpm) Horsepower

Pump 1 (existing) 5,500 125

Pumps 2 and 3 (new) 12,000 400

Pump 4 (existing) 8,700 200

Hydraulic calculations are based on the boundary conditions of the Columbia River 100‐year flood elevation of 28.8 feet using the North American Vertical Datum of 1988 and maximum effluent wet well water surface elevation of 29.4 feet. Design criteria that affect head loss match those used in design of

the Phase 4 effluent pump station improvements. An absolute roughness factor () of 0.0004 feet per American Water Works Association (M9 Concrete Pressure Pipe, Third Edition, 2008) manual of water supply practices design guidelines were used for the entire outfall pipeline and an absolute roughness

factor () of 0.00015 feet per Cameron Hydraulic Data (Heald, 1998) for steel pipe for the outfall diffuser pipe. The Phase 4 project evaluated thrust conditions in the existing pipeline under the Phase 4 flows. The additional head posed by the 30.4 mgd versus the 28.3 mgd can be accommodated by the existing pipe joint thrust restraints on the existing outfall.


4-21


The Criteria for Sewage Works Design and the EPA require that the effluent pump station achieve peak

design flow with the largest unit out of service. Peak-hour flows are expected to be 33.1 mgd (30.4 mgd

attenuated, see Section 4.6.1 for discussion of attenuation of peak flows within the facility and sizing of

effluent pump station). Section C2-1.8 of the Criteria for Sewage Works Design signals that certain

sewage pump station components need to be “designed with redundancy in equipment to provide

capacity for peak design flows.” This pump station meets this requirement.

4.7 Waste Activated Sludge Thickening

4.7.1 Design Criteria

Design criteria for the gravity belt thickener WAS thickening system are presented in Table 4-14.

9BTable 4-14. Design Criteria for WAS Thickening


Unit Process Performance at


Criteria for Sewage

Works Design MOP 8

M&E

(5th Ed.)

MOP

37

Number of Units 2 Existing -- -- -- --

Number in Service 1 Operational

assumption

-- -- -- --

MMWW Loading

Rate, gpm/m

250 Maximum

recommended

-- 100 to

250

-- --

Average Daily

Operation, hours

6.1 Calculated value -- -- -- --


There are no proposed improvements to the WAS thickening system within the scope of the current

improvements project. The need for additional WAS thickening capacity will be reexamined during the

next phase of expansion.


Assuming a maximum month loading rate of 250 gallons per minute per meter (gpm/m), which is the

maximum value recommended by MOP 8, one of the GBTs will need to be operated for 6.1 hours a day.

An increase in WAS production will not impact the normal operation of the system because the SCTP is

operating the GBT continuously at a substantially lower loading rate.


Ecology does not identify redundancy for the WAS thickening process. The EPA does not require backup

pumps or backup power supply. However, a backup GBT is currently installed at SCTP.

4.8 Anaerobic Digestion

4.8.1 Design Criteria

Design criteria for the anaerobic digestion system are presented in Table 4-15.


4‐22

9BTable 4‐15. Operational Parameters for the Anaerobic Digestion System at 17.5 mgd ADMM Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Performance at 17.5 mgd Source of Data

Criteria for Sewage Works

Design MOP 8 M&E (5th Ed.) MOP 37

Number of Units 2 Existing ‐‐ ‐‐ ‐‐ ‐‐

SRT, days 16 Calculated value 10 to 20 15 to 20 15 to 20 ‐‐

VS Loading, lb VS/cubic feet /day (maximum = 0.16)

0.15 Calculated value 0.03 to 0.3 0.11 to 0.16

0.1 to 0.3 ‐‐

4.8.2 Proposed Improvements There are no proposed improvements to the anaerobic digestion system within the scope of the current improvements project. The need for additional anaerobic digestion capacity will be reexamined during the next phase of expansion.

4.8.3 Projected Performance Based on the primary sludge and the WAS produced at 17.5 mgd ADMM and under the operation conditions listed in Table 4‐15, the anaerobic digesters will operate at a volatile solids loading rate of 0.15 pound per cubic foot (lb/ft3) per day and provide an SRT of 16 days. Criteria for Sewage Works Design recommends a volatile solids loading rate of between 0.03 and 0.3 lb/ft3 per day and an SRT of 15 days. Based on these, it was determined that the existing digesters can treat the sludge loading associated with 17.5‐mgd ADMM.

4.8.4 Redundancy Requirements Ecology does not identify redundancy for the anaerobic digestion process. However, the EPA requires two digesters to be in the treatment process, with backup equipment. This requirement is met with existing facilities.

4.9 Digested Biosolids Dewatering

4.9.1 Design Criteria Design criteria for the digested biosolids belt filter press dewatering system are presented in Table 4‐16.

9BTable 4‐16. Operational Parameters for the Digested Biosolids Dewatering System at 17.5 mgd ADMM Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Performance at


Criteria for Sewage Works

Design MOP 8

M&E (5th Ed.)

MOP 37

Number of Units 2 Existing

Number in Service 2 Operations

MMWW Loading Rate, pounds/hour/meter

600 Calculated value

400 to 700

Average Daily Operation, hours

8 Calculated value


4‐23

4.9.2 Proposed Improvements There are no proposed improvements to the digested biosolids dewatering system within the scope of the current improvements project. The need for additional digested biosolids dewatering capacity will be reexamined during the next phase of expansion.

4.9.3 Projected Performance According to MOP 8, typical performance for BFPs dewatering anaerobically digested sludge of combined primary sludge and WAS is 400 to 700 pounds per hour per meter (lb/hr/m). The calculations predict that at a 600 lb/hr/m solids loading rate both BFPs will need to operate a bit less than 8 hours per day, 7 days per week. Even operating below the maximum recommended solids load rate, the existing dewatering system will be able to process the sludge produced while treating 17.5 mgd ADMM load. The dewatering unit process has significant capacity, especially given the variable of extending the weekly hours of operation.

Since solids handling costs are among the largest unit process costs at a wastewater treatment plant (WWTP), the SCTP is interested in investigating methods to optimize the dewatering process: in particular, any approach or system that can improve dewatered cake concentration and overall dewatering performance without replacing the existing equipment. An augmented approach to dewatering would be to condition the sludge prior to dewatering in order to improve performance. An example of this approach is technology manufactured by Orège and given the process name SLG® or “‘solid‐liquid‐gas” conditioned sludge. The process removes bound water through the injection of pressurized air. Air is diffused into the sludge at the same time to aid flocculation (Inman and Capeau, 2015). This yields denser floc and allows the dewatering process to be more efficient

The Orège SLG® equipment has a relatively small footprint (the approximate size of the installation is 4 feet by 6 feet). It has been shown in bench‐ and pilot‐scale tests at several WWTPs in Europe and the United States that this pretreatment process can increase the BFP dewatered cake solids concentration from anaerobically digested biosolids by 3 to 5 percent. It has also been shown to significantly lower polymer consumption and results in an extremely clear filtrate at these WWTPs. At a full‐scale test at the Lehigh, Pennsylvania, WWTP, dewatering anaerobically digested biosolids with BFPs, the Orège SLG® process was successful and increased the cake solids by 3 to 4 percent and reduced the polymer use by 20 to 30 percent. The SCTP has been investigating and evaluating this and other similar systems for applicability at the facility and intends to install the equipment pending confirmation of performance.

4.9.4 Redundancy Requirements Ecology does not identify redundancy for the biosolids dewatering process. The EPA does not require backup pumps or backup power supply.

4.10 Plant Hydraulics An updated hydraulic analysis was completed as part of this Engineering Report. This analysis has determined that the peak influent flow to the plant is 33.1 mgd. An updated hydraulic profile to reflect the proposed changes from Phase 5B is included as Figure 4‐9. The hydraulic capacity of each unit process is displayed in Figure 4‐10.

Due to attenuation in process tankage at the facility, the peak effluent flow has been demonstrated to be less than the peak influent flow. See Table 4‐11, in the section detailing the effluent pump station improvements, which documents the observed peak‐hour effluent flow compared to peak‐hour influent flow, demonstrating attenuation effects. For the 10‐year period of record, the peak‐hour effluent flow is 92 percent of the peak‐hour influent flow.


4‐24

4.11 Selected Alternative Description After evaluating all unit processes at the SCTP, it is concluded that with the proposed improvements, the treatment processes can treat up to an ADMM flow of 17.5 mgd and the associated flows and loads without affecting the ability of the SCTP to reliably and consistently comply with wastewater permit terms and conditions to produce a high‐quality effluent. This evaluation shows that with the proposed improvements, the SCTP is well within acceptable design parameters.

In addition to the improved secondary treatment facilities, the following additional engineering considerations are included in the proposed facility design approach:

Reduced design flows. Previously the project was approved at the planning level as an expansion to 18.0 mgd maximum month flow (MMF). The ER proposal is based on a reduced 17.5 mgd treatment capacity for the facility in order to provide an additional level of conservatism.

Conservative assumptions related to primary treatment. Historical results from SCTP demonstrate a minimum 30‐day average BOD5 removal through the primary treatment of 40 percent. However, using a lower BOD5 removal of 35 percent in design planning calculations provides additional conservativism to the secondary treatment system design.

Enhanced secondary process design features:

– The project will carry a larger biomass with a larger solids retention time (SRT), ensuring reliable nitrification under all design loading and temperature conditions.

– The project will include additional secondary clarifier capacity to ensure reliable settling of the biomass after aeration.

– The project will increase the RAS capacity for all secondary clarifiers (new and existing) and will add a RAS chlorination system to ensure reliable activated sludge settling characteristics.

– The project will add a blower to ensure adequate air supply at all conditions, including peak day loadings and without assuming a credit from the denitrification process.

– The project is designed around the minimum 7‐day effluent temperature, an appropriate and conservative approach. Performance was evaluated at the minimum day temperature as well to assure that the secondary treatment process will perform even at the coldest temperatures.

The performance of the secondary treatment process is important to providing high‐quality effluent with low concentrations of oxygen demanding substances. Treatment performance is influenced by wastewater temperature, with the most challenging treatment performance occurring during cold weather, due to the activated sludge biology treatment kinetics. The proposed facilities are designed for the minimum 7‐day temperature to provide for reliable nitrification performance year‐ round. Therefore, because facilities will provide reliable removal of oxygen demanding substances year‐round, the plant is anticipated to provide exceptional performance during the most critical time of year for DO impairment (July through September). Table 4‐17 shows predicted performance.

Table 4‐17. Projected Effluent Values of Oxygen‐Demanding Substances


Parameter Projected Effluent at 17.5 mgd

(wet weather, 13.4°C)

Projected Effluent at 13.2 mgd

(dry weather, 16.9°C)

Biochemical Oxygen Demand (5 Day)

7.6 mg/L 5.7 mg/L

Total Ammonia (as NH3‐N) 1.5 mg/L 0.2 mg/L


4‐25

After evaluating all unit processes at the SCTP, it is concluded that with the proposed improvements, the treatment processes can treat up to a maximum monthly flow of 17.5 mgd and the associated flows and loads without affecting the ability of the SCTP to reliably and consistently produce a high‐quality effluent with very low concentrations for oxygen‐depleting substances, if that is determined to be required.

The regulatory needs for air quality/odor control improvements drive the recommendation of covering the primary clarifiers and constructing a vapor‐phase bio‐trickling filter odor control facility. The new primary clarifier covers will reduce maintenance access space and visual observation into the primary clarifiers, but access can easily be accommodated during regular maintenance activities that required manned entry into the primary clarifier tanks. The new odor control bio‐trickling filter will run continually and require similar daily operations monitoring as the existing bio‐trickling filter that treats air off the headspace of the sludge blend tank. The instrumentation and equipment associated with the new bio‐trickling filter are similar to others onsite. Staff expects to accommodate such filter system O&M within the existing staffing framework.

Expanding the facility will not have a major impact on the O&M of the plant because significant process modifications are not required. The SCTP O&M manual will be updated to include the improvements to the facility. No changes to the Certified Operator requirements will be required. An operator certified for at least a Class IV plant by the State of Washington shall be in responsible charge of the day‐to‐day operation of the SCTP. An operator certified for at least a Class III plant shall be in charge during all regularly scheduled shifts. The data that are currently collected by the SCTP are sufficient to evaluate and demonstrate the performance and reliability of the facility at the new proposed capacity. As flows and loads increase, the plant performance will be monitored through Daily Monitoring Reports.

A Water Quality Compliance Evaluation, conducted per WAC 173‐201A‐320, has been performed (provided in Appendix C). The results of this analysis show that the proposed improvements are acceptable, with increased flows discharging to the Columbia River through the existing outfall diffuser. Table 4‐18 show the calculated effluent performance at 17.5 mgd for dissolved oxygen, temperature and bacteria.

9BTable 4‐18. Water Quality Compliance Evaluation Results Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Parameter Performance at 17.5 mgd Requirement

Dissolved Oxygen </= 0.1 mg/L change (reduction) in dissolved oxygen

at mixing zone boundary

Reduction in dissolved oxygen less than 0.2 mg/L at mixing zone boundary

Temperature Maximum temperature change (increase) of 0.05 degrees C

No temperature increase greater than 0.3 degrees C

Bacteria Fecal coliform bacteria concentrations will meet all requirements through the

application of ultra‐violet light disinfection at the SCTP

Fecal coliform organism levels must not exceed a geometric mean value of 100 colonies/100 mL [milliliter], with not

more than 10 percent of all samples (or any single sample when less than ten sample points exist) obtained for

calculating the geometric mean value exceeding 200 colonies/100 mL

Figure 4‐10 provides a summary of unit process capacities. A summary of the proposed improvements is presented below in Table 4‐19. Figure 4‐11 presents a schematic process flow diagram of the facility with proposed improvements, Figure 4‐12 illustrates the proposed site plan for the Phase 5B Project,


4‐26

and Table 4‐20 presents a mass balance of biological oxygen demand, total suspended solids, and ammonia through the plant.

9BTable 4‐19. Summary of Proposed Improvements Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Proposed Improvement

Preliminary Treatment Odor Control

Primary Treatment Covers + Odor Control

Aeration Basins New Aeration Basin 7

Blowers New Blower No. 8

Secondary Clarifiers Demolish Secondary Clarifier 2 (90 ft diameter)

New Secondary Clarifier 5 (120 ft diameter)

RAS/WAS New RAS pumps and RAS chlorination

Disinfection ‐‐

Effluent Pump Station New Effluent Pumps

WAS Thickening ‐‐

Anaerobic Digestion ‐‐

Digested Biosolids Dewatering Solids Conditioning System

Projected values for BOD5, TSS, and NH3‐N concentrations in the secondary effluent are below currently permitted levels and would not contribute to further impairment of the receiving water body. Use of the CMAS approach to estimating ammonia‐nitrogen removal predicts a high level of nitrification for the facility.

SECONDARYCLARIFIERSNO. 3 - 5

AERATIONBASINS 5 - 7

PHASE 5A)3-5

TWO - 42"PE/RAS

55.20 54.36

54.17 53.35

53.93 53.25

52.71 52.10

51.90 51.87

51.56 51.25

49.99 48.32

48.69 47.95

47.31 45.93

46.50 46.66

48.03 47.75

46.97 46.84

46.42 46.28

45.26 42.06

42.30 41.30

41.54 41.09

38.03 37.54

37.39 37.36

36.70 36.31

33.16 30.85

51.75

47.25

46.50

46.00

40.50

37.25

44.75

44.00

44.25 42.75 42.00

40.50

37.25

26.67

46.09 45.57

44.89 43.14

44.92 44.43

45.13 44.49

43.65 42.22

43.57 42.17

43.51 41.71

41.89 41.23

41.64 38.96

37.38 37.36

35.35 31.75

36.61 36.30

28.32 27.74

30.75 30.17

26.00 26.00

58 58

42 42

AERATION5,6&7

20.95 23.50

26.35 25.50

CLARIFIER1

CLARIFIERS3,4&5

X X

18"/30"PHF 33.1 MGD, ALL UNITS IN SERVICE

MMWW FLOW 17.5 MGD, ALL UNITS IN SERVICE

19.8 MGD RAS AT PHF, 11.4 MGD AT MMWWMIXED LIQUOR RECYCLE = 5.76 MGD IN AB 1-4 AND 10.37 MGD IN AB 5-7

1

NOTES:1. PLANT EFFLUENT PUMPS REQUIRED ONLY AT

HIGH RIVER STAGE AND HIGH FLOW

AERATION1-4

Figure 3-1Figure 4-9


4‐29

Table 4‐20. Mass Balance of SCTP Flows and Loads at Design ADMM Conditions Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Flow BOD TSS NH3‐N

ADMM (mgd)

ADMM (ppd)

ADMM (mg/L)

ADMM (ppd)

ADMM (mg/L)

ADMM (ppd)

ADMM (mg/L)

RS 18 30,520 209 35,770 245 4,006 27

PE 18 20,728 139 16,046 108 4,633 31

ML 29 350,124 1,428 833,629 3,400 362 1.5

SE 18 1,115 7.6 1,168 8.0 216 1.5

PLE 18 1,115 7.6 1,168 8.0 216 1.5

RAS 12 259,896 2,691 618,799 6,407 143 1.5

WAS 0 7,448 2,691 17,733 6,407 4 1.5

TWAS 0 6,331 23,100 15,073 55,000 0 1.5

PS 0 10,682 19,158 24,069 43,167 17 31

BSD 0 17,013 20,457 39,142 47,066 18 21

DS 0 2,977 3,579 19,845 23,863 1,091 1,312

TF 0 1,117 448 2,660 1,067 4 1.5

DF 0 253 356 1,685 2,371 623 877

FLT 0 1,370 428 4,345 1,356 627 196

DB 0 2,724 22,500 18,160 150,000 468 3,866


4‐30

Figure 4‐10. Unit Process Capacity Assessment Summary Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Figure 4‐11. Schematic Process Flow Diagram of the Salmon Creek Treatment Plant with Proposed Expansions Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

-""'.rSALMON CREEK

NEW 48 INCH PARALLEL PIPE TO NEW OUTFALL

EXISTING SO INCH PIPE

-~- --:~:A~~ ·- ... ~.:a.... ,--..... ~,...... ' .... -----~ /" ---\ --...;..---.....::.-- ----~ - - ~ ~ -----=- -f

\

\ ' ' \

\

' \

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\

\

\

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\ \

\ \

\

\ \

\ \

' ' \

' \ \ .

'

.......... __ ........

-

\

\

@

--· --· --· ' -- .. -

BURLINGTON NORTHERN _/ RAILROAD RIGHT-OF-WAY

\ .

~ ---AGRICULTURAL ACCESS ROAD (PRIVATE)

\\\\

LEGEND:

® WELLHOUSE

® 36TH AVENUE PUMP STATION (NOT SHOWN)

@ FORCE MAIN (NOT SHOWN)

@ PRELIMINARY TREATMENT

@ PRIMARYTREATMENT

@ ML SPLITTERJPE'JRAS MIXING BOX

@ AERATION BASIN NOS. 1-4

@ AERATION BASIN NO.5

@ BLOWER BUILDING

\\

® BLOWER BUILDING (CONVERTED THICKENING BUILDING)

@ SECONDARYCLARIFIERNOS.1AND2

@ SECONDARY CLARIFIER NO.3

@ RASIWM3 PUMP STATION

IQ., ABANDONED CHLORINE CONTACT/ ~ ABANDONED EFFLUENT PUMP STATION

LEGEND: (CONT)

@ EFFLUENT PUMP STATION/LIV DISINFECTION

@ OUTIFALL (NOT SHOWN)

® DIGESTER CONTROL BUILDING

@ SOLIDS PROCESSING CENTER

@ ANAEROBIC DIGESTERS

@ SLUDGE BLEND TANK

@ BIOSOLIDS BLEND TANK (CONVERTED DIGESTER)

@ DIGESTER CONTROL COMPLEX

@ BIOSOLIDS STORAGE

@ TRUCK LOADING FACILITY

@ ELECTRICAL BUILDING

@ OPERATIONS CENTER

@ ABANDONED CONTROL BUIWING

@ ABANDONED MAINTENANCE BUILDING

@

@

---· -

_:§::::!

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NOTE1 ~-, /-,

------------ ..,_...-(--- -'--------------- =-----------....._..,... ___ ..,_-- .....:::;_...,.,__-' --- --- ' --- ' ' ~...... -- ...._ --- --- " '

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0 80 120 180 -- ----Scale In Feet

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PROPERTY LINE

'*'--.,.· ------ '

PHASE 5 CAPACITY EXPANSION NOTE:

1. MODIFY/REPLACE EFFLUENT PUMPS TO WORK IN CONJUNCTION WITH PARALLEL OUTFALL HYDRAULICS.

2. DESIGN FLOWS: 18.0 MGD MAXIMUM MONTH WET WEATHER FLOW AND 34.2 MGD PEAK HOUR FLOW.

\.

'

' ' ' \.

\

FIGURE 5-10 TREATMENT PLANT (SCTP)

PHASE 5 EXPANSION- THROUGH 2018 SALMON CREEK WASTEWATER MANAGEMENT SYSTEM

CLARK COUNTY, WASHINGTON

\ ' . \

\

\ ' '

120 FOOT DIAMETERSECONDARY CLARIFIER NO. 5

AERATION BASIN NO. 7

NOTE 5

SALMON CREEK TREATMENT PLANTPHASE 5B EXPANSION

17.5 MGD

NOTE 2

NOTE 3

NOTE 1

PRELIMINARY/PRIMARYTREATMENT ODORCONTROL SYSTEM

NOTE 6

NOTE 4

48 INCH PIPE TO OUTFALL

30 INCH PIPE TO OUTFALL

TO OUTFALL

NOTE 7

PHASE 5B CAPACITY EXPANSION NOTES:

1. Install covers on primary clarifiers.2. Demolish Secondary Clarifier 2.3. Install RAS chlorination system. Replace RAS Pumps 1, 3, 4, 5, and 6. Remove RAS Pump 2. Install RAS Pumps 7 and 8 in existing RAS Pump Station.4. Demolish Building 87.5. Add 4,500 SCFM Blower. 6. Install new sludge conditioning equipment.7. Replace two existing effluent pumps with larger pumps.

LEGEND

06 WELL HOUSE

10 PRELIMINARY TREATMENT

20 PRIMARY TREATMENT

25 ML SPLITTER/RAS MIXING BOX

30 AERATION BASIN NOS. 1 - 4

32 AERATION BASIN NO. 5

33 AERATION BASIN NO. 6

35 BLOWER BUILDING

37 BLOWER BUILDING 2

40 SECONDARY CLARIFIER NOS. 1 AND 2

45 SECONDARY CLARIFIER NO. 3

46 SECONDARY CLARIFIER NO. 4

47 RAS/WAS PUMP STATION

55 EFFLUENT PUMP STATION/UV DISINFECTION

LEGEND (CONTINUED)

70 DIGESTER CONTROL BUILDING

72 SOLIDS PROCESSING CENTER

73 ANAEROBIC DIGESTERS

74 SLUDGE BLEND TANK

76 BIOSOLIDS BLEND TANK

77 DIGESTER CONTROL COMPLEX

78 BIOSOLIDS STORAGE

79 METALS SHOP

83 ELECTRICAL BUILDING

85 OPERATIONS CENTER

87 ORIGINAL PLANT CONTROL BUILDING

88 MAINTENANCE/STORAGE BUILDING

33

46

Figure 4-12

SECTION 5

5‐1

Air Quality and Odor Control

5.1 Regulatory Context and Requirements The air discharges from SCTP are regulated by the Southwest Washington Clean Air Agency (SWCAA) to limit toxic air pollution and nuisance odors. Individual odor‐causing compounds are quantified as a concentration (mass per volume). Of these compounds, hydrogen sulfide (H2S) is a regulated toxic pollutant and the SWCAA has established a limiting concentration for H2S toxicity. Key regulatory requirements pertaining to required limits of SCTP air emissions are described in more detail below.

5.1.1 Nuisance Odors Because H2S is easily detected by people, it is commonly regulated as a nuisance odor. The SWCAA Regulations (SWCAA 400) contain a “nuisance odor” clause. This clause indicates that procedures be put in place to mitigate odors so that they are not “unreasonable” or a nuisance. Odors in general, are typically quantified using a dilutions‐to‐threshold (D/T) method. However, limiting values are not specifically defined by the SWCAA, so target thresholds were selected based on experience to meet these qualitative nuisance odor requirements.

5.1.2 Toxic Air Pollutants New regulations have been implemented for H2S via WAC 173‐460‐150, which describes an updated Acceptable Source Impact Level (ASIL) for H2S as 2.0 milligrams per cubic meter (mg/m3) over a 24‐hour period. The previous WAC value was 0.9 mg/m3 over a 24‐hour period. SWCAA has not adopted the new less‐stringent state‐regulated value; therefore, the ASIL for the SCTP is 0.9 mg/m3 H2S over a 24‐hour period. To comply with both the state and local agencies, 0.9 mg/m3 over a 24‐hour period is the required criterion.

5.1.3 Odor Criteria Requirements Based on the conclusions above, toxic air pollution requirements and odor criteria requirements include the following:

H2S—For toxic air pollution control, H2S cannot exceed a 24‐hour average of 0.9 mg/m3 per year at the property boundary.

H2S—For nuisance odor control, H2S cannot exceed a 1‐hour average of 10 mg/m3 per year at any receptor (residence).

D/T—For nuisance odor control, D/T cannot exceed a 1‐hour average of 10 D/T per year at any receptor.

5.2 Odor Control

5.2.1 Overview and Current Performance The SCTP Phase 4 Expansion Program included installation of a bio‐trickling filter system for ventilation of the sludge blend tank and a carbon‐based system for the 117th Street Pump Station Force Main discharge.

SECTION 5 – AIR QUALITY AND ODOR CONTROL

5‐2

5.2.2 Alternative Analysis and Projected Performance

5.2.2.1 Previous Analysis

In March 2007, odor sampling and odor dispersion modeling activities were performed to characterize the odor footprint at the SCTP. This analysis summarized the offsite odor goals for the SCTP based on the SWCAA requirements for controlling nuisance odors. The report also summarized the results of an odor survey and the results of a dispersion model describing offsite impacts. Since 2007, changes in the SCTP’s environmental setting require updating the analysis to understand current odor control needs for the facility. These changes include the following:

Residences (odor receptors) have been and are continuing to be constructed in close proximity to the plant. This means that current and future odor receptors are located closer to the SCTP than previously identified.

Emissions (specifically toxic air pollutants) regulatory requirements have changed since completion of the previous work.

Technologies including bio‐trickling filters and biofilter medias have evolved and improved since completion of the previous work. Specifically, acceptable loading rates have gradually increased, making required footprints smaller. In addition, media types have improved, with longer life media now available.

Refer to the technical memorandum in Appendix B for more information regarding the odor control analysis.

5.2.2.2 Technologies Evaluated

CH2M’s recommendation from the 2007 analysis was to cover the primary clarifiers and preliminary treatment channels and ventilate these areas to a new vapor‐phase odor control system. This recommendation was carried forward into the updated analysis. Two odor control technologies were evaluated in this context: (1) bio‐trickling filter, and (2) high rate engineered media biofilter. These are described separately below.

Bio‐trickling Filter

In bio‐trickling filter technology, odorous air is blown into the bottom of the tower and flows up through the media material, exiting through an exhaust stack. The media may be a synthetic material or a natural material such as lava rock. The bacteria also use other odor compounds as a food source, including ammonia and various organic reduced sulfur (ORS) compounds. A schematic diagram of a typical bio‐trickling filter is shown in Figure 5‐1.


5‐3

Figure 5‐1. Simplified Schematic Diagram of a Bio‐trickling filter System Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Earlier design bed velocities for bio‐trickling filters were 50 feet per minute (fpm) maximum. However, advances in this technology have gradually shifted acceptable bed velocities to as high as 100 to 200 fpm; although 100 fpm is a high‐end value that can be achieved by multiple suppliers.

The required empty bed gas residence time ranges from 10 to 14 seconds, depending on odor loading rate. The design head loss through the media bed can range from 0.2‐ to 0.5‐inch water column per foot of bed depth, depending on bed velocity selected. The required footprint for this technology is generally smaller than for biofilters. For some bio‐trickling filter systems, a scrubbant recirculation pump is required to keep the media moist and maintain some biomass in solution. Several suppliers including BioAir, Azzuro, and EcoVerde use a once‐through arrangement by which makeup water is sprayed over the top of the media and drained out the bottom without recirculation. The advantage to this type of arrangement is that a pH gradient is maintained within the media that supports both low pH bacteria (autotrophic thiobacillus—specifically targets H2S) and neutral pH bacteria (heterotrophic bacteria—target ORS compounds). Nutrients are generally added for maintaining biomass health because of the synthetic nature of the media. However, supplemental nutrients are not required if secondary effluent is available and meets specific water quality requirements.

High Rate Engineered Media Biofilter

High rate engineered media biofilters are biofilter systems that utilize a proprietary media that performs under much higher loading rates than organic, soil, or mineral biofilters. High rate engineered media biofilters also exhibit similar or better performance characteristics than organic mediums. These types of systems also have longer lasting media and require smaller footprints due to the higher loading. The media is generally more expensive because it is a unique proprietary composition.

Design flow rates for high rate biofilters range from 5.0 to 11.0 cubic feet per minute per square foot. Media life is normally guaranteed for 10 to 20 years. The appropriate empty bed gas residence time for high rate media is dependent upon the target odor and respective loading rate but will typically range from 30 to 60 seconds.

Generally, high rate biofilter media do not require a nutrient source because they have a nutrient constituent built into the media recipe. The advantages of high rate packaged biofilters include the following:


5‐4

A wide range of odorous constituents may be removed.

The system operations and maintenance (O&M) is relatively simple.

Chemical storage and delivery is not required.

High rate proprietary media requires less frequent change‐out (generally guaranteed for 10 to 20 years).

The control systems are either manually operated or are relatively simple.

The collected leachate is typically not odorous, as with compost biofilters.

The required footprint is approximately half that of organic media biofilters.

The high‐velocity stack allows for better dispersion/dilution than open area biofilters without cover and stack.

However, high rate biofilters have the following disadvantages:

Media costs can be high.

The system can handle gradual cyclic loadings but cannot accommodate rapid load spikes effectively because bacterial populations provide the removal mechanism.

5.2.2.3 Projected Performance Including Dispersion Modeling Results

A dispersion model was developed as part of the updated analysis with current odor control technologies and updated receptors consisting of the housing development south of SCTP. Figures 5‐2 and 5‐3 and Table 5‐1 show the results of the bio‐trickling filter modeling.

Figure 5‐2. Isopleths Showing Lines of Constant H2S Concentration in mg/m3 —1‐Hour Annual Peak, Bio‐trickling Filter Approach



5‐5

Figure 5‐3. Isopleths Showing Lines of Constant Odor Concentration in D/T—1‐Hour Annual Peak, Bio‐trickling Filter Approach


Table 5‐1. Bio‐trickling Filter Approach, 1‐Hour Peak Average H2S Concentrations at Sensitive Receptors Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Receptor

H2S (mg/m3/ppbV) Odor (D/T) Odor Exceedances

Hours/year above 10 D/T

2006 Control Strategy 1 Results

Updated Control Strategy 1



1 1.14/0.75 1.16/0.76 6.1 4.77 ‐

2 1.55/1.01 1.49/0.97 5.2 6.01 ‐

3 2.05/1.34 1.49/0.97 7.6 6.59 ‐

4 1.51/0.99 1.51/0.99 4.7 6.83 ‐

5 0.72/0.47 0.72/0.47 3.4 3.31 ‐

6 1.00/0.65 0.85/0.56 5.4 3.62 ‐

7 NA 4.66/3.05 NA 17.05 1

8 NA 2.60/1.70 NA 9.57 ‐

9 NA 2.94/1.92 NA 7.86 ‐

mg/m3/ppbV = milligrams per cubic meter / per parts per billion volume; NA = not applicable.


5‐6

5.2.2.4 Design Criteria

Table 5‐2 shows design criteria for the bio‐trickling filter odor control system.

Table 5‐2. Bio‐trickling Filter Design Criteria Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Description Criteria

Tower Type Once through—counterflow

Media Type Structured synthetic (for example: BioAir or approved equal)

Media Depth 12 feet

Tower Vessel Two @ 12‐foot‐diameter & 28 feet high

Contact Time 14 seconds

Makeup Water Plant effluent

Fans Type: Fiberglass reinforced plastic centrifugal (1 duty, 1 standby) Capacity: 21, 000 ft3/minute @ 7.3 inches water column Motor: 60 hp

Location Adjacent to primary clarifiers

Footprint 1,660 square feet

5.2.3 Recommended Alternative Based on the updated dispersion model results, the new sensitive receptors are not shown to be a new risk but are still exceeding odor and H2S target thresholds along with other (existing) sensitive receptors without additional odor control measures. The results also indicated that the 0.9 mg/m3 requirement for toxic air pollution control at the plant boundary was exceeded. For these reasons, along with the fact that the potential for nuisance odor complaints remain significant, it is recommended that the primary clarifiers be covered and that the headworks and primary clarifiers be ventilated to an odor control system. Covering the primary clarifiers is essential to capturing all nuisance odors. This project will install aluminum covers, similar to those in the photograph shown in Figure 5‐4, over the primary clarifiers.

Figure 5‐4. Covered Primary Clarifier Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements


5‐7

Due to stringent air quality criteria, it is recommended that a bio‐trickling filter system is installed. Space limitations at SCTP warrant siting the filter system adjacent to the primary clarifiers. The bio‐trickling filter system may provide as much as 94 percent odor removal at the most sensitive receptor (Receptor 3).

Please refer to Figure 5‐5 for the preliminary layout of the bio‐trickling filter odor control system.

AERATION

BASINS

1 AND 2

PLA

NT A

CC

ESS R

OA

D

TREATMENT

PRELIMINARY

MIXING BOX

PE/RAS

TREATMENT

PRIMARY

CENTER

OPERATIONS

688766

FILENAME: PLOT DATE:8/25/2017 PLOT TIME:6:47:06 PM

0 20 40 60

SCALE IN FEET

101 102

103

104

KEY MAP

USS-3

PPSS-1

USS-1

AERATION

BASINS

1 AND 2

SECONDARY

CLARIFIER

NO. 3

BLOWER

BUILDING

(ABANDONED)

(STORAGE)

(STORAGE)

TRUCK

UNLOADING

FACILITY

(ABANDONED)

(STORAGE)

INTERIM

DEWATERING

BUILDING

TRUCK

SCALE

AERATION

BASINS

3 AND 4

STORAGE

BIOSOLIDS

CONVEYOR

CAKE COLLECTION

CENTER

PROCESSING

SOLIDS

BUILDING

CONTROL

DIGESTER

STATION

LOADING

TRUCK

STATION

PUMP

EFFLUENT

UV DISINFECTION

INCINERATOR

WASTE GAS

ELECTRICAL

BUILDING

BIOSOLIDS

BLEND

TANK

SLUDGE

BLEND

TANK

AERATION

BASIN NO. 5

BOX

SPLITTER

ML

PUMP STATION

RAS/WAS

TREATMENT

PRELIMINARY

MIXING BOX

PE/RAS

TREATMENT

PRIMARY

CENTER

OPERATIONS

SECONDARY

CLARIFIER

NO 1

BLOWER

BUILDING

POTABLE

WATER

BUILDING

SECONDARY

CLARIFIER

NO 2

CONTROL

BUILDINGSLUDGE

STORAGE

TANK

MAINTENANCE

BUILDING

DIGESTER

CONTROL

COMPLEX

NO. 2

DIGESTER

ANAEROBIC

NO. 1

DIGESTER

ANAEROBIC

INSTALL COVERS ON PRIMARY CLARIFIERS

PLATE

WITH CHECKERED

REPLACE GRATING

20" OA

30" OA

36" OA

42" OA

TYP

22" OA,

54" OA

54" OA

32" OA, TYP

32" OA

FUTURE BIO-TRICKLING FILTER

TO GROUND LEVEL

ELBOW DOWN

HEADWORKS EXHAUST

TIE INTO EXISTING

44" OA

TO GROUND LEVEL

ELBOW DOWN

NOTE 1DEMOLISH CARBON SYSTEM

LOUVERS, TYP

AIR INTAKE

STREET PUMP STATION

EXISTING 20" OA FROM 117TH

CONNECT NEW 20" OA PIPE TO

22" OA

2.

1.

