north chautauqua lake sewer district wwtp phosphorus ......followed by traditional circular...

North Chautauqua Lake Sewer District

Village of Mayville, Chautauqua County, NY

January 10, 2017

North Chautauqua Lake Sewer District

WWTP Phosphorus Compliance Upgrades

BASIS OF DESIGN REPORT

OBG

O B G T H E R E ’ S A W A Y


JANUARY 10, 2017 | 26959│64077

North Chautauqua Lake Sewer District (NCLSD) – WWTP Phosphorus

Compliance Upgrades

ROBERT C. GANLEY, PE | VICE PRESIDENT

O’Brien and Gere Engineers, Inc.

Prepared for:

North Chautauqua Lake Sewer District Mayville, Chautauqua County, New York


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I:\N-Chautauqua.26959\64077.Wwtp-Phospohoru\Docs\Reports\Basis of Design Report\0c_Report_30%BOD_FINAL.docx

TABLE OF CONTENTS

List of Tables .......................................................................................................................................................................................... 3

List of Figures ........................................................................................................................................................................................ 3

List of Appendicies .............................................................................................................................................................................. 3

1. Introduction................................................................................................................................................................................... 5

1.1 Background ................................................................................................................................................................................ 5

1.2 Purpose and Scope ................................................................................................................................................................. 5

2. Overview of Existing Facility .................................................................................................................................................. 5

3. Basis of Design .............................................................................................................................................................................. 6

3.1 Overview of Proposed Modifications .................................................................................................................................. 6

3.2 Final SPDES Permit Requirements ....................................................................................................................................... 6

3.3 Design Flows and Water Quality ........................................................................................................................................... 7

3.3.1 Design Flows and Water Quality – Continuation of Treating NCLSD Flows Only ............................. 7

3.3.2 Anticipated Design Flows and Water Quality at Future Build-out ........................................................... 7

3.4 Secondary Effluent Pumping Station (SEPS) .................................................................................................................... 8

3.4.1. Pumping Station Design ............................................................................................................................................. 8

3.4.2. Wet Well Design ............................................................................................................................................................. 9

3.4.3. Pumping Station Bypass .......................................................................................................................................... 10

3.4.4. Effluent Force Main and Valve Vault .................................................................................................................. 10

3.4.5. Electrical and I&C Upgrades .................................................................................................................................. 10

3.5 Tertiary Filtration System ..................................................................................................................................................... 10

3.5.1. Filtration Technology Overview .......................................................................................................................... 10

3.5.2. Design Criteria ............................................................................................................................................................. 11

3.6 Chemical Systems...................................................................................................................................................................... 12

3.6.1 Chemical Coagulant Selection for Phosphorus Removal ........................................................................... 12

3.6.2. Secondary Phosphorus Removal ......................................................................................................................... 13

3.6.3. Coagulant Evaluation ................................................................................................................................................ 13

Instrumentation and Controls (I&C) ................................................................................................................................ 14

3.7 Disinfection System upgrades ............................................................................................................................................. 14

3.7.1 Existing Chlorine Gas Disinfection System ................................................................................................. 14

3.7.2 Proposed UV Disinfection System .................................................................................................................. 14

3.8 Architectural Design ................................................................................................................................................................ 16

3.9 Structural Design ....................................................................................................................................................................... 16

3.9.1 Structural Areas of Work ............................................................................................................................................... 16

3.9.2 Structural Design Criteria .............................................................................................................................................. 17

Governing Documents and Building Codes ................................................................................................................... 17

Geotechnical Data..................................................................................................................................................................... 17

Structural Steel .......................................................................................................................................................................... 17


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Concrete ....................................................................................................................................................................................... 17

Precast Concrete ....................................................................................................................................................................... 18

Masonry ........................................................................................................................................................................................ 18

Aluminum .................................................................................................................................................................................... 18

Fiberglass Reinforced Plastic (FRP) ................................................................................................................................. 18

Deflection Criteria .................................................................................................................................................................... 18

Miscellaneous ............................................................................................................................................................................ 18

3.9.3 Loading Requirements .................................................................................................................................................... 18

Dead Loads .................................................................................................................................................................................. 18

Roof Dead Loads ....................................................................................................................................................................... 18

Live Loads .................................................................................................................................................................................... 18

Snow Loads ................................................................................................................................................................................. 18

Wind Loads ................................................................................................................................................................................. 19

Seismic Loads ............................................................................................................................................................................. 19

Hydrostatic Loads .................................................................................................................................................................... 20

Process Equipment Loads .................................................................................................................................................... 20

3.9.4 Material Design Specifications .................................................................................................................................... 20

Structural Steel Fabrications ............................................................................................................................................... 20

Cast-in-place Concrete ........................................................................................................................................................... 21

Reinforcing Steel....................................................................................................................................................................... 21

Precast Concrete ....................................................................................................................................................................... 21

Handrails / Guards .................................................................................................................................................................. 21

Fiberglass Reinforced Plastic .............................................................................................................................................. 21

Joints .............................................................................................................................................................................................. 21

Masonry ........................................................................................................................................................................................ 22

3.10 Electrical Upgrades ................................................................................................................................................................ 22

3.10.1 TFB Electrical Service ................................................................................................................................................... 23

3.10.2 Standby Generator Replacement ............................................................................................................................. 23

Existing System ......................................................................................................................................................................... 23

Proposed Modifications ......................................................................................................................................................... 23

3.11 Instrumentation & Control Upgrades ............................................................................................................................ 23

3.11.1. General ....................................................................................................................................................................... 23

3.11.2. Instrumentation Equipment ............................................................................................................................. 24

Level Measurement ................................................................................................................................................................. 24

Flow Measurement .................................................................................................................................................................. 24

Status Monitoring ..................................................................................................................................................................... 24

Process Control ......................................................................................................................................................................... 24

3.12 Miscellaneous Plant Upgrades .......................................................................................................................................... 25

3.12.1. TFB Heating and Ventilation ............................................................................................................................ 25


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3.12.2. TFB Plumbing ......................................................................................................................................................... 25

3.13 Site/Civil Improvements ..................................................................................................................................................... 26

3.13.1. Regulatory Requirements .................................................................................................................................. 26

3.13.2. Site Layout ................................................................................................................................................................ 26

3.13.3. Grading, Drainage and Stormwater Management ................................................................................... 26

3.13.4. Erosion and Sediment Control ......................................................................................................................... 26

3.13.5. Site Utilities .............................................................................................................................................................. 26

3.13.6. Flood Plain ............................................................................................................................................................... 27

3.13.7. Parking and Truck Access .................................................................................................................................. 27

4. Summary of Recommended Improvements ................................................................................................................. 27

5. Project Costs ............................................................................................................................................................................... 28

Project Impact on User Fee’s ....................................................................................................................................................... 29

6. Project Schedule ....................................................................................................................................................................... 29

LIST OF TABLES

Table 2.1: NCLSD Historical Flow Rates (January 2014 - September 2016)

Table 2.2: NCLSD Historical Phosphorus Concentrations and Loads (January 2014 - September 2016)

Table 3.1: SPDES Permit Limits

Table 3.2: Design Flow Rates – Maintain Current NCLSD Service Area

Table 3.3: Design Phosphorus Concentrations and Loads – Maintain Current NCLSD Service Area

Table 3.4: Future Build-Out Design Flow Rates

Table 3.5: Full Build-Out Design WWTP Influent Phosphorus Concentrations and Loads

Table 3.6: Pumping Station Design Flows

Table 3.7: Tertiary Filter System Characteristics

Table 3.8: Tertiary Filter Performance Requirements

Table 3.9: Chemical Coagulant Comparison

Table 3.10: Alum Dosing Calculations

Table 3.11: PACl Dosing Calculations

Table 3.12: Chemical Consumption and Delivery Schedule

LIST OF FIGURES

Figure 1: NCLSD Secondary Effluent Pumping Station

LIST OF APPENDICIES

Appendix A: Trojan Ultraviolet Disinfection System Proposal

Appendix B: Duperon Mechanically Cleaned Bar Screen Proposal

Appendix C: Cost Estimating Backup


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Appendix D: Updated Project Schedule

