pfos and pfoa mitigation plan

Stewart Air National Guard Base

PFOS AND PFOA MITIGATION PLAN

Final

PFOS/PFOA Interim Mitigation Stewart Air National Guard Base, New York

Contract No. W9128F-14-D-0009 Delivery Order: W9128F19F0079

September 2019

Prepared by:

US Army Corps of Engineers Omaha District Special Projects Program Management Office

With Support From:

Bristol Environmental Remediation Services, LLC 720 Corporate Circle, Suite D

Golden, CO 80401

PFOS/PFOA Mitigation Plan Stewart Air National Guard Base Contract No. W9128F-14-D-0009, DO W9128F19F0079 Bristol Project No. 34190046

September 2019 i Final

TABLE OF CONTENTS

SECTION PAGE

ACRONYMS AND ABBREVIATIONS .................................................................................. iii

1.0 INTRODUCTION ............................................................................................................... 1

1.1 Site Location and Project Background ...................................................................... 1

1.2 Stormwater Quality and Flow Data ........................................................................... 3

1.3 Project Planning and Reports .................................................................................... 3

1.4 Procurement ............................................................................................................... 4

1.5 Mobilization Activities ............................................................................................... 5

1.6 Health and Safety ........................................................................................................ 6

2.0 PROPOSED REDEVELOPMENT ..................................................................................... 8

2.1 Temporary Water Treatment System ........................................................................ 8

2.1.1 Recreational Pond Water Intake and TWTS Feed Pump .............................. 10

2.1.2 Pre-Treatment Enclosure ................................................................................ 11

2.1.3 Treatment System Enclosures ......................................................................... 13

2.1.4 General TWTS System Requirements and Controls ...................................... 14

2.1.5 Conex Enclosures ............................................................................................. 16

2.1.6 TWTS Electrical Service .................................................................................. 17

2.1.7 Interconnecting Process Piping ...................................................................... 17

2.1.8 TWTS Effluent Outfall .................................................................................... 18

2.1.9 Weather Protection Plan ................................................................................. 18

2.1.10 TWTS System Commissioning and Start-up .................................................. 19

2.2 Recreational Pond Storage ....................................................................................... 19

2.2.1 Stormwater Condition Assessment ................................................................. 20

2.2.2 Outlet Structure ............................................................................................... 21

2.2.3 Other Activities ................................................................................................ 23

3.0 AREAS OF ENVIRONMENTAL CONCERN ................................................................. 25

4.0 PERMITS .......................................................................................................................... 27

4.1 Electrical .................................................................................................................... 27


September 2019 ii Final

4.2 SPDES Permit ........................................................................................................... 27

4.3 Stormwater and Earth Disturbance ......................................................................... 27

5.0 SITE MANAGEMENT ACTIVITIES ............................................................................... 29

5.1 Environmental Protection Plan ............................................................................... 29

5.2 Spill Contingency Plan ............................................................................................. 29

5.3 Management of Excavated Soils ............................................................................... 29

5.4 Dewatering ................................................................................................................ 29

5.5 Dust Control .............................................................................................................. 30

5.6 Air Monitoring .......................................................................................................... 30

5.7 Security ...................................................................................................................... 30

6.0 TRAINING PROCEDURES ............................................................................................. 32

7.0 DOCUMENTATION AND REPORTING ....................................................................... 34

ATTACHMENTS

Attachment 1 Site Location Map

Attachment 2 Outfall 010 Stormwater Quality and Flow Data from DMR Records

Attachment 3 Outfall 010 Recreational Pond and Outfall 002 Storm Drain Water Quality Sample Results