NOTES:

FAN ENCLOSURES

DUTY AND STANDBY

44" OA

NOTE 136" OA

FILTERS, NOTE 2

NEW BIO-TRICKLING

AND FAN ENCLOSURES, INCLUDING 4" SSM, 6" PSM 4"W2 AND 6" W3

RELOCATE PIPE FROM UNDER NEW BIO-TRICKLING FILTERS

REPLACE STAIRS TO EXTEND OVER DUCT.

Figure 7-5. Preliminary Layout of Odor Control System65

SECTION 6

6‐1

Financial Considerations, Staffing, and Schedule

6.1 Preliminary Cost Estimate Table 6‐1 provides a preliminary estimate of the total project costs for the proposed project based on the Engineering Report recommendations. The estimate assumes costs for all elements expected to be part of the final design.

The cost estimate is considered to be consistent with Class 5 estimates, as defined by the Estimate Classification system of the Association for the Advancement of Cost Engineering International (formerly known as the American Association of Cost Engineers). The estimate was developed without detailed engineering data and is considered approximate. Class 5 estimates are normally expected to be accurate within minus 50 percent to plus 100 percent. This range implies that there is a high probability that the final project cost will fall within the range.

Table 6‐1. Project Costs Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Item Cost Estimate

Delivery:

Planning $350,000

Engineering & Survey $2,500,000

Environmental & Other Permitting $480,000

Stakeholder Engagement & Outreach $120,000

Project Management $250,000

Construction Management $2,500,000

Total Delivery Cost $6,200,000

Construction:

Preliminary and Primary Treatment (Covers and Odor Control) $3,800,000

Aeration Basin 7 $2,800,000

Blower Addition $365,000

Demolish Secondary Clarifier 2 $300,000

Secondary Clarifier 5 $1,770,000

Demolish Building 87 $200,000

Secondary Treatment (RAS Chlorination Improvements) $250,000

RAS Pumps (Replacement and New) $750,000

Effluent Pump Station Modifications $735,000

Solids Dewatering (Allowance for Orège SLG® implementation) $250,000

Yard Piping $840,000

Contingency $5,740,000

Total Construction Cost $17,800,000

Total Project Cost $24,000,000

SECTION 6 – FINANCIAL CONSIDERATIONS, STAFFING, AND SCHEDULE

6‐2

6.2 Project Funding The capital expenditures portion of proposed project will be funded as an Alliance Capital Project. The Alliance Capital Project work is funded by a combination of Regional Service Charges and debt proceeds to fund larger capital projects. The Alliance costs are then allocated to the Alliance Member Agencies, based on the amount of capacity allocation purchased with the project. In this case, the resulting Alliance charges from the Phase 5B Project have been communicated to the City of Battle Ground and Clark Regional Wastewater District as funding partners. The City and the District, in turn, have included the Alliance costs in their respective financial planning and rate modeling efforts to ensure that retail rates and charges are adequate to fund this project. The allocation of costs for the project is summarized as follows:

City of Battle Ground 19.2% of project cost $4,600,000

Clark Regional Wastewater District 80.8% of project cost $19,400,000

Total 100% of project cost $24,000,000

The O&M costs associated with power and general maintenance for the proposed odor control system will be incorporated into the annual operating costs for SCTP. The current annual O&M budget for SCTP is approximately $4 million per year. The additional costs for this work will be included in the future budgets associated with the construction period and commencement of operations. Similar to the framework for capital costs, operating costs for SCTP are shared between the City and the District based on the relative contribution of flow from each agency.

6.3 Staffing Requirements The overall degree of operator attention required for the proposed facility is similar to that required for the current facility. The new primary clarifier covers will reduce maintenance access space and visual observation into the primary clarifiers, but access can be accommodated during regular maintenance activities that require manned entry into the primary clarifier tanks. The new odor control bio‐trickling filter will run continually, and require similar daily operations monitoring as the existing bio‐trickling filter that treats air off the headspace of the sludge blend tank. The instrumentation and equipment associated with the new bio‐trickling filter are similar to others onsite. The new aeration basin and secondary clarifier will be similar to existing facilities and will not require any significant modifications to staff. Design will provide opportunities to automate processes where possible.

6.4 Project Schedule A preliminary project schedule was developed that shows a total project duration of approximately 4 years. The preliminary project schedule, included as Figure 6‐1, shows design development and permitting occurring in 2018, final design and permitting in 2019, and construction in 2020 – 2022. This schedule will deliver the additional capacity at approximately the timeframe that the facility is reaching the current waste load capacity (see Figure 1‐2).

SECTION 6 – FINANCIAL CONSIDERATIONS, STAFFING, AND SCHEDULE

6‐3

Figure. 6‐1. Project Schedule Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

SECTION 7

7‐1

Compliance with Regulatory Requirements

7.1 Permitting and Regulations In accordance with RCW 90.48.110, all engineering reports, plans, and specifications for new construction or improvements to existing sewage treatment systems shall be submitted to and approved by Ecology before construction may begin. RCW 90.48.110 also allows delegation of this authority to local authorities that meet Ecology’s criteria. The District meets Ecology’s criteria and has entered into a formal delegation agreement with Ecology. As a result, the District will perform as the delegated authority for certain review and approval responsibilities, as indicated below. The Alliance will serve as SEPA lead agency under its adopted SEPA rules.

For the proposed project, the Alliance will obtain or perform the following permits and approvals (except where noted):

1. Review and approval of the Engineering Report per WAC 173‐240‐060 by Ecology.

2. Review and approval of final Plans and Specifications per WAC 173‐240‐020(11) and WAC 173‐240‐070 by the District.

3. Review and approval of Construction Quality Assurance Plan per WAC 173‐240‐020(2) and WAC 173‐240‐075 by the District.

4. Modification of NPDES Permit No. WA0023639 by Ecology.

5. Minor Source Air Discharge Permit from SWCAA.

6. Shoreline Management Act Shoreline Permit (possible Conditional Use Permit) from Clark County.

7. Building Permit from Clark County.

8. Grading and Drainage Permit from Clark County.

9. Review and concurrence of archaeological survey by Department of Archaeology and Historic Preservation (DAHP Project Tracking Code #2017‐12‐08780).

As SEPA lead agency, the Alliance has performed the environmental review, prepared the SEPA checklist, determined the potential for environmental impact, and will be distributing the public notice. The SEPA decision is a determination of non‐significance (DNS). Please refer to SEPA DNS 001‐2018 for all documentation related to the SEPA review for this project.

The Phase 5B Project does not have a federal nexus and will not utilize the Clean Water Act State Revolving Fund loan program. Therefore, neither compliance with the National Environmental Policy Act nor the State Environmental Review Process will be required.

7.2 Environmental Impacts Development of this Engineering Report requires the Alliance to consider environmental values under SEPA. Consequently, the Alliance conducted a SEPA environmental review as lead agency per SEPA rules adopted under WAC 197‐11. The Alliance prepared a SEPA checklist and DNS, taking into account all direct and indirect environmental impacts of the proposed project. Following a SEPA public notice period and response to public comments, the SEPA DNS will be completed and adopted. The SEPA DNS and checklist will be provided to Ecology. Please refer to Alliance SEPA DNS #001‐2018 for all documentation related to the SEPA review for this project.

SECTION 7 – COMPLIANCE WITH REGULATORY REQUIREMENTS

7‐2

All physical improvements to the SCTP would occur within the existing plant site. Consequently, the direct environmental effects would be expressed at the plant. The physical improvements at the plant

site would be in designated Aquatic/Urban Conservancy and within the shoreline area of Salmon

Creek. The project site lies within designated Priority Species Buffer and Priority Habitat Buffer (i.e., Riparian Habitat Area), but the project site does not contain Wetlands, nor does it contain Floodway, Floodway Fringe, or 500 Year Flood Area. There are no known or expected Endangered Species Act‐listed species or critical habitats, or Washington Department of Fish and Wildlife priority species or habitats at the project site. Several Endangered Species Act‐listed fish species, and their critical habitats, occur in the Columbia River where the treated effluent outfall is located.

The SCTP lies within an area of moderately‐high or high archaeological probability for which an Archaeological Site Buffer is designated and sits on a documented cultural property. Munsell (1974) documented pre‐contact site 45CL98 during the preliminary archaeological evaluation prior to construction of the SCTP. There is no map available showing the extent of the 1974 survey area. A subsequent survey by Blukis Onat and Starkey (1979) did not relocate the resource, which may have been destroyed by prior development; the significance or extent of the site was never determined.

The proposed physical improvements are not expected to encounter or disturb cultural properties; however, the Alliance will conduct a professional cultural survey of intact native soil that might be disturbed, prior to construction. The SEPA DNS public notice will include tribes with treaty rights to the Columbia River where plant effluent will be discharged. Several Native American Tribes have an active presence in Clark County. Under established treaty rights, federally recognized Tribes have rights to the annual salmon harvests within the Columbia River and tributary streams. Tribes with usual and accustomed territory within Clark County include:

Cowlitz Indian Tribe, Washington – Area throughout Clark County is usual and accustomed territory

Confederated Tribes and Bands of the Yakama Nation, Washington – South‐central Washington

Chinook Tribe – Not currently federally recognized

Tribes with usual and accustomed territory on shorelines adjacent to Clark County and/or within the upstream Columbia River Basin, downstream of the Bonneville Dam, include:

Confederated Tribes of the Grand Ronde Community of Oregon – Usual and accustomed territory extending throughout the Grand Ronde area of Oregon

Confederated Tribes of the Siletz Reservation, Oregon – Usual and accustomed territory in Western Oregon

During construction, a variety of equipment would be used for material delivery, grading, lifting, and clean up; and may include flat‐bed trucks, dump trucks, cement trucks, loader, trackhoe/excavator, scissor lift, crane, jackhammer, impact wrenches, pumps, and compressors. Construction would be limited to daytime hours, and operation of construction equipment would meet Clark County noise ordinance requirements. (There are no residences within 200 feet of the proposed Phase 5B Project—Salmon Creek Treatment Plant Improvements.)

The total area of ground disturbance would be about 68,502 ft2 (1.6 acres). Filling, excavation, and grading primarily would focus on construction of the Aeration Basin 7 (7,200 ft2) and Secondary Clarifier 5 (11,310 ft2), and installation and relocation of yard piping (4,259 ft2). Relatively minor amounts of filling, excavation, and grading would be associated with demolition of Secondary Clarifier 2 (8,659 ft2) and the former Control Building (3,104 ft2).

The excavation depths for new Aeration Basin 7 and Secondary Clarifier 5 would be about 18 and 15 feet, respectively. The fill depth for Secondary Clarifier 2 would be about 12 feet, and the fill depth for the


7‐3

former Control Building would be about 2 feet. Attempts would be made to balance the excavation volumes for Aeration Basin 7 (4,800 yd3) and Secondary Clarifier 5 (6,283 yd3) with fill volumes for removing Secondary Clarifier 2 (3,848 yd3) and the former Control Building (230 yd3). Cement, gravel, asphalt, and other building materials would be imported from commercial sources, and excess soil would be hauled to an approved disposal facility.

During construction, there would be groundwater from dewatering to construct the 15‐foot‐deep secondary clarifier and 18‐foot‐deep aeration basin. Water generated by dewatering would be detained and filtered by steel tanks, dirt bags, and/or a vegetated filter strip prior to discharge to Salmon Creek; or hauled and discharged at an approved offsite location. If the relocated yard piping needs to be pressure tested prior to operation, the small amount of process water would be routed to the wastewater treatment process stream at the head of the plant. If the relocated yard piping needs to be chlorinated prior to operation (i.e., for a potable water line), the process water would be either dechlorinated through a standard media diffuser at a hydrant or routed to the wastewater treatment process stream at the head of the plant.

Minimal earthwork is required for the odor control improvements. Ground disturbance will include a concrete foundation pad for the 1,300‐square‐foot bio‐trickling filter odor control system and replacement of an existing stairs at the Preliminary Treatment Building. Prior to constructing the foundation, existing utility piping to a depth of about 6 feet under the bio‐trickling filter system site will be relocated to avoid conflicts with the structures. The carbon system removal area will be about 230 square feet.

No earthwork will be associated with improving the RAS Chlorination improvements, RAS Pumps, adding the blower system, modifying the Effluent Pump Station, and improving Solids Dewatering.

It is possible that toxic or hazardous chemicals may be encountered during demolition of existing structures. In addition to asbestos or lead‐based paint, the structures might contain potentially dangerous or hazardous materials, such as polychlorinated‐biphenyl‐containing lamp ballasts, caulking, or paint; fluorescent lamps; treated wood; and wall thermostats containing mercury. Consequently, the Alliance would perform surveys for asbestos‐containing material/lead‐based paint, and other dangerous and hazardous materials and wastes, at structures proposed for demolition; and prepare and implement a hazardous materials handling plan, as appropriate. Dangerous and hazardous materials and wastes will be removed and appropriately managed prior to structure demolition, if possible.

Fuel used in construction equipment would not be stored onsite. Construction equipment would produce emissions of nitrogen oxides (NOx), carbon monoxide (CO), and PM10

1 (dust) during construction, but these amounts would be minor and temporary. The project would be constructed in accordance with applicable state and local health and safety regulations. Temporary erosion and sediment control is entirely manageable within the plant site. After construction, the ground would be stabilized by seeding for lawn or covered by riprap.

The plant would treat about 17 percent more influent. A corresponding increase in treated effluent from the plant would discharge into the Columbia River. Therefore, the plant would be able to treat about 17 percent more influent flow and generate about 17 percent more biosolids and biogas. However, the solids dewatering improvements noted above are expected to reduce the volume of biosolids produced.

RAS chlorination facilities would improve treatment performance reliability under filamentous sludge bulking conditions and reduce risk of these filamentous bacteria causing activated sludge process upsets that result in discharge of suspended solids to the Columbia River. Biosolids removed from the plant are regularly applied to nearby farmlands. From the second week of August through mid‐September, when about half of the biosolids are taken to farms near Woodland, the number of daily truck trips may

1 PM10 describes inhalable particles (particulate matter) with diameters generally 10 micrometers and smaller.


7‐4

increase by 2 to 3 trips. During the remainder of the year, biosolids hauling to farms near Goldendale may increase by about 17 percent subject to the results of the solids dewatering improvements noted above.

No changes to plant lighting are proposed, and no protected views would be altered or obstructed in the immediate project vicinity. The plant would consume about 17 percent more electrical energy. The upsized Effluent Pump Station, RAS chlorination system, new blower, and bio‐trickling filter odor control system would be electrically powered and create additional energy demands, but these would be small percentage increases over the energy use by SCTP operation.

The RAS chlorination equipment requires liquid sodium hypochlorite. The package system includes chemical storage and containment. Hypochlorite has a limited shelf life and is readily available. It would be ordered and delivered to the SCTP (likely in totes) when needed, so onsite storage would be minimal to none during periods of system non‐use. The plant operates under a rigorous spill prevention, containment, and countermeasures plan.

Odors originating from the preliminary and primary treatment process would be captured and treated and dispersed. Odor control would limit H2S concentration below the SWCAA’s Acceptable Source Impact Level (i.e., 0.9 mg/m3) in the airshed within the SCTP property boundary. Existing operational noise at the SCTP includes normal plant O&M activities, including service vehicle operation, and would not be measurably different after the project. Although noise from the existing clarifiers is negligible, the proposed covers and associated ductwork would reduce the noise.

7.3 Compliance with Water Quality Standards A detailed evaluation of discharge compliance with water quality standards (WAC 173‐201A) has been developed for the SCTP Phase 5B improvements. The Phase 5B effluent flows will be discharged into the Columbia River through the existing outfall and diffuser until the replacement outfall and diffuser are completed under the Phase 5A project. The Water Quality Compliance Evaluation, conducted per WAC 173‐201A‐320, is documented in Appendix C of this report.

This evaluation was prepared to be consistent with WAC 173‐201A, and to align with the Water Quality Program Permit Writer's Manual (Ecology, 2015) and Water Quality Program Guidance Manual: Supplemental Guidance on Implementing the Tier II Antidegradation (Ecology, 2011). The elements of this evaluation include the following:

Assessment dilution performance of SCTP existing outfall diffuser with Phase 5B effluent flows,

Assessment of discharge compliance with state water quality standards and antidegradation rules, and

Summary of biological resources and uses of the Columbia River discharge site.

The results of the evaluation show that the proposed improvements will not result in exceedances of water quality standards or antidegradation rules.

SECTION 8

8-1

8Engineering Report Requirements Checklist For the reviewer’s convenience, Table G1-1 Requirements for Engineering Reports, taken from Criteria

for Sewage Works Design, is included as Table 8-1. The table provides a comprehensive list of the

information required for engineering reports and facilities plans and the location where the information

is provided. Additional supporting information regarding the SCTP service area and treatment facility

can be found in the Facilities Plan (CH2M, 2013).

Table 8-1. Requirements for Engineering Reports


Element Requirement Location or Reference

Site Description and Map Well documented A layout of the proposed improvements is

shown in Figure 4-12.

Problem Identification Well documented Refer to Section 1 of the Engineering Report.

Description of Discharge Standards Well documented Refer to the Section 3.3 and Section 7.3,

supplemented by the Water Quality Compliance

Evaluation in Appendix C.

Background Information Existing Environment:

• Water, air, sensitive areas

• Floodplains

• Shorelines

• Wetlands

• Endangered species

• Public health

Demographics and Land Use:

• Current Population

• Present wastewater treatment

• Advanced wastewater

treatment need evaluated

• Infiltration and inflow studies

• Combined sewer overflows

• Sanitary surveys for unsewered

areas

Refer to Section 2 of the Engineering Report and

the SEPA checklist referenced in Section 7 of the

Engineering Report. Further information can be

found in the Salmon Creek Wastewater

Management System Wastewater Facilities

Plan/General Sewer Plan Amendment (Facilities

Plan) (CH2M, 2013).

Future Conditions Demographics and Land Use:

• Projected population levels

• Appropriateness of population

data source, zoning changes

• Future domestic and industrial

flows, and flow reduction

options

• Future flows and coding

• Reserved capacity

• Future environment without

project

Future demand projections for the SCTP are

provided in Figures 1-1 and 1-2. Also refer to

Section 3 of the Engineering Report.

SECTION 8 – ENGINEERING REPORT REQUIREMENTS CHECKLIST

8-2

Table 8-1. Requirements for Engineering Reports


Element Requirement Location or Reference

Alternatives • List specific alternative

categories, including no action

• Collection system alternatives

• Sludge management/use

alternatives

• Flow reduction

• Costs

• Environmental impacts

• Public acceptability

• Rank order

• Recommended alternative

Unit process capacity analysis is discussed in

Section 4 of the Engineering Report. Odor

control analysis and alternatives are discussed in

Section 5 of the Engineering Report.

NA

Refer to Section 4 of the Engineering Report.

NA



NA

NA


Final Recommended Alternative • Site layout

• Flow diagram

• Sizing

• Environmental impacts

• Design life

• Sludge management

• Ability to expand

• O&M/staffing needs

• Design parameters

• Feasibility of implementation

Refer to Figure 4-12 of the Engineering Report.

Refer to Figure 4-11 of the Engineering Report.








Refer to the 2004 Facilities Plan (CH2M, 2004),

as updated by the Facilities Plan (CH2M, 2013)

Financial Analysis • Costs

• User charges

• Financial capability

• Capital financing plan

• Implementation plan


Other • Water quality management

plan

• SEPA approval

• List required permits

Refer to Section 7 of the Engineering Report for

information regarding SEPA approval and

permitting.

For information regarding a Water Quality

Management Plan, refer to the 2004 Facilities

Plan (CH2M, 2004), as updated by the Facilities

Plan (CH2M, 2013).

NA = not applicable.

SECTION 9

9‐1

References American Water Works Association. 2008. M9 Concrete Pressure Pipe. Third Edition.

Bennoit, H., and C. Schuster. 2001. “Improvement of Separation Processes in Waste Water Treatment by Controlling the Sludge Properties.” Fachhochschule Sudwestfalen, 1‐9.

Brown and Caldwell. 2010. Biosolids Processing and Utilization Review for the Salmon Creek Treatment Plant. September.

Brown and Caldwell. 2017. Class A Biosolids Cost Update. May.

CH2M HILL, Inc. (CH2M). 2004. Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan. June.

CH2M HILL, Inc. (CH2M). 2013. Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan Amendment. August.

CH2M HILL, Inc. (CH2M). 2016. Salmon Creek Wastewater Treatment Plant (SCTP) Capacity Evaluation.

Eckenfelder, W. Wesley, and Petr Grau. 1992. Activated Sludge Process Design and Control: Theory and Practice. International Association on Water Pollution Research and Control.

Heald, C.C. (ed.). 1998. Cameron Hydraulic Data. Ingersoll‐Dresser Pumps.

Henze, M., W. Gujer, T. Miro, T. Matsuo, M.C. Wentzel, and G.V.R. Marais. 1995. Activated Sludge Model No. 2. IAWQ Scientific and Technical Reports, No. 3.

Inman, D., and P. Capeau. 2015. “Solids‐Liquid‐Gas (SLG®) Separation Technology for Sludge Treatment: Results from a Pilot Scale Trial by Anglian Water. AquaEnviro. Conference Proceeding/Publication.

International Water Association (IWA). 2003. Manual on the Causes and Control of Activated Sludge Bulking, Foaming, and Other Separations Problems, 3rd Edition.

Leuven, Gert Van, Stefan Henneberger, and Conrad Latham. Undated. Theoretical and Experimental Study on Energy Efficiency of Twin Screw Blowers Compared to Rotary Lobe Blowers.

Metcalf & Eddy (M&E). 2002. Wastewater Engineering, Treatment and Reuse, Fourth Edition.

Metcalf & Eddy (M&E). 2014. Wastewater Engineering, Treatment and Reuse, Fifth Edition.

Orège. 2016. Supercharge Your Dewatering and Thickening. SLG® technology presentation. https://www.dropbox.com/s/4bnl1rtkmkuzrdt/2016%20SLG%20Orege%20Lunch%20and%20learn%20vF.pptx?n=108440598&oref=e

U.S. Environmental Protection Agency (EPA). 1975. Process Design Manual for Nitrogen Control. Technology Transfer.

U.S. Environmental Protection Agency (EPA). 1989. Design Manual: Fine Pore Aeration Systems. EPA/625/1‐89/023.

U.S. Environmental Protection Agency (EPA). 1991. Technical Support Document for Water Quality‐Based Toxics Control.

Washington State Department of Ecology (Ecology). 2008. Criteria for Sewage Works Design.

Water Environment Federation (WEF). 2010. Design of Municipal Wastewater Treatment Plants, 5th Edition – Manual of Practice No. 8. Water Environment Federation, Alexandria, Virginia.

Appendix A Process Calculations

Aeration Basin 7 0.87 Mgal (Same size and configuration as AB 5 and AB 6)Secondary Clarifier 5 120 feet (SC 5 at 120-ft Diameter is replacing SC 2, which is to be demolished to make room for AB 7)Additional aeration capacity and return activated sludge (RAS) capacity as detailed in the Engineering Report

Primary Clarifier Sizing and Evaluation

Primary Clarifier area at design flow & loading criteria: Primary Clarifiers 0.40 MGD Internal Recycle Into Primary Clarifiers a.

Enter Design Average Influent Flow 13.3 MGD 160 ft lengthEnter Design ADMM Influent Flow 17.5 MGD 20 ft wide PC VolumeEnter Design Peak Hour Influent Flow 33.1 11 ft SWD 140800 cfEnter Design Surface Loading Rt 1200 Gal/d/sf 4 each 1.053184 MGOutput Min Required Clarifier Surface Area 11,299 sf 12800 sf (SA)

Design Pk Hour Flow Rate 33.14 MGD 33.54 MGD pk hr 0.7535888 hr HRTEnter Pk Hour Surface Overflow Rt 3,000 Gal/d/sf 2,620 g/d/sf pk (<3000 g/d/sf pk hr)Output Min Required Clarifier Surface Area 11,379 sf 13.66 MGD Average 1.851070436 hr HRT

1,067 g/d/sf Avg (800-1200 g/d/sf at "average design flows" <<<< CH2M/Jacobs interprets this to be the annual average condition, not the average day maximum month valuePrimary Clarifier Waste Rate 13.3 MGD Annual Ave 1.91 (< 2.5 hr HRT @ Average Annual Conditions)

Design PC Effluent Loading

Proportion of TSS Removed 60.00% ADMM Flow --> 17.90 Influent ADMM (mg/L) Influent ADMM Load PC Rem% Recycle Load a.

Plant Flow 17.50 MGD BOD5 --> 20,521 lb/d MMA 209 mg/L 30,520 lb/d 35 1,051 lb/dOutput PC Solids 24,069 lb/d TSS --> 16,046 lb/d MMA 245 mg/L 35,770 lb/d 60 4,345 lb/dEnter Percent Solids in PC Sludge 4.30% (Primary, from WWTP Data) Ammonia -> 4,633 lb/d MMA 27 mg/L 4,006 lb/d 0 627 lb/d

Density of PC Sludge 1.0057 SG a. Recycle Loads from "Plant_Mass_Balance" tabOutput Volume of PC Sludge 66,734 gpd

Secondary Treatment Sizing and Evaluation

Secondary Clarifier Sizing Design PC Effluent Loading Infl Load PC Rem% Recycle LoadEnter Target Solids loading rate 24 lb/sf/d BOD --> 20,521 lb/d MMA 30,520 lb/d 35 1,051 lb/dEnter MLSS concentration 3400 mg/L TSS --> 16,046 lb/d MMA 35,770 lb/d 60 4,345 lb/dEnter PE Flow Rate 17.90 MGD Ammonia -> 4,633 lb/d MMA 4,006 lb/d - 627 lb/dEnter Return Activated Sludge Rate 11.6 MGD MGD <<< Using a design RAS rate of 65% for ADMM conditions average RAS rates are 50 - 55% of PE flow). Note, RAS system sizing allows for higher rates - see below.Output Total mass into Secondary Clarifiers 837,375 lb/dOutput Clarifier Surface Area (total) 34,989 sf At annual aveage at peak day at peak hour Clarifier Diameter Clarifier Diameter Clarifier DiameterOutput Solids loading rate (ADMM) 23.93 lb/sf/d 17.73 30.98 43.43 105 feet (SC 3, SC 4) 90 feet (SC 1) 120 feet (SC 5)Output Loading Criteria Met? (Y/N) Yes < 24 < 36 < 48 8,659 square ft 6,362 square ft 11,310 square ft 34,989. sf Clarifier

AA Overflow Rate 390.3 g/d/sf 2 each total 1 each total 1 each total 26.60 MGD pk day DepthADMM Overflow Rate 522.9 g/d/sf DOE Criteria Table T3-2, CAS 1200 g/d/sf crit 1200 g/d/sf crit 1200 g/d/sf crit 33.54 MGD pk hr 12.25 ft 0.58 MG (Vol of Clar 1)Pk Overflow Rate 970.0 g/d/sf 20.78 MGD cap 7.63 MGD cap 13.57 MGD cap 41.99 MGD pk hr cap. 16.0 ft 1.04 MG (Vol of Clar 3)Specific Gravity of WAS Table 8-34, M&E 5th Ed. 600 g/d/sf crit 600 g/d/sf crit 600 g/d/sf crit 17.90 MGD ADMM 16.0 ft 1.04 MG (Vol of Clar 4)Specific Gravity of Inert Solids 2.5 (generally presumed) 10.39 MGD cap 3.82 MGD cap 6.79 MGD cap 20.99 MGD ADMM Cap. 18.00 ft 1.52 MG (Vol of Clar 5)Specific Gravity of liquid 1 (unless TDS is high)

Enter Proportion of volatile solids 78% (VSS:TSS ratio) (Below nitrogen balance includes the Ammonia coming in from solids recycle to anoxic basin)Output Density of WAS: 1.15 SG Flows in Nitrogen Balance

17.90 MGD 4,633 lb/d NH3-N 3706.662 lb/d NO3-N 10.9 mg/L NO3-N 1,629 lb/d eff NO3-N11.63 MGD 2,254 (NO3-N from recycle) 45.67 MGD ___> secondary clarifier16.14 MGD 450.8 (80% destruction) 4,157 lb/d lb/d tot NO345.67 MGD (total) 10.9 mg/L (NO3-N)

Total Reported Reported ADMM Flow MLR % of Q RAS Recy Reported Anoxic Zone Anoxic ZoneAB Vol MG Anoxic Vol MG % of Qt Cal'c %Qt Length Width Depth Length Width Depth Vol (by dim's_ (MGD) (MGD) % Recy (MGD) Food to Sel. MLVSS in Sel. F:M Ratio SRT (days)

Aeration Basin 1 & 3 0.94 0.20 0.209 0.209 94.0 ft 41.0 ft 14.0 ft 94.0 ft 49.0 ft 15.5 ft 0.94 MG 3.75 MGD 2.88 77% 2.4 MGD 913 lb/d 437. lb 2.09 1.56Aeration Basin 2 & 4 0.94 0.20 0.209 0.209 94.0 ft 41.0 ft 14.0 ft 94.0 ft 49.0 ft 15.5 ft 0.94 MG 3.75 MGD 2.88 77% 2.4 MGD 913 lb/d 437. lb 2.09 1.56

Aeration Basin 5 0.87 0.22 0.194 0.194 323.0 ft 18.0 ft 20.0 ft 0.87 MG 3.47 MGD 3.46 100% 2.3 MGD 1,007 lb/d 490. lb 2.05 1.84Aeration Basin 6 0.87 0.22 0.194 0.194 323.0 ft 18.0 ft 20.0 ft 0.87 MG 3.47 MGD 3.46 100% 2.3 MGD 1,007 lb/d 490. lb 2.06 1.84Aeration Basin 7 0.87 0.22 0.194 0.194 323.0 ft 18.0 ft 20.0 ft 0.87 MG 3.47 MGD 3.46 100% 2.3 MGD 1,007 lb/d 490. lb 2.06 1.84

4.49 MG Total Tank Volume 3.43 MG Oxic Vol 4.485 MG 17.90 MGD 16.14 11.6 MGD 2.07 1.73

1.06 MG anoxic Volume 600 Kcf 34.2 lb/KCF 92% RAS %Q 65%

NOTE: This Ecology spreadsheet has been updated by CH2M/Jacobs to reflect the capacity of the Phase 5B Expansion at the Salmon Creek WWTP. The following unit processes are included in the expansion:

PROPOSED Phase 5B Capacity Expansion

SLR under various conditions

Overall MLR Recy %Q

Input CellIntermediate Calculation

Result meets Required Target/LimitRequired Target/Limit

Legend

Page 1 of 51

Proposed Phase 5B Improvements Sizing Calculations

Engineering Report for the Phase 5B Project - Salmon Creek Treatment Plant Improvements Appendix A

Anoxic % 24% Sludge AgeTime in ANX 33.4 minutes (ave)HRT @MMA 6.02 hrs EPA "Manual - Nitrogen Control" 9/1993 notes:Oxic HRT (sys) 4.60 hrs (MMA) Total Forward Flow Contact Time (MMA) Table 2-4: Solids residence time 7-10 days when Temp < 15C

AB 1-4 Selector Size 0.40 MG 7.49 MGD infl 4.87 MGD RAS 5.76 MGD Recy 18.12 MGD 31.8 minutes (Basins 1-4) Table 2-4: F:M = 0.1 - 0.15 lb CBOD5 / lb MLVSS / dAB 5-7 Selector Size 0.66 MG 10.40 MGD infl 6.76 MGD RAS 10.38 MGD Recy 27.55 MGD 34.5 minutes (Basins 5-7) or: 0.12 - .18 lbBOD5/lb MLVSS/d at CBOD5 = 25/30 * BOD5

Nitrate 4,006 lb/d NH3 26.84 mg/L MMA 118.8646931 mg/L NO3 49.15 mg/L NO3 Figure 2-10 (p.75) notes "Nitrification systems are typicallydesigned and operated at MCRT > 7d"

Single Stage Nitrification from Table 8-19 of M-E 5th Ed (2014) <<< See following sheets in this workbook for predicted bioreactor performance under various conditions Figure 2-10 (p.75) notes at MCRT = 3-7d, degree of nitrificationMetric Low range High range Proposed: Eval: can vary from trace to significant"F:M 0.2 0.6 lb BOD5/lb MLVSS 0.207 lb/lb/d YesSRT (days) 3 15 days 7.30 days Yes EPA "Nitrogen Control" Manual suggests 7-10 d SRTVol loading rt 20 40 lb BOD5/Kcf/d 34.2 lb/Kcf Yes M&E 5th Ed., Table 8-19: Conventional plug flow, 20 - 40 lb BOD5/Kcf*dMLSS mg/L 1000 3000 mg/L 3,400 mg/L Ok, Selectors are present, meets DOE Orange Book CriteriaV/Q, h 4 8 hr 6.0 hrs YesQr/Q 0.5 1.5 ratio 1.11 gal/gal Yes Note: Design RAS rate of 65% of ADMM conditions (typically operated at 45 - 55% of PE)Clar Sol Ld 1.2 2 lb/sf/hr MMA = 1.54 Pk Hr = 2.07 lb/sf/hr - Yes (from table 10-12 M&E 3rd Ed.)