Appendix E: Anticipated Specifications Table of Contents

Appendix F: Anticipated Drawing List

Appendix G: Geotechnical Report (SJB Services, Inc)


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1. INTRODUCTION

1.1 BACKGROUND

The North Chautauqua Lake Sewer District (NCLSD) Wastewater Treatment Plant (WWTP) is owned and operated by the NCLSD, and located in the Town of Mayville, Chautauqua County, NY. The facility treats an average of 0.3 million gallons of municipal wastewater per day (mgd), and has the capability to treat approximately 1.6 mgd during high flow/wet weather events. The plant provides primary, biological secondary treatment and chlorine disinfection, prior to discharging into either Chautauqua Lake (Outfalls 001 & 003) or Mud Creek (Outfall 002). Until recently, sludge generated through the process was digested and dewatered on site, but the NCLSD is implementing a program to truck all sludge offsite for disposal at another local POTW. Full secondary treatment facilities were constructed in 1979, and the plant has remained largely unchanged since.

In 2012, Chautauqua Lake received a Total Maximum Daily Load (TMDL) restriction for phosphorus, in response to increased levels of algae growth and blooms, and overall diminished water quality within the Lake. In December of 2013, the NYS Department of Environmental Conservation (NYSDEC) issued a modified State Pollution Discharge Elimination System (SPDES) Permit to the NCLSD WWTP, as well as to other wastewater treatment facilities that discharge to the Lake, limiting the amount of phosphorus that each plant can discharge in the form of treated effluent. In order to meet the interim and final phosphorus discharge limits defined in the revised SPDES Permit and described below in Section 3.2, significant upgrades are required at the Treatment Plant.

1.2 PURPOSE AND SCOPE

The purpose of this Map and Plan Report is to document the Basis of Design of the specific improvements proposed under this WWTP Phosphorus Compliance Upgrades Project. This project addresses improvements needed to meet the phosphorus limitation, as well as a revised limit on total residual chlorine concentration (TRC). Further, in a Lake-wide effort to address the TMDL, it is anticipated that the NCLSD WWTP will likely accept and treat flow from areas currently served by other Lake treatment systems. As a result, upgrade components will be designed to accommodate the additional flow and phosphorus loads. Specific project components include the design of a new submersible Pumping Station to convey secondary effluent to a new tertiary filtration system consisting of tertiary cloth disk media filters, design of a new chemical coagulation system to aid in solids and phosphorus removal from the secondary effluent, design of an Ultraviolet (UV) Disinfection system to replace the existing chlorine gas system, a new Tertiary Filter Building (TFB), various plant-wide electrical upgrades to support new facilities, including a new standby generator sized to serve all existing and proposed facilities under this project; and the design of new instrumentation and control equipment to effectively monitor and control new processes proposed under this project.

2. OVERVIEW OF EXISTING FACILITY

The existing facility provides service to the residential, commercial and industrial users within the Village of Mayville and portions of the Town of Chautauqua. A summary of historical flow rates is provided in Table 2.1, with historical phosphorus loads contained in Table 2.2. As stated previously, the NCLSD WWTP was upgraded in the late 1970’s to include full secondary treatment in the form of Rotating Biological Contactors (RBC’s) followed by traditional circular clarifier tanks. Treatment begins in the Administration Building, in which the bar rack, grit chamber, chlorination and ferric chloride dosing are located. Following the headworks, three (3) Archimedes-type screw pumps lift the wastewater to the two (2) circular primary settling tanks, where heavy solids, including precipitated phosphorus, are removed as primary sludge. Following primary clarification are the three (3) RBC’s, which provide time for the attached-growth biological media to contact the wastewater and remove organics and nutrients from the process. Wastewater flows from the RBC’s to the two (2) final clarifier tanks, which settle out much of the remaining suspended solids, including organic phosphorus-containing solids. Chlorine gas is injected into the secondary effluent as it enters the Chlorine Contact Tank (CCT), which provides approximately 10 minutes of contact time to allow for disinfection. Depending on flow conditions, the disinfected final effluent is discharged through permitted outfalls to either Chautauqua Lake or Mud Creek.


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Table 2.1: NCLSD Historical Flow Rates (January 2014 - September 2016)

Average Daily Flow (mgd)

Maximum Month Flow

(mgd)

Peak Hourly Flow (mgd)

Treatment Plant Rated Capacity (Permitted Capacity) (mgd)

0.313 0.56 2.00 0.5

Table 2.2: NCLSD Historical Phosphorus Concentrations and Loads (January 2014 - September 2016)

Parameter Concentration (mg/L) Load (lb/d)

WWTP Influent Phosphorus Daily Average 4.2 11.0

WWTP Influent Phosphorus WWTP Effluent Phosphorus1

Monthly Maximum 6.8 22.4

Daily Average 0.75 1.9

WWTP Effluent Phosphorus1

Monthly Maximum 2.95 5.9

1. Treatment includes chemical phosphorus removal via enhanced primary clarification (ferric chloride coagulant dosing)

and biological uptake of phosphorus in the RBCs.

Since the TMDL was issued for Chautauqua Lake in 2012 reducing phosphorus effluent limits, the WWTP has been unable to meet its future SPDES permit discharge limits for phosphorus. Additional revisions to the SPDES permit reduced the concentration of total residual chlorine (TRC), amount of chlorine remaining in effluent after initial application in the effluent as well. The SPDES Permit requirements cannot be achieved by the plant in its current operating condition, and the requirement to meet the effluent limits is the driving factor behind this Phosphorus Compliance Upgrades Project.

3. BASIS OF DESIGN

3.1 OVERVIEW OF PROPOSED MODIFICATIONS

To comply with the reduced phosphorus effluent limits defined in the facility’s revised SPDES Permit, installation of Cloth Disk Media Filters is recommended in conjunction with multi-point chemical coagulant addition to precipitate phosphorus from secondary effluent and subsequently filter out phosphorus floc prior to effluent discharge into the Lake. Required ancillary equipment includes a new submersible-type Secondary Effluent Pumping Station (SEPS) to convey secondary effluent through the new Tertiary Filter Building (TFB), as well as control and electrical equipment within the new TFB. The existing Chlorine gas disinfection system will be demolished and replaced with an in-channel Ultraviolet (UV) disinfection system to address the reduced TRC limit in the final SPDES permit. To aid in overall facility performance, the existing manually-cleaned bar screen will be removed and replaced with a new mechanically-cleaned bar screen, designed with greater screening removal capability and reduced headloss.

In addition to the physical treatment upgrades, the existing ferric chloride system will be replaced under this project. Ferric chloride is the coagulant currently utilized at the plant to aid in floc formation and removal of phosphorus however, it can be incompatible with UV systems. A new chemical coagulant system will be installed within the TFB, providing multi-point chemical injection to aid in solids precipitation. Lastly, once construction is complete at the facility, the existing WWTP roadways will be repaved when the new roadways serving the TFB are installed .

3.2 FINAL SPDES PERMIT REQUIREMENTS

In response to the TMDL issued for Chautauqua Lake, the NCLSD WWTP was issued a modified SPDES Permit with interim discharge limits effective as of August 1, 2015, expiring on May 31, 2018. The final discharge limits become effective on June 1, 2018, and include a significant reduction in phosphorus discharge in the form of a mass-based effluent discharge limit. The interim and final permit limits are outlined below in Table 3.1.