Attachment 4 Recreation Pond Outfall Stage Discharge Curves

Attachment 5 –Stormwater Review Technical Memorandum


September 2019 iii Final

ACRONYMS AND ABBREVIATIONS

AFFF Aqueous Film Forming Foam APP Accident Prevention Plan BWS BERS-Weston Services JVA, LLC CAD Computer Aided Design CFR Code of Federal Regulations CWA Clean Water Act DMR discharge monitoring records EPP Environmental Protection Plan FAA Federal Aviation Administration FAR Federal Acquisition Regulations ft feet GAC granular activated carbon gpm gallons per minute HDPE high density polyethylene kW kilowatt LHA Lifetime Health Advisory MCLs Maximum Contaminate Levels mg/L milligrams per liter NY New York NYDOT New York Department of Transportation NYNJPA New York and New Jersey Port Authority OEC Onion Equipment Company OSHA Occupational Safety & Health Administration PDT Project Delivery Team PFAS per-and polyfluoroalkyl substances PFOA perfluorooctanoic acid PFOS perfluorooctanesulfonic acid PLC programmable logic controller ppt parts per trillion psi pounds per square inch PSIG Pounds per Square Inch Gauge QA/QC Quality Assurance/Quality Control


September 2019 iv Final

QC Quality Control SANGB Stewart Air National Guard Base SSHP Site-Specific Safety and Health Plan SPDES State Pollutant Discharge Elimination System TAA Tennant Alteration Application TWTS Temporary Water Treatment System UPS uninterrupted power supply USACE United States Army Corps of Engineers VFD variable frequency drive


September 2019 1 Final

1.0 INTRODUCTION

1.1 SITE LOCATION AND PROJECT BACKGROUND

BERS-Weston Services JVA, LLC (BWS), under Contract W9128F-14-D-0009 with the

United States Army Corps of Engineers (USACE), is required to provide time-sensitive

response actions for Stewart Air National Guard Base (SANGB), Newburgh, New York (NY)

whose stormwater discharge is contaminated with perfluorooctanesulfonic acid (PFOS) and

perfluorooctanoic acid (PFOA). PFOS and PFOA are two constituents of aqueous film

forming foam (AFFF), that have been detected above the U.S. Environmental Protection

Agency (EPA) drinking water lifetime health advisory (LHA) standard of 70 parts per trillion

(ppt) (individually or combined) in the off-base stormwater discharge into the Recreational

Pond. Flow out of the Recreational Pond is through a weir outfall, which then flows into

Silver Stream, which flows into Moodna Creek and eventually the Hudson River. A

diversionary channel could also direct Silver Stream to Lake Washington, which is the

drinking water reservoir for the City of Newburgh, NY. This diversionary channel was

closed in 2016 when per- and polyfluoroalkyl substances (PFAS) contamination was

detected. This action is being undertaken by SANGB to protect drinking water under the

Clean Water Act (CWA). A site location map is included as Attachment 1.

As part of the response actions under this Contract, BWS is required to develop and

implement interim mitigation measures for the treatment of stormwater runoff by reducing

PFOS/PFOA concentrations to acceptable levels. A Temporary Water Treatment System

(TWTS) will be mobilized to withdraw waters from the Recreational Pond, reduce

PFOS/PFOA, and discharge treated water to the existing pond outfall location.

The TWTS described in this mitigation plan is just one of several initiatives being undertaken by

the Air National Guard (ANG) to mitigate PFAS from being discharged to the Recreational

Pond. Other ANG activities not part of this current project include stormwater drainage

monitoring, sampling and modeling of PFAS contributions into the pond, and collection of data



that will allow for evaluating long term strategies to mitigate or remediate PFAS from

stormwater discharges.

Stormwater runoff from the SANGB is diverted to the Recreational Pond, located at the

south side of the base via four main storm drains commonly referred to as Outfall’s A, 002,

003, and the 17K outfall. The existing detention pond is approximately 2.5 acres and the

pond depth to the top of sediment is believed to range between 3 to 8.3 feet deep with an

average pond depth of approximately 5.5 feet deep. The Recreational Pond has an average of

approximately 1.8 feet of sediment in the bottom based on 2017 soundings completed by

Aqua Survey, Inc. The detention pond outfall consists of an overflow structure equipped

with a 15’-6” crest width concrete trapezoidal weir that is approximately 7-feet high

measured from the water surface.