RAS System Sizing - Determine maximum firm capacity required. Required RAS Concentrations RAS conc Capacity Peak Day Ld Solids Rem Hrs until RAS Pumps Firm Capacity ADMM SC Influen Pk Day Pk Hr MLSS ADMM Peak Day Peak Hour SVI Req'd Pk Day SVI Pk Hr SVI Volume at SVI=150 lb (FULL) lb/hr Per Hr Shortfall washout:Clarifier #1 3.6 MGD 3.18 MGD 4.73 MGD 5.96 MGD 3400 mg/L 6,405. mg/L 7,866. mg/L 9,032. mg/L 156. mL/g 127. mL/g 111. mL/g 0.58 MG 6,667. mg/L 32,411. lb 9,841 lb/hr 8,340 lb/hr 1,501 lb/hr 21.6 hrClarifier #3 4.9 MGD 4.33 MGD 6.44 MGD 8.12 MGD 3400 mg/L 6,405. mg/L 7,866. mg/L 9,032. mg/L 156. mL/g 127. mL/g 111. mL/g 1.04 MG 6,667. mg/L 57,619. lb 13,394 lb/hr 11,352 lb/hr 2,043 lb/hr 28.2 hrClarifier #4 4.9 MGD 4.33 MGD 6.44 MGD 8.12 MGD 3400 mg/L 6,411. mg/L 7,875. mg/L 9,043. mg/L 156. mL/g 127. mL/g 111. mL/g 1.04 MG 6,667. mg/L 57,619. lb 13,382 lb/hr 11,329 lb/hr 2,054 lb/hr 28.1 hrClarifier #5 6.4 MGD 5.66 MGD 8.41 MGD 10.60 MGD 3400 mg/L 6,405. mg/L 7,866. mg/L 9,032. mg/L 156. mL/g 127. mL/g 111. mL/g 1.52 MG 6,667. mg/L 84,664. lb 17,495 lb/hr 14,827 lb/hr 2,668 lb/hr 31.7 hrFirm Max RAS 19.8 MGD 17.50 MGD 26.01 MGD 32.80 MGD AVE: 6,407. mg/L 7,869. mg/L 9,035. mg/L 156. mL/g 127. mL/g 111. mL/g 232,313. lb 54,112 lb/hr 45,847 lb/hr 8,265 lb/hr 28.1 hrMMA Flow 17.90 MGD MLSS Mass 127,318 lb (Under 150 @ MMA Flows) (Above analysis presumes no compaction, and so is somewhat conservative)Potential Max S 37.7 MGD Food Mass 20,521 lbRAS Recy Rt 111% Yield 0.85 lb/lbMLSS Conc 3,400 mg/L Sludge Age 7.3 days (Some ref's suggest limit MLSS to 3,000 mg/l, others 3,500 mg/l) Wasting Rate (WAS), lbs/day 17,443

(check) 1,068,665 lb/d (MMA infl solids load)(check) 1,057,398 lb/d (MMA RAS @ conc in O45)

ADMM Peak Day ADMM Peak DayAeration Power Requirements, ADMM: Oxygen AOR to SOR SOR Flow Split Oxygen ConcentraMass Percent 0.23 0.23 0.23 0.23Influent BOD 20,521 lb/d 1.2 24,625 lb/d AB 1 - 4 42% Standard Density olbs/ft3 0.075 0.075 0.075 0.075Total NH3-N 4,633 lb/d 4.6 21,313 lb/d AB 5 - 7 58% Aeration Basin 1 - 4NO3 Used 1,803 lb/d 2.6 -4,689 lb/d SOR, AB 1 - 4 45,952 lb/d SOTE Percent 0.25 0.25 0.25 0.25Total Actual Oxygen Requirement: 41,250 lb/d 2.66 109,894 lb/d SOR, AB 5 - 7 63,942 lb/d Required Air Rate SCFM 7,400 8,482 8,241 9,323

BOD Peaking factor (Peak Day) 1.15 per 2011-2017 data Aeration Basin 5 - 7Ammonia Peaking factor (Peak Day) 1.15 per 2012-2017 data SOTE Percent 0.35 0.35 0.35 0.35Aeration Power Requirements, Peak Day: Oxygen AOR to SOR SOR Flow Split Required Air Rate SCFM 7,355 8,431 8,176 9,252 Influent BOD 23,599 lb/d 1.2 28,319 lb/d AB 1 - 4 42%

Total NH3-N 5,328 lb/d 4.6 24,510 lb/d AB 5 - 7 58% Total Required Air Rate a.SCFM 14,754 16,913 16,417 18,575

NO3 Used 1,803 lb/d 2.6 -4,689 lb/d SOR, AB 1 - 4 52,675 lb/dTotal Actual Oxygen Requirement: 48,141 lb/d 2.62 125,970 lb/d SOR, AB 5 - 7 73,296 lb/d

Firm Capacity AB 1-4 9,900 SCFM <<< Firm capacity with 3x3,300 scfm blowers (1x3,300 scfm blower out of service)

Firm Capacity AB 5, 6, and 7 a.11,500 SCFM <<< Firm capacity with 2x4,500 scfm & 1x2,500 scfm blowers (1x4,500 scfm blower out of service)

a. Additional 4,500-scfm blowerTotal Firm Capacity 21,400 SCFM <<< Firm Capacity Exceeds Peak Day conditions with or without Denitrification Credit

Total Firm Cap (scf/day) 30,816,000 ADMM lb BOD5 applied/day 20,521 scf/lb BOD5 applied 1,502 > 1,500 <<< Exceeds Ecology criteria. Additional details on blower modifications to be provided under design evaluation

w/Denitrification Credit w/o Denitrification Credit

Single Stage Nitrification: In single‐stage nitrification , both BOD and ammonia reduction occur in a single biological stage. Reactor configurations can be either a series of complete‐mix reactors or plug flow. (M‐E 3ed, Table 10‐3)

Page 2 of 51

Proposed Phase 5B Improvements Sizing Calculations


Required AB Vol (MG)

Calculated Yield (mg TSS/mg BOD)

Aerobic SRT (days)

Eff NH3-N (mg/L)

Eff BOD5 (mg/L)

3.40 MG 0.849 5.5 2.65 7.64

Proposed DesignProposed AB Vol (MG)

Yield Observed at Plant(mg TSS/mg BOD)

Aerobic SRT (days)

3.43 MG 0.85 5.5

GIVEN: Designer Comments:

influent Design Flow 67,750 (M3/D) equals: 17.89757 mgd Flow of Primary EffluentOxygen conc. leaving AB 2 %O2 Conversion: 17.9 MGD 67,750. M3/d (equivalent M3/d)

influent Peak:Ave TKN Load Ratio 1.33 (used ONLY to establish the sludge age for nitrification process) Adjusted to reflect peak day:avg day NH3-N observed at plantprimary clarifier eff Value(ppm) Equivalent Loading Loading

influent BOD 137 mg/l 20,521 lb/d load 9,328 kg/d load Based on plant data of BOD loading in Primary Effluentinfluent sBOD 69 mg/l 10,253 lb/d load 4,661 kg/d load Maintained BOD fractionation ratio from M&E influent COD 256 mg/l 38,200 lb/d load 17,364 kg/d load Adjusted to target 0.85 mg TSS/mg BOD yield observed at plant

influent sCOD 113 mg/l 16,808 lb/d load 7,640 kg/d load Maintained COD fractionation ratio from M&E

influent rbCOD 68 mg/l 10,187 lb/d load 4,630 kg/d load Maintained COD fractionation ratio from M&E influent TSS 107 mg/l 16,046 lb/d load 7,294 kg/d load Based on plant data of TSS loading in Primary Effluent

influent VSS 99 mg/l 14,762 lb/d load 6,710 kg/d load Based on plant data reflecting 92% VSS/TSS in Primary Effluent

influent TKN 41.8 mg/l 6,239 lb/d load 2,836 kg/d load Maintained TKN:NH3 ratio from M&E

influent TKN (PEAK) 55.6 mg/l 8,298 lb/d load 3,772 kg/d load

influent Nh4-N 31.0 mg/l 4,633 lb/d load 2,106 kg/d load Based on plant data of NH3-N loading in Primary Effluentinfluent Alkalinity (as CaCO3) 221 mg/l 32,988 lb/d load 14,994 kg/d load

Target Alkalinity 70 mg/l 10,449 lb/d load 4,749 kg/d load

bCOD/BOD ratio 1.6effluent tgt Effluent sBOD 1.86 mg/l <------- (Effluent BOD target (not soluble BOD) = 15mg/L) Based on calcs from DMR data using M&E UBOD & eff VSS valueseffluent tgt Effluent TSS 8 mg/l Average Wet Weather effluent TSS (2010-2017)effluentq tgt NH4-N (nitrifying) 2.65 mg/l (= SNH4) Reflects the achievable NH3-N conc in the available basin by CMAS method

Clarifier Loading rate 24 m3/m2*d (Std range = 16-28 m3/m2*d) 589 gpd/sf

Note: relationship between TSS and VSS (above) establishes the inert TSS, which is important to sludge age determination by these formulas

Calculation Results

NOTE 8 (by CH2M/Jacobs): A proof of concept for the reactor-in-series methodology is presented in the worksheet: "Proof-of-Concept_Ex 8-6", detailing how the spreadsheet calculations match the example presented in M&E.

NOTE 5 (by CH2M/Jacobs): The example provided as a courtesy from the Washington Department of Ecology [Ecology] is updated by CH2M/Jacobs Engineering to reflect the proposed Phase 5B Capacity Expansion. Two methodologies are presented in the worksheet: 1) Single-stage Complete-mix Activated Sludge (CMAS) system for BOD5 Removal with Nitrification and 2) Reactors-in-series evaluation of staged reactors for Nitrification.

NOTE 6 (by CH2M/Jacobs): The Phase 5B Expansion at the Salmon Creek WWTP includes - New Aeration Basin (AB 7), New Secondary Clarifier (SC 5, replacing SC 2), Additional RAS pumping, Additional aeration blowers (as detailed in Chapter 6 of the updated Engineering Report, currently in development).NOTE 7 (by CH2M/Jacobs): These methodologies are presented in M&E (Metcalf & Eddy/AECOM, Wastewater Engineering - Treatment and Resource Recovery, 5th Edition McGraw-Hill Education, New York, NY. 2014), for single-stage CMAS (Example 8-3, page 783) and for the evaluation of staged reactors for nitrification (Example 8-6, page 783).

NOTE 3: Example appears valid if constrained to require SRT = 7.0 d or more for nitrification

NOTE 4: Example continues with anoxic internal recirculation tank sizing (beg row 224)

SCTP Aeration Basin Performance -- Wet Weather Minimum 7-Day Temperature (CMAS Method)Adapted from Design Example of Metcalf & Eddy "Wastewater Engineering" 5th International Edition (2014), Example 8-3NOTE 1: Example is for treating primary clarifier effluent, primary clarifiers not designed here.NOTE 2: Values in Yellow are "site specific" data (confirm these are valid if using this format to validate a different scenario)

SCTP Aeration Basin Performance Calculations - Wet Weather Minimum 7-Day Temperature - CMAS Method


Number of Clarifiers 1 ea (low range should be used when peaking factors are high)

Number of Aeration Basins 1 ea

Diffuser clean H2O OTE 31%Depth of diffusers 5.5 (meters) (Total tank depth = 4.9 M)

plant Site Elevation 10 m a factor (aerator) 0.5 0.65 (0.5 for BOD, & .65 for nitrification)b factor (aerator) 0.95F fouling factor (aerator) 0.9

tgt SRT for BOD removal 5 days

MLSS (design) 3400 mg/l

RAS Concentration 8000 mg/l (per section 8-3 middle of listed range of 4K-12K)influent Temperature 13.4 C Note a RAS of 8,000 equates to an SVI=125 ml/g Minimum 7-day temperature (2010-2017)

Standard Temp 20 C

PART 1 Determine data needed

to use formulas: bCOD = So = 219.9662832 calculated as 1.6*BOD

nbCOD = 35.95313662 mg/l = COD-bCOD(renamed from sCODe) nbsCODe = 2.699906431 mg/l = sCOD-1.6*sBOD

nbVSS = 23 mg/l =VSS*[1-{1.6*(BOD-sBOD)/(COD-sCOD)}]iTSS = 8.599933497 mg/l =TSS-VSS

Part 2 Design suspended growth So = 219.9662832 mg/l =bCODYH 0.45 gVSS/gbCOD (from Table 8-14)

bH,20 0.120 g/g*d (from Table 8-14)

fd 0.150

mmax = 6.000 g/g*d (from Table 8-14)q = 1.070 for 'umax' mm,T = 3.839

q = 1.040 for 'b' (from Table 8-14)bH,T 0.093 g/g*d (from Table 8-14)Ks 8.000 g/m3 (from Table 8-14)

S = 0.66 g bCOD/m3 = (Ks*(1+(bH*SRT))/((SRT*(umax-bH))-1)

(heterotrophic biomass) Px,vss1 4,569.6 kg VSS/d = Q*YH*(So-S)/(1+BH*SRT) (term 1 of Px, vss)

(cell debris) Px,vss2 317.5 kg VSS/d = ((fd*bH)*Q*YH*(So-S)*SRT)/(1+bH*SRT)) (term 2 of Px, vss)

Px,bio 4,887.1 kg VSS/d (sum of term1 + term2)

Part 3 Determine mass of VSS Px,vss 6,442 kg/d = Px,bio + Q*nbVSS)

and TSS in aeration basin Px,TSS 7,887 kg/d = Px,bio/0.85 + [Q*Yn*Nox/(0.85*(1+bn*SRT))] + Q*nbVSS + Q*(TSSo-VSS0) NOTE: Second term ignored in BOD example)Mass of VSS in basins MVSS 32,209 kg = Xvss*V = Px,vss*SRT

Mass of TSS in basins MTSS 39,434 kg = XTSS*V = Px,tss*SRT

Part 4 Determine AB vol AB Volume 11,598.3 m3 = MTSS*1000/XTSS

HRT t 4.1 Hr = V/QMLVSS 2,777 mg/l = Fraction VSS*MLSS)

Fraction VSS 0.817 = MVSS/MTSS)

Part 5 Determine F:M F:M 0.29 kg/kg*d = (Q*So)/(X*V))



Volumetric BOD Loading 0.80 kgBOD/m3*d = Q*So/V)

Part 6 Determine the yield

(based on TSS) Yobs,TSS 0.531 gTSS/g bCOD = Px,tss / (Q*(So-S))

Yobs,TSS 0.849 gTSS/gBOD = Yobs,TSS * bCOD/BOD ratio(based on VSS) Yobs,VSS 0.434 gVSS/g bCOD = Px,tss / (Q*(So-S))

Yobs,VSS 0.694 gVSS/gBOD = Yobs,VSS * bCOD/BOD ratio

(NOTE - Example shows the product 0.42 * 1.6 equals 0.64 whereas 0.42*1.6 = 0.672. If prior results are not rounded = 0.677)Part 7 Calculate O2 demand Ro = Q*(So-S)-1.42*Px,bio (=AOTR)

Required Oxygen Ro 7918 Kg/d 329.9 kg/hr (Note, hourly value doesn't account for diurnal loading fluctuations!!)

Part 8 Determine Airflow rate AOTR = SOTR((b*Cs,T,H-CL)/Cs,20)*(1.024^(T-20))(a)(F)

Pa 10.33 m (constant - see definitions) (Where Cs,T,H is the average O2 saturation conc over the water column)

de 0.4 (presumed - see definitions)

for fine bubble diffusers Pb/Pa = 1.00 = g*M*(zb-za)/(R*T) DEFINITIONS:

Patm,H = 10.32 m 14.68 psi SOTR = standard oxygen transfer rate at site kg/h

0.4 Cs,T 10.430 mg/l (derived formula - see O2 saturation sheet) OTRf = actual oxygen transfer rate at site, kg/h

0.00757 Cs,20 9.071 mg/l (using same formula to calculate DO sat at 20C) a = relative transfer rate to clean water

0.000072 Coo20 11.01 mg/l b = relative DO saturation to clean water (0.95-0.98)

0.00000012 Cs,T,H = 10.4 mg/l = Dosat * Pb/Pa F = diffuser fouling factorAVE Cs,T,H = 8.49 mg/l = 10.84*1/2*((9.74+4.4)/9.74+19/21)) Cst = saturated DO at sea level and operating temperature, mg/L

SOTR = 943 kg/H = AOTR((Cs,20/(b*Cs,T,H-CL)(1.024^(T-20))(a)(F)) Cs20 = saturated DO value at sea level and 20C, mg/L

Air Press 101.20 kPa = 101.325pa * (Pb/Pa) COO,20 = Saturated DO value at sea level and 20C for diffused aeration, mg/L

Air Density 1.23 Kg/M3 COO,20 = CS20*(1+de*(Df/Pa)) in mg/L

O2 Density 0.2853 Kg/M3 0.0201 lb/f3 Pa = standard pressure at sea level (760 mm)Air Flow Rt 178.86 m3/min (For BOD Removal ONLY) Pb = pressure at the plant site based on elevation, m

Df = depth of diffusers in basin Part 9 NITRIFICATION C = operating DO in basin, mg/L

mAOB = ( = mmax,AOB*[SNH4/(SNH4+KNH4)]*[S0/(S0+K0AOB)] - bAOB T = aeration basin temperature Cmmax,AOB 0.90 g/g*d (Table 8-10) de = mid-depth correction factor; may vary from 0.25 - 0.45 (0.40)

bAOB 0.17 g/g*d (Table 8-10)

kNH4 0.50 g/m3 (Table 8-10)k0,AOB 0.50 g/m3 (Table 8-10)

mmax,AOB at T 0.569 g/g*d = mmax,AOB*(1.072^(T-20))bAOB,T 0.141 g/g*d = bAOB*(1.029^(T-20))mAOB = 0.2420 g/g*d

Part 10 Theoretical and design SRTt = 1/mAOB

Solids Retention Time SRTt = 4.13 days (Due to rounding errors, the book answer is a little different - 14.0))(sludge age) SRT = SF * SRTt

SRT = 5.5 days (with factor of safety)

Part 11 Determine Biomass Prod S = (= Ks*(1+(bH*SRT))/((SRT*(um-bH))-1))

S = 0.62 g bCOD/m3Yn 0.15 gVSS/g Nox (Table 8-14)

fD 0.15 (Table 8-14)



Nox 31.0 g/m3 NOTE: initially assume Nox = 0.8 * TKN, then use D142 - (iterative approach)

(heterotrophic biomass) Px,vss1 4431.6 kg/d =Q*YH*(So-S)/(1+bH*SRT)

(cell debris) Px,vss2 338.4 kg/d =((fd*bH*Q*YH*(So-S)*SRT)/(1+bH*SRT))

(nitrifying biomass) Px,vss3 177.9 kg/d =(Q*Yn*Nox)/(1+kdn*SRT)

TOTAL biomass PxrVSS = 4947.9 kg/d (KG VSS / day)

Part 12 Determine N oxidized

to nitrate Nox = 30.39 g/m3 (TKN - Ne - .12*Px,bio) / Q (equation 8-24)

Part 13 Determine VSS &TSSrate of VSS produced Px,vss(inert+a 6502.6 kg/d =Px,bio +Q*nbVSS (equation 8-20)rate of TSS produced Px,tss 7,958 kg/d =(Px,vss/.85) + Px,vss(inert) + mass of mlvss Xvss*V 35,731 kg =Px,vss*SRTmass of mlss Xtss*V 43,731 kg =Px,tss *SRT

Part 14 Determine AB volume V =Mtss / XtssV = 12,862 m3 454,219 f3 basin size

determine AB HRT t= 4.6 hr =V/Qcalculate MLVSS frac VSS= 0.817 =(Xvss/Xtss)

MLVSS 2,778 mg/l =(VSS/TSS)*(MLSS)

Part 15 Determine F:M and volumetric loading ratefood to micro-organism F:M = 0.26 kg/kg/d = (Q*So)/(X*V)volumetric loading rates Lorg = 0.72 kg/m3*d = (Q+So)/V

Part 16 Calculate Observed Yield Yobs = = TSS/bCODbCODrem= 14,861 kg/d = Q(So-S)

Based on TSS YobsTSS = 0.536 gTSS/ gbCOD = Px,TSS / bCODrem

YobsTSS = 0.857 g TSS/g BOD = YobsTSS *(1.6 bCOD / g BOD)

Based on VSS YobsVSS = 0.438 g TSS / g bCOD = YobsVSS * frac VSS

YobsVSS = 0.700 g TSS / g BOD = YobsVSS *(1.6 bCOD / g BOD)

Part 17 Calculate O2 Demand (Ro = OTR) = (Q*(So-S)-1.42*Px,bio + 4.57*Q*Nox)Ro = 17,496 kg O2/d 38,571 lb/d O2 Ro = 729 kg O2/hr

Part 18 Determine Supply Oxygen Transfer Requirement (Note: Example uses the Ro and OTR interchangeably)

SOTR = 1,603 kg/hr = (OTR/a*F)*((Coo,20/(b*(Cs/C20)*(Pb/Pb)*Coo20-C))*(1.024^(T-20))

Air flow rate m3/min Qair = 303.99 m3/min

Part 19 Check Alkalinity Inf Alk = 221 mg/lAlkalinity used in Nitrif. Alk consum= 217.0 g/m3 = 7.14 * Nox

Target Alk 70.0 mg/lCaCO3 mw=50 Alk Short= 66.0 mg/l = Target effluent alkalinity + alkalinity consumed - alkalinity availableNaHCO3 mw=84 Alk Demand 4,469 Kg/d 9,851 lb/d alkalinity needed (as CaCo3) lime(as Na(HCO3)) Alk Demand 7,507 Kg/d 16,550 lb/d alkalinity needed as Na(HCO3) sodium bicarbonate

Part 20 Estimate effluent BOD BODe = sBODe + (.85BOD/1.42VSS)*(.85*VSS/1.0TSS)*(TSS)BODe = 7.6 mg/l NOTE: Formula in book doesn't follow equation in book (omits dividing by 1.42)



Part 21 Secondary Clar Design Qr = RAS flowrate m3/d Qr*Xr = (Q+Qr)(X)RAS concentration: Xr = 8000 g/m3 NOTE: This presumption is higher than recommended by CSWD unless selectors are includedRAS recycle ratio: R = 0.739 = X/(Xr-X)total clarifier flow: Qclar = 117,826 m3/d Qr = Q*X/(Xr-X)total area of clarifiers: Clar Acs = 2,823 m2 30,470 f2 = Q / Clarifier loading ratearea per clarifier Each clar 2823 m2 = Acs / number of clarifiersReq'd dia of each clarifier clar dia = 59.95 m dia 197 ft diaSelected clarifier diameter clar dia = 20.00 m dia 66 ft dia This step is done to round up to the next nearest size clarifiertotal area of clarifiers: Clar Acs = 314 m2solids loading SLR = 53.132 kgMLSS/m2*hr NOTE: (recommended range is 4 - 6 )

DESIGN SUMMARY VALUE FOR VALUE FOR English UnitsPARAMETER: UNIT: BOD REMOVAL NITRIFICATION (Nitrifying)

Average wastewater flow m3/d 67,750 67,750 17.90 MGDAverage BOD load kg/d 9,314 9,314 20,491. lb/dAverage TKN load kg/d 2,832 2,832 6,243. lb/dAerobic SRT days 5 5.5 5.49 hrAeration basins number 1 1 1Aeration tank vol each m3 11598 12,862 3.40 MG

Hydraulic detention time Hours 4.1 4.6 4.56 hrMLSS ppm 3400 3400 3,400. mg/lMLVSS ppm 2,777 2,778 2,778. mg/l <-- Results differ slightly from example because intermediate answers not roundedF:M (BOD/MLVSS basis) lb/lb/d 0.29 0.26 0.26 lb/lb/d

BOD Loading kg/m3*d 0.80 0.72 56.4 lb/1000cfSludge Production kg/d 7,887 7,958 17,545. lb/dObserved Yield VSS / BOD 0.69 0.70 0.70 <-- Results differ slightly from example because intermediate answers not roundedObserved Yield TSS / BOD 0.85 0.86 0.60 <-- Results differ slightly from example because intermediate answers not roundedOxygen Required kg/hr 329.9 729.0 1,607. lb/hrAir Flowrate (ave) sm3/min 178.86 303.99 10,735. scfmRAS ratio 0.739130435 0.739130435 0.6Clarifier overflow rate m3/m2*d 24 24 589. gpd/sfClarifiers number 1 1 1Clarifiers dia (m) 60.0 60.0 196.7 ftAlkalinity needs (CaCO3) kg/d 0 4,469 9,851. lb/dEffluent BOD ppm <30 7.6 7.64 mg/lEffluent TSS ppm <30 8 8.00 mg/lEffluent Ammonia (NH4-N) ppm 30.39 2.65 2.65 mg/l

Sensitivity Analysis - Total Tank Size for Varying NH4 Target & Temp's

Ammonia Target Conc. T=10C T=12C T=14C T=16C BOD only

0.3 mg/l 35535 22314 16001 44500.5 mg/l 17271 13465 10790 8804 44501.0 mg/l 9933 8247 6902 5813 44502.0 mg/l 7617 6420 5436 4621 4450



5.0 mg/l 6435 5459 4647 3968 445015 mg/l 5946 5056 4314 3690 445025 mg/l 5850 4978 4248 3635 4450(Results in orange are lower than value for BOD removal only)(Numbers reflect size required for all tanks in M3)(All other variables held constant)

Metcalf & Eddy 5th International Edition, Example 8-7, Part A (Continuation of design of Example 8-3)Preanoxic Denitrification Process Design for MLE ProcessGiven (same as for example above - variables will be pulled from above example where called for)Assumptions:Nitrate Conc in RAS 6.00 g/m3 (Which one might also call the target effluent nitrate concentration)Mixing HP for Anoxic 5.00 kW/1000m3 (general design presumption)

Solution: Part 1 Determine Active Biomass Conc. (Xb) Using Eq 7-42

1 Xb 1898.62487 g/m3 = (Q*SRT/V)*(Yn*(S.-S)/(1+(Bn*SRT))

Ne = aerobic tank NO3-N 6.00 g/m3 Presumed value, not calculated2 IR = internal recycle ratio 3.33 unitless = NO3 / Ne -1.0 - R

Flowrate to anoxic tank3 Qanox 275,359 m3/d <-- note result shown in M&E has numbers juxtaposed

Nox feed 1,652,157 g/d = Anoxic tank flow * nitrate concentration4 Determine the anoxic vol

Anoxic Tank Proportion 0.176 v/v (Initially used 20%, but then rounded down to t=2.5hrs which equates to a proportion of 17.6%)t (initial presumption) 0.8 hr NOTE: Example uses "as a first approximation" value of 2.5 hrs instead of 2.8 hrs - unclear whyt 0.033 dvnox 2,264 m3 = t * Q

5 F/Mb 2.17 = (Q*So)/(Vnox*Xb)6 Determine the SDNR (equation 8-57)

SDNR 0.34 gNO3-N/gMLVSS = bo + b1 * [ln (F/Mb)] (variables identified below)

rbCOD % 0.266666667 (round to 30%) (example rounds up to 30% for estimation of bo and b1 at table 8-22bo 0.235 From Table 8-22 - interpolation between the 20% and 30% values for rbCOD would be more accurateb1 0.141 From Table 8-22 SDNR12 at q temp corr: 0.290 g/g*d = SDNR * 1.026^(T-20)

SDNRadj 0.256 = SDNR12 - 0.029 (ln F/Mb) - 0.012

7 Determine the overall SDNR based on MLVSS

SDNR 0.20 gNO3-N/gMLVSS = SDNRb(MLVSSb / MLVSS)

8 Determine amt of NO3-N that can be reduced (equation 8-51)NOr 1,248,271 g/d = (Vnox) * (SDNR) * (MLVSS,biomass)

Excess Capacity -24.4459498 % excess9 Estimate Oxygen Credit

Oxygen Credit 4,725 kg/d = (2.86g O2 / g NO3) * (NO3created - NO3e) * Q * (1kg/1000g)Oxygen Credit 196.9 kg/hr = kg/d / 24 hr/dNet O2 Required 532.1 kg/hr

10 Check AlkalinityAlkalinity Produced 87.1 g/m3 = 3.57 * (28.9 - 6 ) = 81.8 g/m3Alkalinity needed -21.1 g/m3 = (residual alkalinity - initial alkalinity + alkalinity consumed - alkalinity regained)mass of alkalinity req'd -1,430 kg/d as CaCO3Alkalinity Savings 5,898 kg/d as CaCO4



11 Anoxic mixing energy 11 kW = Vol * ( Energy /vol )

12 SUMMARY TABLE: Unit

Effluent NO3-N g/m3 6.00Internal Recycle Ratio Unitless 3.3RAS Recycle Ratio Unitless 0.739130435Anoxic Volume m3 2264MLSS g/m3 3400Overall SDNR g/g NO3/MLVSS 0.20Detention Time h 0.8Reduction in O2 Demand % 27.0%Mixing Power kW 11Alkalinity Required kg/d as CaCO3 -1,430 132% less alkalinity



As a result, there are 4 reactors-in-series for each treatment train.

even though there are not specific reactors separated by internal baffle walls.

a. The calculation for equivalent continuously-stirred tank reactors (CSTRs) in series is found in USEPA's Design Manual - Fine Pore Aeration Systems (1989) with the following:

b. Conservatively, the number of reactors for AB 5, 6, and 7 are: N = 1 (anoxic zone), N = 4 (aerobic zones)c. The aeration grid layout will be evaluated in more detail to ensure that the design accommodates the proposed aeration demands.

Effluent NH3-N (mg/L) 1.457

Nitrogen mass balances for AB 1-4 and AB 5-7 individually

Flow Fraction going to AB 1-4 0.42Q1-4 28455 m3/dV1-4 7101 m3

HRT 0.250 days

Qr/Q 2.02 RAS + MLR recycle ratioSRT 5.49NOX 31.0 mg N/L

Xn = (SRT*Yn*Nox)/((V/Q)*[1 + bn*SRT]) 57.80 g/m3 (Concentration of nitrifiers)

Number of equivalent reactors in series 4Rate Expression for nth stage Rn,i=(mumax,AOB at T/YAOB)(SNH4/SNH4+KNH4)(So/So+Ko,AOB)XAOB

Iterative solution Initial Guess -- Ni 1.95 g/m30.8 at 13.0 deg-C, 0.68 at 13.4 deg-C

Iterative solutions (must use Solver in Excel) DO in react

N4 = 1.9 g/m3 = ((1 + QR/Q)*N1+(mumax,aob at T/Yn)*(N1/(N1+KNH4)*(So/(So+KO,aob))*XAOB)*(V/Q)-NOx)/(QR/Q) 0 N1= 11.58 g/m3

N1 = 11.6 g/m3 = ((1 + QR/Q)*N2+(mumax,aob at T/Yn)*(N2/(N2+KNH4)*(So/(So+KO,aob))*XAOB)*(V/Q))/(1+QR/Q) 2 N2= 8.17 g/m3



Iteration Check OK

Is target nitrification met by Final Reactor? OK

Flow Fraction going to AB 5-7 0.58

Design Example of Metcalf & Eddy "Wastewater Engineering" 5th International Edition (2014), Example 8-61. The SCTP utilizes two different bioreactor configurations, both of which are more represented by a reactor-in-series (e.g. - staged CSTRs for Nitrification) methodology to determine the associated nitrification performance.2. Aeration Basins 1 - 4 (operating with flow from AB 1 to AB 3, AB 2 to AB 4) result in two trains, each with one anoxic zone followed by three aerobic zones. These zones all of fixed baffles walls separating the environments.

3. Aeration Basins 5, 6, and (New) 7 utilize long, narrow channels representing more of a plug-flow environment. This plug-flow environment is best represented using a reactor-in-series methodology,

Solver Results

SCTP Aeration Basin Performance -- Wet Weather Minimum 7-Day Temperature (CSTR-in-Series Method)

How to use the Solver function to iterate the equations below:Enable Excel SOLVER Add‐on.1. Enter initial guess for final reactor concentration in Cell Q262. Go to Data tab, click Solver, and configure Solver with the following parameters

Set Objective: Q28; By Changing Variable Cells: V28; Subject to the Constraints: Q28=Q263. Go to Data tab, click Solver, and configure Solver with the following parameters

Set Objective: Q29; By Changing Variable Cells: V29; Subject to the Constraints: Q29=V284. Go to Data tab, click Solver, and configure Solver with the following parameters


Set Objective: Q31; By Changing Variable Cells: V31; Subject to the Constraints: Q31=V306. Check Cell Q32 to see if iterative result is sufficiently close to initial guess.

SCTP Aeration Basin Performance Calculations - Wet Weather Minimum 7-Day Temperature - CSTR-In-Series Method


Q5-7 39295 m3/d

V5-7 9880 m3

HRT 0.251 daysQr/Q 2.02 RAS recycle ratioSRT 5.49Number of equivalent reactors in series 5Xn = (SRT*Yn*Nox)/((V/Q)*[1 + bn*SRT]) 57.38 (Concentration of nitrifiers)

Rate Expression for nth stage Rn,i=(mumax,AOB at T/YAOB)(SNH4/SNH4+KNH4)(So/So+Ko,AOB)XAOB








Iteration Check OKIs target nitrification met by Final Reactor? OK

Solver Results

How to use the Solver function to iterate the equations above:Enable Excel SOLVER Add‐on.1. Enter initial guess for final reactor concentration in Cell Q482. Go to Data tab, click Solver, and configure Solver with the following parameters






SCTP Aeration Basin Performance Calculations - Wet Weather Minimum 7-Day Temperature - CSTR-In-Series Method




Aerobic SRT (days)

Eff NH3-N (mg/L)

Eff BOD5 (mg/L)

3.43 MG 0.852 5.5 3.00 7.64



Aerobic SRT (days)

3.43 MG 0.85 5.5


influent Design Flow 67,749 (M3/D) equals: 17.897451 mgd Flow of Primary EffluentOxygen conc. leaving AB 2 %O2 Conversion 17.9 MGD 67,749. M3/d (equivalent M3/d)










bCOD/BOD ratio 1.6


NOTE 6 (by CH2M/Jacobs): The Phase 5B Expansion at the Salmon Creek WWTP includes - New Aeration Basin (AB 7), New Secondary Clarifier (SC 5, replacing SC 2), Additional RAS pumping, Additional aeration blowers (as detailed in Chapter 6 of the updated Engineering Report, currently in development).

NOTE 7 (by CH2M/Jacobs): These methodologies are presented in M&E (Metcalf & Eddy/AECOM, Wastewater Engineering - Treatment and Resource Recovery, 5th Edition McGraw-Hill Education, New York, NY. 2014), for single-stage CMAS (Example 8-3, page 783) and for the evaluation of staged reactors for nitrification (Example 8-6, page 783).


Calculation Results



NOTE 2: Values in Yellow are "site specific" data (confirm these are valid if using this format to validate a different scenario)

NOTE 3: Example appears valid if constrained to require SRT = 7.0 d or more for nitrification

SCTP Aeration Basin Performance -- Wet Weather Minimum Day Temperature (CMAS Method)Adapted from Design Example of Metcalf & Eddy "Wastewater Engineering" 5th International Edition (2014), Example 8-3NOTE 1: Example is for treating primary clarifier effluent, primary clarifiers not designed here.

SCTP Aeration Basin Performance Calculations - Wet Weather Minimum Day Temperature - CMAS Method


effluent tgt Effluent sBOD 1.86 mg/l <------- (Effluent BOD target (not soluble BOD) = 15mg/L) Based on calcs from DMR data using M&E UBOD & eff VSS values

effluent tgt Effluent TSS 8 mg/l Average Wet Weather effluent TSS (2010-2017)

effluentq tgt NH4-N (nitrifying) 3 mg/l (= SNH4) Reflects the achievable NH3-N conc in the available basin by CMAS methodClarifier Loading rate 24 m3/m2*d (Std range = 16-28 m3/m2*d) 589 gpd/sfNumber of Clarifiers 1 ea (low range should be used when peaking factors are high)

Number of Aeration Basins 1 eaDiffuser clean H2O OTE 31%Depth of diffusers 5.5 (meters) (Total tank depth = 4.9 M)

plant Site Elevation 10 m

a factor (aerator) 0.5 0.65 (0.5 for BOD, & .65 for nitrification)

b factor (aerator) 0.95F fouling factor (aerator) 0.9



RAS Concentration 8000 mg/l (per section 8-3 middle of listed range of 4K-12K)

influent Temperature 13 C Note a RAS of 8,000 equates to an SVI=125 ml/g Minimum 7-day temperature (2010-2017)

Standard Temp 20 C

PART 1 Determine data neededto use formulas: bCOD = So = 219.967748 calculated as 1.6*BOD





fd 0.150















Part 5 Determine F:M F:M 0.29 kg/kg*d = (Q*So)/(X*V))Volumetric BOD Loading 0.80 kgBOD/m3*d = Q*So/V)
































fD 0.15 (Table 8-14)































BOD Loading kg/m3*d 0.80 0.72 55.9 lb/1000cfSludge Production kg/d 7,909 7,970 17,571. lb/dObserved Yield VSS / BOD 0.70 0.70 0.70 <-- Results differ slightly from example because intermediate answers not roundedObserved Yield TSS / BOD 0.85 0.86 0.60 <-- Results differ slightly from example because intermediate answers not roundedOxygen Required kg/hr 328.8 723.6 1,595. lb/hrAir Flowrate (ave) sm3/min 177.74 300.93 10,627. scfmRAS ratio 0.739130435 0.739130435 0.6Clarifier overflow rate m3/m2*d 24 24 589. gpd/sfClarifiers number 1 1 1Clarifiers dia (m) 60.0 60.0 196.7 ftAlkalinity needs (CaCO3) kg/d 0 4,291 9,459. lb/d

35000

40000

Tank Sizes v.s. Varying Eff NH4 Target at varying Temps



Effluent BOD ppm <30 7.6 7.64 mg/lEffluent TSS ppm <30 8 8.00 mg/lEffluent Ammonia (NH4-N) ppm 30.02 3 3.00 mg/l



0.3 mg/l 35535 22314 16001 44500.5 mg/l 17271 13465 10790 8804 44501.0 mg/l 9933 8247 6902 5813 44502.0 mg/l 7617 6420 5436 4621 44505.0 mg/l 6435 5459 4647 3968 445015 mg/l 5946 5056 4314 3690 445025 mg/l 5850 4978 4248 3635 4450(Results in orange are lower than value for BOD removal only)(Numbers reflect size required for all tanks in M3)(All other variables held constant)











SDNRadj 0.252 = SDNR12 - 0.029 (ln F/Mb) - 0.012


0

5000

10000

15000

20000

25000

30000

0.3 mg/l 0.5 mg/l 1.0 mg/l 2.0 mg/l 5.0 mg/l 15 mg/l 25 mg/l

T=12C T=14C T=16C T=10C BOD only




8 Determine amt of NO3-N that can be reduced (equation 8-51)NOr 1,243,143 g/d = (Vnox) * (SDNR) * (MLVSS,biomass)



10 Check AlkalinityAlkalinity Produced 85.7 g/m3 = 3.57 * (28.9 - 6 ) = 81.8 g/m3Alkalinity needed -22.4 g/m3 = (residual alkalinity - initial alkalinity + alkalinity consumed - alkalinity regained)mass of alkalinity req'd -1,519 kg/d as CaCO3Alkalinity Savings 5,809 kg/d as CaCO4



Effluent NO3-N g/m3 6.00Internal Recycle Ratio Unitless 3.3RAS Recycle Ratio Unitless 0.739130435Anoxic Volume m3 2285MLSS g/m3 3400Overall SDNR g/g NO3/MLVSS 0.20Detention Time h 0.8Reduction in O2 Demand % 26.8%Mixing Power kW 11Alkalinity Required kg/d as CaCO3 -1,519 135% less alkalinity










HRT 0.250 days










Iteration Check OK




Solver Results

2. Aeration Basins 1 - 4 (operating with flow from AB 1 to AB 3, AB 2 to AB 4) result in two trains, each with one anoxic zone followed by three aerobic zones. These zones all of fixed baffles walls separating the environments.