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Table 3.1: SPDES Permit Limits

Effluent Parameter Type Interim Limit Final Limit

Flow Monthly Average 0.5 mgd 0.5 mgd

BOD5 Monthly Average 30 mg/L 30 mg/L

BOD5 7-Day Average 45 mg/L 45 mg/L

TSS1 Monthly Average 30 mg/L 30 mg/L

TSS 7-Day Average 45 mg/L 45 mg/L

TP (as P)2 Monthly Average 1.0 mg/L 1.0 mg/L

TP (as P) – Plant only 12-Month Total NA 339.5 lb/yr

TP (as P) – Aggregate3 12-Month Total NA 375.6 lb/yr

TRC Daily Maximum 2.0 mg/L 0.1 mg/L 1. Total Suspended Solids 2. Total Phosphorus, as phosphorus 3. Aggregate includes NCSLD WWTP, and regional flows from Town of Chautauqua and Chautauqua Heights Sewer District. 0.22mg/L daily

average is equivalent to 339.5 lb/yr.

3.3 DESIGN FLOWS AND WATER QUALITY

3.3.1 Design Flows and Water Quality – Continuation of Treating NCLSD Flows Only

The design WWTP flow rates, phosphorus concentration, and loads for treating NCLSD flows only are presented in Tables 3.2 and 3.3, respectively. Upgrade modifications must meet these design parameters since they are valid for current conditions as well as one possible future scenario; treatment of NCLSD flows only (no additional flow from other nearby, existing treatment systems).

Table 3.2: Design Flow Rates – Maintain Current NCLSD Service Area

Average Daily Flow (mgd)

Maximum Month Flow

(mgd)

Peak Hourly Flow (mgd)

Treatment Plant Rated Capacity (Permitted Capacity) (mgd)

0.31 0.6 2.00 0.5

Table 3.3: Design Phosphorus Concentrations and Loads – Maintain Current NCLSD Service Area

Parameter Type Concentration (mg/L) Load (lb/d)

WWTP Influent Phosphorus Daily Average 4.2 11.0

WWTP Influent Phosphorus Monthly Maximum 6.8 22.4

3.3.2 Anticipated Design Flows and Water Quality at Future Build-out

Future scenarios (future build-out) include adding flow from areas that are currently served by nearby, existing wastewater treatment systems, including Chautauqua Heights Sewer District (CHSD) WWTP, and up to 360 individual septic systems in the Shorelands and Point Chautauqua areas that may someday be included in the service area. At future build-out, the design flows, phosphorus concentrations, and loads are displayed in Tables 3.4 and 3.5, respectively. Proposed upgrade modifications must acknowledge these anticipated design parameters, and when possible, incorporate features that could facilitate potential future upgrades to meet these values. However, treatment of these additional flows would require SPDES permit modifications, including adjustment of the plant rated capacity and discharge quantities, as well as upgrade of equipment and processes that are beyond the scope of this project.


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Table 3.4: Future Build-out Design Flow Rates

Service Area

Average Daily Flow

(mgd)

Maximum Month Flow

(mgd)

Peak Hourly Flow

(mgd)

Treatment Plant Rated Capacity (Permitted Average

Capacity) (mgd)

NCLSD and CHSD

0.35 0.59 2.25 0.75

NCLSD, CHSD and Point Chautauqua

0.5 0.71 2.5 0.75

Table 3.5: Full Build-out Design WWTP Influent Phosphorus Concentrations and Loads

Parameter WWTP Influent Concentration (mg/L) Load (lb/d)

NCLSD and CHSD Daily Average 3.8 11.3

Maximum Day 6.8 22.6

NCLSD, CHSD and Point Chautauqua

Daily Average 4 16.1

Maximum Day 121 29.3

1. Conservatively based on maximum value of typical influent phosphorus concentration (Design Standards for Intermediate Sized Wastewater Treatment Systems, pg B-13.)

3.4 SECONDARY EFFLUENT PUMPING STATION (SEPS)

3.4.1. Pumping Station Design

The new tertiary filtration system proposed as part of the enhanced phosphorus removal upgrades at the NCLSD WWTP will require a new Secondary Effluent Pumping Station (SEPS) to lift flows to the new TFB. The SEPS will be constructed just downstream of the existing secondary clarifiers, before the Chorine Contact Tank (CCT), in order to divert flows to the tertiary filtration system in the TFB prior to disinfection. See Drawing C-102 for proposed Pumping Station location. The SEPS will consist of a wet well with submersible centrifugal sewage pumps, a Grade 316 stainless steel guide rail system, and a liquid level control system. Pump isolation valves will be located in a separate valve vault adjacent to the wet well, and the motor control center (MCC) and motor starters will be located in the new TFB Electrical Room.

The wet well will be a 10-foot by 10-foot by 15-foot deep concrete structure to house up to four submersible sewage pumps. The SEPS will initially house three submersible pumps of equal size, each sized at approximately 0.84 mgd at 52 ft TDH, rated at 12 hp. Initially, the three pumps will serve a range of flows from minimum winter flows, up to the current peak hourly maximum of 1.6 mgd (two pumps at 90% speed), with one pump in standby. Pump speed will be adjusted with variable frequency drives (VFDs), also located in the TFB Electrical Room.

One pump will serve an average design flow (0.5 mgd) at full or reduced speed with high efficiency, two pumps together will convey the existing peak hourly flow of 1.6 mgd, and the third pump will initially provide redundancy. As flows increase to an anticipated peak hourly flow of 2.5 mgd when the CHSD service area reaches full build-out, a fourth identical pump could be installed, or all three pumps upgraded to meet the new service conditions. The wet well will be sized to provide space for the additional pump, for redundancy, when the sewer district is expanded and the future peak flows occur at the WWTP. This design is in accordance with applicable Ten States Standards for Wastewater Pumping Station Design.


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Table 3.6 – Pumping Station Design Flows

Flow - mgd (gpm)

Minimum Flow 0.05 (35)

Average Flow 0.5 (350)

Plant Rated Capacity 0.75 (525)

Current Peak Flow 1.6 (1,100)

Future Peak Hourly Flow 2.5 (1,750)

Figure 1: NCLSD Secondary Effluent Pumping Station

3.4.2. Wet Well Design

The proposed wet well is a 10-foot by 10-foot by 15-foot concrete structure with a working volume of approximately 5,200 gallons. The wet well size is in accordance with design and regulatory standards which recommend that the wet well be sized based on a design fill time at average flow not to exceed 30 minutes and a minimum pump cycle time of 5 minutes, or as required by the selected pump manufacturer. To reduce pump cycling, the wet well design includes appropriate volume to equalize flow during high flow periods and store flow during low flow periods.

The proposed wet well bottom is located approximately at elevation 1303 feet and will be refined based on final pump selection and geotechnical considerations. As noted in the Geotechnical Report included in Appendix G, the approximate level of groundwater in the area of the proposed pumping station is between 1310 and 1311 feet. Final design will take into account groundwater and localized soil conditions.


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The proposed wet well will be located in the FEMA delineated flood plain and the top of the structure will be located a minimum of 1 foot above maximum flood level (currently estimated at 1314 feet). Construction of an open top wet well is recommended as the treated wastewater is not odorous. Additionally, maintenance of the pumps and wet well can be more easily performed without a concrete top. Facility operators have expressed a desire for an open top configuration. A removable railing system will be provided around the perimeter of the wet well for operator safety.

The submersible pumps will be readily removable from the wet well via the stainless steel guide rails, and replaceable without dewatering the wet well or disconnecting any piping in the wet well. The proposed design will include access to the wet well sufficient to support hoisting equipment for equipment removal, maintenance and installation.

The wet well floor will be sloped toward the pump intakes and have a smooth finish to operate as a self-cleaning wet well. There will be no wet well projections that will allow deposition of solids under normal operating conditions.

3.4.3. Pumping Station Bypass

The SEPS will be designed with an overflow weir so that in the event the secondary effluent flows exceed the maximum pumping capacity, the effluent will bypass the pumping station by gravity and enter the CCT. The CCT will be activated during these events and liquid chlorine (sodium hypochlorite) can be manually added to the CCT during these conditions as needed.

A separate piped bypass will be installed to allow for the installation of a temporary pump located in the CCT inlet chamber to convey flow to the TFB for filtration.