Interim mitigation shall include drawing down the dry weather pond level in order to

provide storage in the pond for rain events that exceed a determined runoff quantity. The

stored volume will then be treated and discharged at the existing overflow weir via a new

outfall structure. This Mitigation Plan clarifies proposed implementation methods for the

interim response actions.

Services required to successfully execute this task order will include but are not limited to:

development and installation of the approved PFOA & PFOS mitigation system, including an

interim TWTS; complete with needed ancillary infrastructure required for start-up,

operation, maintenance, and monitoring of the system.

Mitigation measures shall result in the discharge of treated water that is below the 70 ppt

lifetime health advisory (LHA) standard, in drinking water, for PFOS and PFOA

(individually or combined). Discharge water shall also meet local and state standards and be

in accordance with the CWA, and the conditions set forth in the existing State Pollutant

Discharge Elimination System (SPDES) Permit as it relates to the water quality requirements.

Concurrently with implementation of this interim mitigation, the State of New York is



working on establishing more stringent Maximum Contaminant Levels (MCLs) for PFOS and

PFOA compounds at 10 ppt respectively. Although the current system has not been

Contracted or designed for these future standards, the TWTS should have the ability to

comply with the proposed lower state standards for PFOS and PFOA.

1.2 STORMWATER QUALITY AND FLOW DATA

Available discharge monitoring records (DMRs) including historical flow and water quality

data for stormwater overflowing the outfall structure are included in Attachment 2. This

outfall location is referred to as Outfall 010. There is limited water quality data available for

PFAS at Outfall 010. However the available data confirms the presence of PFAS compounds

at the outfall between 300 and 700 ppt, which exceed the 70 ppt LHA. BWS collected

additional stormwater quality samples in early April 2019 for PFAS, along with SPDES water

quality parameters and other wet chemistry parameters that will help confirm the interim

TWTS design requirements. These samples were collected at the existing Outfall 010 weir

structure as well as Outfall 002 entering the pond. These locations were selected to provide

additional water quality data that can be used for TWTS design purposes and verify the

limited available data set. The BWS sample results are included and summarized in

Attachment 3. As part of other concurrent initiatives being undertaken by SANGB,

additional sampling and monitoring is being performed by SANGB to further define the

concentrations and sources of PFAS contamination throughout the overall drainage system

including the Recreational Pond and outfall 010.

1.3 PROJECT PLANNING AND REPORTS

In addition to this Mitigation Plan, the following plans and planning activities have been or

are planned to be performed:

• Right of Entry (ROE) access agreements will be obtained for access to the Recreational Pond for both planning and construction purposes.

• BWS has prepared and submitted the following plans prior to mobilization: Uniform Federal Policy Quality Assurance Project Plan (UFP-QAPP), Contractor Quality



Control Plan (CQCP), Accident Prevention Plan (APP)/Site-Specific Health and Safety Plan (SSHP), Environmental Protection Plan (EPP), Waste Handling/Management Plan, Community Involvement Plan, and a Restoration Advisory Committee Development Plan prior to mobilization.

• The TWTS and existing outfall structure are located on land owned by the New York Department of Transportation (NYDOT) and leased to New York and New Jersey Port Authority (NYNJPA). BWS and the Project Delivery Team (PDT) will coordinate the project activities with the NYNJPA and SANGB as the property tenant. The BWS team has submitted a Tenant Alteration Application (TAA) for implementation of the TWTS to the NYNJPA for review and approval. This TAA was prepared by a licensed engineer in the State of New York, referred to as the Engineer of Record (EOR) and submitted to the NYNJPA for approval. It is anticipated that TAA approval by NYNJPA will be provided in advance of mobilization.

• BWS has prepared and submitted a Work Plan for this project. The Work Plan further describes the procedures and work required to implement construction and operation of the TWTS.

• A project schedule will be submitted and updated weekly during planning and construction.

• Prior to TWTS operation, the following additional plans will be prepared and submitted for approval: Weatherization Plan, Startup and Maintenance Plan, Operations and Maintenance (O&M) Manual and a Transition Plan,

• BWS is procuring required site supplies and subcontractor services needed to implement this project.