SCTP Aeration Basin Performance -- Wet Weather Minimum Day Temperature (CSTR-in-Series Method)Design Example of Metcalf & Eddy "Wastewater Engineering" 5th International Edition (2014), Example 8-61. The SCTP utilizes two different bioreactor configurations, both of which are more represented by a reactor-in-series (e.g. - staged CSTRs for Nitrification) methodology to determine the associated nitrification performance.






SCTP Aeration Basin Performance Calculations - Wet Weather Minimum Day Temperature - CSTR-In-Series Method


Q5-7 39295 m3/d

V5-7 9880 m3

HRT 0.251 days

Qr/Q 2.02 RAS recycle ratioSRT 5.54Number of equivalent reactors in series 5Xn = (SRT*Yn*Nox)/((V/Q)*[1 + bn*SRT]) 57.92 (Concentration of nitrifiers)










Solver Results

How to use the Solver function to iterate the equations above:Enable Excel SOLVER Add‐on.1. Enter initial guess for final reactor concentration in Cell Q482. Go to Data tab, click Solver, and configure Solver with the following parameters





Set Objective: Q55; By Changing Variable Cells: V55; Subject to the Constraints: Q55=V54

SCTP Aeration Basin Performance Calculations - Wet Weather Minimum Day Temperature - CSTR-In-Series Method




Aerobic SRT (days)

Eff NH3-N (mg/L)

Eff BOD5 (mg/L)

3.43 MG 0.820 7.1 0.725 5.750



Aerobic SRT (days)

3.43 MG 0.85 6.8


influent Design Flow 57,216 (M3/D) equals: 15.114946 mgd Flow of PE (Reduced by PF of 1.218 based on DMR data 2010-2017)Oxygen conc. leaving AB 2 %O2 Conversion 17.8 MGD 67,445. M3/d (equivalent M3/d)










bCOD/BOD ratio 1.6


NOTE 6 (by CH2M/Jacobs): The Phase 5B Expansion at the Salmon Creek WWTP includes - New Aeration Basin (AB 7), New Secondary Clarifier (SC 5, replacing SC 2), Additional RAS pumping, Additional aeration blowers (as detailed in Chapter 6 of the updated Engineering Report, currently in development).

NOTE 7 (by CH2M/Jacobs): These methodologies are presented in M&E (Metcalf & Eddy/AECOM, Wastewater Engineering - Treatment and Resource Recovery, 5th Edition McGraw-Hill Education, New York, NY. 2014), for single-stage CMAS (Example 8-3, page 783) and for the evaluation of staged reactors for nitrification (Example 8-6, page 783).


Calculation Results



NOTE 2: Values in Yellow are "site specific" data (confirm these are valid if using this format to validate a different scenario)NOTE 3: Example appears valid if constrained to require SRT = 7.0 d or more for nitrification

SCTP Aeration Basin Performance -- Dry Weather Minimum 7-Day Temperature (CMAS Method)Adapted from Design Example of Metcalf & Eddy "Wastewater Engineering" 5th International Edition (2014), Example 8-3NOTE 1: Example is for treating primary clarifier effluent, primary clarifiers not designed here.

SCTP Aeration Basin Performance Calculations - Dry Weather Minimum 7-Day Temperature - CMAS Method


effluent tgt Effluent sBOD 0.76 mg/l <------- (Effluent BOD target (not soluble BOD) = 15mg/L) Based on calcs from DMR data using M&E UBOD & eff VSS values

effluent tgt Effluent TSS 6.89 mg/l Average Dry Weather effluent TSS (2010-2017)

effluentq tgt NH4-N (nitrifying) 0.725 mg/l (= SNH4) Reflects lowest achiev NH3-N conc in avail volume by CMAS methodClarifier Loading rate 24 m3/m2*d (Std range = 16-28 m3/m2*d) 589 gpd/sfNumber of Clarifiers 1 ea (low range should be used when peaking factors are high)

Number of Aeration Basins 1 eaDiffuser clean H2O OTE 31%Depth of diffusers 5.5 (meters) (Total tank depth = 4.9 M)

plant Site Elevation 10 m

a factor (aerator) 0.5 0.65 (0.5 for BOD, & .65 for nitrification)

b factor (aerator) 0.95F fouling factor (aerator) 0.9



RAS Concentration 8000 mg/l (per section 8-3 middle of listed range of 4K-12K)

influent Temperature 16.9 C Note a RAS of 8,000 equates to an SVI=125 ml/g Min 7-day Dry Weather temperature (2010-2017)

Standard Temp 20 C

PART 1 Determine data neededto use formulas: bCOD = So = 223.1931915 calculated as 1.6*BOD





fd 0.150















Part 5 Determine F:M F:M 0.30 kg/kg*d = (Q*So)/(X*V))Volumetric BOD Loading 0.83 kgBOD/m3*d = Q*So/V)
































fD 0.15 (Table 8-14)































BOD Loading kg/m3*d 0.83 0.61 47.8 lb/1000cfSludge Production kg/d 6,527 6,219 13,711. lb/dObserved Yield VSS / BOD 0.67 0.63 0.63 <-- Results differ slightly from example because intermediate answers not roundedObserved Yield TSS / BOD 0.82 0.78 0.60 <-- Results differ slightly from example because intermediate answers not roundedOxygen Required kg/hr 291.6 676.8 1,492. lb/hrAir Flowrate (ave) sm3/min 161.43 288.24 10,179. scfmRAS ratio 0.739130435 0.739130435 0.6Clarifier overflow rate m3/m2*d 24 24 589. gpd/sfClarifiers number 1 1 1Clarifiers dia (m) 55.1 55.1 180.8 ftAlkalinity needs (CaCO3) kg/d 0 4,900 10,803. lb/d

35000

40000

Tank Sizes v.s. Varying Eff NH4 Target at varying Temps



Effluent BOD ppm <30 5.7 5.75 mg/lEffluent TSS ppm <30 6.89 6.89 mg/lEffluent Ammonia (NH4-N) ppm 33.14 0.725 0.73 mg/l



0.3 mg/l 35535 22314 16001 44500.5 mg/l 17271 13465 10790 8804 44501.0 mg/l 9933 8247 6902 5813 44502.0 mg/l 7617 6420 5436 4621 44505.0 mg/l 6435 5459 4647 3968 445015 mg/l 5946 5056 4314 3690 445025 mg/l 5850 4978 4248 3635 4450(Results in orange are lower than value for BOD removal only)(Numbers reflect size required for all tanks in M3)(All other variables held constant)











SDNRadj 0.215 = SDNRI1 - 0.0166 (ln F/Mb) - 0.078


0

5000

10000

15000

20000

25000

30000

0.3 mg/l 0.5 mg/l 1.0 mg/l 2.0 mg/l 5.0 mg/l 15 mg/l 25 mg/l

T=12C T=14C T=16C T=10C BOD only




8 Determine amt of NO3-N that can be reduced (equation 8-51)NOr 878,827 g/d = (Vnox) * (SDNR) * (MLVSS,biomass)



10 Check AlkalinityAlkalinity Produced 96.9 g/m3 = 3.57 * (28.9 - 6 ) = 81.8 g/m3Alkalinity needed -11.3 g/m3 = (residual alkalinity - initial alkalinity + alkalinity consumed - alkalinity regained)mass of alkalinity req'd -644 kg/d as CaCO3Alkalinity Savings 5,544 kg/d as CaCO4



Effluent NO3-N g/m3 6.00Internal Recycle Ratio Unitless 3.8RAS Recycle Ratio Unitless 0.739130435Anoxic Volume m3 2287MLSS g/m3 3400Overall SDNR g/g NO3/MLVSS 0.14Detention Time h 1.0Reduction in O2 Demand % 27.3%Mixing Power kW 11Alkalinity Required kg/d as CaCO3 -644 113% less alkalinity










HRT 0.296 days










Iteration Check OK




Solver Results

2. Aeration Basins 1 - 4 (operating with flow from AB 1 to AB 3, AB 2 to AB 4) result in two trains, each with one anoxic zone followed by three aerobic zones. These zones all of fixed baffles walls separating the environments.

SCTP Aeration Basin Performance -- Dry Weather Minimum 7-day Temperature (CSTR-in-Series Method)

1. The SCTP utilizes two different bioreactor configurations, both of which are more represented by a reactor-in-series (e.g. - staged CSTRs for Nitrification) methodology to determine the associated nitrification performance.






SCTP Aeration Basin Performance Calculations - Dry Weather Minimum 7-Day Temperature - CSTR-In-Series Method


Q5-7 33185 m3/d

V5-7 9880 m3

HRT 0.298 days

Qr/Q 2.02 RAS recycle ratioSRT 7.10Number of equivalent reactors in series 5Xn = (SRT*Yn*Nox)/((V/Q)*[1 + bn*SRT]) 59.10 (Concentration of nitrifiers)










Solver Results







SCTP Aeration Basin Performance Calculations - Dry Weather Minimum 7-Day Temperature - CSTR-In-Series Method


Scenario Calculation MethodTemperature

(deg-C)Inf NH3-N

(mg/L)Eff NH3-N

(mg/L)Eff BOD5

(mg/L)Eff TSS (mg/L)

Aer SRT (d)

Overall SRT (d)

Yield(lb/d)

CMAS 13.4 31.0 2.7 7.6 8.0 5.5 7.2 0.85CSTR-in-Series 13.4 31.0 1.5 7.6 8.0 5.5 7.2 0.85



Wet Weather Min 7-Day Temp

Wet Weather Min Day Temp

Dry Weather Min 7-Day

Aeration Basin Performance Summary

SCTP Phase 5B Aeration Basin Performance Summary


Flowstream ID Flow Designer Comments

ADMM (MGD) ADMM (lb/d) ADMM (mg/L) ADMM (lb/d) ADMM (mg/L) ADMM (lb/d) ADMM (mg/L)

RS 17.5 30520 209 35770 245 4006 27.5 Values linked from "Proposed_Phase_5B_Sizing" tab

PE 17.8975 20521 137 16046 107 4633 31.0 Values linked from "Proposed_Phase_5B_Sizing" tab

ML 29.5 351698 1428 837375 3400 359 1.46 BOD of ML assumed at 42% of TSS based on designer experience

SE 17.5 1115 7.64 1168 8.00 213 1.46 Values linked from "AB_Perf_WW_MinWeekTemp" tab

PLE 17.5 1115 7.64 1168 8.00 213 1.46 Values linked from "AB_Perf_WW_MinWeekTemp" tab

RAS 11.6 248632 2563 621580 6407 141 1.46 BOD of RAS assumed at 40% of TSS (same as ML)

WAS 0.413 9079 2563 17545 6407 652.68 1.46 BOD of WAS assumed at 40% of TSS (same as ML)

TWAS 0.033 5965 22000 14913 55000 0.395 1.46 BOD of TWAS assumed at 40% of TSS (same as WAS)

PS 0.067 10682 19192 24069 43245 17.3 31.0 TSS linked from "Proposed_Phase_5B_Sizing"

BSD 0.099 16647 20112 40666 49131 17.7 21.4

DS 0.099 3093 3736 20618 24909 1134 1370 BOD of DS=15% of TSS, NH3 of DS=5.5%. Using VSR=42%

TF 0.380 1053 332 2632 830 4.62 1.46

DF 0.084 263 374 1750 2494 648 923 BOD of DF=15% of TSS, NH3 of DF=37% based on designer experience

FLT 0.464 1053 272 2632 680 648 167 Combined TF & DF

DB 0.015 2830 22500 18867 150000 486 3866

BOD TSS NH3‐N

Plant Mass Balance

SCTP Phase 5B Mass Balance


SOR to AOR Ratio Calculation Index Num 1 Water Temp Maximum Vapor Press

Maximum Water Temperature: 22.8oC Altitude Atm Press deg C DO mm of Hg

Aeration Basin Side Water Depth: 15.50 feet 0 14.70 0 14.62 4.579ALPHA (): 0.55 250 14.57 1 14.22 4.926

Fouling Factor (F): 0.90 500 14.43 2 13.83 5.294ALPHA Correctional Factor (F): 0.50 750 14.38 3 13.46 5.685

BETA Correctional Factor (): 0.95 1000 14.22 4 13.11 6.101

MLSS Residual Oxygen Required: 2.0 mg/L 1500 13.88 5 12.77 6.543

Plant Altitude: 30 feet 2000 13.62 6 12.45 7.013

Air Pressure at Plant Altitude: 14.68 psia 2500 13.36 7 12.14 7.513

Effective Saturation Depth Ratio (de): 18% 3000 13.11 8 11.84 8.045

Water Pressure at de: 1.21 psig 3500 12.86 9 11.56 8.609

Water Vapor Pressure at Maximum Water Temperature: 0.38 psig 4000 12.62 10 11.29 9.209OMEGA - D.O. Pressure Correction Factor (): 0.9990 4500 12.38 11 11.03 9.844

Surface Saturated D.O. Concentration @ 20 C & 1 atm (C*s20): 9.09 mg/L 5000 12.15 12 10.78 10.518

Surface Saturated D.O. Concentration @ 23 C & 1 atm (C*s23): 8.74 mg/L 5500 11.91 13 10.54 11.231Average Saturated D.O. Concentration at 20 C & 1 atm ('C*): 9.86 mg/L 6000 11.69 14 10.31 11.987

TAU - D.O. Temperature Correction Factor (): 0.9615 6500 11.47 15 10.08 12.788

THETA - KLa Temperature Correction Factor (): 1.024 7000 11.22 16 9.87 13.634

AOR to SOR Conversion Factor: 2.664 7500 11.04 17 9.67 14.530

8000 10.82 18 9.47 15.477

19 9.28 16.477

Atm. Press at Elevation Interpolation 20 9.09 17.535

14.7 14.565 21 8.91 18.650

0 250 22 8.74 19.827

23 8.58 21.068

24 8.42 22.377

25 8.26 23.756

26 8.11 25.209

27 7.97 26.739

28 7.83 28.349

29 7.69 30.043

30 7.56 31.824

31 7.43 33.695

32 7.31 35.663

33 7.18 37.729

34 7.07 39.898

35 6.95 42.175

36 6.84 44.563

37 6.73 47.067

38 6.62 49.692

39 6.52 52.442

40 6.41 55.324

Aeration Basins 1‐4

SCTP Aeration Basins 1 - 4 AOR to SOR Calculations


SOR to AOR Ratio Calculation Index Num 1 Water Temp Maximum Vapor Press

Maximum Water Temperature: 22.8oC Altitude Atm Press deg C DO mm of Hg

Aeration Basin Side Water Depth: 20.00 feet 0 14.70 0 14.62 4.579ALPHA (): 0.55 250 14.57 1 14.22 4.926

Fouling Factor (F): 0.90 500 14.43 2 13.83 5.294ALPHA Correctional Factor (F): 0.50 750 14.38 3 13.46 5.685

BETA Correctional Factor (): 0.95 1000 14.22 4 13.11 6.101

MLSS Residual Oxygen Required: 2.0 mg/L 1500 13.88 5 12.77 6.543

Plant Altitude: 30 feet 2000 13.62 6 12.45 7.013

Air Pressure at Plant Altitude: 14.68 psia 2500 13.36 7 12.14 7.513

Effective Saturation Depth Ratio (de): 26% 3000 13.11 8 11.84 8.045

Water Pressure at de: 2.25 psig 3500 12.86 9 11.56 8.609

Water Vapor Pressure at Maximum Water Temperature: 0.38 psig 4000 12.62 10 11.29 9.209OMEGA - D.O. Pressure Correction Factor (): 0.9990 4500 12.38 11 11.03 9.844

Surface Saturated D.O. Concentration @ 20 C & 1 atm (C*s20): 9.09 mg/L 5000 12.15 12 10.78 10.518

Surface Saturated D.O. Concentration @ 23 C & 1 atm (C*s23): 8.74 mg/L 5500 11.91 13 10.54 11.231Average Saturated D.O. Concentration at 20 C & 1 atm ('C*): 10.52 mg/L 6000 11.69 14 10.31 11.987

TAU - D.O. Temperature Correction Factor (): 0.9615 6500 11.47 15 10.08 12.788

THETA - KLa Temperature Correction Factor (): 1.024 7000 11.22 16 9.87 13.634

AOR to SOR Conversion Factor: 2.617 7500 11.04 17 9.67 14.530

8000 10.82 18 9.47 15.477

19 9.28 16.477

Atm. Press at Elevation Interpolation 20 9.09 17.535

14.7 14.565 21 8.91 18.650

0 250 22 8.74 19.827

23 8.58 21.068

24 8.42 22.377

25 8.26 23.756

26 8.11 25.209

27 7.97 26.739

28 7.83 28.349

29 7.69 30.043

30 7.56 31.824

31 7.43 33.695

32 7.31 35.663

33 7.18 37.729

34 7.07 39.898

35 6.95 42.175

36 6.84 44.563

37 6.73 47.067

38 6.62 49.692

39 6.52 52.442

40 6.41 55.324

Aeration Basins 5‐7

SCTP Aeration Basins 5 - 7 AOR to SOR Calculations


Appendix B Salmon Creek Treatment Plant Phase

4 Odor Control Update

T E C H N I C A L M E M O R A N D U M

1

Salmon Creek Treatment Plant Phase 4 Odor Control Update

PREPARED FOR: John Peterson/Clark Regional Wastewater District

COPY TO: File

PREPARED BY: Alex Demith/CH2M

DATE: July 28, 2017

PROJECT NUMBER: 688766.03.30.04

Introduction The Salmon Creek Treatment Plant (SCTP) is a typical secondary treatment plant comprised of common unit processes that, in addition to the important work of treating wastewater, also generate odors as a byproduct of the various physical and biological treatment processes. These odors are primarily hydrogen sulfide (H2S) and smaller amounts of other organic reduced sulfur compounds (methyl mercaptans, dimethyl disulfide, etc.), all traditionally associated with secondary treatment plants. These odors can drift across plant property lines and affect nearby residents. This technical memorandum (TM) provides a comprehensive evaluation of odor control offsite impacts related to the SCTP and makes recommendations for meeting regulatory requirements pertaining to odor emissions.

Background In 2005, CH2M completed a preliminary design for the Phase 4 Expansion Program for the SCTP where a variety of odor control upgrades were explored. As a result of this effort, an odor control system was constructed for treating foul air from the Sludge Blend Tank, and a separate odor control system was constructed for serving the 117th Street Pump Station (also known as the Klineline Pump Station) force main discharge at SCTP. A preliminary design was also completed which included a bioscrubber/bio-trickling filter to treat foul air from the headworks and primary clarifiers. However, the implementation of this odor control system was deferred due to lack of an explicit regulatory permit driver at the time and lack of financial resources available for the program.

In March 2007, odor sampling and odor dispersion modeling activities were performed pertaining to the SCTP for the purpose of characterizing the odor footprint at the SCTP.

Since the work was completed in 2005 and 2007, multiple changes have occurred that justify updating the previous analysis for understanding future needs for the facility. These changes include the following:

• Residences (odor receptors) have been and are continuing to be constructed in close proximity to the plant. This means that current and future odor receptors are located closer to the SCTP than previously identified.

• Emissions (specifically toxic air pollutants) regulatory requirements have changed since completion of the previous work.

• Technologies including bio-trickling filters and biofilter medias have evolved and improved since completion of the previous work. Specifically, acceptable loading rates (both bed velocity and inlet

PHASE 4 ODOR CONTROL UPDATE

2

odor loadings) have gradually increased, making required footprints smaller. In addition, media types have improved, with longer life media now available.

Purpose This TM provides an update to previous work completed, including the following:

• Dispersion model update to account for additional odor receptors encroaching closer to the SCTP boundary.

• Dispersion model update to determine how toxic air pollutant (TAP) emissions regulatory requirements can be met.

• Updated technology evaluation of specific biological technologies to capture recent advances in the field and make recommendations for most preferred vapor phase odor control approach for SCTP.

• Updated costs for selected vapor phase odor control systems.

This TM provides a comprehensive odor evaluation that builds on previous work completed and provides a current update for facilitating funding decisions and capital improvements implementation plans moving forward.

Phase 4 Odor Control System Preliminary Design In 2005, CH2M completed a preliminary design for the Phase 4 Expansion Program for the SCTP. This effort included an evaluation of various odor control technologies capable of serving preliminary treatment (headworks) and primary treatment (primary clarifiers).

Odor Control System Sizing Criteria As part of the Phase 4 effort, detailed ventilation calculations were completed. These ventilation rates were identified as meeting the following objectives:

• Provide adequate ventilation to protect maintenance personnel within occupied spaces per National Fire Protection Association (NFPA) 820, Fire Protection in Wastewater Treatment and Collection Facilities, 1999 Edition.

• Maintain a minimum negative pressure of 0.1-inch water column (wc) within wastewater holding tanks and raw wastewater sewers to contain odors under the following conditions:

− Dynamic liquid level changes − Estimated crack openings in storage tank covers treated as sharp-edged orifices

• When a single access cover is removed, maintain sufficient velocities across the opening to prevent fugitive odors.

• Provide adequate turnover rate and air scavenging within storage tanks to reduce corrosion resulting from H2S pockets.

These criteria remain applicable with the exception of the 1999 edition of NFPA 820, which has been superseded by the 2016 version, adopted in June 2015. It should be noted that the 2016 version has no substantive changes pertaining to preliminary or primary facilities and therefore the ventilation values identified during the previous work remain applicable.

The previous predicted foul air flows from each preliminary/primary source at SCTP are summarized in Table 1.


3

Table 1. Foul Air Flow Rates and Sizing Criteria Summary

Location Air Flow

(ft3/minute) Air

(ACH) Sizing Criteria Summary

Headworks

Dumpster Room 1,000 7.2 Flow rate necessary to prevent buildup of interior odors by introducing sufficient dilution air. Based on past experience at similar process facilities.

Screen Channel 500 NA Flow rate necessary to maintain a negative 0.1-inch wc within channel under normal operating conditions assuming normal checkered plate, closed covers, and open cracks around checker plate openings. Flow rate necessary to maintain high capture velocity of > 50 fpm across open hatches.

Screen Room 11,100 15.5 Flow rate necessary to provide (1) adequate cooling in summer months due to heat generation, (2) exceedance of NFPA 820 ventilation criteria of 12 ACH, and (3) prevention of buildup of interior odors by introducing sufficient dilution air.

Primary Clarifiers

Underside of Covers 8,000 8.3 Flow rate necessary to (1) maintain a negative 0.1-inch wc under clarifier covers under normal operating conditions assuming typical cover tightness (crack opening of 0.02%), (2) maintain high capture velocity of > 50 fpm across open hatches, and (3) prevent pockets of corrosive H2S from accumulating by creating adequate scavenging velocities (~ 25 fpm).

Total at All Locations

Total 21,100 N/A N/A

ACH = air changes per hour; fpm = feet per minute; ft3/minute = cubic feet per minute; N/A = not applicable.

Vapor-phase Odor Control Technology Evaluation Four technologies were evaluated in the previous TM. These included packed chemical towers, mineral biofilters, organic biofilters, and bio-trickling filters.

Packed Chemical Towers

Packed chemical towers are a common form of wet scrubbers used for odor control in municipal wastewater treatment plants. They are a proven technology and have been the technology of choice for many wastewater treatment facilities. Odor constituents including H2S, ammonia, and various organic reduced sulfur (ORS) compounds may be reduced to very low levels using multistage packed towers. These systems are extremely effective in situations with high odor concentrations and large airflows. However, when compared to other technologies such as bio-trickling filters (or bio-trickling filters [BTFs] as described herein), these systems can be costlier and pose more safety concerns due to storage and handling of chemicals. These systems also exhibit greater complexity regarding operation due to


4

additional equipment and instrumentation when compared to other technologies. For these reasons, this technology was not selected after the evaluation in the previous TM.

Mineral Biofilters and Organic Biofilters

In an organic biofilter, organic material such as wood chips and compost are used as a medium to grow sulfur-consuming bacteria. Foul air is forced into the bottom of the biofilter bed and treated air is released from the surface. The bacteria also use other odor compounds as a food source, including ammonia, amines, and various ORS compounds.

The concept and components of a mineral (or sand) biofilter are the same as for an organic biofilter, but a different medium (proprietary sandy loam) is used to host the microbial population.

Both of these types of biofilters require large footprints and the organic media requires more frequent media replacement than a bio-trickling filter or chemical packed tower. The land needed based on the estimated required airflow made these systems less favorable than the bio-trickling filter system in the evaluation.

Selected Vapor-phase Odor Control System (Bio-trickling filter)

In the previously selected bio-trickling filter technology, odorous air is blown into the bottom of the tower and flows up through the media material, exiting through an exhaust stack. The media may be a synthetic material or a natural material such as lava rock. The bacteria also use other odor compounds as a food source, including ammonia and various ORS compounds. A typical bio-trickling filter schematic is shown in Figure 1. It should be noted that two types of systems are available; a bio-trickling filter (also known as a bioscrubber) in which scrubbant is recirculated over the media, and a BTF in which once-through irrigation water is applied over the top of the media. Bioscrubbers are generally more suitable for targeting H2S odors while BTF’s are more capable of treating a broad spectrum of odorants. This is because a gradient of bacteria (both low pH and neutral pH) generally exists within the BTF media bed, allowing for a greater removal of complex odorants. Low pH bacteria (autotrophic thiobacillus) specifically targets H2S) while neutral pH bacteria (heterotrophic bacteria) targets ORS compounds.

Earlier design bed velocities for bio-trickling filters were limited to 50 fpm maximum. However, advances in this technology as well as BTFs have gradually shifted acceptable bed velocities to as high as 100 to 200 fpm; although 100 fpm is considered an appropriate high end value that can be achieved by multiple suppliers.

The required empty bed gas residence time (EBGRT) ranges between 10 and 14 seconds, depending on odor loading rate. The design head loss through the media bed can range between 0.2 and 0.5 inch water column (WC) per foot of bed depth, depending on bed velocity selected and type of media. The required footprint for this technology is generally smaller than for biofilters. For all bioscrubber systems, a scrubbant recirculation pump is required to keep the media moist and maintain some biomass in solution. This is not the case with BTFs, in which makeup water is sprayed over the top of the media and

Figure 1. Simplified Schematic Diagram of a Bio-trickling filter System


5

drained out the bottom without recirculation. BTF suppliers include BioAir, Azzuro, and EcoVerde. Because of the synthetic nature of the media, supplemental nutrients are generally added for maintaining biomass health. However, if secondary effluent is available and meets specific water quality requirements, then supplemental nutrients are not required.

Preliminary Design Findings for Vapor-phase Odor Control Technology

The four vapor-phase odor control technologies were evaluated based on both cost and non-cost criteria. As a result of the evaluation findings, the recommended preliminary/primary odor control system for the previous Phase 4 work was determined and is summarized in Table 2.

Table 2. Bio-trickling filter Design Criteria


Tower Type Counterflow

Media Type Synthetic

Media Depth 12 feet (two 6-foot stages)

Tower Vessel Three @ 12-foot-diameter & 28 feet high

Bed Velocity 67 fpm (three duty units); 100 fpm (with one vessel down for maintenance)



Fan Type: FRP Centrifugal Capacity: 22,600 ft3/minute @ 7.2-inches wc Motor: 60 hp



FRP = fiberglass-reinforced plastic; hp = horsepower.

Bio-trickling filter technology was previously selected based on its low life-cycle cost, high qualitative rating, and consistent approach when considering the blend tank bio-trickling filter system currently operated at the plant. The main unfavorable factor related to this technology was the relatively high initial capital cost compared to the other technologies evaluated. The mineral biofilter alternative requires extensive footprint, which makes this alternative unfavorable. The compost biofilter alternative exhibits high initial costs associated with concrete work to enable media change-out in addition to high operating costs associated with frequent media change-out, which makes this alternative less favorable. The chemical packed tower scrubber alternative was the least favorable alternative, primarily because of high operation and maintenance (O&M) costs from chemical consumption as well as system complexity and safety.

One biofilter media type that was not previously considered is high-rate long-life engineered media. This media type biofilter option is compared to an updated BTF option herein.

2007 Odor Analysis Report The Odor Analysis Report completed in 2007 summarized the offsite odor goals for the SCTP based on the Southwest Washington Clean Air Agency (SWCAA) requirements for controlling nuisance odors. The report also summarized the results of an odor survey completed in August 2006 and the results of a dispersion model predicting offsite impacts. Two control scenarios were then developed to provide options for future consideration and long-range planning/programming.


6

Offsite Odor Goals The offsite odor goals described in the Odor Analysis Report were based on controlling nuisance odors, described by the SWCAA, at nearby sensitive receptor locations (neighboring houses). Target threshold values were selected for both H2S and total odor. The target chosen for H2S concentration at sensitive receptor locations adjacent to SCTP was 10 micrograms per cubic meter (µg/m3) (6.54 parts per billion by volume [ppbV]). The target chosen for total odor concentration at sensitive receptor locations adjacent to SCTP was 10 dilutions-to-threshold (D/T) with 100 percent compliance.

D/T is defined via odor tests conducted in an odor laboratory where air samples containing a combination of odorous compounds are diluted with clean air to below detectable concentrations and then introduced to a gas delivery system. A panel of eight members trained in odor response serves as the odor “detectors” for the sample. Panel members are asked to smell air samples delivered to a nose cone piece. By depressing buttons, the panelist introduces three distinct samples, one with the diluted sample and two with clean dilution air. Panel members are then asked whether they can detect a difference in the odor of the samples. If they cannot, the sample concentration is then increased by a given dilution amount, and the test is repeated. This process continues until half the panel members can detect the sample odor. This final level of sample concentration is called detection threshold (DT). Field olfactometry utilizes a field olfactometer, which dynamically dilutes the ambient air with carbon-filtered air in distinct dilution ratios known as D/T, indicating the number of dilutions of pure air required to get to the threshold of detection. The calculation method for field olfactometry (D/T) is slightly different from the calculation of the dilution factor in laboratory olfactometry (DT).

These target threshold values were chosen based on the concentrations of D/T and H2S that typically cause odor complaints. The target threshold for H2S is higher than its actual odorant detection thresholds. The detection threshold for H2S is approximately 0.5 - 1 ppbV. However, based on prior experience, odor complaints do not typically occur until H2S concentrations reach 7–10 ppbV (10.7–15.3 µg/m3). Similarly, the concentration in air at which odors from wastewater plants typically cause nuisance odor complaints is approximately 10 D/T.

Odor Survey The odor survey described in the previous report consisted of a sampling effort completed in August of 2006 that involved measuring H2S, dissolved sulfides, and odor (D/T) at the following sources:

• Primary clarifiers • Aeration basins • Secondary clarifiers • Sludge blend tank odor control • Biosolids blend tank • Biosolids Storage bunkers

It should be noted that the headworks, which is a major contributor to offsite odors/H2S, is not in the list above and was not measured as a part of this survey in 2006. This source was already identified as a large contributor and was previously measured during an earlier study.

All sources were selected based on their potential to emit odors and H2S offsite and cause complaints. Findings from this sampling effort are illustrated in Table 3.

Table 3. H2S and Total Odor Concentrations Measured During the 2006 Odor Survey

Source Description H2S (µg/m3)/(ppbV) Total Odor (D/T)

Primary Clarifiers 1–4 244 / 160 1100

Aeration Basins 1–6 18.3 / 12.0 160


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Table 3. H2S and Total Odor Concentrations Measured During the 2006 Odor Survey

Source Description H2S (µg/m3)/(ppbV) Total Odor (D/T)

Secondary Clarifiers 1–4 13.7 / 9.0 55

Biosolids Blend Tank 825 / 540 2100

Sludge Blend Tank Odor Control Stack 10.7 / 7.0 980

Biosolids Storage Bunkers 12.2 / 8.0 70

Headworks* 3057*/ 2000* 8000*

*Headworks was not sampled as a part of the survey in 2006. These values are from a prior survey and are included in table for comparison.

The conclusions of the study showed that the headworks, primary clarifiers, and biosolids blend tank had the highest concentrations and therefore the highest potential to create offsite odors. Detailed results, conclusions, and sampling methodology are further described in the Odor Analysis Report.

Air Dispersion Model

ISCST3 The previous air dispersion model was built using the Source Complex Short Term Version 3 (ISCST3) algorithm. ISCST3 is a steady-state Gaussian plume model that is used to assess pollutant concentrations from a wide variety of sources associated with an industrial complex such as a wastewater treatment plant. The ISCST3 model can account for the following:

• Settling and dry deposition of particles • Building downwash • Point, area, line, and volume sources • Plume rise as a function of downwind distance • Separation of point sources • Limited terrain adjustment

It should be noted that prior to the end of 2005, ISCST3 was the model that was recommended by the U.S. Environmental Protection Agency (EPA) for dispersion modeling. Since 2005, AERMOD became the EPA preferred model. ISCST3 is similar to AERMOD because they both use the steady-state Gaussian plume algorithm. However, ISCST3 is now considered an outdated model that is no longer supported or being used for EPA permitting.

Terrain Data Terrain data were used in the ISCST3 Model. These were taken from WebGIS.com in the form of DEM (Digital Elevation Model) files. These data were processed using AERMAP and were used to define base elevations for receptors, buildings, and sources based on the terrain surrounding the SCTP.

Meteorological Data The meteorological data used were from the year 1987. These data are now 30 years old, but they were used in the 2006 model because they are local data and considered the most representative data.

Receptors Gridded receptors, fence line receptors, along with sensitive receptors (nearby houses) were included in the modeling. The gridded receptors were defined as follows:

• Grid 1: 500-meter receptor spacing placed at 5,000 meters from the fence line.

• Grid 2: 100-meter receptor spacing placed at 1,000 meters from the fence line.


8

• Grid 3: 50-meter receptor spacing placed at 550 meters from the fence line.

• Fence line: 25-meter spacing along the fence line.

• Sensitive receptors: Located at Easting and Northings of nearby houses. See Table 4 for locations. These also are illustrated graphically herein.

Table 4. Sensitive Receptors Locations: NAD

Receptor No. Easting X (m) Northing Y (m)

1 520988 5063657

2 521300 5063532

3 521413 5063682

4 521700 5064020

5 520940 5064676

6 520763 5064644

SCTP Baseline Odor/ H2S Characterization The measured D/T and H2S concentrations for the sources previously described in Table 3 were used to create the baseline odor characterization model for the SCTP. These concentrations, combined with the geometry of each source and estimated flux rates, were used to estimate odor and H2S emission rates. These emission rates were then input into the dispersion model to create a baseline for characterizing the odors and H2S being emitted from the plant.

Two separate baseline models were created from the model, one for H2S and one for D/T. Each baseline included the sources indicated in Table 3, along with the addition of the mixed liquor splitter box, primary effluent splitter box, and 117th Street Pump Station Force Main carbon stack. The model input concentrations for each baseline scenario are described in Table 5.

Table 5. Odor and H2S Average and Peak Emissions at Current Level of Odor Control*

Source Source Type

Average H2S (µg/m3/ppbV)

Average Odor (D/T)

Peak H2S (µg/m3/ppbV)

Peak Odor (D/T)

Primary Clarifier 1 Area 1,528/1,000 2,500 7,644/5,000 5,000




Aeration Basin 1 &2 Area 38.2/25 250 153/100 500

Aeration Basin 3 &4 Area 38.2/25 250 153/100 500

Aeration Basin 5 Area 38.2/25 250 153/100 500

Aeration Basin 6 Area 38.2/25 250 153/100 500

Secondary Clarifier 1 Area 153/100 100 382/250 200





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Table 5. Odor and H2S Average and Peak Emissions at Current Level of Odor Control*

Source Source Type

Average H2S (µg/m3/ppbV)

Average Odor (D/T)

Peak H2S (µg/m3/ppbV)

Peak Odor (D/T)

Primary Effluent Splitter Box Area 764/500 0.25 1,528/1,000 0.5

Mixed Liquor Splitter Box Area 764/500 0.25 1,528/1,000 0.5

Headworks Point 3,057/2,000 8,000 15,288/10,000 16,000

Biosolids Blend Tank Point 825/540 2,100 1,528/1,000 4,200

Sludge Blend Tank Odor Control Stack Point 10.7/7 980 10.7/7 1,960

Pump Station Carbon Stack Point 15.3/10 375 76.4/50 750

Biosolids Storage Bunkers Point 1,528/1,000 1.0 764/500 2.0

*Input concentrations for both peak and average are based on the measured values multiplied by correction factor.