3.4.4. Effluent Force Main and Valve Vault

A cast-in-place concrete valve vault (approximately 8-foot by 10-foot) will be constructed as part of the SEPS. Manual swing check and non-rising stem isolation valves for each of the pumps will be located in this chamber.

The SEPS pumps will convey flow into a common force main that will discharge to atmosphere at the influent end of the tertiary filters at an approximate elevation of 1335 feet. Design and regulatory guidance recommend maintaining a velocity within the force main between 2 and 8 feet per second (fps). With anticipated flows ranging from 35 gpm to 1111 gpm, it is difficult to maintain the velocity range across the wide range of flows in a single pipe. However, the range in flows will provide scouring of the pipe in the event that solids deposition occurs within the pipe. For this application, it is recommended that an 8-inch ductile iron pipe be installed from the valve vault to the TFB.

3.4.5. Electrical and I&C Upgrades

A new MCC will be located in the TFB Electrical Room and will house the VFDs for the SEPS pumps. A local disconnect panel will be installed adjacent to the pumping station to allow for manual pump shutoff during maintenance operations and for emergency shutdown, as needed.

Pump operation will be controlled through the Tertiary Filter Process panel and will respond to wet well levels. An ultrasonic level sensor will be installed in the wet well to measure water height and an emergency high level float will be provided.

3.5 TERTIARY FILTRATION SYSTEM

3.5.1. Filtration Technology Overview

The filtration technology recommended for this project is Cloth Disk Media Filtration. Cloth Disk Media Filtration systems offer an alternative to traditional granular media filtration systems, and provide improved flexibility in terms of both installation and operation. Typical cloth disk media filters utilize several modular-type cloth disks (rigid frame, cloth blanketed), mounted within a common filter basin, that can be made from a number of cloth types with different pore sizes for different filtration applications. Filter influent (in this case,


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secondary effluent) will flow into the filter units, where it is forced through the cloth filter media by head pressure created within the filter unit, and will drain by gravity from the filters to the UV channel. The filter units feature dry-mounted drive motors and gearboxes, differential pressure-based automatic backwash of the filter disks, several basin material options, on-board solids collection and recycle back to the treatment train, and are PLC programmed and controlled. Each filter unit is easily serviceable, compact, and can be easily removed from service for isolation and servicing.

For municipal wastewater treatment, specifically tertiary treatment for ultra-low phosphorus removal applications, three major manufacturers produce cloth disk media filters that will be considered for this project:

Aqua-Aerobic Systems, Inc

WesTech, Inc

Kruger (Veolia Water Technology)

Aqua-Aerobic Systems, Inc, introduced the first cloth disk filter system in the early 1990’s, and now manufacture several variations of the original AquaDisk®, tailored to different applications and sized treatment facilities. WesTech manufactures the SuperDisc® high-rate cloth disk media filter, and Kruger/Veolia manufactures the Hydrotech Diskfilter®. All three filter options improve on traditional granular media filtration systems based on the following:

Modular design: reduced site assembly required, increased potential for retrofit applications, reduced installed footprint, easy to achieve redundancy

High Flow applications: can achieve greater treatment capacity by adding additional units, disks offered in several diameters and quantity of disks per filter unit

Maintenance: modular filter disks, few moving parts, automatic backwash cycles, floor mounted equipment allows easy access to key equipment

Design Considerations: several basin material offerings, minimal head required for operation (~1ft), indoor and outdoor installations, effluent backwash waste & solids piped to headworks, low backwash rates

3.5.2. Design Criteria

Tables 3.7 and 3.8 below outline the current treatment process effluent characteristics (to become TFB influent) and the proposed filter performance requirements, respectively. The performance requirements reflect the performance necessary to comply with the final SPDES Permit effluent limits, specifically for phosphorus and total suspended solids (TSS).

Table 3.7: Tertiary Filter System Characteristics

System Characteristics

Peak Flow Rate1 1.6 mgd (1111 gpm)

Design Flow Rate1 0.5 mgd (350 gpm)

Minimum Flow Rate 0.05 mgd (35 gpm)

Maximum phosphorus concentration to filters 1.0 mg/L

Maximum TSS concentration to filters 20.0 mg/L

Maximum solids size to filters 10 micron 1. Assume one filter in service (duty), one filter in standby

Table 3.8: Tertiary Filter System Performance Requirements

Performance Requirements

Hydraulic loading @ peak flow1 5.0 gpm/ft2 (max)

Hydraulic loading @ average flow1 1.0 gpm/ft2 (max)

Minimum filter surface area 225 ft2

Maximum Headloss through Filter at Peak Flow Rate 18 inches


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Performance Requirements

Maximum influent phosphorus concentration 1.0 mg/L

Required effluent phosphorus concentration 339.5lb/year, 12-month total (0.22mg/L)

Required effluent TSS concentration 30mg/L (monthly average), 45mg/L (7-day average)

Filter Disk Orientation Vertical

Filter Disk type Modular, replaceable

Backwash system Automatic, level or differential pressure-based, waste

piped to headworks

Backwash rate/duration


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3.6.2. Secondary Phosphorus Removal

For this project, three coagulant dosing locations are proposed. However, it is anticipated that only two dosing points will be used for routine phosphorus removal: at the headworks (current coagulant dosing location) and upstream of the tertiary filtration unit. The third dosage location upstream of the secondary clarifiers is recommended to provide operational flexibility at a minimal cost (valved and capped piping extension to dosage location).

Although coagulant dosing has routinely been conducted in the primary clarifiers to reduce influent phosphorus concentrations, there are compliance and operational concerns associated with continuing this practice under the stringent phosphorus limitation (discussed above). Dosing coagulant upstream of the secondary clarifiers would eliminate balancing concerns associated with primary treatment dosing. The main disadvantage to dosing at this location is the RBCs would be loaded with higher BOD and TSS levels. These loads would be equal to loads exerted prior to implementation of the primary phosphorus removal system (pre-2012) and therefore would be within the facility’s design operating range.

3.6.3. Coagulant Evaluation

As discussed above, it is recommended that both Alum and PACl are tested and evaluated for performance prior to finalizing the selection of a chemical coagulant to replace the existing ferric chloride system. Both Alum and PACl are aluminum-based chemical coagulants, and have little effect on the function and effectiveness of other treatment processes. Below in Table 3.10 is an evaluation of the dosing and storage requirements associated with both chemical coagulant options.

Table 3.10: Alum Dosing Calculations

Flow Condition Daily Dosages

(gpd) Weekly Dosages

(gal) 10-day Storage Required (gal)

Average Flow (0.3 mgd)

NCLSD Flows only 23.6 165.2 236

NCLSD + CHSD + Point Chautauqua 29.2 204.4 292

Design Flow (0.5 mgd)

NCLSD Flows only 35.0 245 350


Table 3.11: PACl Dosing Calculations

Flow Condition Daily Dosages

(gpd) Weekly Dosages

(gal) 10-day Storage Required (gal)

Average Flow (0.3 mgd)

NCLSD Flows only 15.1 105.7 15.1


Design Flow (0.5 mgd)

NCLSD Flows only 22.3 156.1 223


The values above are flow weighted chemical dosages based on an average plant influent phosphorus concentration of 4 mg P/L. A 1:1 ratio of chemical-to-phosphorus is assumed for Primary phosphorus removal (through primary clarification), and a 4:1 ratio of chemical-to-P is assumed for tertiary phosphorus removal (through tertiary filtration).

Currently, the facility receives ferric chloride deliveries in the form of 275 gallon totes, delivered approximately once per month. The chemical is pumped from the totes to two small storage tanks located in the headworks area, for injection into the treatment stream immediately downstream of the bar screen. Typically for


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applications requiring similar volumes of coagulant dosing, bulk chemical storage tanks are utilized to reduce the quantity of chemical deliveries and take advantage of bulk chemical purchasing at reduced cost. These deliveries are accomplished utilizing a tanker truck and a tank fill station located on the exterior of the building in which the bulk tanks are housed. Based on discussion with facility operators and design concerns with providing tanker truck access to the TFB, it is recommended that the use of chemical totes be continued at the TFB, regardless of the new chemical selection. Adequate storage space will be provided in the Chemical Storage Room in the TFB for four chemical totes and a duplex chemical feed pump skid, and the room will be large enough to house a bulk storage tank if the decision to end the use of totes is made in favor of a bulk tank.

Ten States Standards for the Design of Wastewater Facilities (Ten States) recommends a minimum 10-day storage volume be kept on site, based on average plant flow and average phosphorus influent concentration. In this case, with average flow of 0.3 mgd and influent phosphorus concentrations of 4 mg P/L, it is recommended that four - 275 gallon totes be kept on site at all times. The two dosing locations discussed above (after primary treatment and prior to tertiary) will each be fed by a separate peristaltic chemical feed pump, both mounted on a duplex pump skid located within the chemical containment area in the Chemical Storage Room. Each feed pump will be supplied with one duty tote, and one full additional tote, for a total of four. Table 3.12 below details the proposed chemical delivery schedule for both chemical options.

Table 3.12: Chemical Consumption and Delivery Schedule Alum PACl

Totes Recommended Onsite 4 4

Total Storage Volume (gallons) 1,100 1,100

Chemical Dosage at Average Flow, NCLSD only (gpd) 35.0 22.3

Chemical Dosage at Build-Out, NCLSD + CHSD + Point Chautauqua (gpd) 52.4 33.5

Time until Delivery at Current Flow (days)1 28 days 44 days

Time until Delivery at Future Build-Out Flow (days)1 19 days 30 days

1. Ten States Standards recommends delivery be scheduled when chemical storage has reached 10% capacity. Delivery times reflect point at which remaining chemical is 10% capacity (165 gallons).

Instrumentation and Controls (I&C)

Chemical coagulant dosage will be flow paced and controlled via a signal from the new magnetic flow meter to be installed on the effluent piping upstream of the new UV disinfection channel. Additional I&C details are discussed below in Section 3.11.

3.7 DISINFECTION SYSTEM UPGRADES

3.7.1 Existing Chlorine Gas Disinfection System

The existing chlorine gas system is located in the Chlorine Room in the Administration Building and consists of a manually adjusted chlorine gas system with 150-lb gas cylinders, cylinder scale, vacuum regulator and injector. The chlorine solution is conveyed by water pressure from the Administration Building to the CCT, where the chlorine solution is added to the secondary effluent entering the tank. The CCT provides approximately 10 minutes of contact time for disinfection. Based on discussion with facility operators, and acknowledging that transporting and storing compressed chlorine gas is becoming more regulated and possesses an inherent danger, it is recommended that the NCLSD remove the existing chlorine disinfection system and install a new in-channel UV Disinfection System in the TFB. Additional details supporting the use of UV are presented below.

3.7.2 Proposed UV Disinfection System

Based on evaluation of the facility operating characteristics and anticipated tertiary effluent quality once the tertiary filters are online, UV disinfection is suitable for use at the NCLSD WWTP. It is recommended that an in-channel type UV unit be installed within the footprint of the TFB, and be sized for peak flow and handle average and design flows with full redundancy. UV technology is especially suitable for this specific project as the facility is provided power at reduced cost, compared to most treatment facilities, a factor that can price UV disinfection out of consideration when compared to traditional chemical methods. Additionally, the implementation of UV


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disinfection in lieu of chlorine gas also eliminates the only source of chlorine in the plant effluent, therefore eliminating the requirement for dechlorination to comply with the TRC limit in the final SPDES permit. The facility will benefit immediately from the elimination of the chlorine gas system and requirement to install a new dechlorination system in the form of reduced capital cost in purchasing and maintaining these systems. These cost savings will also help offset the higher initial capital cost of the UV system. Project costs are discussed in detail in Section 5.

The UV System proposed for use at the facility is an in-channel type UV unit, with 2 separate UV banks comprised of 12 lamps per bank. The system will be sized to disinfect the design and average flows of 0.3 mgd and 0.5 mgd, respectively, with full redundancy; peak hourly flow of 1.6 mgd, and provide the capability to expand disinfection capacity through the installation of additional lamps in the 2 existing banks. The banks will be mounted within a floor-recessed concrete effluent channel measuring approximately 16 inches wide by 46 inches deep by 28 feet in length. The in-channel configuration provides easy access for operators when lamp maintenance or replacement is required, and does not infringe on the usable floor space within the Filter Room. This design complies with Ten States recommendations for equipment redundancy, and will allow the facility to expand its treatment capacity with minimal modifications to the existing UV System if future flow conditions warrant an increase in treatment capacity. A manufacturer’s proposal for the UV system is included in Appendix A.

As stated previously, the quality of the tertiary effluent at the NCLSD WWTP makes the facility especially suitable to utilize UV technology. The following driving factors demonstrate this suitability:

Low Electricity Cost: The NCLSD WWTP is provided electricity at a cost of between $0.05 and $0.06 per kWh. This cost is approximately half of what other municipal facilities incur, on average.

Tertiary Effluent vs. Secondary Effluent: The majority of WWTP’s do not provide tertiary treatment to remove fine particles that can limit UV transmittance and the effectiveness of the technology. Once the TFB is online, the effluent water quality will be more amenable to UV disinfection. Additional sampling and testing during detailed design will be performed to confirm design parameters.

O&M Procedures and Cost:

» Maintaining an in-channel UV system requires minimal effort on the part of plant operators, especially when the units are sized as required for this project. The lamp banks can be pulled upward out of the water column via an overhead bridge crane, or rolling gantry crane, for replacement and cleaning. For daily cleaning, each bank is equipped with a hydraulically driven lamp wiper system, to minimize scaling and deposition of particulates onto the UV lamps.

» As shown in Appendix A, the annual O&M costs for the UV system are approximately $3,600. Based on initial calculations, the annual O&M cost of a traditional chlorine gas and SMBS Dechlorination system is approximately $13,000. This resultant savings can help offset the cost for miscellaneous plant-wide upgrades and costs that the NCLSD normally incurs throughout the year.

Easily Upgraded to Provide Additional Treatment Capacity: The in-channel type UV proposed for use on this project is easily modified to include additional lamps in the existing banks, providing treatment capacity above its current capability.

Availability of Emergency Power: UV disinfection systems require a constant source of power and in the case of a power outage, require lengthy reset times to allow lamps sufficient time to warm to operating temperature. Under this project, a new generator will be provided at the facility, and sized sufficiently to provide power to the UV system during power outages. To ensure there is no interruption of power for the control system during the period from initial outage until the generator comes online, an uninterruptable power source (UPS) will be provided in the TFB to supply the control system with continuous power. This ensures that as soon as the generator is online, the control system will reset the UV lamps and begin power up on generator power.


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3.8 ARCHITECTURAL DESIGN

The TFB will be a one story, 3,100 sq-ft masonry structure with a brick façade. An exterior load bearing concrete masonry unit (CMU) cavity wall system will provide a durable, low maintenance building structure. Interior walls will be painted masonry and the flooring will be sealed, slab-on-grade concrete. Precast roof planks, tapered rigid insulation, and an ethylene propylene diene monomer (EPDM) membrane will comprise the roof assembly. The roof will drain into a series of gutters and downspouts coordinated with site drainage.

Individual rooms will be provided for electrical equipment, coagulant storage and application, a facility maintenance room for tool storage and equipment maintenance, as well as a mezzanine with ladder access in the north east corner of the building. The mezzanine will provide space for HVAC equipment, as well as light-duty storage.

Doors and frames constructed of fiberglass reinforced plastic (FRP) will be utilized throughout the building, as FRP is strong, corrosion resistant, and well suited for wet process and chemical areas. Based on facility operator preference, motor operated or hand operated insulated overhead sectional doors will allow additional access for filter maintenance.