As indicated in Table 5, two scenarios were completed for both the H2S baseline and D/T baseline models. One was based on average concentrations and the other was based on peak concentrations. The results for the peak emissions scenario are briefly described below. However, both average and peak scenarios are defined in detail in the Odor Analysis Report completed in 2007.

Hourly Peak H2S Baseline For the hourly peak H2S baseline, the dispersion model indicated that the headworks facility is the largest contributor to the offsite H2S concentrations followed by the primary clarifiers and aeration basins. The maximum offsite impact was 287 μg/m3 (188 ppbV) at the fence line.

The 1-hour annual peak H2S concentrations at the six sensitive receptors identified in Table 4 are summarized in Table 6. Figure 2, which was obtained from the Odor Analysis Report, represents H2S concentrations in μg/m3.

Table 6. Peak H2S Concentrations at Sensitive Receptors with Current Level of Odor Control

Receptor No. H2S Concentration (µg/m3) H2S Concentration (ppbV)

1 29.6 19.36

2 32.9 21.52

3 87.3 57.10

4 39.6 25.90

5 45.5 29.76

6 43.7 28.58


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Figure 2. Isopleths Showing Lines of Constant H2S Concentration in µg/m3—1-Hour Annual Peak

Hourly Peak Odor (D/T) Baseline For the hourly peak odor baseline, the model, similarly to the H2S baseline, indicated that the headworks facility is also the largest contributor to the offsite odor concentrations. The maximum offsite impact was 328 D/T at a point just outside of the fence line.

The 1-hour annual peak odor concentrations at the six sensitive receptors identified in Table 4 are summarized in Table 7. The isopleths shown in Figure 3 represent lines of constant odor concentrations in D/T.

Table 7. Peak Odor Concentrations at Sensitive Receptors with Current Level of Odor Control

Receptor No. Odor Concentration (D/T)

1 35

2 40

3 147

4 47

5 54

6 52


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Figure 3. Isopleths Showing Lines of Constant Odor Concentration in D/T—1-Hour Annual Peak

The peak H2S and peak D/T exceedances at each of the sensitive receptors for each baseline case are indicated in Table 8. This is based on the number of hours, over a 1 year period (8,760 hours), that the H2S and D/T concentrations were greater than 10 μg/m3 and 10 D/T, respectively.

Table 8. Number of 1-hour Exceedances per Year for Peak H2S and Peak Odor

Receptor No. H2S exceeding 10 µg/m3 Odor exceeding 10 D/T

1 41 133

2 361 857

3 637 1103

4 41 93

5 30 79

6 20 111


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Odor Control Alternatives Two odor control strategies were evaluated in the Odor Analysis Report, Odor Control Strategy 1 and Odor Control Strategy 2.

Odor Control Strategy 1 included covering the primary clarifiers and preliminary treatment channels and providing an odor control system for both the clarifiers and the preliminary treatment facility. This option would reduce maximum offsite H2S and odor concentrations from 287 µg/m3 (188 ppbV) and 328 D/T, respectively, to 11.3 µg/m3 (7.39 ppbV) and 53 D/T, respectively. See Figures 4 and 5.

Figure 4. 1-Hour Peak Hydrogen Sulfide Concentrations in µg/m3—Odor Control Option 1


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Figure 5. Isopleths Showing Lines of Constant Odor Concentration in D/T for Control Strategy 1—1-Hour Annual Peak

Odor Control Strategy 2 includes covering and treating air from the aeration basins in addition to the odor control system in Odor Control Strategy 1. The predicted offsite D/T and H2S concentrations with this option would be reduced to near the nuisance threshold value at the fence line. This further level of odor control was not considered to provide added benefit at the time since no homes were built closer than approximately 500 feet from the plant. See Figures 6 and 7.


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Figure 6. Isopleths Showing Lines of Constant H2S Concentration in µg/m3 for Control Strategy 2—1-Hour Annual Peak


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Figure 7. Isopleths Showing Lines of Constant Odor Concentration in D/T for Control Strategy 2—1-Hour Annual Peak

CH2M recommended Option 1, which involved covering the primary clarifiers and preliminary treatment channels and then ventilating these areas to a new odor control system. This was the best option since it provided enough odor control to maintain odors below the nuisance value at all nearby receptors. This recommendation has been carried forward programmatically as part of the definition of the Phase 6 Expansion project for the facility.

Air Emission Regulatory Requirement Update The air discharges from SCTP are regulated by the SWCAA to limit toxic air pollution and nuisance odors. Individual odor-causing compounds are quantified as a concentration (mass per volume). Of these compounds, H2S is a regulated toxic pollutant and the SWCAA has established a limiting concentration for H2S toxicity. This section describes the key regulatory requirements pertaining to required limits of SCTP air emissions.

Nuisance Odors Because H2S is easily detected by the human nose, it is also commonly regulated as a nuisance odor. The SWCAA Regulations (SWCAA 400) contain what is best termed as a “nuisance odor” clause. Section 400-


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040(4)(a) states: “Any person who shall cause or allow the generation of any odor from any ‘source,’ which may unreasonably interfere with any other property owner’s use and enjoyment of his property must use recognized good practice and procedures to reduce these odors to a reasonable minimum.” This clause indicates that procedures be put in place to mitigate odors so that they are not “unreasonable” or a nuisance. Odors in general are typically quantified using a D/T method. However, limiting values are not specifically defined by the SWCAA, so target thresholds were selected based on experience to meet these qualitative nuisance odor requirements.

Toxic Air Pollutants Since the 2006 model was completed, new regulations have been implemented for H2S at the state level but have not yet been adopted at the local level. At the state level, the Washington Administrative Code- Title 173-Chapter 460- Section 150 (WAC 173-460-150) describes an updated Acceptable Source Impact Level (ASIL) for H2S as 2.0 µg/m3 over a 24-hour period. The previous value was 0.9 µg/m3 over a 24-hour period. At the local level, which is regulated by the SWCAA, the new regulated value has not been adopted and the ASIL for H2S is 0.9 µg/m3 over a 24-hour period. To be in compliance with both the local agencies, the value 0.9 µg/m3 over a 24-hour period should be used as the required criteria. This discussion is further outlined in the Control Technology Considerations for Permitting the Expansion of the Salmon Creek Wastewater Treatment Plant report completed by CH2M in June 2016.

For the state level, these regulatory requirements can be found at http://apps.leg.wa.gov/WAC/default.aspx?cite=173-460-150. For the Local level (SWCAA), http://www.swcleanair.org/docs/regs/wac173460-1998.pdf.

Odor Criteria Requirements Based on the conclusions above, toxic air pollution requirements and odor criteria requirements include the following:

• H2S—For toxic air pollution control, H2S cannot exceed a 24-hour average of 0.9 µg/m3 at the property boundary per year.

• H2S—For nuisance odor control, H2S cannot exceed a 1-hour average of 10 µg/m3 at any receptor (residence) per year

• D/T—For nuisance odor control, D/T cannot exceed a 1-hour average of 10 D/T at any receptor per year.

Updated Odor Control Evaluation This section provides an updated odor control evaluation that builds on the previous Phase 4 work completed in 2005 as well as the previous odor survey work completed in 2007 and in the context of the current regulatory environment. This evaluation is based on influent flow and load consistent with the Phase 4 capacity of the facility.

Updated Baseline Air Dispersion Model The same model developed from the 2006 evaluation was used in this evaluation. This includes meteorological data, the modeling algorithm (ISCST3), gridded receptors, terrain data, and sources input data.

It should be noted that the meteorological data are 29 years old and the ISCST3 model algorithm used is no longer the recommended model by the EPA. This does not make the results invalid, but does affect the accuracy of the results because newer models such as AERMOD have shown to be more accurate. The year of meteorological data used is also a factor that affects the results of the model. The older the weather data and the farther the specific receptor is from the plant, the less accurate the model results will be. Ideally, the most recent onsite data are recommended. However, this requires the data to be

http://apps.leg.wa.gov/WAC/default.aspx?cite=173-460-150


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specially processed for use with the dispersion model. This processing is considered beyond the scope of this work, so the original meteorological data were used.

Further, it should be noted that while the permitting methodology is focused on incremental H2S emissions (above current permit), this analysis considers total H2S emissions compared to WAC, rather than current SWCAA, requirements. This is intended to focus the discussion specific to the potential for odor complaints and to anticipate the future possibility that SWCAA may adopt the updated WAC standards.

The only changes to the baseline model are the addition of three new sensitive receptors to account for a future housing development south of the plant. This development is much closer to the plant than the sensitive receptors described previously in the 2006 model. For this reason, the model was updated to account for these new sensitive receptor locations. See Figure 8 for illustration of these new locations (shown as yellow).

Figure 8. Google Earth Map Showing 2006 Sensitive Receptors and 2016 Sensitive Receptors

Future Housing Development


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As shown in Figure 8, the new receptors account for the future housing development and are much closer to the southwest side of the plant than any of the other receptors from the 2006 study.

The updated baseline model used the same source input concentrations as described in Table 5.

Table 9 lists two types of inputs for both H2S and odors: measured concentration without a peaking correction factor and measured concentration with a peaking correction factor. The correction peaking factor was used to account for grab sample inaccuracies, diurnal variations, and decay rates known to occur during sample hold times. The correction factor used for each source ranged between 3 and 32 based on the source and measured value.

Table 9. Baseline Peak Odor and H2S Input Concentrations, with and without Correction Factors

Area Sources H2S Measured (µg/m3/ppbV)

Peak H2S (µg/m3 /ppbV) with CF

Measured Odor (D/T)

Peak Odor (D/T) with CF

Primary Clarifier 1 245/160 7,644/5,000 1,100 5,000




Aeration Basins 1 & 2 18.3/12 153/100 160 500

Aeration Basins 3 & 4 18.3/12 153/100 160 500

Aeration Basin 5 18.3/12 153/100 160 500

Aeration Basin 6 18.3/12 153/100 160 500

Secondary Clarifier 1 13.8/9 382/250 55 200


Secondary Clarifier 3 13.8/9 382250 55 200


Primary Effluent Splitter Box NM 1,528/1,000 NM 0.5

Mixed Liquor Splitter Box NM 1,528/1,000 NM 0.5

Point Sources

Headworks NM 15,288/10,000 NM 16,000

Biosolids Blend Tank 826/540 1,588/1,000 2,100 4,200

Sludge Blend Tank Odor Control Stack 10.7/7 10.7/7 980 1,960

Pump Station Carbon Stack NM 76.4/50 NM 750

CF = correction factor; NM= not measured, peak value with correction factor was used in place.


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These correction factors, which were used for the baseline D/T and H2S nuisance model in 2006, were also used for this updated D/T and H2S nuisance baseline model (for meeting maximum thresholds of 10 µg/m3 (6.5 ppbV) H2S and 10 D/T over a 1-hour average interval). The correction factors were not used for the TAP ASIL Air Dispersion Model Analysis (H2S threshold of 0.9 µg/m3 (1.3 ppbV) over a 24-hour period) described herein.

Updated H2S and Odor Nuisance Baseline Model

Figures 9 through 12, and Table 10 illustrates the results for the updated peak odor (D/T) and H2S (µg/m3) nuisance baseline.

Figure 4. Isopleths Showing Lines of Constant H2S Concentration in µg/m3—1-Hour Annual Peak


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Figure 5. Isopleths Showing Lines of Constant H2S Exceedance of 10 µg/m3 in Hours—1-Hour Annual Peak


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Figure 6. Isopleths Showing Lines of Constant Odor Concentration in D/T—1-Hour Annual Peak


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Figure 7. Isopleths Showing Lines of Constant Odor Exceedance of 10 D/T in Hours—1-Hour Annual Peak

Table 10. H2S and Odor Nuisance Baseline Peak, 1-Hour Average Concentration and Exceedances at Sensitive Receptors

Receptor

Concentration Exceedances

Baseline H2S (µg/m3/ppbV) with CF

Baseline Odor (D/T) with CF

Hours/year above 2 µg/m3 (1.3 ppbV)1 with

CF Hours/year above 10 D/T

Baseline with CF

1 26.28 / 17.2 29 54 133

2 31.15 / 20.4 35 361 857

3 87.39 / 57.2 103 637 1,103

4 39.58 / 25.9 41 60 93

5 45.47 / 29.7 30 46 79

6 43.65 / 28.55 20 50 111

7 44.32 / 28.99 47 68 75

8 70.16 / 45.89 73 147 147

9 62.3 / 28.99 64 285 291


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Table 10. H2S and Odor Nuisance Baseline Peak, 1-Hour Average Concentration and Exceedances at Sensitive Receptors

Receptor

Concentration Exceedances

Baseline H2S (µg/m3/ppbV) with CF

Baseline Odor (D/T) with CF

Hours/year above 2 µg/m3 (1.3 ppbV)1 with

CF Hours/year above 10 D/T

Baseline with CF

1 Pertains to future WAC ASIL limit for H2S

The results shown in Table 10 indicate that Receptor 3, which is a receptor from the previous 2006 model, still represents the highest offsite impact. Figures 10 and 12 show that the highest concentrated plume touches down directly on the Receptor 3 location outside the south tip of the plant fence line. Based on these facts, unless new developments are being constructed on the south tip of the plant, Receptor 3 is likely to remain the worst-case receptor. The conclusions from the odor analysis in 2006 therefore remain largely unchanged.

Toxic Air Pollutant ASIL Air Dispersion Model Analysis Since the 2006 model was completed, Washington State TAP regulations have been revised, including those pertaining to H2S. As previously discussed herein, the WAC ASIL for H2S concentration offsite is likely to be regulated at 2.0 µg/m3 (1.3 ppbV) over a 24-hour averaging period. This is approximately 5 times less than the H2S concentration threshold used in the nuisance model (10 µg/m3 [6.5 ppbV] over a 1-hour period). However, SWCAA has yet to adopt those revisions and still requires a value of 0.9 µg/m3 (0.6 ppbV) over a 24-hour period to be met. This is approximately 10 times less that the H2S concentration threshold used in the nuisance model (10 µg/m3 [6.5 ppbV] over a 1-hour period).

To understand potential compliance with the WAC ASIL, the H2S baseline nuisance model was updated with both the old threshold of 0.9 µg/m3 (0.6 ppbV) and the new H2S threshold of 2.0 µg/m3 (1.3 ppbV). This model also included the new sensitive receptors to account for the future housing development located south of the SCTP. Again, the threshold for compliance is based on incremental emissions associated with a change to the permitted facility; this modeling looks at total, rather than incremental, H2S emissions.

Since this model is to inform understanding of regulatory compliance based on a 24-hour average, a correction factor of 2 was used for accounting for grab sample inaccuracies . The measured H2S values for each source and the measured values with the correction factor of 2 are shown in Table 11.



H2S Measured (µg/m3/ppbV) with CF of 2.0

Primary Clarifier 1 245/160 489/320




Aeration Basins 1 & 2 18.3/12.0 37.0/24.0

Aeration Basins 3 & 4 18.3/12.0 37.0/24.0

Aeration Basin 5 18.3/12.0 37.0/24.0

Aeration Basin 6 18.3/12.0 37.0/24.0

Secondary Clarifier 1 13.8/9.0 27.5/18.0


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H2S Measured (µg/m3/ppbV) with CF of 2.0




Primary Effluent Splitter Box NM 764/500

Mixed Liquor Splitter Box NM 764/500

Point Sources

Headworks 114/75.0 305/200

Biosolids Blend Tank 825/540 1682/1100

Sludge Blend Tank Odor Control Stack 10.7/7.0 21.4/14.0

Pump Station Carbon Stack NM 15.3/10.0

Biosolids Storage 12.2/8.0 24.5/16.0

The results of the TAP dispersion model are shown in Figure 13 and Table 12 below.


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Figure 8. Isopleths Showing Lines of Constant H2S Concentration in µg/m3 —24-Hour Annual Peak

Table 12. Toxic Air Pollutant Baseline- Peak, 24-Hour Average H2S Concentrations at Sensitive Receptors

Receptor Maximum H2S (µg/m3/ppbV)

Exceedances hours/year above 0.9 µg/m3

Exceedances hours/year above 2.0 µg/m3

Highest (fence line) 3.33/2.18 23 3

1 0.24/0.16 0 0

2 0.730.48 0 0

3 1.98/1.30 3 0

4 0.51/0.33 0 0

5 0.51/0.33 0 0

6 0.22/0.14 0 0

7 0.91/0.60 1 0

8 0.42/0.27 0 0

9 0.73/0.48 0 0


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For H2S, the results from Table 12 show that, without any odor control (baseline), the fence line, and Receptors 3 and 7 all exceed the old threshold of 0.9 µg/m3 (0.6 ppbV). However, Receptor 3 is the only receptor that comes close to the ASIL for H2S of 2.0 µg/m3 (1.3 ppbV). The highest value recorded was at the fence line and was 3.33 µg/m3 (2.18 ppbV) and exceeded the new threshold 3 hours out of the 8,760 hours in the year. These results show that the plant in its current state is not in compliance at the property boundary for both thresholds. Due to the lack of compliance, odor control will be needed during the Phase 4 expansion.

Updated Odor Control Alternatives

Two strategies were described in the previous analysis, Odor Control Strategy 1 and Odor Control Strategy 2. Since Odor Control Strategy 1 was the recommended option, it was the only alternative that was updated. Strategy 2 would only be updated if the conclusions or recommendations changed.

Odor Control Strategy 1 involves covering the primary clarifiers and the headworks and ventilating these sources to three bio-trickling filters.

The results of the updated baseline model and the TAP analysis showed that Receptor 3 is still the worst-case receptor and that both the new and the old ASIL for H2S at the property boundary are not in compliance. A revised strategy was developed based on an engineered media biofilter approach and reduced number of bio-trickling filter/BTF vessels. The engineered media approach was modeled because of its simplicity, it’s ease of maintenance, and because it has now become a proven cost-effective technology. Only two bio-trickling filters/BTFs are needed to treat current loads as opposed to three because of improvements in the media and its ability to handle a higher rate of loading. Because bio-trickling filters/BTFs and engineered media biofilters have similar removal efficiencies, this revised strategy changed only the number and location of odor control stacks. Only one odor control stack is modeled for the biofilter strategy instead of the previous three (one per bio-trickling filter vessel). Only two odor control stacks are modeled for the revised bio-trickling filter/BTF strategy instead of the previous three (one per vessel). The revised control strategy was also updated to include the latest receptors. A summary of updated Odor Control Strategy 1 is indicated below:

• Updated with new receptors based on future housing development.

• Updated based on an engineered media biofilter instead of three bio-trickling filters.

• Updated based on new location of the odor control system.

• Biofilter operating efficiency assumed to have 99 percent H2S removal and 90% Odor (D/T) removal, which is the same as the bio-trickling filters modeled previously.

• All other source Inputs based on updated baseline model described above.

• Primary clarifiers and headworks sources are deleted from baseline model since they are contained.

The results for the bio-trickling filter/BTF approach are shown in Figures 14 and 15 and Table 13.


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Figure 9. Isopleths Showing Lines of Constant H2S Concentration in µg/m3 —1-Hour Annual Peak, Revised Control

Strategy 1—Bio-trickling filter/BTF Approach


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Figure 10. Isopleths Showing Lines of Constant Odor Concentration in D/T—1-Hour Annual Peak, Revised Control

Strategy 1—Bio-trickling filter/BTF Approach

Table 13. Revised Control Strategy 1—Bio-trickling filter/BTF Approach, 1-Hour Peak Average H2S Concentrations at Sensitive Receptors

Receptor

H2S (µg/m3/ppbV) H2S (µg/m3/ppbV) Odor (D/T) Odor (D/T) Odor Exceedances






1 1.14/0.75 1.16/0.76 6.1 4.77 -

2 1.55/1.01 1.49/0.97 5.2 6.01 -

3 2.05/1.34 1.49/0.97 7.6 6.59 -

4 1.51/0.99 1.51/0.99 4.7 6.83 -

5 0.72/0.47 0.72/0.47 3.4 3.31 -

6 1.00/0.65 0.85/0.56 5.4 3.62 -

7 N/A 4.66/3.05 N/A 17.05 1

8 N/A 2.60/1.70 N/A 9.57 -

9 N/A 2.94/1.92 N/A 7.86 -


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The results of Revised Odor Control Strategy 1 show that Receptor 7 is the only receptor to exceed the nuisance odor threshold of 10 D/T. However, this only happens 1 hour per year. This is less than 0.01 percent of the time. Since this is such a small percentage of time, it is not considered a high enough risk to consider more conservative alternatives.

Table 13 also shows the values from the previous study as comparison. The slight differences are due to the change in the number of stacks for the bio-trickling filter/BTF approach.

The results for the biofilter approach are shown in Figures 16 and 17 and Table 14.

Figure 16. Isopleths Showing Lines of Constant H2S Concentration in µg/m3 —1-Hour Annual Peak, Revised Control

Strategy 1—Biofilter Approach


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Figure 17. Isopleths Showing Lines of Constant Odor Concentration in D/T – 1-Hour Annual Peak, Revised Control

Strategy 1—Biofilter Approach

Table 14. Revised Control Strategy 1—Biofilter Approach, 1-Hour Peak Average H2S Concentrations at Sensitive Receptors

Receptor

H2S (µg/m3/ppbV) H2S (µg/m3/ppbV) Odor (D/T) Odor (D/T) Odor Exceedances






1 1.14/0.75 1.16/0.76 6.1 4.73 -

2 1.55/1.01 1.49/0.97 5.2 5.83 -

3 2.05/1.34 1.47/0.97 7.6 7.02 -

4 1.51/0.99 1.51/0.99 4.7 4.68 -

5 0.72/0.47 0.72/0.47 3.4 3.31 -

6 1.00/0.65 0.85/0.56 5.4 3.62 -

7 N/A 4.66/3.05 N/A 17.05 1

8 N/A 2.60/1.70 N/A 9.57 -

9 N/A 2.94/1.92 N/A 7.86 -


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The results of Revised Odor Control Strategy 1 with the biofilter approach, indicated in Table 14, are similar to the results for the Bio-trickling filter/BTF approach shown in Table 13. Receptor 7 is the only receptor to exceed the nuisance odor threshold of 10 D/T. Similar to the bio-trickling filter/BTF approach, Table 14 shows that this exceedance only happens 1 hour per year, which is less than 0.01 percent of the time. Since this is such a small percentage of time, it is not considered a high enough risk to consider more conservative alternatives.

Table 14 also shows the values from the previous study for comparison. The slight differences are due to the change in the number of stacks from three to one.

The results for both approaches are similar and indicate that either the biofilter or bio-trickling filter/BTF approach will meet the nuisance criteria with only 1 hour of exceedance in the year.

Control Strategy 1 was also modeled to ensure compliance with the ASIL threshold of 0.9 µg/m3 over a 24-hour averaging period at the fence line. The results of this model run showed that the maximum H2S concentration at the fence line was 0.855 µg/m3. This is less than the 0.9 µg/m3 as required by the SWCAA, and, therefore, Control Strategy 1 also meets the regulatory permitting requirements. Figure 18 below illustrates the results.

Figure 18. Isopleths Showing Lines of Constant H2S Concentration in µg/m3—24-Hour Average, Revised Control

Strategy 1—Bio-trickling filter Approach


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Technology Evaluation

Originally, the proposed Control Strategy 1 system consisted of three 12-foot-diameter, once through, packed media bio-trickling filters/BTFs. This was considered the best available system that provided the most benefit to cost in the 2005 evaluation. Since 2005, BTFs and biofilters have improved in performance and efficiency. To ensure the best technology is selected, the evaluation from 2005 was revisited to account for these technology advancements. For this evaluation, two alternatives were evaluated for the SCTP odor control system: structured media BTF, as previously described herein, and a high rate engineered media biofilter.

High rate engineered media biofilters are biofilter systems that utilize a proprietary media that performs under much higher loading rates than organic, soil, or mineral biofilters. High rate engineered media biofilters also exhibit similar or better performance characteristics than organic mediums. These types of systems also have longer lasting media and require less footprint due to the higher loading. The media is generally more expensive because it is a unique proprietary composition.

Design flow rates for high rate biofilters range from 5.0 to 11.0 cubic feet per minute per square foot. Media life is normally guaranteed for 10 to 20 years. The appropriate EBGRT for high rate media is dependent upon the target odor and respective loading rate but will typically range between 30 to 60 seconds.

Generally, high rate biofilter media do not require a nutrient source because they have a nutrient constituent built into the media recipe. The advantages of high rate packaged biofilters include the following:

• A wide range of odorous constituents may be removed.

• The system O&M is relatively simple.

• Chemical storage and delivery is not required.

• High rate proprietary media requires less frequent change-out (generally guaranteed for 10 to 20 years).

• The control systems are either manually operated or are relatively simple.

• The collected leachate is typically not odorous, as with compost biofilters.

• The required footprint is approximately half that of organic media biofilters.

• High-velocity stack that allows for better dispersion/dilution than open area biofilters without cover and stack.

However, high rate biofilters have the following disadvantages:

• Media costs can be high.

• Because bacterial populations provide the removal mechanism, the system can handle gradual cyclic loadings but cannot accommodate rapid load spikes effectively.

• Can require larger footprint than BTFs

Alternative 1—Structured Media BTF This alternative is similar to the recommended alternative from the 2005 evaluation but consists of revised BTF technology that includes structured synthetic media as opposed to random packed media. Structured synthetic media improves uniformity in the BTF media and has much more resistance to breakdown and compaction. This design improvement has allowed BTFs to handle up to 200 fpm loading capacity with little to no loss in removal efficiency. Previously, the 2005 evaluation was based on bio-trickling filters with a maximum loading rate of 50 to 75 fpm. The designed loading rate for this


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alternate is now based on 100 to 150 fpm, which reduces the number of vessels required for the design H2S loading rate. The revised alternative now consists of only two (instead of three) FRP towers with structured synthetic media and an exhaust fan with acoustical enclosure. The BTF configuration evaluated is also a once-through type BTF to minimize maintenance and create a pH gradient to increase ORS removal. System drainage water would exhibit low pH and would be drained back to a process flow stream or storage tank. Further design criteria associated with this alternative are described in Table 15.

Table 15. Alternative 1—BTF Design Criteria


Tower Type Once through—counterflow

Media Type Structured synthetic

Media Depth 12 feet

Tower Vessel Two @ 12-foot-diameter & 28 feet high



Fans Type: FRP centrifugal (1 duty, 1 standby) Capacity: 21, 000 ft3/minute @ 7.3-inches wc Motor: 60 hp



For layout drawings, see previous report completed in 2005. Note that the layout in 2005 has three vessels and only one fan. The updated evaluation herein now considers space and costs for an extra standby fan and is based on two vessels.

Alternative 2—Engineered Media Biofilter This alternative involves an in ground engineered media biofilter located next to the primary clarifiers. The biofilter consists of high rate proprietary media placed in two cells approximately 35 feet by 40 feet in size designed for 45 seconds of EBGRT. Each cell is approximately 12 feet deep in the ground, which accounts for 6 feet of media, 3 feet for the underground air distribution system, and 3 feet for concrete and space above the biofilter. Three feet of the biofilter is assumed to be above grade. Each cell will be covered with aluminum covers and ventilated through a common 15-foot stainless steel stack or coated carbon steel stack. Two odor control exhaust fans will be used to ventilate the primary clarifiers and headworks. There will be one duty fan and one standby. Table 16 summarizes this alternative.

Table 16. Alternative 2—Engineered Media Biofilter


Biofilter Type At-grade w/concrete retaining walls

Media Type Engineered media

Media Depth 6 feet

Gas Residence Time (GRT) 45 seconds

Loading Rate 8 ft3/minute/square feet

Humidification Primary: humidification chamber Secondary: irrigation type sprinklers


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Table 16. Alternative 2—Engineered Media Biofilter


Fans Type: FRP centrifugal (1 duty, 1 standby) Capacity: 21,000 ft3/minute @ 7.3 inches wc Motor: 60 hp


Footprint 5,600 square feet (80 feet x 70 feet)

Both economic (cost) and non-economic (benefit) criteria were used to evaluate the two technologies described above. A technology with the lowest cost to benefit ratio is the most appropriate technology for the SCTP.

Economic Evaluation Economic criteria include capital cost and life-cycle cost.

A conceptual level cost estimate has been developed for each evaluated technology. The cost estimates are considered a study or feasibility, Class 4 estimate as defined by the Association for the Advancement of Cost Engineering International. These estimates are considered accurate from +20 to +50 percent on the high side to -15 to -30 percent on the low side, based on a preliminary design, level of information available, and estimating techniques used.

Capital costs for all odor control technology alternatives include site work, odor control equipment, mechanical, electrical, instrumentation and control, piping, and ductwork. Site work includes excavation for equipment pads and biofilter vessels. Odor control equipment costs include the odor control fans, media, and vessels. The ductwork costs include an estimated 550 feet of collection duct from the headworks and primary clarifiers. Also included are aluminum covers for the primary clarifiers as well as a $100,000 place holder for modifying the headworks heating, ventilation, and air conditioning (HVAC) system. Capital costs are estimated using the following approach:

• Equipment costs are based on recent equipment supplier cost quotes received.

• Percentage markups applied for unknown costs such as site work, instrumentation, electrical, and yard piping.

Additional project costs were developed by escalating the equipment sub-cost by the markups illustrated below.

Markups applied to equipment cost were as follows:

• Equipment Installation: 10% • Field Painting/Finishes: 1% • Mechanical: 8% • Electrical: 8% • Instrumentation: 5%

Contractor markups applied to equipment subtotal + project costs were as follows:

• General Conditions: 7% • Overhead: 5% • Profit: 5% • Bonds/Insurance: 2.5%


35

• Contingency: 20% • Escalation (3% per year): 6% (construction completed end of 2018)

Non-construction cost markups applied to construction cost after contractor markups and escalation were as follows:

• Permitting 3% • Engineering 10% • Services during Construction: 5% • Commissioning/Startup: 5% • Sales Tax: 8.4% (Sales tax in Washington)

O&M and life-cycle costs were developed using the following inputs:

• Electricity Costs: $0.06/ kilowatt-hour • Operator Labor Costs: $40/hour • Financing Costs: 20-year life, 6 percent discount rate • Nutrient Costs: $10/gallon

Table 17 summarizes the cost estimate for evaluated odor control technologies.

Table 17. Cost Estimate Summary of Technologies

Item BTF

(x$1,000) Engineered Media Biofilter

(x$1,000)

Capital Equipment Costs:

Odor Control Equipment $794 $372

Biofilter Aluminum Cover $0 $91

Primaries Aluminum Cover $239 $239

HVAC For Headworks $100 $100

Ducting and Stack $234 $243

Site work $18 $279

Subtotal- Equipment Costs $1,386 $1,324

Capital Mark-up Costs:

Allowance Costs $460 $440

Contractor Markups $360 $344

Contingency (20%) $441 $422

Escalation (3% per year) $238 $228

Non-construction Capital Costs:

Engineering $289 $276

Permitting $87 $83

Services During Construction $144 $138

Commissioning and Start-Up $144 $138

Sales Tax $242 $232


36

Table 17. Cost Estimate Summary of Technologies

Item BTF

(x$1,000) Engineered Media Biofilter

(x$1,000)

Annual Costs:

Electrical Power $10.94 $11.06

Maintenance $25.87 $36.79

Nutrients $19.16 $0.00

R&R Costs $7.70 $12.59

Water $5.37 $5.37

Subtotal – Annual Costs $70.00 $66.00

Present Worth Annual Costs $873 $823

Total Capital Cost $3,794 $3,623

Total Project Present Worth $4,667 $4,446

The updated cost evaluation shows that the total project present worth cost for the BTF is approximately $221,000 more than the engineered media biofilter. Furthermore, costs associated with the biofilter are shown to be less in every category including capital cost and annual cost.

Non-economic Evaluation The non-economic evaluation criteria have been updated to be slightly different but more applicable than those of the evaluation in 2005, as follows:

• Safety and Health: This criterion refers to day-to-day operator safety related to the type of odor control system. Both BTFs and biofilters are considered equally safe to operate and pose no major safety or health concerns.

• Risk of Odor Breakthrough: Because odor receptors are located close to the plant, this criterion is weighted high for the odor control systems evaluated. Both biofilters and BTFs are susceptible to odor breakthrough under certain peak conditions because both require a certain bacterial population to reduce different concentrations of H2S. However, engineered media biofilters tend to be a little more effective at handing these spikes due to the adsorption capabilities of the media.

• Technology Maturity and Reliability: Some alternatives evaluated have a more proven track record of success when designed and operated correctly. Others are newer technologies that have recently been introduced to the market. Both of the control technologies evaluated, BTFs and engineered media biofilters, have many proven installations in the marketplace. Both are considered equal in maturity and reliability.

• Level of Maintenance Required: This criterion refers to the day-to-day maintenance that would be performed by County staff. Biofilters and once-through BTFs both require a minimal amount of maintenance because the fans are usually the only pieces of mechanical equipment in each system. However, because BTFs require nutrient addition, they require slightly more maintenance than engineered media biofilters.

• Level of Operating Complexity: Similar to maintenance requirements, this criterion refers to the day-to-day need for operator attention. Generally, engineered media biofilters and once-through BTFs require minimum operator attention, involving periodic monitoring for odors or checking of the


37

biofilter media for moisture content. Because the BTFs require nutrient addition, the complexity is considered slightly greater than that of an engineered media biofilter.

• Energy Usage: This is based on the energy required by the entire system. For both systems the fans will be the main source of energy usage. The biofilter is slightly higher because it requires two stack fans to add static pressure that is lost due to covering the biofilter. In addition, the expected pressure drop across the biofilter media is expected to exceed that for the BTF.

• Space Requirements: Space requirements include footprint areas for odor control equipment as well as space for access for equipment. Engineered media biofilters require larger footprints than BTFs.

• Odor Removal Efficiency: Odor removal efficiency relates to the ability of a particular odor treatment technology to remove odor constituents such as H2S, reduced sulfur compounds, and other constituents. Once-through BTFs and engineered media biofilters can effectively remove both H2S and ORS compounds effectively. However, due to longer EBGRT biofilters will have slightly better efficiency.

Each criterion was given a weighting factor, depending on the importance of the criterion for this specific application. Then a score was given for each criterion to each technology. The final score is a weighted overall score of all criteria. Table 18 summarizes the weighing of the criteria and score of each evaluated technology. Figure 19 illustrates the results.

Table 18. Non-economic Evaluation of Technologies

Evaluation Criteria Criteria Weight

Weighed Score

Engineered Media Packaged Biofilter BTF

Safety/Health 10 73.68 73.68 Risk of Odor Break-through 15 47.37 31.58 Technology Maturity and Reliability 15 31.58 31.58 Level of Maintenance Required 10 84.21 63.16 Level of Operating Complexity 10 84.21 63.16 Energy Usage 10 63.16 73.68 Space Requirements 10 42.11 84.21 Odor Removal Efficiency 15 78.95 78.95

Total Weighed Score (out of 100)

63.16 62.50

Ranking

1 2


38

Figure 19. Non-economic Scores for Alternatives 1 and 2

Both the BTF and engineered media biofilter technologies are ranked very close to each other. However, due to slightly less risk with odor breakthrough and less complexity and maintenance, the engineered media biofilter ranks slightly better than the BTF.

Cost-benefit Analysis The cost-benefit of each technology was estimated by dividing the 20-year life-cycle cost by the non-economic weighed score. Figure 20 shows the cost-to-benefit ratio of each odor control technology. The alternative with the lowest cost-to-benefit ratio would be the most desirable technology, since it represents the system that costs the least when providing the same non-economic benefit. As Figure 20 shows, the cost-benefit ratio is lower for the engineered media biofilter. Since both technologies exhibit essentially equal rankings in the non-economic analysis, this chart is based mainly on the cost difference between the two technologies.


39

Figure 20. Cost-benefit Analysis Results for Alternatives 1 and 2

Conclusions and Recommendations Conclusions The odor control offsite criteria were determined to be the following:

• H2S—For toxic air pollution control, H2S cannot exceed a 24-hour average of 0.9 µg/m3 at the property boundary per year.

• H2S—For nuisance odor control, H2S cannot exceed a 1-hour average of 10 µg/m3 at any receptor (residence) per year

• D/T—For nuisance odor control, D/T cannot exceed a 1-hour average of 10 D/T at any receptor per year.

In reviewing the regulatory requirements, without any odor control (baseline), the fence line, and Receptors 3 and 7 all exceed the current WAC threshold of 0.9 µg/m3 (0.6 ppbV). However, Receptor 3 is the only receptor that comes close to the future ASIL for H2S of 2.0 µg/m3 (1.3 ppbV). The highest value recorded was at the fence line and was 3.33 µg/m3 (2.18 ppbV). These results showed that the plant currently is not meeting these requirements and odor control is necessary.

The results of the updated baseline nuisance dispersion model indicate that that the new receptors located south of the SCTP do have potential for odor impacts but are still not as high as Receptor 3 from


40

the 2006 analysis, which is located southeast of the SCTP fence line. This confirms that the conclusions from the 2006 report remain valid. The potential for nuisance odors are still present based on the current plant operation.

Odor Control Strategy 1, which was recommended in 2006, was updated with the new receptors and with the latest odor control systems. The results indicate that only Receptor 7 exceeds the target odor threshold of 10 D/T with implementation of this strategy, but at less than 0.01 percent of the year. The results also showed that Odor Control Strategy 1 meets the 0.9 µg/m3 requirement for toxic air pollution control at the plant boundary.

The updated evaluation comparing the latest odor control technology alternatives indicate that both the engineered media biofilter and BTF are viable options.

Recommendations Based on the updated dispersion model results, the new sensitive receptors are not shown to be a new risk but are still exceeding odor and H2S target thresholds along with other (existing) sensitive receptors without additional odor control measures. The results also indicated that the 0.9 µg/m3 requirement for toxic air pollution control at the plant boundary is currently being exceeded. For these reasons, along with the fact that the potential for nuisance odor complaints remains significant, it is recommended that the revised Odor Control Strategy 1 continue to be carried forward for implementation. This alternative includes covering and ventilating the primary clarifiers and ventilating the headworks facility to an odor control system.

Based on the alternative evaluation results, it is recommended that both the BTF and engineered media biofilter be considered as part of a predesign effort. Considerations beyond the scope of this work that should be considered in more detail include aesthetics of the installation as well as expandability to address future process expansions and overall site constraints.

Appendix C Water Quality Compliance Evaluation

T E C H N I C A L M E M O R A N D U M

1

Water Quality Compliance Evaluation for the Phase 5B Project – Salmon Creek Treatment Plant Improvements

PREPARED FOR: John Peterson/Clark Regional Wastewater District

PREPARED BY: David Wilson/CH2M-Jacobs

Erin Thatcher/EIT, CH2M-Jacobs

Brady Fuller/PE, CH2M-Jacobs

DATE: August 6, 2018

PROJECT NUMBER: 688766.03.30.04

Summary This technical memorandum provides an evaluation of the Salmon Creek Treatment Plant (SCTP) Phase

5B plant capacity expansion with regard to water quality in the Columbia River and Washington water

quality standards (Washington Administrative Code [WAC] 173-201A). The Phase 5B effluent flows will

be discharged into the Columbia River through the existing SCTP outfall and multi-port diffuser until the

replacement outfall and diffuser are completed under the Phase 5A project in 2023.

This evaluation has been prepared to be consistent with WAC 173-201A, and to align with the

Washington State Department of Ecology (Ecology) Water Quality Program Permit Writer's Manual

(Permit Writer’s Manual) (2015) and Water Quality Program Guidance Manual: Supplemental Guidance

on Implementing the Tier II Antidegradation (Ecology, 2011). The elements of the water quality and

antidegradation evaluations and the results are summarized as follows:

1. Assessment of dilution performance of the existing SCTP outfall diffuser with Phase 5B effluent

flows:

� Dilution modeling for acute aquatic life criteria conditions yield a minimum dilution factor of 14

at the acute zone boundary under low river flow and the highest daily maximum effluent flow.

� Dilution modeling for chronic aquatic life criteria conditions yield 59 under critical dry season

low river stage and velocities, and 54 under critical wet season conditions and maximum

monthly effluent flows.

� Model-predicted dilution factors for human-health-criteria non-carcinogen conditions and

human-health-criteria carcinogen conditions are 63 and 114, respectively.

� These dilution factors that represent critical acute and chronic aquatic-life-criteria conditions

and human-health-criteria conditions have been applied in the evaluation of compliance with

water quality standards and antidegradation rules.

2. Assessment of compliance with state water quality standards:

� Dissolved oxygen - The calculated worst-case decrease in dissolved oxygen at the mixing zone

boundary is limited to 0.1 mg/L during the summer salmon rearing and migration period and

during the September–June spawning, rearing and migration period. According to WAC 173-

201A-200(1)(d), a reduction in dissolved oxygen of less than 0.2 mg/L is allowed, even in

waterbodies that do not meet the applicable dissolved oxygen criterion. Therefore, the Phase 5B

WATER QUALITY COMPLIANCE EVALUATION FOR THE

2

SCTP discharge would not cause or contribute to a violation of DO criteria. Furthermore, field

measurements of Columbia River dissolved oxygen levels in the dry season in 2015, showed no

violation of DO concentration criteria or saturation criteria.

� Temperature – The temperature standards include biologically-based criteria and criteria for

preventing acute lethality and barriers to migration of salmonids. The estimated maximum

excess temperature for the SCTP discharge at the Phase 5B effluent flows is 0.05°C, and it is not

a “measurable” temperature increase which is defined as greater than 0.3°C in the temperature

standards. In addition, the Phase 5B discharge to the river does not exceed any of the criteria

preventing acute lethality and barriers to migration of salmonids.

� pH - Based on calculation of the mixed pH at the SCTP mixing zone boundary, the mixed pH

would not be less than 6.5 or more than 8.5, and therefore would not cause or contribute to a

violation of the pH criteria.

� Toxic Substances - Evaluation of the dilution factors required for the SCTP effluent maximum

effluent concentrations to comply with the aquatic life and human health-based water quality

criteria demonstrate that the existing SCTP diffuser with Phase 5B flow will provide sufficient

dilutions to comply with acute and chronic aquatic life criteria for ammonia, metals, and organic

chemicals. The Phase 5B discharge will comply with human health-based criteria, with two

chemicals to be resolved. The 2016 EPA-approved human health criteria for arsenic is lower

than the measured background arsenic concentrations in the Columbia River by an order of

magnitude and is therefore not attainable. The plasticizer, Bis(2-Ethylhexyl) Phthalate, is

ubiquitous in municipal wastewater effluents due to PVC piping and other plastics and

additional source monitoring is needed to reduce their sources to sewage systems.

3. Assessment of compliance with state antidegradation rules:

� Ecology has specified in Washington’s antidegradation rule (WAC 173-201A-300) that a Tier II

review “will only be conducted for new or expanded actions conducted under authorizations

including NPDES permits”. The SCTP Phase 5B is neither a new or expanded action, and this

additional assessment demonstrates that the Phase 5B discharge will not create any

degradation or measurable change in water quality in the Columbia River.

4. Review of biological resources and uses of the Columbia River discharge site:

� The biological resources of the Columbia River include listed salmonid species, eulachon,

sturgeon and their aquatic habitat. This water quality evaluation documents that the SCTP Phase

5B discharge will not cause or contribute to violations of water quality standards. These

standards have been developed to protect sensitive aquatic organisms, including ESA-listed

species, and aquatic organisms using the lower Columbia River are protected by these

standards.

Outfall Dilution Assessment This assessment of the dilution performance of the existing SCTP outfall diffuser reviews the dilution

modeling assumptions and inputs and presents the modeling results. These dilution results are applied

in the evaluation of compliance with water quality standards and are provided for Ecology’s use in the

National Pollutant Discharge Elimination System (NPDES) permit renewal.

Updated dilution modeling of projected Phase 5B effluent flows was developed to provide predicted

dilution performance of the existing SCTP outfall diffuser under critical (worst-case) receiving water

conditions for a range of effluent flows and receiving water conditions at the discharge site. This

additional dilution analysis was specifically performed because the Phase 5B project is proposing an


3

incremental increase in permitted effluent flows in 2022 to be discharged through the existing outfall

and diffuser prior to the construction and operation of the replacement outfall and diffuser under Phase

5A. Phase 5A dilution modeling has evaluated projected effluent flows for 2025, 2040, and buildout

conditions with these flows discharged through the Phase 5A replacement outfall and diffuser. Outfall

dilution modeling was conducted for specific effluent flows and temperatures and critical receiving

water conditions of temperatures, discharge depth, tidal direction, and current velocities in accordance

with guidance provided in Chapters 6 and 7 and Appendix C of the Permit Writer’s Manual.

The modeling assumptions and specific inputs of effluent flow and temperature and receiving water

conditions are defined in the following section. The modeling conditions that produce the lowest

predicted dilutions identify the site-specific critical conditions for the discharge. Previous dilution

modeling analyses of the existing SCTP outfall diffuser include the Outfall Dilution Study Report for the

SCTP (CH2M HILL, January 2004) and the Addendum to the Outfall Dilution Study Report for the SCTP

(CH2M HILL, May 2004) include detailed documentation and justification for the selection and

application of the model UM3 (Frick et al., 2003). This model selection was developed using the results

of the field tracer study performed in 2003, including the review and input from Ecology technical staff.

Dilution Modeling Assumptions and Inputs

Dilution modeling input and analyses were based on the site-specific current and water column

measurements collected during the low river flow period in 2015 (a historically low flow water year),

available effluent flow and temperature data and statistics between 2010 and 2016, and projected

effluent flows for SCTP Phase 5B. Modeling was conducted to represent discharge scenarios specified in

the Permit Writer’s Manual.

The existing SCTP outfall is located in the Columbia River near River Mile 96, and it terminates with a

diffuser composed of five risers at 10-foot spacing, at an average port depth of approximately 17 feet

during low river flows (each riser has three 5-inch by 5-inch ports). The current NPDES Permit authorizes

a mixing zone boundary of 217 feet in all directions from the diffuser, and an acute zone boundary of 22

feet in all directions from the diffuser. These mixing zone boundaries were established based on the

WAC 173-201A-400(7)(b) for discharges to estuaries (where tidal-induced flow reversals occur), as well

as the average diffuser port depth under 7Q10 low river flow.

Eleven combinations of discharge and ambient receiving water conditions were modeled to represent

the range of critical discharge conditions for the existing SCTP outfall and diffuser. The model-predicted

flux-average dilutions are presented at the acute criteria exceedance boundary (acute zone boundary)

and at the chronic criteria compliance boundary (or mixing zone boundary) for the various effluent flows

and critical receiving water conditions. Seasonal discharge scenarios were developed to match guidance

provided in the following Permit Writer’s Manual tables: Table 11 (Effluent and Receiving Water Design

Conditions for Temperature), Table 12 (Applicable Criteria/Design Conditions), and Appendix C Table C-1

(Point Source Steady-State Flow for Mixing Zone Analysis) and Table C-3 (Critical Ambient Conditions).

The dry season (May through October) modeling scenarios are summarized as follows:

• Acute Criteria Conditions—7Q10 dry season low river flow and the maximum daily dry weather

effluent flow for Phase 5B (Year 2022)

• Chronic Criteria Conditions—7Q10 dry season low river flow and maximum month dry weather


• Human Health (Non-carcinogen) Criteria Condition—30Q5 low river flow and maximum month dry

weather effluent flow for Phase 5B (Year 2022)

• Human Health (Carcinogen) Criteria Condition—harmonic mean river flow and annual average



4

The wet season (November through April) scenarios are summarized as follows:

• Acute Criteria Condition—7Q10 wet season river flow and the maximum daily wet weather effluent

flow for Phase 5B (Year 2022)

• Chronic Criteria Condition—7Q10 wet season river flow and the maximum month wet weather


These dry and wet season scenarios align with the guidance defined in Tables 11 and 12 of the Permit

Writer’s Manual for critical-low-flow conditions and human-health-criteria conditions for carcinogens

and non-carcinogens. The 7Q10 river flow is defined as the 7-day low flow period with a recurrence

interval of 10 years, and the 30Q5 river flow is defined as the 30-day low flow period with a recurrence

interval of 5 years. The modeling scenarios, including effluent flows and temperature used, river flow,

current velocities, and temperatures, and discharge port depths, are summarized in Table 1.

Effluent flow values were developed based on the Phase 5B Engineering Report and applying

interpolation between actual 2016 and projected 2025 flows from the Salmon Creek Wastewater

Management System Wastewater Facilities Plan/ General Sewer Plan Amendment (Facilities Plan)

(CH2M, 2013) to represent the Phase 5B effluent flows in 2022. Effluent flow projection for 2022 are

summarized in Table 1 and applied in dilution modeling. The record period used to develop effluent

temperatures for modeling was January 2010 through April 2016. A 99th percentile effluent

temperature of 23.0 degrees Celsius (°C) was calculated to represent dry season conditions, and a 99th

percentile effluent temperature of 19.8°C was calculated to represent wet season conditions. Both

temperatures were used to represent maximum temperature for acute water quality criteria. A 95th

percentile effluent temperature of 22.7°C was calculated to represent dry season conditions, and a 95th

percentile effluent temperature of 19.5°C was calculated to represent wet season conditions. These

temperatures were used to represent maximum temperature for chronic water quality criteria. An

effluent temperature of 17.8°C was calculated to represent annual average conditions.

Columbia River receiving water conditions used in the modeling were developed from field

measurements at the replacement offshore diffuser site, and these were collected by CH2M during

August to October 2015 under low river flow conditions. The receiving water characteristics applied in

the modeling of the selected outfall diffuser configuration are also summarized in Table 1.

Other key model inputs include ambient temperature and water (discharge) depth. The current meter

records and water column profiles collected in 2015 were also used to validate ambient river

temperatures used for the modeling of dry season conditions. Long-term records collected by the U.S.

Geological Survey (USGS) at Vancouver, Washington (Gage 14144700) for the 13-year period from

August 1967 to October 1979 were used to develop a cumulative frequency distribution of river

temperature.

Based on these data sources, a 90th percentile ambient river temperature of 21.1°C was calculated to

represent typical dry season (May through October) conditions. Similarly, a 90th percentile ambient

river temperature of 10.7°C was calculated to represent typical wet weather (November through April)

conditions. An annual average temperature of 12.4°C is based on the 13-year period of record (1967 to

1979) collected by the USGS for the Columbia River at Vancouver, Washington. Discharge depths in the

modeling evaluation represent the average depth of the existing diffuser ports relative to 7Q10 low flow

conditions. The dilution performance of the SCTP outfall diffuser was modeled using UM3 and the

following model input parameters:

• Number, diameter, and spacing of discharge ports: five, 9.8-inch diameter ports with a spacing of

10 feet on center. Note: the actual port configuration is as follows: five risers each with three, 5-inch

by 5-inch square ports oriented in a triangular arrangement. Because the UM3 model cannot

simulate this type of discharge configuration, the equivalent port size of a single 9.8-inch-diameter


5

port on each riser was modeled. This modeling configuration was accepted by Ecology in previous

analyses as a conservative representation of the 3-port turreted diffuser risers.

• Effluent flows and temperatures: refer to Table 1.

• Ports’ horizontal angle: 169° relative to the ambient current direction.

• Ports’ vertical angle: 0° relative to the water surface.

• Angle of diffuser axis relative to ambient current direction: 90°.

• Discharge depth: refer to Table 1.

• Ambient temperature: 21.1°C (dry season, 90th percentile), 10.7°C (wet season, 90th percentile),

and 12.4°C (annual average).

• Ambient current speeds: 12.9, 31.1, and 37.6 centimeters per second (cm/sec) (10th, 50th, and

90th percentile dry season ebb tide, respectively); 4.2, 15.5, and 25.1 cm/sec (10th, 50th, and 90th

percentile dry season flood tide, respectively); 17.1 cm/sec (50th percentile, flood tide-7Q10 high,

wet season); 32.0 cm/sec (50th percentile, ebb tide-30Q5 flow); 34.4 cm/sec (50th percentile, ebb

tide-7Q10 high, wet season); and 59.4 cm/sec (50th percentile, ebb tide-harmonic mean).

Dilution Modeling Results

Table 1 is the modeling summary table and it includes the defined scenarios (based on water quality

criteria, effluent flow scenario, and critical river flow scenario), effluent flow and temperatures, river

flow and temperature, ambient current velocity, diffuser discharge depth, and model-predicted dilution

factors at the acute zone boundary (AZB) and mixing zone boundary (MZB) for the existing SCTP diffuser.

The column at the right side of the summary table shows modeling results for the chronic water quality

criteria. For chronic mixing zones located in tidally-influenced freshwater, Appendix C of the Permit

Writer's Manual specifies that the critical receiving water current velocity is defined as the 50th-

percentile current velocity derived from a cumulative frequency distribution analysis over at least one

tidal cycle. Since site-specific current velocities (measured during the low river flow period)

demonstrated that flood tide currents occur approximately 24 percent of the time at the proposed

discharge site, a time-weighted proportion (i.e., 24 percent flood tide/76 percent ebb tide, calculated

based on 2015 site-specific current measurements under lowest river flows) was applied to the dilution

factors to conservatively represent tidally-averaged results at the chronic mixing zone boundary. Since

chronic water quality criteria for aquatic life are based on average four-day exposure concentrations,

this method provides representative dilution factors at the chronic mixing zone boundary.

The model-predicted dilution factors are summarized in Table 1 for the projected Phase 5B effluent

flows. The Permit Writer’s Manual specifies that dilutions in a tidally influenced river to be flux-average

dilutions at both the AZB and at the MZB. The results of the dilution modeling for dry and wet season

acute dilution conditions are represented by Model Case Nos. 5B1 to 5B5; dry and wet season chronic

dilution conditions by Model Case Nos. 5B6 to 5B9; and for human health conditions by Model Case Nos.

5B10 and 5B11. The UM3 model input and output are included in Attachment 1.

The modeling results for acute aquatic life criteria conditions show predicted dilution factors at the AZB

(22 feet from the diffuser) range from 14 to 24 under all seasonal effluent and receiving water

conditions. The worst-case acute dilution factor (DF) of 14 is predicted to occur under dry season

conditions, a 7Q10-low river flow (83,506 cfs), the lowest 10th percentile flood tide current velocity (4.2

cm/sec), and the highest daily maximum effluent flow (16.5 million gallons per day).

The modeling results also show that the predicted dilution factors at the chronic MZB (217 feet from the

diffuser) are 59 under critical dry season conditions of low river stage and velocities, and 54 under


6

critical wet season conditions and maximum monthly effluent flows. The lowest predicted dilution

factor at the chronic MZB is based on the tidally-averaged/time weighted DF of 54 (represented by

Model Case Nos. 5B8 and 5B9). Model-predicted dilution factors applicable for human-health-criteria

non-carcinogen conditions and human-health-criteria carcinogen conditions are 63 and 114,

respectively. These dilution factors that represent critical acute and chronic aquatic-life-criteria

conditions and human-health-criteria conditions have been applied in the evaluation of compliance with

water quality standards and antidegradation rules, which is presented in the following section.

7

Model Seasonal River River Temperature Tidal Current Flow Equivalent No./Size Ports Diffuser Discharge Acute Zone Mixing Zone Tidally-Averaged & Time

Case No. Basisa

Discharge Flow (cfs) (deg. C) Condition Speed (cm/sec) Rate (mgd) Frequency (deg. C) & Spacing (ft) Depth (feet)c

(22 feet)e

(217 feet)f

Weighted (Chronic Only)g

SCTP-5B1 dry 7Q10-dry 83,506 21.1 ebb 12.9 16.5 99th percentile 23.0 5-9.8" ports at 10-ft 17.0 18 n/a n/a

(90th percentile) (downstream) (10th percentile) (highest daily (dry season) spacing

SCTP-5B2 37.6 maximum) 24 n/a n/a

(90th percentile)

SCTP-5B3 flood 4.2 14 n/a n/a

(upstream) (10th percentile)

SCTP-5B4 25.1 22 n/a n/a

(90th percentile)

SCTP5-5B5 wet 7Q10-wet 108,766 10.7 ebb 34.4 23.0 99th percentile 19.8 5-9.8" ports at 10-ft 17.6 22 n/a n/a

(90th percentile) (downstream) (50th percentile) (highest daily max.) (wet season) spacing

SCTP-5B6 dry 7Q10-dry 83,506 21.1 ebb 31.1 13.2 95th percentile 22.7 5-9.8" ports at 10-ft 17.0 n/a 62

(90th percentile) (downstream) (50th percentile) (highest monthly avg.) (dry season) spacing

SCTP-5B7 flood 15.5 n/a 48


SCTP-5B8 wet 7Q10-wet 108,766 10.7 ebb 34.4 17.5 95th percentile 19.5 5-9.8" ports at 10-ft 17.6 n/a 56

(90th percentile) (downstream) (50th percentile) (maximum monthly) (wet season) spacing

SCTP-5B9 flood 17.1 n/a 47


SCTP-5B10 annual harmonic 191,106 12.4 ebb 59.4 13.3 50th percentile 17.8 5-9.8" ports at 10-ft 18.2 n/a 114 n/a

mean (50th percentile) (downstream) (50th percentile) (annual average) spacing

SCTP-5B11 annual 30Q5 99,893 12.4 ebb 32.0 13.2 50th percentile 17.8 5-9.8" ports at 10-ft 17.1 n/a 63 n/a

(50th percentile) (downstream) (50th percentile) (highest monthly avg.) spacing

Notes:a Dry season is assumed to be the period from May 1 to October 31, wet season from November 1 to Apri l 30.

b Effluent temperature values are based on effluent measurements from January 2010 through April 2016. Effluent flow values were interpolated between actual 2016 and projected 2025 flows from the Facil ities Plan, tp develop projected 2022 effluent flows.

c Discharge depth represents the average depth of the diffuser ports based on (relative to) 7Q10 low flow conditions, which have been measured at the existing SCTP diffuser site (RM 96) in the Columbia River.

d Based on procedures in the Water Quality Program Permit Writer's Manual (Ecology, revised 2015), model-predicted dilution factors for discharges in 'marine and rotating direction' environments (i .e., estuaries) are flux-average values for both acute and chronic conditions.

e The zone where the acute criteria may be exceeded (i .e., acute zone boundary) is a distance of 22 feet (6.7 meters) from any discharge port in both the upstream and the downstream direction.

f The mixing zone boundary is 217 feet (66.2 meters) in all directions from the diffuser, both the upstream and the downstream directions.

g For chronic mixing zones located in salt water and tidally-influenced freshwater, Appendix C of the Water Quality Program Permit Writer's Manual (Washington Department of Ecology, January 2015) specifies that the critical receiving water current velocity is defined as the

50th percenti le current velocity derived from a cumulative frequency distribution analysis over at least one tidal cycle. Since site-specific current velocities (measured during the low river flow period) demonstrated that flood tides occur approximately 24 percent of the

time at the proposed outfal l site, this time-weighted proportion (i .e., 24% flood tide/76% ebb tide) was applied in order to represent tidally-averaged results at the chronic mixing zone boundary.

Table 1

Model-Predicted Dilution Factors Under Critical Dry Season, Wet Season, and Annual Average Discharge Conditions for the Existing Salmon Creek Outfall - Projected 2022 Effluent Flows

Salmon Creek WWTP Phase 5B Project

Columbia River Receiving Water Conditions Effluent Conditionsb

Outfall Diffuser Configuration Model-Predicted Dilution Factors (DF) at Mixing Zone Boundariesd

Human Health Criteria: Carcinogen

Human Health Criteria: Non-Carcinogen

Temperature

Acute Water Quality Criteria

Chronic Water Quality Criteria

59

54

8

Discharge Compliance with Water Quality Standards

Water Quality Standards and Assessments

The Water Quality Standards for Surface Waters of the State of Washington (WAC Chapter 173-201A)

include narrative and numerical receiving water quality standards, as well as antidegradation rules in

Chapter 173-201A-300 that are consistent with the federal Clean Water Act. These standards address

many water quality parameters: dissolved oxygen, temperature, toxicity, turbidity, pH, coliform

bacteria, dissolved gases, aesthetic water conditions, radioisotope concentrations, and toxic substances.

Effects on each of these water quality parameters have been evaluated in the sections below using

projected Phase 5B effluent flows, existing wastewater data, updated dilution factors for the existing

SCTP outfall diffuser, and background Columbia River receiving water data.

Ecology has designated the lower Columbia River for spawning, rearing, and migration of aquatic life in

WAC 173-201A-602, and this designation is protective of rearing and migration year-round as well as

salmon and trout spawning and emergence during the non-summer period (defined as September 17 to

June 13). This designation is relevant to the application of water quality numeric standards for dissolved

oxygen, temperature, pH, and turbidity.

Ecology’s 2014 303(d) list includes approximately 13 miles of the lower Columbia River from the

confluence of the Willamette River (RM 102) to the confluence of the Lewis River (RM 88) as impaired

for temperature and dissolved oxygen. The existing SCTP outfall is located at RM 96. This reach of the

Columbia River is also listed as impaired for bacteria based on the 1998 Water Quality Assessment, and

no new bacteria data have been incorporated into the assessment since the 1998 listing.

Ecology’s 2014 303(d) list was approved by the U.S. Environmental Protection Agency (EPA) in July 2016.

Both are Category 5 listings, meaning that a total maximum daily load (TMDL) study is expected to be

developed unless additional data collections result in reclassify or removal of the Category 5 listings.

Reaches of the lower Columbia River have been listed for temperature for decades, and EPA has taken

the lead of developing temperature TMDLs for the Columbia and Snake Rivers. The dissolved oxygen

listing is more recent and based on shallow shoreline measurements collected in 2006-2009 to assess

impact of aquatic plant growth areas on water quality, and these data are not considered representative

of the flowing Columbia River.

In August through October of 2015, the Alliance had three months of water quality monitoring

conducted at RM 96 as part of the SCTP Phase 5A project for outfall replacement design and these

extensive data collections have been submitted to Ecology’s EIM for application in the next 303(d) water

quality assessment. Figures 1 and 2 provide plots of the 2015 dissolved oxygen data collected near RM

96 during critical low flow conditions. Figure 1 shows both 2015 and historical dissolved oxygen

measurements relative to the DO criteria; and Figure 2 shows the DO saturation values for these 2015

water quality monitoring data. These data plots clearly illustrate dissolved oxygen compliance during the

dry season low river flow conditions in 2015.

In addition, the Alliance and City of Vancouver are conducting dry season water quality monitoring of

the Columbia River in 2018 to provide Ecology with new field measurements of dissolved oxygen, pH,

temperature and conductivity conditions between RM 110 and RM 95 under low river flow conditions.

The 2018 Columbia River Water Quality Monitoring Program is being conducted in accordance with a

Quality Assurance Project Plan that was reviewed by Ecology prior to the start of monitoring. The SCTP

discharge compliance with temperature, dissolved oxygen, bacteria, and other standards are discussed

below.

9

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

5-Jun 25-Jun 15-Jul 4-Aug 24-Aug 13-Sep 3-Oct 23-Oct

Dis

solv

ed

Oxy

ge

n (

mg

/L)

Dry Season Period

Figure 1. Comparison of 2015 Dissolved Oxygen Data and Historical 303(d) Listing Data to DO Criteria

2015 Dissolved Oxygen Measurements

303d Listing Data (Columbia Riverkeepers)

8.0 mg/L Dissolved

Oxygen Criteria in

Columbia River

(Sept. 17 - June 13)

1,490 DO

Measurements

1,759 DO

Measurements

1,670 DO

Measurements

1,990 DO

Measurements

6.5 mg/L Dissolved

Oxygen Criteria in

Columbia River

(June 14-Sept. 16)

10

50.0

60.0

70.0

80.0

90.0

100.0

110.0

120.0

130.0

140.0

25-Jul 4-Aug 14-Aug 24-Aug 3-Sep 13-Sep 23-Sep 3-Oct 13-Oct 23-Oct

Dis

solv

ed

Ox

yg

en

Sa

tura

tio

n (

%)

Dry Season Period

Figure 2. 2015 Dissolved Oxygen Saturation Data Near RM 96 in Columbia River

90% Dissolved

Oxygen Saturation

Criteria in

Columbia River

1,490 DO

Measurements

1,759 DO

Measurements

1,670 DO

Measurements

1,990 DO

Measurements

Note: No Dissolved Oxygen

Saturation Data Recorded

for Past 303(d) WQ

Assessments

Water Quality Compliance Evaluation

This section provides evaluations of the SCTP Phase 5B discharge compliance with water quality

standards for dissolved oxygen, temperature, turbidity, pH, coliform bacteria, dissolved gases, aesthetic

water conditions, radioisotope concentrations, toxicity, and toxic substances.

Dissolved Oxygen

The applicable water quality standard for dissolved oxygen (WAC 173-201A-200(1)(d)) specifies a lowest

1-day minimum dissolved oxygen of 6.5 milligrams per liter (mg/L) during the summer period when

salmon rearing and migration may occur, and a lowest 1-day minimum dissolved oxygen of 8.0 mg/L

during the period when salmon spawning, rearing, and migration may occur (September 17 to June 13).

The aquatic life dissolved oxygen criteria also state that “when a water body's dissolved oxygen (DO) is

lower than the criteria in Table 200 (1)(d) (or within 0.2 mg/L of the criteria) and that condition is due to

natural conditions, then human actions considered cumulatively may not cause the DO of that water

body to decrease more than 0.2 mg/L.” Site-specific criteria for the lower Columbia River also specify

that “dissolved oxygen shall exceed 90 percent saturation.”

As presented in Figures 1 and 2, these 2015 dissolved oxygen data collected near the SCTP existing

outfall at RM 96 during critical low flow conditions show 2015 dissolved oxygen measurements and DO

saturation values were in compliance with dissolved oxygen criteria. The ongoing 2018 dry season

water quality monitoring of the Columbia River will provide Ecology with new field measurements of

dissolved oxygen (as well as temperature, pH, and conductivity) under low river flow conditions.

The wastewater discharge influence on the receiving waters can be identified as immediate dissolved

oxygen demand that occurs during the rapid dilution process in the river and farfield dissolved oxygen

demand that occurs over days as the discharge plume is transported away from the diffuser. To evaluate

Columbia River water dissolved oxygen concentrations at the completion of wastewater dilution (at the

MZB) Ecology’s spreadsheet calculation “Dissolved oxygen concentration following initial dilution” was

applied assuming the lowest model-predicted dilution factor at the MZB boundary under 7Q10 low river

flow conditions (applied worst-case DF = 59 for dry season; see Table 1). This calculation assumes a

conservative effluent dissolved oxygen concentration of 2 mg/L, and an immediate effluent dissolved

oxygen demand (DOD) of 2 mg/L. These spreadsheet calculations are provided in Exhibit 1 and 2 in

Attachment 2.

Using the mass balance calculation in Ecology’s spreadsheet and a conservative assumption that the

ambient DO concentration is just above the criteria, the dissolved oxygen concentration in the Columbia

River at the SCTP discharge MZB is determined as follows:

��

6.6� ! "3� ! � 2� ! � 6.6� !54 ' � 6.5� !

And

8.1� ! "3� ! � 2� ! � 8.1� !54 ' � 8.0� !

The calculated worst-case decrease in dissolved oxygen is the difference between the dissolved oxygen

concentration of the effluent and ambient (DOmixed) and the ambient dissolved oxygen (DOambient).

According to WAC 173-201A-200(1)(d), a reduction in dissolved oxygen of less than 0.2 mg/L is allowed,

even in waterbodies that do not meet the applicable dissolved oxygen criterion. Under these worst-case

12

scenarios, the decrease in dissolved oxygen at the MZB is limited to 0.1 mg/L (during the summer

salmon rearing and migration period) and 0.1 mg/L (during the September–June spawning, rearing and

migration period). Therefore, the SCTP discharge proposed in the Phase 5B Engineering Report would

not cause or contribute to a violation of these DO criteria.

The farfield dissolved oxygen demand on the Columbia River dissolved oxygen concentrations have been

evaluated using Ecology’s PermitCalc_DOSag spreadsheet model that applies the Streeter-Phelps farfield

dissolved model. Ecology’s PermitCalc_DOSag calculates the critical DO concentration, travel time to

the critical DO concentration, and the distance downstream to the critical DO concentration. The model

inputs applied in the farfield DO demand modeling are listed in the model sheets and these include:

Effluent discharge flows for Phase 5B (2022) - applied both maximum day dry weather (16.5 mgd) and

maximum month dry weather (13.2 mgd);

Effluent CBOD for Phase 5B treatment operations – 3.83 mg/L;

Effluent NBOD for Phase 5B treatment operations – 0.69 mg/L;

Effluent DO and temperature – 2 mg/L DO and 23.0 degrees C;

River discharge flow at 7Q10 low flow condition – 83,506 cfs;

River upstream CBOD and NBOD – 0.5 mg/L and 1.75 mg/L, respectively; and

River DO and temperature – 8.1 mg/L and 21.1 degrees C;

Reaeration rate in river – 0.20/day (base e) [Based on large river reaeration rate in Bennett & Rathbun

(1972) and EPA Surface WQ Modeling Guidance (1985)]

BOD decay rate in river – 0.07 /day (base e) [Based on BOD decay reaction rates in Willamette River by

McCutcheon (1983) and EPA Surface WQ Modeling Guidance (1985)]

These Streeter-Phelps DO Sag calculations are provided in Exhibit 3 and 4 in Attachment 2 for the two

effluent discharge flows. These farfield DO Sag modeling analyses show a critical DO concentration of

8.09 mg/L for both maximum day and maximum month dry weather effluent discharges for the Phase

5B operations under critical dry season low river flow conditions. The critical DO concentration is 0.01

mg/L below the initial or background river concentration of 8.1 mg/L. The travel time and distance to

the critical DO concentration is 1.2 days and 19.9 miles for both Phase 5B effluent discharge rates

modeled. Under these worst-case scenarios, the farfield decrease in dissolved oxygen is limited to 0.01

mg/L during critical low river flow conditions and therefore, the SCTP Phase 5B advanced treated

effluent would not cause or contribute to an exceedance of DO criteria in the Columbia River.

Temperature

The temperature standards (WAC 173-201A-200(1)(c)) include narrative and numeric criteria. The lower

Columbia River has specific temperature criteria that are defined in WAC 173-201A-602, Table 602. The

numeric criteria for the lower Columbia River are:

“Temperature shall not exceed a 1-day maximum (1-DMax) of 20.0°C due to human activities. When

natural conditions exceed a 1-DMax of 20.0°C, no temperature increase will be allowed which will

raise the receiving water temperature by greater than 0.3°C; nor shall such temperature increases,

at any time, exceed 0.3°C due to any single source or 1.1°C due to all such activities combined.”

In addition, WAC 173-201A-200(1)(c) stipulates that the maximum incremental temperature increase

allowed and resulting from an individual point source cannot exceed 28/T+7 (in °C) at the MZB, where T

is background temperature. This maximum incremental temperature is only relevant when background

river temperatures are equal to or less than 16.3°C.

The temperature standards also have guidelines for preventing acute lethality and barriers to migration

of salmonids in WAC 173-201A-200(1c)(vii), as follows:

“(vii) The department will incorporate the following guidelines on preventing acute lethality and

barriers to migration of salmonids into determinations of compliance with the narrative

requirements for use protection established in this chapter (e.g., WAC 173-201A-310(1), 173-201A-

400(4), and 173-201A-410 (1)(c)). The following site-level considerations do not, however, override

the temperature criteria established for waters in subsection (1)(c) of this section or WAC 173-201A-

600 through 173-201A-602:

(A) Moderately acclimated (16-20°C, or 60.8-68°F) adult and juvenile salmonids will generally be

protected from acute lethality by discrete human actions maintaining the 7-DADMax

temperature at or below 22°C (71.6°F) and the 1-day maximum (1-DMax) temperature at or

below 23°C (73.4°F).

(B) Lethality to developing fish embryos can be expected to occur at a 1-DMax temperature

greater than 17.5°C (63.5°F).

(C) To protect aquatic organisms, discharge plume temperatures must be maintained such that

fish could not be entrained (based on plume time of travel) for more than two seconds at

temperatures above 33°C (91.4°F) to avoid creating areas that will cause near instantaneous

lethality.

(D) Barriers to adult salmonid migration are assumed to exist any time the 1-DMax temperature

is greater than 22°C (71.6°F) and the adjacent downstream water temperatures are 3°C

(5.4°F) or more cooler.”

The compliance temperatures at the MZB in the river for the SCTP wastewater discharge are

summarized below. Based on an assumed maximum SCTP effluent temperature of 23°C and minimum

dry season dilution factor of 59 at the MZB, each compliance temperature condition has been assessed

and the estimated maximum allowable effluent temperature is identified for each, as follows, with

answers provided in brackets.