The following preliminary code analysis is based on the 2016 NYS Uniform Supplement, 2015 International Building Code and the 2016 Supplement to the NYS Energy Code (2015 IECC):

Building occupancy: Utility and Miscellaneous Group U

Construction Class: IIB

Building Area: 3115 sq-ft

Building Height: 17-feet 6-inches

No. of Stories: 1

No. of Occupants based on Table 1004.1.2: 23 occupants

Table 1017.2 Exit Access Travel Distance: Allowed (without sprinkler system): 300 ft. Actual Max ETD: 55 ft.

Table 1104.18 Common Path of Travel Limit: Allowed (without sprinkler system): 100 ft. Actual Max CPT: 50 ft.

Table 1104.18 Dead End Travel Limit: Allowed (without sprinkler system): 20 ft.

2015 IECC County/Zone: Chautauqua/5A

Unheated slab insulation: R10 (10 required)

Exterior wall insulation: R12.5ci (11.4ci required)

Roof/ceiling insulation: R30ci (30ci required)

Exterior Doors: U value .29

3.9 STRUCTURAL DESIGN

3.9.1 Structural Areas of Work

The TFB will generally consist of cast-in-place concrete shallow foundations below grade and masonry/brick cavity walls above grade with exterior dimensions of approximately 88-feet 6-inches by 34-feet 6-inches.

The Wet Well will consist of a below grade cast-in-place concrete vault with exterior plan dimensions of approximately 10-feet 0-inches by 10-feet 0-inches and a depth of up to 15-feet 0-inches.


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3.9.2 Structural Design Criteria

Governing Documents and Building Codes

2016 New York State Uniform Fire Protection and Building Code (Uniform Code)

International Building Code (IBC), 2015 Edition

American Society of Civil Engineers, “Minimum Design Loads for Buildings and Other Structures” (ASCE/SEI 7-10)

Geotechnical Data

Foundation design is based on a geotechnical engineering report by SJB Services, Inc., dated November 15, 2016 (refer to Appendix G for full report).

The geotechnical report includes recommendations for seismic site classification, bearing capacity and modulus of subgrade reaction. Refer to geotechnical report included in Appendix G for additional information.

According to the geotechnical report, approximately 4-10 feet of fill soil exists at the surface of the building site. The nature of the fill materials is inconsistent with depth and location. It is required that all fill soils be removed from beneath willow foundations and replaced as necessary with structural fill.

The geotechnical report identifies the potential for perched groundwater conditions in excavations for both the TFB and the wet well. Should this occur, construction dewatering methods will be required.

According to the geotechnical report, wet well excavations will likely require sheeting and shoring, in addition to dewatering methods in order to prevent undermining of adjacent footings and foundation walls.

Structural Steel

AISC Steel Construction Manual, Allowable Stress Design, 14th Edition

AISC Seismic Provisions for Structural Steel Buildings, 2010

Design of Welded Structures, Blodgett

Design Guide 9, Torsional Analysis of Structural Steel Members, Seaburg & Carter

Design Guide 7, Industrial Buildings: Roofs to Column Anchorages, 2nd Edition, Fisher

RCSC Structural Bolting Specification

AWS D1.1, Structural Welding Code – Steel

Concrete

ACI 302.1R, Guide for Concrete Floor & Slab Construction

ACI 318-14, Building Code Requirements for Structural Concrete

ACI 350-06/350R-06, Environmental Engineering Concrete Structures

ACI 350.1, Tightness Testing of Environmental Engineering Concrete Structures

ACI 350.3-06, Seismic Design of Liquid-Containing Concrete Structures

ACI 360R-06, Design of Slabs on Grade

ANSI/ASCE 3-91, Standard for the Structural Design of Composite Slabs

Portland Cement Association (PCA) Design Standard for Circular and Rectangular Reinforced Concrete Structures

PCA Publication, Slab Thickness Design for Industrial Concrete Floors on Grade, R.G. Packard, 1976

Sanitary Structures - Tanks and Reservoirs, Seidendstricker and Hoffman


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AWS D1.4, Structural Welding Code – Reinforcing Steel

Precast Concrete

PCI Design Handbook for Precast and Prestressed Concrete

Masonry

ACI530-05/530.1-05: Building Code Requirements for Masonry Structures & Specs for Masonry Structures & Commentaries

Reinforced Masonry Engineering Handbook, James E. Amrhein, 5th Edition

Aluminum

Aluminum Design Manual: Specifications and Guidelines for Aluminum Structures, The Aluminum Association, 2015 Edition

Fiberglass Reinforced Plastic (FRP)

Morrison Molded Fiberglass Co. (MMFG) Design Manual (or similar design standard)

Deflection Criteria

The deflection of all structural reinforced concrete, steel and masonry members will be subject to the requirements of ACI 318, AISC-ASD, and ACI 530, respectively.

Dead and live load deflection of members supporting flows, roofs, and walls will not exceed the limitations listed in IBC 2015.

Miscellaneous

OSHA Regulations

3.9.3 Loading Requirements

Dead Loads

Weight of permanent structure

Weight of the fixed service equipment, such as process equipment, plumbing stacks and risers, electrical feeders, heating, ventilating and air conditioning systems and fire sprinkling systems.

Roof Dead Loads

Roofing Materials & Insulation TBD

M/E Collateral Load 10psf

Live Loads

In accordance with IBC 2015 Table 1607.1

Occupancy or Use Uniform Load (psf) Concentrated Load (psf)

Manufacturing Heavy 2501 2000

1. Values above indicating minimum live loads for each occupancy. Actual loads of equipment (including impact and vibratory loading) will be included in addition to designated loads.

Snow Loads

Snow Importance Factor (Is) 1.1 ASCE 7, Table 1.5-2

(Risk Category III)

Ground Snow Load (pg) 40 psf 2016 New York State Uniform

Fire Protection and Building Code, Figure R301.2(5)


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Snow Exposure Factor (Ce) 1.0 ASCE 7, Table 7-2

(Terrain Category C – Partially Enclosed)

Thermal Factor (Ct) ASCE 7, Table 7-3

Unheated Structure 1.2

Structure Kept Just Above Freezing 1.1

All Other Structures 1.0

Flat Roof Snow (pf) pf = 0.7CeCtIspg ASCE 7, Eqn. 7.3-1

Sloped Roof Snow (ps) ps = Cspf ASCE 7, Eqn. 7.4-1

Unbalanced Roof Snow Loads ASCE 7, Section 7.6

Drift Loads ASCE 7, Section 7.7

Wind Loads

Basic Wind Speed 120 mph ASCE 7, Figure 26.5-1B

Exposure Category (C) ASCE 7, Section 26.7

Directional Procedure ASCE 7, Chapter 27

Envelope Procedure ASCE 7, Chapter 28

Seismic Loads

Seismic Importance Factor 1.25 ASCE 7, Table 1.5-2

(Risk Category III)

Site Class E SJB Services Inc.

Draft Geotechnical Evaluation Report dated November 15, 2016

Mapped Spectral Accelerations

Short Period (Ss) 0.140 SJB Services Inc.


1-second Period (S1) 0.052 SJB Services Inc.


Site Coefficients

Fa 2.5 IBC, Table 1613.13 (1)

Fv 3.5 IBC, Table 1613.13 (2)

Maximum Considered Earthquake Spectral Response Accelerations

Short Period (SMS) 0.350 IBC, Equation 16-37

1-second Period (SM1) 0.182 IBC, Equation 16-38

Design Spectral Response Accelerations

Short Period (SDS) 0.233 IBC, Equation 16-39


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1-second Period (SD1) 0.121 IBC, Equation 16-40

Seismic Design Category B IBC, Table 1613.3.5 (2)

Response Modification Factors (R)

Filter Building:

Ordinary Reinforced Masonry Shear Walls 2 ASCE 7, Table 12.2-1

Fundamental Period (T) TBD

Approximate Fundamental Period (𝑇𝑎) 𝑇𝑎 = 𝐶𝑡ℎ𝑛𝑥 ASCE 7, Equation 12.8-7

or

𝑇𝑎 = 0.0019

√𝐶𝑤ℎ𝑛 ASCE 7, Equation 12.8-8

or

𝑇𝑎 = 0.0019

√𝐶𝑤ℎ𝑛 ASCE 7, Equation 12.8-9

Seismic Response Coefficient (Cs)

Initial Value for Each Structure TBD ASCE 7, Equation 12.8-2

Lower Limit 0.0135 ASCE 7, Equation 12.8-5

Upper Limit TBD ASCE 7, Equation 12.8-3 or 18.8-4

Lower Limit Non-Building Structures 0.0135 ASCE 7, Equation 15.4-1

Equivalent Lateral Force Procedure ASCE 7, Section 12.8

Hydrostatic Loads

Internal fluid loading will be determined by the specific gravity of the fluids.

New tank walls will be designed for maximum hydraulic levels assuming no support or earth pressure on the opposite side of the wall (design case is necessary due to the leakage testing conducted for new tank structures before backfilling).

Structures constructed below estimated maximum groundwater level will be designed to resist uplift forces with a factor of safety of 1.1 on maximum flood or groundwater elevation, whichever is higher, when there are only dead loads acting to resist uplift forces.

Process Equipment Loads

Vibration loads will be considered based on information supplied by equipment manufacturers. Certain requirements are applicable for vibration. Metal supporting systems will not be used for vibrating equipment unless special project requirements dictate their use. Instead, a concrete base at grade will be provided, the mass of which must equal to ten times the rotating mass of the equipment or a minimum of three times the gross mass of the machine, whichever is greater.

Embedded anchor bolts, adhesive anchors and vibration-resistant expansion anchors will be used for anchorage to the concrete foundation. Also, use of vibration isolators or dampeners will be used where appropriate.

3.9.4 Material Design Specifications

Structural Steel Fabrications

Structural Steel


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W- Shapes: ASTM A992, Grade 50

Channels, Angles, Plates: ASTM A36

Structural Tubing (HSS): ASTM A500, Grade B

Fy=46ksi

Structural Steel Pipe (HSS): ASTM A500, Grade B

Fy=42ksi

High Strength Bolts: ASTM F3125, Grade 325

Anchor Rods: ASTM F1554

Welds: E70XX electrodes

Cast-in-place Concrete

Structural Concrete Not Exposed to Freeze-Thaw Conditions

Concrete Compressive Strength (f’c) 4000 psi

W/CM Ratio 0.45

Structural Concrete Exposed to Freeze-Thaw Conditions in a Saturated Environment:

Concrete Compressive Strength (f’c) 4500 psi

W/CM Ratio 0.42

ACI 360 R-10 and ACI 302.1 R-15 for concrete floor and slab design and construction recommendations.

Reinforcing Steel

All instances: ASTM A615, Grade 60

Precast Concrete

Minimum Compressive strength (fc’) 5000 psi

Handrails / Guards

Will be chosen based on the corrosiveness of the environment and the OSHA and IBC 2015 requirements.

Anodized Aluminum will be used for handrails and guards, unless otherwise specified.

Fiberglass Reinforced Plastic

Will be designed based in accordance with any manufacturer’s supplied loading information and with the MMFG Design Manual

Deflection, stress and brittleness due to impact loads will be considered

Joints

Control Joints: Building wall control joints, if permitted by the design, will be placed approximately “30 x t” ft (t = thickness of the structural element) on center and approximately 10 to 15 ft from the corners. Building slab control joints, if permitted by the design, will be located and spaced at a maximum of 20-ft squares or “30 x t” ft, whichever is less, or as best suited for each building. For tank or sanitary structures, wall and slab control joints will be placed as recommended by the ACI 350 report (wall control joints are not permitted in circular, non-prestressed concrete tanks). All control joints located in structures containing fluids or that are below the ground water level will have waterstops and dowels to maintain water tightness and transfer shear across the joint. The type of waterstop used will be a function of the type of fluid contained. Crack control (shrinkage and temperature) reinforcing steel will be provided in accordance with ACI 350.

Vertical Construction Joints: For vertical wall construction joints and slab construction joints, reinforcing will be extended through the joints. If vertical construction joints are required, adjacent bar lap splices will be


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staggered such that adjacent splices will not occur at the same location. Shear keys will be used in design. All vertical construction joints located in structures containing fluids or that are below the ground water levels will have waterstops and shear keys to maintain water tightness and transfer shear across the joint. They type of waterstop used will be a function of the type of fluid contained.

Horizontal Construction Joints: Horizontal construction joints will be located at the base of the walls, top of walls intersecting slabs and at mid-height of walls. All horizontal construction joints located in structures containing fluids or that are below the ground water levels will have waterstops and reinforcing to maintain water tightness and transfer shear across the joint. The type of waterstop used will be a function of the type of fluid contained.

Isolation Joints: Isolation joints will be located where slabs abut walls or their foundations and around columns, column foundations, and other foundations that carry permanent dead load other than stored material.

Masonry

Concrete Masonry Units (CMU): ASTM C90, Grade N, Type 1, normal weight, load-bearing masonry units with a minimum compressive strength of 1900 psi on the net area.

Reinforcing bars: ASTM A615, Grade 60. Use of reinforcing will be that required by calculations or by the minimum required by the referenced code and design method used. Joint reinforcing will be used at horizontal joints spaced at a maximum of 16 inches vertically to control cracking.

Mortar: ASTM C270, type M or S

Grout for CMU and Bond Beams: ASTM C476, maximum aggregate size of 3/8 inch and minimum compressive strength of 3000 psi. Masonry walls below grade and elevator shaft walls will be grouted solid.

Reinforced masonry will have a strength of f’m = 1500 psi

Horizontal Joint Reinforcing: Ladder-type reinforcing made of 9-gauge side and intermediate rods of cold drawn steel wire meeting the requirements of ASTM A-82. Intermediate bar spacing will be 16” on center and will have a hot dipped galvanized finish. Horizontal joint reinforcement will be continuous around wall corners and through wall intersections, unless intersecting walls are separated.

Masonry Lintels: Deflection limitation of L/600. Use of precast concrete lintels in high humidity locations.

Control Joints: Locate near corners of insulated, cavity-type walls. Control joints in CMU walls will contain shear keys to allow for the transfer of lateral loads through the CMU. If avoidable, do not extend the joints through bond beams. Spacing and placement of control joints will be in accordance with NCMA TEK 10-2C or 10-3.

3.10 ELECTRICAL UPGRADES

The existing electrical service consists of a 300kVA pad-mount transformer with an 8,320-volt primary and 480/277 volt secondary. This system feeds an MCC that distributes power throughout the facility. The existing distribution system appears to be in good condition, however, facility staff have expressed concern that replacement parts for the current MCC are becoming difficult to locate when devices fail. Branch panelboards are located throughout the facility for distributing 208/120v power to smaller equipment.

Electrical load calculations have determined the existing 300kVA utility transformer has the capacity to feed existing equipment, as well as proposed equipment in the TFB and SEPS.

Electrical upgrades will reuse the existing transformer and modify the distribution system to incorporate a new standby generator for providing electrical back-up power to the entire facility and provide a new feeder circuit to the TFB for filter and pumping station equipment. A new distribution panelboard and automatic transfer switch (ATS) will be located in the existing Administration Building Electrical Room where sufficient wall space is available for mounting this equipment.


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3.10.1 TFB Electrical Service

The TFB will receive a new 200-amp, 480/277-volt electrical feed from the Administration Building distribution equipment. The circuit will be routed with Schedule 80 PVC conduit underground and PVC-coated rigid steel conduit above ground. The TFB will be constructed with an isolated 12-foot 0-inch by 21-foot 4-inch electrical room which will house a majority of the electrical equipment for the TFB and the pumping station. The UV disinfection system Power Distribution Modules will also be located in the Electrical Room, and suppled with 480v, 3.1kVA power.