1. Aquatic life temperature criteria (1-day maximum temperature at or below 23°C)—[Maximum

effluent temperature prior to discharge = 23.1°C]

2. Site-specific temperature criteria (year-round) = 20.0°C (1-DMax) due to human activities—

[Maximum mixed effluent temperature at MZB = 20.06°C]

3. Site-specific temperature criteria (year-round) when natural conditions > 1-DMax of 20.0 °C, then no

temperature increase greater than 0.3°C—[Maximum mixed effluent temperature at MZB = 20.06°C;

temperature change of 0.06°C]

4. Individual point source (year-round) cannot exceed 28/T+7 at the MZB, where T is background

temperature—[not relevant due to high dilutions]

5. Acute lethality protection (adult and juvenile salmon) = 7-DADMax temperature =/< 22°C, and 1-

DMax temperature =/< 23°C —[Maximum mixed effluent temperature at AZB = 20.2°C]

6. Acute lethality protection (fish embryo) = 1-DMax temperature < 17.5°C—[not applicable to

Columbia River site]

7. Acute lethality protection (fish) = plume discharge temperature after 2 seconds < 33.0°C—

[Maximum effluent temperature 23.1°C]

8. Migration protection (adult salmon) = 1-DMax temperature < 22°C, and background river

temperature =/> 3°C cooler—[Maximum mixed effluent temperature at MZB = 20.06°C]

To support this screening-level temperature compliance assessment of the SCTP Phase 5B discharge, the

temperature calculations described below have been developed.

An energy (mass) balance equation was applied to calculate the excess temperature at the MZB (the

difference between the mixed temperature of effluent and river water and the background river

14

temperature or temperature criteria). The worst-case temperature screening evaluation assumed that

the river water temperature equals the temperature criterion of 20.0°C (year-round), and applied the

maximum measured effluent temperature of 23.10°C (based on effluent data for the period of May

2010 through April 2016).

Using a mass balance equation and applying the following inputs, the mixed temperature increase at the

MZB was calculated:

+,- × /�� 0 1,��2�� × /32��2�4�5 � 1,- ,��2��5 × 1/��5 where Tcriterion is the temperature of the receiving stream (based on applicable temperature criterion,

Tcriterion = 20.0°C), Teffluent is the maximum daily effluent temperature (Teffluent = 23.0°C), Q0 represents the

effluent dilution factor prior to dilution (Q0 = 1), and Qentrain is the river dilution portion that mixes with

the effluent, Qentrain = 59.

Using the model-predicted dry season minimum dilution factor of 59 at the MZB, Qo = 1 (by definition)

and Qentrain = 58, solving the equation for Tmixed yields: 11 × 23.10℃5 158 × 20.0℃559 � /�� 20.05℃

The average temperature increase is the difference between the temperature of combined wastewater

and stream mixture at the mixing zone boundary (Tmixed) and the applicable stream temperature

criterion (Tcriterion), or (20.05°C) – (20.0°C) = 0.05°C. Therefore, at the flows proposed in the Phase 5B

Engineering Report, the estimated worst-case excess temperature difference is 0.05°C, and it is,

therefore, not a “measurable” temperature increase (defined as greater than 0.3°C).

Turbidity

The turbidity criterion allows a maximum turbidity change at the MZB of 5 nephelometric turbidity units

(NTU) when background river turbidity is 50 NTU or less, and up to a 10 percent increase in stream

turbidity when background river turbidity is greater than 50 NTU (WAC 173-201A-200(1)(e). SCTP is not

required to monitor effluent turbidity or receiving water turbidity, and there are no turbidity values.

Based on the model-predicted dilution factors at the MZB summarized in Table 1, the effluent

discharged through the SCTP outfall diffuser will be diluted by a minimum dry season dilution factor of

59 and a minimum wet season dilution factor of 54, and the mixed effluent and river turbidity will not

exceed the turbidity criterion.

Total Dissolved Gas

The numeric and narrative standards for total dissolved gas are set forth in WAC 173-201A-200(1)(f),

which limits dissolved gases in freshwater to less than 110 percent of saturation. The SCTP discharge will

not release dissolved gases such as hydrogen sulfide, carbon dioxide, or other gases that would cause or

contribute to a violation of this criterion in the Columbia River. The treated wastewater discharged to

the Columbia River will contain dissolved oxygen as the only significant dissolved gas and will not exceed

110 percent saturation for dissolved gases. Therefore, the SCTP discharge would not cause or contribute

to a violation of this criterion.

pH

The effluent pH limit in the NPDES permit is a daily maximum of 6.0 to 9.0 standard units. The applicable

pH standard for the Columbia River (WAC 173-201A-200(1)(g)) is between 6.5 and 8.5. According to

effluent data from January 2010 through June 2015, effluent pH has remained between 6.13 and 7.39.

Based on a calculation of the mixed pH at the MZB using Ecology’s Reasonable Potential Analysis (RPA)

calculation spreadsheet (March 2015 version), the worst-case mixed pH at the MZB would not be less

than 6.5 or more than 8.5. Therefore, the SCTP discharge would not cause or contribute to a violation of

this criterion.

Bacteria

The numeric and narrative bacterial standards are set forth in WAC 173-201A, Table 200(2)(b). The

freshwater bacteria criterion for primary contact recreation applicable in the lower Columbia River

specify that “fecal coliform organism levels must not exceed a geometric mean value of 100

colonies/100 mL [milliliter], with not more than 10 percent of all samples (or any single sample when

less than ten sample points exist) obtained for calculating the geometric mean value exceeding 200

colonies/100 mL.” Because the SCTP uses ultraviolet light disinfection to treat the wastewater before

discharge, and the capacity of the disinfection unit process exceeds the Phase 5 flows, discharge would

not cause or contribute to a violation of this criterion.

Radioisotopes

WAC 173-201A-250 prohibits radioisotope concentrations in excess of maximum permissible

concentrations defined in federal statutes. The influent flow and loads are not known to contain

radioisotopes, and SCTP treatment unit processes are not known to create or concentrate such

isotopies. Therefore, the discharge is not expected to contain any radioisotopes.

Toxic Substances

WAC 173-201A-240 prohibits discharge of toxic pollutants in amounts that may be harmful to beneficial

uses. WAC 173-201A-240, Table 240(3), establishes numeric criteria for the protection of aquatic

organisms in freshwater and marine water, and the EPA-approved numeric criteria for the protection of

human health were established in November 2016. An evaluation of the dilution factors required for the

SCTP effluent maximum discharge concentrations to comply with the aquatic life and human health-

based water quality criteria is presented in Table 2.

The dilution factors required for SCTP effluent compliance with acute aquatic life criteria is 8 (based on

copper) and 13 (based on cyanide method detection limits, not measured cyanide). The minimum

model-predicted acute dilution factor is 14 under dry season conditions. The dilution factors required

for SCTP effluent compliance with chronic aquatic life criteria is 12 (based on copper) and 20 (based on

ammonia in the wet season). The minimum model-predicted chronic dilution factor is 59 under dry

season conditions and 54 under wet season conditions. The effluent ammonia concentrations applied in

this screening analysis (Table 2) represents effluent concentrations in 2011-2015 (9.4 mg/L maximum in

wet season and 11.0 mg/L in dry season), and the SCTP Phase 5B effluent ammonia concentration will

be lower as a result of treatment improvements.

For human health-based criteria, a required dilution factor of 125 is calculated for arsenic; however, the

receiving water data show that the current approved human health criteria for arsenic is lower than the

measured background arsenic concentrations in the Columbia River by an order of magnitude and is

therefore not attainable. In addition, three other detected chemicals that require high dilution factors

were Bis(2-Ethylhexyl)Phthalate and pesticides beta-BHC and heptachlor. The pesticides beta-BHC and

heptachlor are legacy pesticides and no longer sold, so these may be due to a private residence’s

improper disposal of old pesticides into the sewage system, and ongoing monitoring will resolve these

sources. Bis(2-Ethylhexyl)Phthalate is ubiquitous in municipal wastewater effluents and state and

federal restriction could be needed to reduce their sources to sewage systems.

Antidegradation Rule

Washington’s antidegradation rule is defined in WAC 173-201A-300, and the rule specifies the following

purpose of the antidegradation policy:

“(a) Restore and maintain the highest possible quality of the surface waters of Washington;

(b) Describe situations under which water quality may be lowered from its current condition;

16

(c) Apply to human activities that are likely to have an impact on the water quality of a surface

water;

(d) Ensure that all human activities that are likely to contribute to a lowering of water quality, at a

minimum, apply all known, available, and reasonable methods of prevention, control, and treatment

(AKART); and

(e) Apply three levels of protection for surface waters of the state, as generally described below:

(i) Tier I is used to ensure existing and designated uses are maintained and protected and

applies to all waters and all sources of pollution.

(ii) Tier II is used to ensure that waters of a higher quality than the criteria assigned in this

chapter are not degraded unless such lowering of water quality is necessary and in the

overriding public interest. Tier II applies only to a specific list of polluting activities.

(iii) Tier III is used to prevent the degradation of waters formally listed in this chapter as

"outstanding resource waters," and applies to all sources of pollution.”

Washington’s antidegradation rule provides the three levels of protection (Tiers I, II, and III) listed

above. Tier I protections include maintaining and protecting existing designated uses, improving water

quality conditions to align with water quality standards and protect existing designated uses, and

identifying where natural conditions (exclusive of human actions) do not allow water quality standards

to be met. Washington’s antidegradation rule also provides that waterbodies “may not be further

degraded” except as authorized by the rule (refer to WAC 173-201A-310(1)).

Tier II antidegradation protections address “new or expanded actions … that are expected to cause a

measurable change in the quality of the water,” and such actions “may not be allowed unless the

department determines that the lowering of water quality is necessary and in the overriding public

interest” (refer to WAC 173-201A-320(1)). Ecology has specified in the rule that a Tier II review will only

be conducted for new or expanded actions. Public involvement with the Tier II review are conducted in

accordance with the processes associated with NPDES discharge permits, as well as other permitting.

Ecology has interpreted “degradation” as a “measurable change in water quality” away from conditions

unaffected by the source area (after allowing for mixing consistent with WAC 173-201A-400(7)). In the

context of this rule, a measurable change is defined by Ecology as a:

(a) Temperature increase of 0.3°C or greater

(b) Dissolved oxygen decrease of 0.2 mg/L or greater

(c) Bacteria level increase of 2 colony forming units/100 mL or greater

(d) pH change of 0.1 units or greater

(e) Turbidity increase of 0.5 NTU or greater, or

(f) Any detectable increase in the concentration of a toxic or radioactive substance

Ecology rules specifies that “to determine that a lowering of water quality is necessary and in the

overriding public interest, an analysis must be conducted for new or expanded actions when the

resulting action has the potential to cause a measurable change in the physical, chemical, or biological

quality of a water body.” The preceding evaluation of water quality standards compliance for the SCTP

Phase 5B wastewater discharge to the Columbia River provides specific results to demonstrate that the

discharge will not cause a measurable change in the river water quality.

17

Acute Chronic

Parameter (µg/L) b (µg/L) c (µg/L)

Antimony -- -- 6 19 0.22 1.39 0.55 0.1 0.1 -- -- 0.04

Arsenic i 360 190 0.018 19 1.85 1.39 0.55 1.24 0.01 0.02 125

Cadmium 2.1 0.7 -- 19 0.03 1/2 DL 1.39 -- 0.1 0.1 0.2 --

Chromium (+3) 336 112 -- 19 0.56 1.39 -- 0.44 0.004 0.01 --

Copper 10.3 7.0 1300 19 59.6 1.39 0.55 0.8 8 12 0.03

Lead 36.1 1.4 -- 19 0.47 1.39 -- 0.13 0.02 1 --

Mercury 2.1 0.012 0.14 9 0.0024 1.81 0.70 0.0068 0.01 1 0.1

Nickel 904.5 97.7 80 19 1.5 1.39 0.55 0.83 0.003 0.03 0.02

Selenium 20 5.0 60 19 0.2 1.39 0.55 0.5 0.5 0.04 0.2 0.01

Silver 1.4 -- -- 19 0.03 1.39 -- 0.01 0.01 0.04 -- --

Thallium -- -- 1.7 19 0.05 1/2 DL 1.39 0.55 0.01 0.01 -- -- 0.02

Zinc 73.1 64.9 1000 19 60.0 1.39 0.55 4.5 1 1 0.04

Cyanide 1.0 5.2 9 4 5.0 1/2 DL 2.59 0.93 0.0 0 13 2 1

Bis(2-Ethylhexyl)Phthlate -- -- 0.045 4 16.8 2.59 0.93 0.0 0 -- -- 349

1,2-Dichloroethane -- -- 8.9 4 0.5 1/2 DL 2.59 0.93 0.0 0 -- -- 0.1

Dichlorobromomethane -- -- 0.73 4 0.5 1/2 DL 2.59 0.93 0.0 0 -- -- 1

Benzene -- -- 0.44 4 0.5 1/2 DL 2.59 0.93 0.0 0 -- -- 1

beta-BHC (pesticide) 0.0013 4 0.02 j 2.59 0.93 0.0 0 -- -- 14

Heptachlor (pesticide) 0.53 0.0036 0.00000034 4 0.019 j 2.59 0.93 0.0 0 0.1 14 52172

Chloroform -- -- 100 4 0.5 1/2 DL 2.59 0.93 0.0 0 -- -- 0.005

Napthalene -- -- -- 4 0.2 1/2 DL 2.59 0.93 0.0 0 -- -- --

Toluene -- -- 72 4 1.1 2.59 0.93 0.0 0 -- -- 0.01

Phenol -- -- 9000 4 10 1/2 DL 2.59 0.93 0.0 0 -- -- 0.001

Ammonia 2011-15 (Dry Season) h 2310 299 -- 264 11000 1.0 50 5 37 --

Ammonia 2011-15 (Wet Season) 2310 473 -- 256 9400 1.0 50 4 20 --

Note:

a Freshwater acute & chronic criteria from Chapter 173-201A-240 WAC (2016) Water Quality Standards for Washington. Human health criteria are existing 2016 water quality standards. Mixed river and effluent hardness of 58.5 mg/L (acute) and 55.6 mg/L (chronic).

b The freshwater acute criteria is a 1-hour average concentration not to be exceeded more than once every three years on the average, with the exception of silver, which is an instantaneous concentration not to be exceeded at any time.

c The freshwater chronic criteria is a 4-day average concentration not to be exceeded more than once every three years on the average.

d The reasonable potential multiplying factor assumes a coefficient of variation of 0.6, based on guidance on Table 3-2 (p.54) in the Technical Support Document (EPA, 1991) and Ecology's RPA spreadsheet.

e Background receiving water analytical data collected during ebb tide conditions in August to October 2015 near Columbia River RM 96. These background river data are based on clean sampling and low detection analytical methods.

f The acute zone boundary for the outfall is point of acute aquatic life criteria compliance and the chronic mixing zone boundary is the point of chronic aquatic life and human health criteria compliance.

g The revised water quality criteria for human health (HHC) were made effective by EPA on 12/28/2016. The lowest HHC - water & organisms or organisms only - is presented in this table for compliance assessment.

h Total ammonia as N. Criteria calculated using worst-case receiving water pH of 8.5 and temperature of 22.0°C (summer-dry season; May-Oct) and worst-case pH of 8.5 and temperature of 15 °C (winter- wet season; Nov-April).

i Note that the current HHC for arsenic is lower than the concentration in the Columbia River and therefore not attainable.

j Single detected values reported from priority pollutant samples collected in 2012 and no other detected values in 2011, 2013, and 2014 samples.

Table 2

Evaluation of Dilution Requirements for Water Quality Compliance for the Salmon Creek Treatment Plant Outfall 001 Discharge to the Columbia River

Salmon Creek WWTP Phase 5B Project

Water Quality Criteriaa

No. of

Effluent

Samples

Maximum Effluent

Concentration

(2011-2015) (ug/L)

Reasonable Potential

Multiplying Factor

(95% Confidence Limit

& 95% Probability) d

Human Health

Reasonable

Potential

Multiplying

Factor

Upper 90th-%

Background

River

Concentration

(µg/L) e

Median

Background

River

Concentration

(µg/L) e

0.0068

Aquatic Life Human Health

Aquatic Life 2016 Final CWA-

Effective Human

Health Criteria g

Minimum Dilution

to Meet WQ

Criteria at Acute

Zone Boundary f

Minimum Dilution

to Meet WQ

Criteria at Mixing

Zone Boundary f

Minimum Dilution to

Meet HH-WQ Criteria

at Mixing Zone

Boundary f

1.24

0.1

0.44

0.8

0.13

30

30

0.83

4.5

18

Acute and Chronic Toxicity

The most recent permit requires the SCTP to perform quarterly acute and bi-annually chronic whole

effluent toxicity (WET) testing. All of the required WET test results have been in compliance with the

permit effluent limits for both acute and chronic toxicity since 2011 through 2015. Because the

projected Phase 5B discharge is not expected to result in an increase in pollutant concentrations, it is

not expected to cause or contribute to a violation of acute and chronic toxicity criteria.

Biological Resources and Uses of the Columbia River The Columbia River supports both anadromous and non-anadromous (resident) species of fish. At the

SCTP outfall discharge site, the Columbia River is used by anadromous fish primarily for migration.

Fourteen salmonids are federally listed as threatened or endangered within this watershed. Juvenile

salmon occur in the river estuary all year, as different species, size classes, and life history types

continually move downstream and enter tidal waters from upstream.

StreamNet (2012) shows the following fish uses in the Columbia River in the vicinity of the SCTP outfall

site:

• Spring, summer, and fall Chinook—migration

• Coho—rearing and migration

• Summer and winter steelhead—migration

• Sockeye—migration

• Chum—migration

• Pink—migration

• Bull trout—migration

Lower Columbia River Chinook salmon and Lower Columbia River steelhead are federal threatened

species under the Endangered Species Act (ESA), and critical habitat was designated for both species in

2000 (National Marine Fisheries Service [NMFS] and National Oceanic and Atmospheric Administration

[NOAA], 2000). The Columbia River is included as critical habitat for the lower Columbia River Chinook

salmon and lower Columbia River steelhead (StreamNet, 2012). These species use the lower Columbia

River for rearing and migration.

Lower Columbia River coho salmon is a state endangered and federal threatened species, and no critical

habitat has been designated for the lower Columbia River coho salmon. Columbia River chum salmon is

a federal threatened species, and critical habitat was designated for Columbia River chum salmon in

2000 (NMFS and NOAA, 2000).

NOAA NMFS listed river eulachon (also known as “smelt”) for protection under the ESA on May 17,

2010. Eulachon (Thaleichthys pacificus) ascend the Columbia River to spawn in the lower mainstem and

tributaries. The lower Columbia River is included in the listing of critical habitat areas for eulachon

(NOAA, 2012).

The SCTP discharge is rapidly diluted and it does not have any adverse effects on the listed salmonid

species, eulachon, or their aquatic habitat. As reviewed in the preceding section, the SCTP discharge

does not and will not cause or contribute to violations of temperature or other instream water quality

standards. These standards have been developed to protect sensitive cold-water aquatic organisms,

including ESA-listed species, and there are no uniquely sensitive species using the lower Columbia River

that would not be adequately protected by these standards.

19

References Bennett, J.P., and R.E. Rathbun. 1972. Reaeration in Open-Channel Flow,

U.S. Geological Survey Professional Paper 737.

CH2M HILL. 2004. Outfall Dilution Study Report for the Salmon Creek Treatment Plant. January.

CH2M HILL. 2004. Addendum to the Outfall Dilution Study Report for the Salmon Creek Treatment Plant.

May.

CH2M HILL, Inc. (CH2M). 2013. Salmon Creek Wastewater Management System Wastewater Facilities

Plan/ General Sewer Plan Amendment. August.

CH2M. 2016. Columbia River Bedform Analysis near Salmon Creek WWTP. Technical Memorandum

prepared for the Discovery Clean Water Alliance. June 19.

Frick, W.E., P.J.W. Roberts, L. R. Davis, J. Keyes, D.J. Baumgartner, and K.P. George. 2003. Dilution

Models for Effluent Discharges, 4th Edition (Visual Plumes). Environmental Research Division, NERL,

ORD. U.S. Environmental Protection Agency. March 4.

Mccutcheon, S.C. 1983. Evaluation of Selected One-Dimensional Stream Water-Quality Models with

Field Data. U.S. Army Engineer Waterways Experiment Station Technical Report E-83-11. Vicksburg,

Mississippi.

National Marine Fisheries Service (NMFS) and National Oceanic and Atmospheric Administration

(NOAA). 2000. Designated Critical Habitat: Critical Habitat for 19 Evolutionarily Significant Units of

Salmon and Steelhead in Washington, Oregon, Idaho, and California. Final Rule. Federal Register 65(32):

7764-7787. February 16.

National Oceanic and Atmospheric Administration (NOAA). 2012. Office of Protected Resources.

http://www.nmfs.noaa.gov/pr/species/fish/. Accessed on January 19, 2012.

StreamNet. 2012. StreamNet: Fish Data for the Northwest. http://www.streamnet.org/index.html.

Accessed on January 19, 2012.

U.S. Environmental Protection Agency (EPA). 1985. Rates, Constants, and Kinetics Formulations in Surface

Water Quality Modeling. 2nd Edition. EPA/600/3-85/O40. June.

Washington State Department of Ecology (Ecology). 2011. Water Quality Program Guidance Manual:

Supplemental Guidance on Implementing Tier II Antidegradation. Publication No. 11-10-073. September.

Washington State Department of Ecology (Ecology). 2015. Water Quality Program Permit Writer's Manual.

Publication No. 92-109. January 2015 (revised).

Attachment 1

UM3 Model Input and Output

/ UM3. 7/26/2017 8:17:33 AM

Case 5B1; ambient file c:\plumes\VPplume 10.001.db; Diffuser table record 1:00 ----------------------------------

Ambient Table:

Depth Amb-cur Amb-dir Amb-sal Amb-tem Amb-pol Decay Far-spd Far-dir Disprsn Density

m m/s deg psu C kg/kg s-1 m/s deg m0.67/s2 sigma-T

0 0.129 90 0.08 21.1 0 0 0.129 90 0.00068 -1.906

6 0.129 90 0.08 21.1 0 0 0.129 90 0.00068 -1.906

Diffuser table:

P-dia P-elev V-angle H-angle Ports Spacing AcuteMZ ChrncMZ P-depth Ttl-flo Eff-sal Temp Polutnt

(m) (m) (deg) (deg) () (m) (m) (m) (m) (MGD) (psu) (C) (%)

0.249 0.61 0 169 5 3.05 7.4 74 5.18 16.5 0 23 100

Simulation:

Froude number: 85.44; effleunt density (sigma-T) -2.399; effleunt velocity 2.969(m/s);

Depth Amb-cur P-dia Polutnt Dilutn CL-diln x-posn y-posn Time Distance

Step (m) (m/s) (m) (%) () () (m) (m) (s) (m)

0 5.18 0.129 0.249 100 1 1 0 0 0.0; 0.00

10 5.18 0.129 0.3 82.03 1.219 1 -0.115 0.023 0.0442; 0.12

20 5.18 0.129 0.366 67.3 1.486 1 -0.251 0.0516 0.108; 0.26

30 5.18 0.129 0.445 55.21 1.811 1 -0.411 0.0873 0.199; 0.42

40 5.18 0.129 0.541 45.29 2.207 1.133 -0.597 0.132 0.329; 0.61

50 5.18 0.129 0.658 37.15 2.691 1.376 -0.813 0.188 0.512; 0.83

60 5.179 0.129 0.8 30.48 3.28 1.669 -1.06 0.258 0.768; 1.09

70 5.179 0.129 0.971 25 3.998 2.021 -1.341 0.346 1.122; 1.38

80 5.178 0.129 1.176 20.51 4.874 2.442 -1.657 0.456 1.607; 1.72

90 5.177 0.129 1.423 16.83 5.941 2.94 -2.008 0.593 2.263; 2.09

100 5.175 0.129 1.716 13.8 7.242 3.526 -2.391 0.764 3.137; 2.51

110 5.173 0.129 2.064 11.32 8.827 4.205 -2.804 0.974 4.285; 2.97

120 5.169 0.129 2.471 9.289 10.76 4.983 -3.243 1.231 5.77; 3.47

124 5.168 0.129 2.651 8.582 11.65 5.321 -3.424 1.349 6.473; 3.68 bottom hit;

128 5.165 0.129 2.837 7.958 12.56 5.687 -3.624 1.488 7.316; 3.92 merging;

130 5.163 0.129 2.946 7.649 13.07 5.951 -3.827 1.635 8.22; 4.16

140 5.139 0.129 3.805 6.275 15.93 7.83 -5.111 2.661 14.68; 5.76

18 6.7 acute zone (6.7 m)

149 5.097 0.129 5.03 5.251 19.04 11.2 -6.451 3.908 22.79; 7.54

150 5.092 0.129 5.198 5.148 19.42 11.52 -6.604 4.062 23.8; 7.75

160 5.02 0.129 7.294 4.223 23.67 13.54 -8.104 5.726 34.96; 9.92

170 4.929 0.129 10.34 3.464 28.85 15.89 -9.463 7.517 47.26; 12.09

178 4.85 0.129 13.68 2.957 33.81 18.08 -10.4 8.967 57.41; 13.73 matched energy radial vel = 0.117m/s;

180 4.829 0.129 14.67 2.842 35.17 18.68 -10.61 9.327 59.95; 14.13

190 4.729 0.129 20.75 2.331 42.87 22.02 -11.55 11.1 72.57; 16.02

192 4.709 0.129 22.23 2.241 44.61 22.77 -11.72 11.44 75.07; 16.38 surface;

Const Eddy Diffusivity. Farfield dispersion based on wastefield width of 26.4 m

conc dilutn width distnce time

(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

2.23727 44.68 27.07 20 0.0078 0 0 0.129 6.80E-04

2.2391 44.64 27.98 25 0.0186 0 0 0.129 6.80E-04

2.2397 44.63 28.85 30 0.0293 0 0 0.129 6.80E-04

2.23865 44.65 29.7 35 0.0401 0 0 0.129 6.80E-04

2.23431 44.73 30.53 40 0.0509 0 0 0.129 6.80E-04

2.22553 44.91 31.33 45 0.0616 0 0 0.129 6.80E-04

2.21282 45.17 32.11 50 0.0724 0 0 0.129 6.80E-04

2.19666 45.5 32.88 55 0.0832 0 0 0.129 6.80E-04

2.17763 45.9 33.63 60 0.0939 0 0 0.129 6.80E-04

2.1566 46.35 34.36 65 0.105 0 0 0.129 6.80E-04

2.13379 46.84 35.07 70 0.115 0 0 0.129 6.80E-04

2.11026 47.37 35.78 75 0.126 0 0 0.129 6.80E-04

count: 12

;

8:17:33 AM. amb fills: 2

1 OF 14

/ UM3. 7/26/2017 8:18:28 AM


Ambient Table:



0 0.376 90 0.08 21.1 0 0 0.376 90 0.00068 -1.906

6 0.376 90 0.08 21.1 0 0 0.376 90 0.00068 -1.906

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.18 16.5 0 23 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s) (m)

0 5.18 0.376 0.249 100 1 1 0 0 0.0; 0.00

10 5.18 0.376 0.3 82.03 1.219 1 -0.0916 0.0192 0.0352; 0.09

20 5.18 0.376 0.364 67.3 1.486 1 -0.195 0.0442 0.0836; 0.20

30 5.18 0.376 0.441 55.21 1.811 1 -0.311 0.0766 0.15; 0.32

40 5.18 0.376 0.534 45.29 2.207 1.095 -0.438 0.118 0.238; 0.45

50 5.18 0.376 0.645 37.15 2.691 1.311 -0.577 0.172 0.356; 0.60

60 5.18 0.376 0.775 30.48 3.28 1.559 -0.726 0.239 0.509; 0.76

70 5.18 0.376 0.927 25 3.998 1.841 -0.882 0.323 0.706; 0.94

80 5.179 0.376 1.103 20.51 4.874 2.154 -1.044 0.427 0.954; 1.13

90 5.179 0.376 1.301 16.83 5.941 2.498 -1.21 0.554 1.264; 1.33

100 5.179 0.376 1.523 13.8 7.242 2.873 -1.378 0.709 1.646; 1.55

110 5.178 0.376 1.766 11.32 8.827 3.288 -1.548 0.898 2.12; 1.79

120 5.177 0.376 2.029 9.289 10.76 3.758 -1.723 1.133 2.713; 2.06

124 5.177 0.376 2.14 8.582 11.65 3.981 -1.795 1.242 2.992; 2.18 merging;

127 5.177 0.376 2.228 8.175 12.23 4.219 -1.898 1.409 3.418; 2.36 bottom hit;

130 5.175 0.376 2.361 7.703 12.98 4.563 -2.074 1.709 4.186; 2.69

140 5.17 0.376 3.029 6.319 15.82 6.573 -2.669 2.86 7.143; 3.91

150 5.162 0.376 4.063 5.184 19.28 9.428 -3.221 4.155 10.49; 5.26

160 5.152 0.376 5.541 4.253 23.5 11.25 -3.717 5.561 14.14; 6.69


165 5.147 0.376 6.479 3.852 25.95 12.31 -3.944 6.307 16.09; 7.44

170 5.141 0.376 7.572 3.489 28.65 13.48 -4.159 7.086 18.12; 8.22

180 5.127 0.376 10.3 2.862 34.92 16.24 -4.56 8.767 22.52; 9.88

190 5.112 0.376 13.9 2.348 42.57 19.62 -4.931 10.65 27.48; 11.74


200 5.095 0.376 18.33 1.926 51.9 23.76 -5.287 12.86 33.29; 13.90

208 5.071 0.376 21.61 1.644 60.8 27.73 -5.688 15.84 41.14; 16.83 surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

1.63888 60.99 25.98 20 0.00234 0 0 0.376 6.80E-04

1.64081 60.92 26.3 25 0.00604 0 0 0.376 6.80E-04

1.64166 60.88 26.61 30 0.00973 0 0 0.376 6.80E-04

1.64217 60.87 26.92 35 0.0134 0 0 0.376 6.80E-04

1.64252 60.85 27.22 40 0.0171 0 0 0.376 6.80E-04

1.64277 60.84 27.53 45 0.0208 0 0 0.376 6.80E-04

1.64295 60.84 27.83 50 0.0245 0 0 0.376 6.80E-04

1.64304 60.83 28.12 55 0.0282 0 0 0.376 6.80E-04

1.643 60.83 28.41 60 0.0319 0 0 0.376 6.80E-04

1.64277 60.84 28.7 65 0.0356 0 0 0.376 6.80E-04

1.6423 60.86 28.99 70 0.0393 0 0 0.376 6.80E-04

1.64154 60.89 29.27 75 0.043 0 0 0.376 6.80E-04

count: 12

;

2 OF 14

/ UM3. 7/26/2017 9:01:43 AM

Case 5B3; ambient file C:\Plumes\sctp-5b-dry.vpp.001.db;Diffuser table record 1:00 ----------------------------------

Ambient Table:



0 0.042 90 0.08 21.1 0 0 0.042 90 0.00068 -1.906

6 0.042 90 0.08 21.1 0 0 0.042 90 0.00068 -1.906

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.18 16.5 0 23 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s) (m)

0 5.18 0.042 0.249 100 1 1 0 0 0.0; 0.00

10 5.18 0.042 0.3 82.03 1.219 1 -0.126 0.0247 0.0485; 0.13

20 5.18 0.042 0.366 67.3 1.486 1 -0.278 0.0551 0.12; 0.28

30 5.18 0.042 0.446 55.21 1.811 1 -0.461 0.0925 0.224; 0.47

40 5.18 0.042 0.543 45.29 2.207 1.142 -0.681 0.138 0.377; 0.69

50 5.18 0.042 0.662 37.15 2.691 1.391 -0.944 0.195 0.6; 0.96

60 5.179 0.042 0.806 30.48 3.28 1.694 -1.256 0.265 0.924; 1.28

70 5.178 0.042 0.982 25 3.998 2.062 -1.627 0.351 1.391; 1.66

80 5.177 0.042 1.195 20.51 4.874 2.509 -2.065 0.458 2.063; 2.12

90 5.175 0.042 1.454 16.83 5.941 3.051 -2.577 0.591 3.023; 2.64

100 5.171 0.042 1.768 13.8 7.242 3.708 -3.174 0.755 4.385; 3.26

110 5.165 0.042 2.149 11.32 8.827 4.501 -3.863 0.96 6.302; 3.98

120 5.156 0.042 2.609 9.289 10.76 5.455 -4.65 1.214 8.973; 4.81

127 5.145 0.042 2.986 8.087 12.36 6.235 -5.263 1.427 11.43; 5.45 bottom hit;

128 5.144 0.042 3.044 7.928 12.61 6.371 -5.355 1.46 11.83; 5.55 merging;

130 5.138 0.042 3.174 7.62 13.12 6.695 -5.646 1.567 13.12; 5.86


138 5.094 0.042 3.915 6.504 15.37 8.358 -7.21 2.174 20.87; 7.53

140 5.076 0.042 4.156 6.251 15.99 8.891 -7.689 2.369 23.47; 8.05

150 4.923 0.042 5.758 5.128 19.49 12.87 -10.58 3.636 41.25; 11.19

160 4.603 0.042 8.199 4.207 23.76 15.83 -14.16 5.408 68.09; 15.16


170 4.044 0.042 11.81 3.451 28.96 19 -18.14 7.648 104.4; 19.69

180 3.22 0.042 17.03 2.831 35.3 22.73 -22.15 10.24 148.8; 24.40 stream limit reached;

182 3.026 0.042 18.32 2.721 36.73 23.55 -22.92 10.78 158.5; 25.33 surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

2.7197 36.75 24.92 30 0.0309 0 0 0.042 6.80E-04

2.68927 37.17 27.28 35 0.064 0 0 0.042 6.80E-04

2.61054 38.29 29.46 40 0.097 0 0 0.042 6.80E-04

2.5117 39.8 31.48 45 0.13 0 0 0.042 6.80E-04

2.41025 41.47 33.38 50 0.163 0 0 0.042 6.80E-04

2.31347 43.21 35.18 55 0.196 0 0 0.042 6.80E-04

2.22371 44.95 36.89 60 0.229 0 0 0.042 6.80E-04

2.14168 46.67 38.53 65 0.262 0 0 0.042 6.80E-04

2.06669 48.37 40.1 70 0.295 0 0 0.042 6.80E-04

1.99826 50.03 41.61 75 0.329 0 0 0.042 6.80E-04

count: 10

;


3 OF 14

/ UM3. 7/26/2017 8:19:29 AM


Ambient Table:



0 0.251 90 0.08 21.1 0 0 0.251 90 0.00068 -1.906

6 0.251 90 0.08 21.1 0 0 0.251 90 0.00068 -1.906

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.18 16.5 0 23 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s) (m)

0 5.18 0.251 0.249 100 1 1 0 0 0.0; 0.00

10 5.18 0.251 0.3 82.03 1.219 1 -0.102 0.0209 0.0393; 0.10

20 5.18 0.251 0.365 67.3 1.486 1 -0.22 0.0475 0.0944; 0.23

30 5.18 0.251 0.443 55.21 1.811 1 -0.355 0.0814 0.171; 0.36

40 5.18 0.251 0.538 45.29 2.207 1.116 -0.508 0.125 0.278; 0.52

50 5.18 0.251 0.652 37.15 2.691 1.347 -0.678 0.179 0.422; 0.70

60 5.18 0.251 0.789 30.48 3.28 1.621 -0.867 0.249 0.617; 0.90

70 5.179 0.251 0.951 25 3.998 1.94 -1.072 0.336 0.875; 1.12

80 5.179 0.251 1.143 20.51 4.874 2.309 -1.291 0.444 1.212; 1.37

90 5.178 0.251 1.366 16.83 5.941 2.728 -1.523 0.578 1.645; 1.63

100 5.178 0.251 1.624 13.8 7.242 3.196 -1.763 0.741 2.192; 1.91

110 5.177 0.251 1.916 11.32 8.827 3.712 -2.01 0.94 2.877; 2.22

120 5.175 0.251 2.242 9.289 10.76 4.281 -2.26 1.18 3.726; 2.55

124 5.175 0.251 2.382 8.582 11.65 4.525 -2.362 1.29 4.12; 2.69 bottom hit;

126 5.174 0.251 2.454 8.249 12.12 4.673 -2.413 1.348 4.331; 2.76 merging;

130 5.173 0.251 2.615 7.71 12.96 5.054 -2.626 1.604 5.257; 3.08

140 5.163 0.251 3.353 6.325 15.8 6.865 -3.435 2.702 9.283; 4.37

150 5.148 0.251 4.532 5.188 19.26 10.07 -4.24 4.012 14.16; 5.84


160 5.128 0.251 6.261 4.256 23.48 11.88 -4.97 5.442 19.54; 7.37

161 5.125 0.251 6.47 4.173 23.95 12.08 -5.038 5.589 20.09; 7.52

170 5.105 0.251 8.698 3.492 28.63 14.09 -5.603 6.937 25.22; 8.92

180 5.08 0.251 12.05 2.864 34.9 16.8 -6.147 8.491 31.18; 10.48


190 5.054 0.251 16.59 2.35 42.54 20.13 -6.62 10.13 37.49; 12.10

199 5.029 0.251 21.96 1.966 50.84 23.78 -7.001 11.71 43.62; 13.64 surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

1.95913 51.02 26.26 15 0.0015 0 0 0.251 6.80E-04

1.96287 50.92 26.73 20 0.00704 0 0 0.251 6.80E-04

1.96403 50.89 27.2 25 0.0126 0 0 0.251 6.80E-04

1.96466 50.87 27.66 30 0.0181 0 0 0.251 6.80E-04

1.96505 50.86 28.11 35 0.0236 0 0 0.251 6.80E-04

1.96521 50.86 28.56 40 0.0292 0 0 0.251 6.80E-04

1.965 50.87 29 45 0.0347 0 0 0.251 6.80E-04

1.96421 50.89 29.43 50 0.0402 0 0 0.251 6.80E-04

1.96261 50.93 29.85 55 0.0458 0 0 0.251 6.80E-04

1.96006 50.99 30.27 60 0.0513 0 0 0.251 6.80E-04

1.95647 51.09 30.69 65 0.0568 0 0 0.251 6.80E-04

1.95174 51.21 31.09 70 0.0624 0 0 0.251 6.80E-04

1.94619 51.36 31.5 75 0.0679 0 0 0.251 6.80E-04

count: 13

;


4 OF 14

/ UM3. 7/26/2017 7:54:28 AM

Case 5B5; ambient file C:\Plumes\sctp-5b5-8-9.vpp.001.db;Diffuser table record 1:00 ----------------------------------

Ambient Table:



0 0.344 90 0.08 10.7 0 0 0.344 90 0.00068 -0.238

6 0.344 90 0.08 10.7 0 0 0.344 90 0.00068 -0.238

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.4 23 0 19.8 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s) (m)

0 5.4 0.344 0.249 100 1 1 0 0 0.0; 0.00

10 5.4 0.344 0.3 82.03 1.219 1 -0.103 0.021 0.0282; 0.11

20 5.4 0.344 0.365 67.3 1.485 1 -0.221 0.0476 0.068; 0.23

30 5.4 0.344 0.443 55.21 1.81 1 -0.356 0.0816 0.123; 0.37

40 5.4 0.344 0.538 45.29 2.206 1.116 -0.51 0.125 0.2; 0.53

50 5.4 0.344 0.652 37.15 2.689 1.347 -0.682 0.18 0.305; 0.71

60 5.4 0.344 0.789 30.48 3.277 1.621 -0.872 0.249 0.445; 0.91

70 5.399 0.344 0.951 25 3.995 1.942 -1.079 0.336 0.632; 1.13

80 5.399 0.344 1.143 20.51 4.869 2.312 -1.301 0.444 0.877; 1.37

90 5.398 0.344 1.368 16.83 5.936 2.733 -1.535 0.578 1.191; 1.64

100 5.397 0.344 1.626 13.8 7.235 3.204 -1.779 0.742 1.589; 1.93

110 5.396 0.344 1.92 11.32 8.819 3.725 -2.029 0.941 2.087; 2.24

120 5.394 0.344 2.249 9.289 10.75 4.298 -2.283 1.181 2.705; 2.57

124 5.394 0.344 2.39 8.582 11.64 4.544 -2.386 1.291 2.993; 2.71 bottom hit;

126 5.393 0.344 2.463 8.249 12.11 4.691 -2.438 1.35 3.146; 2.79 merging;

130 5.391 0.344 2.623 7.709 12.95 5.071 -2.654 1.605 3.821; 3.10

140 5.38 0.344 3.364 6.324 15.79 6.874 -3.473 2.701 6.743; 4.40

150 5.363 0.344 4.546 5.188 19.25 10.09 -4.29 4.011 10.29; 5.87


160 5.341 0.344 6.284 4.256 23.46 11.9 -5.033 5.443 14.22; 7.41

170 5.315 0.344 8.735 3.491 28.6 14.11 -5.676 6.941 18.37; 8.97

180 5.288 0.344 12.11 2.864 34.86 16.82 -6.229 8.493 22.7; 10.53


190 5.259 0.344 16.68 2.35 42.5 20.14 -6.707 10.12 27.29; 12.14

200 5.229 0.344 22.79 1.928 51.81 24.23 -7.132 11.88 32.25; 13.86 surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

1.91958 52.02 27.04 15 9.27E-04 0 0 0.344 6.80E-04

1.92346 51.92 27.39 20 0.00496 0 0 0.344 6.80E-04

1.92475 51.88 27.74 25 0.009 0 0 0.344 6.80E-04

1.92545 51.86 28.09 30 0.013 0 0 0.344 6.80E-04

1.92591 51.85 28.43 35 0.0171 0 0 0.344 6.80E-04

1.92624 51.84 28.76 40 0.0211 0 0 0.344 6.80E-04

1.92647 51.83 29.09 45 0.0252 0 0 0.344 6.80E-04

1.92657 51.83 29.42 50 0.0292 0 0 0.344 6.80E-04

1.92651 51.83 29.74 55 0.0332 0 0 0.344 6.80E-04

1.9262 51.84 30.06 60 0.0373 0 0 0.344 6.80E-04

1.92555 51.86 30.38 65 0.0413 0 0 0.344 6.80E-04

1.9245 51.89 30.7 70 0.0453 0 0 0.344 6.80E-04

1.92299 51.93 31.01 75 0.0494 0 0 0.344 6.80E-04

count: 13

;


5 OF 14

/ UM3. 7/26/2017 8:20:35 AM


Ambient Table:



0 0.311 90 0.08 21.1 0 0 0.311 90 0.00068 -1.906

6 0.311 90 0.08 21.1 0 0 0.311 90 0.00068 -1.906

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.18 13.2 0 22.7 100

Simulation:


Depth Amb-cur P-dia Polutnt Dilutn CL-diln x-posn y-posn Time

Step (m) (m/s) (m) (%) () () (m) (m) (s)

0 5.18 0.311 0.249 100 1 1 0 0 0.0;

10 5.18 0.311 0.3 82.03 1.219 1 -0.0906 0.0191 0.0435;

20 5.18 0.311 0.364 67.3 1.486 1 -0.193 0.0439 0.103;

30 5.18 0.311 0.441 55.21 1.811 1 -0.307 0.0761 0.185;

40 5.18 0.311 0.534 45.29 2.208 1.092 -0.432 0.118 0.294;

50 5.18 0.311 0.644 37.15 2.691 1.307 -0.569 0.171 0.438;

60 5.18 0.311 0.774 30.48 3.28 1.553 -0.714 0.238 0.625;

70 5.179 0.311 0.925 25 3.998 1.83 -0.866 0.322 0.865;

80 5.179 0.311 1.098 20.51 4.874 2.138 -1.024 0.425 1.167;

90 5.179 0.311 1.294 16.83 5.941 2.475 -1.184 0.552 1.542;

100 5.178 0.311 1.513 13.8 7.242 2.844 -1.347 0.706 2.006;

110 5.178 0.311 1.751 11.32 8.828 3.252 -1.513 0.895 2.58;

120 5.177 0.311 2.009 9.289 10.76 3.717 -1.683 1.129 3.301;

124 5.176 0.311 2.112 8.629 11.58 3.925 -1.756 1.243 3.653; merging;

128 5.175 0.311 2.245 8.015 12.47 4.287 -1.946 1.564 4.649; bottom hit;

130 5.174 0.311 2.338 7.704 12.98 4.528 -2.065 1.775 5.302;

140 5.167 0.311 3 6.32 15.82 6.559 -2.644 2.93 8.902;

150 5.156 0.311 4.021 5.184 19.28 9.385 -3.18 4.224 12.96;

160 5.144 0.311 5.477 4.253 23.5 11.21 -3.661 5.631 17.39;

165 5.136 0.311 6.399 3.852 25.95 12.27 -3.882 6.38 19.75; acute zone;

170 5.129 0.311 7.473 3.489 28.65 13.45 -4.092 7.165 22.23;

180 5.112 0.311 10.15 2.862 34.92 16.2 -4.484 8.86 27.61;

190 5.092 0.311 13.67 2.348 42.57 19.58 -4.847 10.77 33.69;

192 5.088 0.311 14.49 2.257 44.29 20.35 -4.917 11.19 35.0; matched energy radial vel = 0.227m/s;

200 5.068 0.311 17.78 1.926 51.9 23.73 -5.215 13.14 41.23;

209 5.03 0.311 21.36 1.612 62.02 28.24 -5.68 16.73 52.68; surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

1.6066 62.22 25.71 20 0.00208 0 0 0.311 6.80E-04

1.60889 62.13 26.09 25 0.00655 0 0 0.311 6.80E-04

1.60977 62.09 26.46 30 0.011 0 0 0.311 6.80E-04

1.61027 62.08 26.83 35 0.0155 0 0 0.311 6.80E-04

1.6106 62.06 27.2 40 0.0199 0 0 0.311 6.80E-04

1.61082 62.05 27.56 45 0.0244 0 0 0.311 6.80E-04

1.61091 62.05 27.91 50 0.0289 0 0 0.311 6.80E-04

1.61079 62.06 28.27 55 0.0333 0 0 0.311 6.80E-04

1.61037 62.07 28.61 60 0.0378 0 0 0.311 6.80E-04

1.60954 62.1 28.95 65 0.0423 0 0 0.311 6.80E-04 Chronic MZ (66 m)

1.60822 62.15 29.29 70 0.0467 0 0 0.311 6.80E-04

1.60636 62.23 29.63 75 0.0512 0 0 0.311 6.80E-04

count: 12

;


6 OF 14

/ UM3. 7/26/2017 8:21:16 AM


Ambient Table:



0 0.155 90 0.08 21.1 0 0 0.155 90 0.00068 -1.906

6 0.155 90 0.08 21.1 0 0 0.155 90 0.00068 -1.906

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.18 13.2 0 22.7 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s)

0 5.18 0.155 0.249 100 1 1 0 0 0.0;

10 5.18 0.155 0.3 82.03 1.219 1 -0.108 0.0218 0.0518;

20 5.18 0.155 0.365 67.3 1.486 1 -0.234 0.0493 0.125;

30 5.18 0.155 0.444 55.21 1.811 1 -0.379 0.084 0.229;

40 5.18 0.155 0.54 45.29 2.208 1.125 -0.546 0.128 0.374;

50 5.18 0.155 0.655 37.15 2.691 1.362 -0.736 0.183 0.575;

60 5.179 0.155 0.794 30.48 3.28 1.645 -0.949 0.253 0.85;

70 5.179 0.155 0.961 25 3.998 1.981 -1.185 0.341 1.222;

80 5.178 0.155 1.159 20.51 4.874 2.375 -1.443 0.451 1.717;

90 5.177 0.155 1.394 16.83 5.941 2.832 -1.72 0.587 2.366;

100 5.176 0.155 1.669 13.8 7.242 3.354 -2.014 0.754 3.204;

110 5.174 0.155 1.987 11.32 8.828 3.941 -2.321 0.959 4.27;

120 5.171 0.155 2.35 9.289 10.76 4.593 -2.638 1.207 5.608;

124 5.17 0.155 2.507 8.582 11.65 4.872 -2.766 1.32 6.231; bottom hit;

127 5.169 0.155 2.622 8.135 12.29 5.089 -2.868 1.415 6.761; merging;

130 5.166 0.155 2.761 7.689 13 5.419 -3.096 1.638 8.01;

140 5.146 0.155 3.547 6.308 15.85 7.211 -4.074 2.709 14.11;

150 5.114 0.155 4.814 5.175 19.32 10.61 -5.105 4.054 21.94;

156 5.088 0.155 5.858 4.595 21.75 11.68 -5.696 4.944 27.19; acute zone;

160 5.069 0.155 6.695 4.245 23.55 12.46 -6.068 5.557 30.84;

170 5.017 0.155 9.383 3.482 28.7 14.69 -6.905 7.124 40.26;

180 4.962 0.155 13.14 2.857 34.99 17.4 -7.61 8.712 49.93;


190 4.906 0.155 18.29 2.344 42.65 20.71 -8.2 10.32 59.79;

195 4.877 0.155 21.52 2.123 47.09 22.64 -8.46 11.13 64.85; surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

2.11558 47.25 25.85 15 0.00182 0 0 0.155 6.80E-04

2.12006 47.15 26.61 20 0.0108 0 0 0.155 6.80E-04

2.12118 47.12 27.35 25 0.0197 0 0 0.155 6.80E-04

2.12161 47.11 28.07 30 0.0287 0 0 0.155 6.80E-04

2.12096 47.13 28.77 35 0.0377 0 0 0.155 6.80E-04

2.11822 47.19 29.46 40 0.0466 0 0 0.155 6.80E-04

2.11267 47.31 30.13 45 0.0556 0 0 0.155 6.80E-04

2.10404 47.51 30.78 50 0.0645 0 0 0.155 6.80E-04

2.09291 47.76 31.43 55 0.0735 0 0 0.155 6.80E-04

2.07958 48.07 32.05 60 0.0825 0 0 0.155 6.80E-04

2.0643 48.42 32.67 65 0.0914 0 0 0.155 6.80E-04 Chronic MZ (66 m)

2.04766 48.82 33.28 70 0.1 0 0 0.155 6.80E-04

2.02961 49.25 33.87 75 0.109 0 0 0.155 6.80E-04

count: 13

;


7 OF 14

/ UM3. 7/26/2017 7:57:06 AM


Ambient Table:



0 0.344 90 0.08 10.7 0 0 0.344 90 0.00068 -0.238

6 0.344 90 0.08 10.7 0 0 0.344 90 0.00068 -0.238

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.4 17 0 19.5 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s)

0 5.4 0.344 0.249 100 1 1 0 0 0.0;

10 5.4 0.344 0.3 82.03 1.219 1 -0.0949 0.0197 0.0354;

20 5.4 0.344 0.364 67.3 1.485 1 -0.203 0.0452 0.0843;

30 5.4 0.344 0.442 55.21 1.81 1 -0.324 0.078 0.152;

40 5.4 0.344 0.535 45.29 2.206 1.102 -0.459 0.12 0.243;

50 5.4 0.344 0.647 37.15 2.689 1.323 -0.608 0.174 0.365;

60 5.399 0.344 0.78 30.48 3.278 1.58 -0.768 0.242 0.526;

70 5.399 0.344 0.935 25 3.995 1.874 -0.938 0.327 0.734;

80 5.398 0.344 1.116 20.51 4.87 2.205 -1.117 0.433 0.999;

90 5.398 0.344 1.323 16.83 5.936 2.572 -1.3 0.562 1.332;

100 5.397 0.344 1.556 13.8 7.236 2.974 -1.487 0.719 1.746;

110 5.395 0.344 1.814 11.32 8.82 3.415 -1.678 0.911 2.258;

120 5.394 0.344 2.096 9.289 10.75 3.907 -1.871 1.145 2.895;

125 5.392 0.344 2.239 8.468 11.79 4.185 -1.973 1.286 3.281; merging;

126 5.392 0.344 2.267 8.328 11.99 4.26 -2.01 1.34 3.429; bottom hit;

130 5.389 0.344 2.436 7.711 12.95 4.685 -2.249 1.705 4.434;

140 5.376 0.344 3.124 6.326 15.79 6.61 -2.896 2.83 7.554;

150 5.358 0.344 4.2 5.189 19.24 9.578 -3.505 4.109 11.13;

160 5.335 0.344 5.751 4.257 23.46 11.39 -4.05 5.493 15.03;

164 5.325 0.344 6.531 3.933 25.39 12.22 -4.25 6.072 16.67; acute zone;

170 5.309 0.344 7.9 3.492 28.6 13.61 -4.53 6.972 19.22;

180 5.28 0.344 10.81 2.865 34.86 16.35 -4.957 8.566 23.75;

190 5.248 0.344 14.67 2.35 42.49 19.71 -5.344 10.32 28.77;


200 5.212 0.344 19.74 1.928 51.8 23.83 -5.704 12.31 34.46;

204 5.197 0.344 22.12 1.781 56.07 25.73 -5.842 13.18 36.96; surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

1.77304 56.32 26.33 15 4.70E-04 0 0 0.344 6.80E-04

1.77722 56.19 26.68 20 0.00451 0 0 0.344 6.80E-04

1.77852 56.15 27.03 25 0.00854 0 0 0.344 6.80E-04

1.77921 56.13 27.37 30 0.0126 0 0 0.344 6.80E-04

1.77965 56.11 27.7 35 0.0166 0 0 0.344 6.80E-04

1.77996 56.1 28.04 40 0.0207 0 0 0.344 6.80E-04

1.78017 56.1 28.37 45 0.0247 0 0 0.344 6.80E-04

1.78027 56.09 28.69 50 0.0287 0 0 0.344 6.80E-04

1.78021 56.1 29.01 55 0.0328 0 0 0.344 6.80E-04

1.77991 56.11 29.33 60 0.0368 0 0 0.344 6.80E-04

1.77928 56.13 29.64 65 0.0408 0 0 0.344 6.80E-04 Chronic MZ (66 m)

1.77827 56.16 29.96 70 0.0449 0 0 0.344 6.80E-04

1.77681 56.2 30.26 75 0.0489 0 0 0.344 6.80E-04

count: 13

;


8 OF 14

/ UM3. 7/26/2017 7:58:04 AM


Ambient Table:



0 0.171 90 0.08 10.7 0 0 0.171 90 0.00068 -0.238

6 0.171 90 0.08 10.7 0 0 0.171 90 0.00068 -0.238

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.4 17.5 0 19.5 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s)

0 5.4 0.171 0.249 100 1 1 0 0 0.0;

10 5.4 0.171 0.3 82.03 1.219 1 -0.111 0.0223 0.0413;

20 5.4 0.171 0.365 67.3 1.485 1 -0.241 0.0502 0.1;

30 5.4 0.171 0.444 55.21 1.81 1 -0.392 0.0853 0.184;

40 5.4 0.171 0.54 45.29 2.206 1.128 -0.566 0.13 0.302;

50 5.399 0.171 0.656 37.15 2.689 1.367 -0.766 0.185 0.467;

60 5.399 0.171 0.796 30.48 3.278 1.655 -0.993 0.255 0.694;

70 5.398 0.171 0.965 25 3.995 1.998 -1.247 0.343 1.004;

80 5.397 0.171 1.166 20.51 4.87 2.403 -1.527 0.453 1.422;

90 5.395 0.171 1.406 16.83 5.936 2.878 -1.832 0.59 1.976;

100 5.392 0.171 1.689 13.8 7.236 3.427 -2.16 0.759 2.701;

110 5.388 0.171 2.02 11.32 8.82 4.052 -2.506 0.966 3.635;

120 5.383 0.171 2.401 9.289 10.75 4.753 -2.867 1.218 4.819;

125 5.38 0.171 2.611 8.414 11.87 5.133 -3.051 1.363 5.52; bottom hit;

127 5.379 0.171 2.699 8.087 12.35 5.302 -3.125 1.425 5.822; merging;

130 5.374 0.171 2.838 7.671 13.02 5.63 -3.343 1.615 6.756;

140 5.34 0.171 3.652 6.293 15.87 7.441 -4.429 2.667 12.04;

150 5.281 0.171 4.967 5.162 19.35 10.95 -5.615 4.029 19.05;

153 5.258 0.171 5.48 4.864 20.53 11.49 -5.966 4.48 21.4; acute zone;

160 5.197 0.171 6.932 4.235 23.58 12.85 -6.748 5.578 27.2;

170 5.098 0.171 9.758 3.474 28.75 15.11 -7.743 7.205 35.91;

180 4.992 0.171 13.74 2.85 35.04 17.84 -8.573 8.834 44.77;


190 4.887 0.171 19.24 2.338 42.72 21.16 -9.256 10.45 53.65;

194 4.846 0.171 21.98 2.16 46.24 22.69 -9.496 11.09 57.24; surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

2.15035 46.44 26.21 15 6.46E-04 0 0 0.171 6.80E-04

2.15671 46.3 26.91 20 0.00877 0 0 0.171 6.80E-04

2.15804 46.27 27.59 25 0.0169 0 0 0.171 6.80E-04

2.15866 46.26 28.25 30 0.025 0 0 0.171 6.80E-04

2.15866 46.26 28.9 35 0.0331 0 0 0.171 6.80E-04

2.15742 46.29 29.53 40 0.0413 0 0 0.171 6.80E-04

2.15423 46.36 30.15 45 0.0494 0 0 0.171 6.80E-04

2.14865 46.48 30.76 50 0.0575 0 0 0.171 6.80E-04

2.14055 46.65 31.36 55 0.0656 0 0 0.171 6.80E-04

2.13046 46.87 31.94 60 0.0737 0 0 0.171 6.80E-04

2.11848 47.14 32.52 65 0.0819 0 0 0.171 6.80E-04 Chronic MZ (66 m)

2.10502 47.44 33.08 70 0.09 0 0 0.171 6.80E-04

2.09026 47.78 33.64 75 0.0981 0 0 0.171 6.80E-04

count: 13

;


9 OF 14

/ UM3. 7/26/2017 7:42:43 AM

Case 5B10; ambient file C:\Plumes\sctp-5b10-11.001.db;Diffuser table record 1:00 ----------------------------------

Ambient Table:



0 0.594 90 0.08 12.4 0 0 0.594 90 0.00068 -0.422

6 0.594 90 0.08 12.4 0 0 0.594 90 0.00068 -0.422

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.5 12.9 0 17.8 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s)

0 5.5 0.594 0.249 100 1 1 0 0 0.0;

10 5.5 0.594 0.299 82.03 1.219 1 -0.0689 0.0155 0.0338;

20 5.5 0.594 0.361 67.3 1.485 1 -0.143 0.0368 0.078;

30 5.5 0.594 0.434 55.21 1.811 1 -0.221 0.0655 0.135;

40 5.5 0.594 0.52 45.29 2.207 1.011 -0.302 0.103 0.207;

50 5.5 0.594 0.617 37.15 2.69 1.173 -0.385 0.151 0.297;

60 5.5 0.594 0.723 30.68 3.258 1.339 -0.466 0.209 0.403;

70 5.5 0.594 0.834 25.5 3.919 1.51 -0.545 0.277 0.528;

80 5.499 0.594 0.953 21.2 4.713 1.696 -0.624 0.362 0.678;

90 5.499 0.594 1.085 17.52 5.705 1.915 -0.707 0.471 0.872;

100 5.499 0.594 1.229 14.37 6.954 2.186 -0.799 0.617 1.127;

110 5.498 0.594 1.383 11.79 8.476 2.52 -0.897 0.809 1.462;

120 5.498 0.594 1.547 9.67 10.33 2.94 -1.004 1.066 1.907;

123 5.498 0.594 1.597 9.133 11.00 3.099 -1.043 1.175 2.095; merging;

130 5.495 0.594 1.796 7.953 12.63 3.82 -1.323 2.026 3.558;

140 5.489 0.594 2.268 6.524 15.4 5.899 -1.724 3.462 6.02;

147 5.483 0.594 2.73 5.68 17.34 8.061 -1.979 4.551 7.883; bottom hit;

150 5.48 0.594 2.965 5.352 18.77 8.534 -2.084 5.046 8.727;

160 5.47 0.594 3.918 4.391 22.88 10.34 -2.419 6.841 11.79;

161 5.468 0.594 4.029 4.304 23.81 10.54 -2.451 7.035 12.12; acute zone;

170 5.454 0.594 4.996 3.602 27.89 12.55 -2.779 9.223 15.84;

180 5.424 0.594 6.085 2.955 34 15.26 -3.273 13.18 22.56;

190 5.383 0.594 7.411 2.424 41.45 18.58 -3.769 18.04 30.8;

200 5.328 0.594 9.027 1.988 50.52 22.62 -4.264 23.95 40.8;

210 5.256 0.594 11 1.631 61.59 27.56 -4.757 31.13 52.95;

220 5.164 0.594 13.4 1.338 75.08 33.59 -5.248 39.87 67.71;


230 5.048 0.594 16.32 1.098 91.52 40.94 -5.738 50.5 85.65;

240 4.902 0.594 19.89 0.901 111.6 49.9 -6.227 63.43 107.5;

242 4.869 0.594 20.69 0.866 113.8 51.91 -6.324 66.33 112.4; surface; Chronic MZ (66 m)



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

0.86256 115.8 24.99 70 0.00157 0 0 0.594 6.80E-04

0.86356 115.7 25.19 75 0.00391 0 0 0.594 6.80E-04

count: 2

;


10 OF 14

/ UM3. 7/26/2017 7:45:36 AM

Case 5B11; ambient file C:\Plumes\sctp-5b10-11.001.db;Diffuser table record 1:00 ----------------------------------

Ambient Table:



0 0.32 90 0.08 12.4 0 0 0.32 90 0.00068 -0.422

6 0.32 90 0.08 12.4 0 0 0.32 90 0.00068 -0.422

Diffuser table:



0.249 0.61 0 169 5 3.05 7.4 74 5.2 13.2 0 17.8 100

Simulation:



Step (m) (m/s) (m) (%) () () (m) (m) (s)

0 5.2 0.32 0.249 100 1 1 0 0 0.0;

10 5.2 0.32 0.3 82.03 1.219 1 -0.0898 0.0189 0.0431;

20 5.2 0.32 0.364 67.3 1.485 1 -0.191 0.0436 0.102;

30 5.2 0.32 0.441 55.21 1.811 1 -0.303 0.0757 0.182;

40 5.2 0.32 0.533 45.29 2.207 1.09 -0.427 0.117 0.29;

50 5.2 0.32 0.643 37.15 2.69 1.303 -0.561 0.17 0.432;

60 5.199 0.32 0.772 30.48 3.279 1.546 -0.703 0.237 0.615;

70 5.199 0.32 0.922 25 3.997 1.82 -0.852 0.321 0.85;

80 5.199 0.32 1.094 20.51 4.872 2.123 -1.006 0.424 1.144;

90 5.198 0.32 1.288 16.83 5.939 2.455 -1.162 0.549 1.509;

100 5.197 0.32 1.503 13.8 7.239 2.817 -1.321 0.703 1.961;

110 5.196 0.32 1.738 11.32 8.824 3.219 -1.482 0.892 2.521;

120 5.194 0.32 1.992 9.289 10.76 3.68 -1.649 1.126 3.225;

124 5.193 0.32 2.092 8.632 11.58 3.889 -1.72 1.241 3.57; merging;

128 5.191 0.32 2.226 8.013 12.47 4.255 -1.909 1.568 4.56; bottom hit;

130 5.189 0.32 2.318 7.702 12.97 4.498 -2.025 1.78 5.2;

140 5.177 0.32 2.974 6.318 15.81 6.548 -2.59 2.935 8.709;

150 5.16 0.32 3.984 5.183 19.28 9.348 -3.109 4.222 12.64;

160 5.138 0.32 5.42 4.252 23.5 11.17 -3.575 5.623 16.93;

165 5.127 0.32 6.329 3.851 25.94 12.23 -3.789 6.367 19.22; acute zone;

170 5.114 0.32 7.386 3.488 28.64 13.41 -3.992 7.146 21.62;

180 5.086 0.32 10.01 2.862 34.92 16.17 -4.371 8.833 26.82;

190 5.054 0.32 13.47 2.347 42.56 19.56 -4.725 10.75 32.73;


200 5.011 0.32 17.3 1.926 51.88 23.7 -5.106 13.28 40.58;

210 4.938 0.32 21.2 1.58 63.25 28.77 -5.62 17.4 53.38; surface;



(%) (m) (m) (hrs) (kg/kg) (s-1) (m/s)(m0.67/s2)

1.57412 63.47 25.5 20 0.00149 0 0 0.32 6.80E-04

1.5768 63.36 25.87 25 0.00583 0 0 0.32 6.80E-04

1.57775 63.33 26.23 30 0.0102 0 0 0.32 6.80E-04

1.57827 63.31 26.59 35 0.0145 0 0 0.32 6.80E-04

1.57862 63.29 26.95 40 0.0188 0 0 0.32 6.80E-04

1.57886 63.28 27.3 45 0.0232 0 0 0.32 6.80E-04

1.57898 63.28 27.64 50 0.0275 0 0 0.32 6.80E-04

1.57893 63.28 27.98 55 0.0319 0 0 0.32 6.80E-04

1.57863 63.29 28.32 60 0.0362 0 0 0.32 6.80E-04

1.57798 63.32 28.65 65 0.0405 0 0 0.32 6.80E-04 Chronic MZ (66 m)

1.5769 63.36 28.98 70 0.0449 0 0 0.32 6.80E-04

1.57532 63.42 29.31 75 0.0492 0 0 0.32 6.80E-04

count: 12

;


11 OF 14

0.0832m/s;

14 OF 14

Attachment 2

Dissolved Oxygen Calculations

0.0832m/s;

14 OF 14

Dissolved oxygen concentration following initial dilution.

References: EPA/600/6-85/002b and EPA/430/9-82-011

Based on Lotus File IDOD2.WK1 Revised 19-Oct-93

INPUT

1. Dilution Factor at Mixing Zone Boundary (Dry Season): 59

2. Ambient Dissolved Oxygen Concentration (mg/L): 6.6

3. Effluent Dissolved Oxygen Concentration (mg/L): 2

4. Effluent Immediate Dissolved Oxygen Demand (mg/L): 2

OUTPUT

DifferenceDissolved Oxygen at Mixing Zone Boundary (mg/L): 6.49 0.111864

pwspread_v20101108_SCTP 20170727.xls\idod2, Printed 7/16/2018

Dissolved oxygen concentration following initial dilution.

References: EPA/600/6-85/002b and EPA/430/9-82-011

Based on Lotus File IDOD2.WK1 Revised 19-Oct-93

INPUT

1. Dilution Factor at Mixing Zone Boundary (Dry Season): 59

2. Ambient Dissolved Oxygen Concentration (mg/L): 8.1

3. Effluent Dissolved Oxygen Concentration (mg/L): 2

4. Effluent Immediate Dissolved Oxygen Demand (mg/L): 2

OUTPUT

DifferenceDissolved Oxygen at Mixing Zone Boundary (mg/L): 7.96 0.137288

pwspread_v20101108_SCTP 20170727.xls\idod2, Printed 7/16/2018

1. EFFLUENT CHARACTERISTICS

Discharge (cfs) - Max. Day Dry Weather Flow (2022): 25.529279

CBOD5 (mg/L) Phase 5b (2022): 3.83

NBOD (mg/L) Phase 5b (2022): 0.69

Dissolved Oxygen (mg/L) Phase 5b (2022): 2

Temperature (deg C): 23

2. RECEIVING WATER CHARACTERISTICS

Upstream Discharge (cfs): 83506

Upstream CBOD5 (mg/L): 0.5

Upstream NBOD (mg/L): 1.75

Upstream Dissolved Oxygen (mg/L): 8.1

Upstream Temperature (deg C): 21.1

Elevation (ft NGVD): 8.5

Downstream Average Channel Slope (ft/ft): 0.00022

Downstream Average Channel Depth (ft): 45

Downstream Average Channel Velocity (fps): 1.02

3. REAERATION RATE (Base e) at 20 deg C (day-1

) (Note 1): 0.20

Applic. Applic. Suggested

Reference Vel (fps) Dep (ft) Values

Churchill 1.5 - 6 2 - 50 0.02

O'Connor and Dobbins 0.1 - 1.5 2 - 50 0.04

Owens 0.1 - 6 1 - 2 0.02

Tsivoglou-Wallace 0.1 - 6 0.1 - 2 0.52

4. BOD DECAY RATE (Base e) AT 20 deg C (day-1

) (Note 2): 0.07

(or use Wright and McDonnell eqn, 1979, for small rivers.) Enter this value --> 0.04

1. INITIAL MIXED RIVER CONDITION

CBOD5 (mg/L): 0.5

NBOD (mg/L): 1.7

Dissolved Oxygen (mg/L): 8.1

Temperature (deg C): 21.1

2. TEMPERATURE ADJUSTED RATE CONSTANTS (Base e)

Reaeration (day^-1): 0.21

BOD Decay (day^-1): 0.07

3. CALCULATED INITIAL ULTIMATE CBODU AND TOTAL BODU

Initial Mixed CBODU (mg/L): 0.7

Initial Mixed Total BODU (CBODU + NBOD, mg/L): 2.5

4. INITIAL DISSOLVED OXYGEN DEFICIT

Saturation Dissolved Oxygen (mg/L): 8.895

Initial Deficit (mg/L): 0.80

5. TRAVEL TIME TO CRITICAL DO CONCENTRATION (days): 1.19

6. DISTANCE TO CRITICAL DO CONCENTRATION (miles): 19.89

7. CRITICAL DO DEFICIT (mg/L): 0.81

8. CRITICAL DO CONCENTRATION (mg/L): 8.09

1). Based on Bennett & Rathbun (1972) and EPA Surface WQ Modeling Guidance (1985).

2). Based on BOD decay rates in Willamette River by McCutcheon (1983).

Streeter-Phelps Analysis of Critical Dissolved Oxygen Sag

INPUT

OUTPUT

SCTP Phase 5B Projected Effluent with Existing 5-Port Outfall Diffuser (MDDWF)

1. EFFLUENT CHARACTERISTICS

Discharge (cfs) - Max. Month Dry Weather Flow (2022): 20.423423

CBOD5 (mg/L) Phase 5b (2022): 3.83

NBOD (mg/L) Phase 5b (2022): 0.69

Dissolved Oxygen (mg/L) Phase 5b (2022): 2

Temperature (deg C): 23

2. RECEIVING WATER CHARACTERISTICS

Upstream Discharge (cfs): 83506

Upstream CBOD5 (mg/L): 0.5

Upstream NBOD (mg/L): 1.75

Upstream Dissolved Oxygen (mg/L): 8.1

Upstream Temperature (deg C): 21.1

Elevation (ft NGVD): 8.5

Downstream Average Channel Slope (ft/ft): 0.00022

Downstream Average Channel Depth (ft): 45

Downstream Average Channel Velocity (fps): 1.02

3. REAERATION RATE (Base e) at 20 deg C (day-1

) (Note 1): 0.20

Applic. Applic. Suggested

Reference Vel (fps) Dep (ft) Values

Churchill 1.5 - 6 2 - 50 0.02

O'Connor and Dobbins 0.1 - 1.5 2 - 50 0.04

Owens 0.1 - 6 1 - 2 0.02

Tsivoglou-Wallace 0.1 - 6 0.1 - 2 0.52

4. BOD DECAY RATE (Base e) AT 20 deg C (day-1

) (Note 2): 0.07

(or use Wright and McDonnell eqn, 1979, for small rivers.) Enter this value --> 0.04

1. INITIAL MIXED RIVER CONDITION

CBOD5 (mg/L): 0.5

NBOD (mg/L): 1.7

Dissolved Oxygen (mg/L): 8.1

Temperature (deg C): 21.1

2. TEMPERATURE ADJUSTED RATE CONSTANTS (Base e)

Reaeration (day^-1): 0.21

BOD Decay (day^-1): 0.07

3. CALCULATED INITIAL ULTIMATE CBODU AND TOTAL BODU

Initial Mixed CBODU (mg/L): 0.7

Initial Mixed Total BODU (CBODU + NBOD, mg/L): 2.5

4. INITIAL DISSOLVED OXYGEN DEFICIT

Saturation Dissolved Oxygen (mg/L): 8.895

Initial Deficit (mg/L): 0.80

5. TRAVEL TIME TO CRITICAL DO CONCENTRATION (days): 1.20

6. DISTANCE TO CRITICAL DO CONCENTRATION (miles): 19.95

7. CRITICAL DO DEFICIT (mg/L): 0.81

8. CRITICAL DO CONCENTRATION (mg/L): 8.09

1). Based on Bennett & Rathbun (1972) and EPA Surface WQ Modeling Guidance (1985).

2). Based on BOD decay rates in Willamette River by McCutcheon (1983).

Streeter-Phelps Analysis of Critical Dissolved Oxygen Sag

SCTP Phase 5B Projected Effluent with Existing 5-Port Outfall Diffuser (MMDWF)

INPUT

OUTPUT

draft sctp phase 5b engineering report v10...investments to the salmon creek treatment plant (sctp)...

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