A new motor control center (MCC-TFB) will be located in the electrical room and contain the necessary protective and control devices for the filter equipment, heating and ventilation equipment, and low voltage distribution.

Low voltage equipment and devices in the TFB will be supplied by a 100 amp 208/120v lighting panelboard fed from MCC-TFB and a 30kVA step-down transformer. This panelboard will supply lighting circuits, door opener circuits, chemical pumps, and instrumentation & controls devices requiring 120v power.

The TFB will be provided with vapor tight LED fixtures mounted to the underside of the structure to provide approximately 50-60 foot-candela light levels at the floor. Battery-backed LED exit signs will be located in the building where required.

Raceways inside the TFB will include Galvanized Rigid Conduit inside the Electrical and Filter Rooms, and Schedule-40 PVC conduit inside the Chemical Room. Exterior conduits at the SEPS will consist of PVC-coated rigid steel conduit for exposed, above ground applications, and Schedule-80 PVC conduits for underground application. Conduits will be placed into the concrete floor between equipment locations wherever possible to maximize usable floor space.

Electrical devices for the Chemical Storage Room will be kept to a minimum, with switches for fans and lights located outside at the entrance to this room. A labeled signal light indicating fan operation will be provided at the entrance.

3.10.2 Standby Generator Replacement

Existing System

The existing standby electrical system consists of a 125kW, 480/277v, 3-ph, 4w, diesel powered generator, automatic transfer switch, and diesel fuel system. The existing generator is located in a utility room adjacent to the Administration Building laboratory, and creates undesirable noise for the facility personnel when operating. The existing back-up generator system is currently capable of supplying approximately half of the facility power requirements when normal utility power is unavailable. Facility staff have requested that the new electrical generator system be located outdoors and sized to supply full back-up power to the entire facility when the utility is down.

Proposed Modifications

The existing generator system will be removed in its entirety, including the generator set, automatic transfer switch, and diesel fuel storage system. A new 275kW, 480/277v, 3-ph, 4w, electrical generator is proposed and will be located outdoors, near the existing utility pad-mount transformer. The new generator is proposed to be fueled by natural gas with a new gas service installed to the facility as explained in Section 3.12 of this report. The new ATS for the generator system will be located in the Administration Building electrical room.

3.11 INSTRUMENTATION & CONTROL UPGRADES

3.11.1. General

Existing plant control equipment consists of simple status indication lights and local equipment controls. Graphical Chart Recorders on the face of the annunciator panel in the Administration Building provide the NCLSD facility operators with historical trend logging of influent and effluent flow data. Additional pilot lights on the panel provide operators visual indication of equipment status.


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The existing control system will remain largely unchanged. A new Programmable Logic Controller-based (PLC) process control system (PCS-1) will be located in the Electrical Room in the TFB. The new control panel will be designed to control the SEPS operation, provide supervisory control of packaged equipment systems, as well as provide remote monitoring of process operations. The control panel will house an Allen-Bradley CompactLogix PLC, which will control pump operation, sequence, and speed to match influent flow based on wet well level. Ancillary systems will be incorporated into the PLC for remote monitoring. Each skid-mounted tertiary disk filter will be provided with a dedicated, pre-wired control panel.

A new Operator Interface Terminal (OIT) with Ethernet (LAN) connectivity and XML-based process graphic displays will be added to the Annunciator panel in the Administration Building for remote monitoring of the TFB processes. The graphic displays will be the same as the PCS-1 OIT graphic displays, however locked for monitoring only.

Two (2) new fiber optic communications cables will be installed between the TFB and the Administration Building. Fiber optic connection will allow for smooth communication of PLC and equipment data between the buildings, as the distance is too large for traditional copper conductor communications.

3.11.2. Instrumentation Equipment

Level Measurement

Wet well level will be measured using an ultrasonic level transmitter, with a range spanning the usable well depth. This will provide continuous water level measurement in the wet well chamber for local and remote monitoring by operations staff, and for level alarming and action setpoints for safe pumping operation. High and low level floats will be provided to back up the level transmitter. The control system will use a programmed PID control algorithm to automatically adjust the number and speed of the pumps to achieve and maintain the setpoint wet well level.

Flow Measurement

Flow rate from the filters will be continuously measured using a magnetic flow meter and will be monitored locally and remotely with flow alarming. The flowmeter will be located immediately upstream of the UV channel, and the flow measurement will be used to flow-pace the Chemical Metering Equipment used for coagulant application, and the UV dosage.

Status Monitoring

Equipment, environment, condition, and event status monitoring will be provided locally at the Electrical Room and remotely at the Administration Building annunciator panel, for the following points:

Mechanical Bar Screen – Equipment condition and event status monitoring

Wet well high and low level alarm conditions

Pumping Station – Equipment condition and event status monitoring

Tertiary Filters – Equipment condition and even status monitoring

Filter discharge flow rate

Chemical Feed Pump Skid

Ultraviolet Disinfection System – Equipment condition and event status monitoring

Fire, Trouble, and Alarm condition

Equipment condition and event status monitoring for the standby generator

Process Control

The new control system will consist of a single Allen-Bradley CompactLogix PLC. The Control System will be mounted in a free-standing industrial enclosure, located within the Electrical Room. The PLC will be designed to send and receive signals from field equipment (VFD, ATS, generator system, chemical metering equipment,


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packaged equipment systems, instrumentation, etc.) to automatically control the TFB, while allowing for manual control should the PLC malfunction or operator intervention is required.

All PLC Input/Outputs (I/O) will be conventional signals (4-20mA-DC, 24V-DC inputs, and dry contact outputs) over hardwired copper conductors. No intelligent I/O networks will be used. The industrial enclosure will have a door-mounted OIT with Ethernet (LAN) connectivity and XML-based process graphic displays for local control of the process. Additional selector switches, speed potentiometers and pilot lights on the door of the TFB MCC (MCC-TFB) will allow for manual operation of the pumps, bypassing the PLC logic and touch-screen display.

An Ethernet (LAN) connection will be provided from PCS-1 to the VFD’s for remote configuration and monitoring.

3.12 MISCELLANEOUS PLANT UPGRADES

3.12.1. TFB Heating and Ventilation

Heating and ventilation scope will be limited to the new TFB. The systems will include unit heaters, exhaust fans, and make-up air units.

Forced mechanical ventilation will be installed in the Chemical Storage Room, which will provide one complete air change per minute when the room is occupied, per applicable Ten States Standards. The entrance to the air exhaust duct from the room will be located near the floor. The point of discharge will be located as to not contaminate the air inlet to any other buildings or ventilation systems.

The Chemical Storage Room will have a separate dedicated exhaust fan and make-up air unit (MUAU) for providing the ventilation rates as recommended by applicable Ten States Standards. The Chemical Storage Room MUAU will be capable of 5,000 cubic-feet-per-minute (cfm) ventilation when the room is occupied. The exhaust fan for Chemical Storage Room will be located on the exterior of the building with the MUAU’s located on the mezzanine above the Electrical and Facility Maintenance Rooms. The ventilation rate in the Chemical Storage Room will be kept to 6-air changes per minute when the room is unoccupied, with controls for the fan located at the entrance of the room to increase ventilation rates prior to entering. A unit heater will be installed in the chemical room to supplement heating requirements.

The Electrical, Maintenance and Filter Rooms will have a combined MUAU with separate exhaust fans. The Electrical room will have a limited ventilation rate for climate control. The Filter Room will be provided with a ventilation rate of 6 air changes per hour with an approximate 6,000 cfm system. Unit heaters will be provided for supplemental heating. Ventilation rates in the Filter and Electrical rooms will be constant whether occupied or unoccupied.

3.12.2. TFB Plumbing

Plumbing scope will consist of installation of a new natural gas service to the facility. Currently, the facility is not serviced with natural gas.

New natural gas servic