• A submittal register and project submittals are on-going and being prepared and approved for all materials incorporated into the work.

• BWS will, set-up a field office, and conduct a Project Kickoff meeting with all PDT members.

• BWS will monitor the effectiveness of the stormwater interception and treatment measures to determine if additional mitigation measures are needed.

• A completion report will be prepared at the end of the project.

1.4 PROCUREMENT

Procurement of the following equipment and subcontractors will be necessary to implement

this project:



• Site facilities (trailer, restroom, hand wash station, site security, and temporary power);

• Private underground utility locating survey services for all areas to be disturbed;

• Civil works services including; erosion and sediment controls installation, gravel pad construction, access road improvements, utility trenching/backfill, TWTS equipment rigging and installation/testing of interconnecting piping.;

• Pre-manufactured TWTS treatment system;

• Temporary outfall structure installed at the existing Recreation Pond overflow weir;

• Site power connection to the SANGB electrical system;

• Electrical services including 3-phase transformer, electrical distribution, and interconnecting communications and

• Operations subcontractor services during operations and maintenance (O&M).

All procurement activities are performed and administered in accordance with the Service

Contract Act, Federal Acquisition Regulations (FAR), and the Defense Federal Acquisition

Regulations Supplement (DFARS).

1.5 MOBILIZATION ACTIVITIES

Mobilization will commence after Prior to initiating any subsurface work on any site, Dig

Safely of NY will be contacted to mark-out utilities for each applicable work area. BWS will

also retain an independent underground utility locating firm utilizing ground penetrating

radar equipment to locate on-site utilities in disturbed areas. Mobilization/setup includes set-

up of a temporary job trailer; sanitary facilities and a portable generator for temporary power

to job trailer.

Placement of the TWTS enclosures will require use of a crane. BWS has received a Federal

Aviation Administration (FAA) determination (ASN 2019-AEA-7292-OE) allowing

operation of a temporary 120 ton crane with a maximum height of 100 feet above ground

level at the Recreation pond area. BWS and the Crane operator will perform the required

notifications prior to mobilization and when the crane is dismantled in accordance with the

determination.



1.6 HEALTH AND SAFETY

An SSHP and APP has been prepared and approved for this project. The SSHP and APP

contains health and safety criteria, procedures, and work practices sufficient to protect on-

site personnel and the environment.

BWS will utilize qualified personnel, including a field dedicated Site Safety and Health

Officer (SSHO) to oversee the development and implementation of required safety and

health documents and all activities will comply with the following:

• Federal Acquisition Regulation, F.A.R. Clause 52.236 13: Accident Prevention.

• U.S. Army Corps of Engineers (USACE), Safety and Health Requirements Manual, EM 385 1 1 (Nov 2014).

• Occupational Safety & Health Administration (OSHA) Construction Industry Standards, Title 29 Code of Federal Regulations Chapter 1926 (29 CFR 1926), and General Industry Standards, 29 CFR 1910.

• Other applicable Federal, State, and local safety and health requirements.



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2.0 PROPOSED REDEVELOPMENT

2.1 TEMPORARY WATER TREATMENT SYSTEM

BWS has procured and will install, test, and make fully operational Pre-manufactured

containerized mitigation systems for temporary treatment of stormwater for PFOS/PFOA

prior to discharge from the Recreational Pond to include pretreatment (screening/filtration),

granular activated carbon (GAC), followed by PFAS adsorption using ion exchange media.

The TWTS will be located in the open area south east of the existing overflow structure at

the approximate location shown on Figure 1.

The TWTS will be pre-engineered to treat water up to 500 gallons per minute (gpm). The

TWTS is to be housed in three (3) Conex enclosures to provide protection from weather and

freezing temperatures. The first Conex will enclose the pretreatment filtration system and

controls. The other two enclosures will house parallel trains of one Pre-treatment GAC

vessel and two primary treatment of ion exchange media vessels arranged in a lead/lag series

configuration. The treatment system conceptual design is shown on Figure 2. The TWTS

shall be engineered and constructed by Onion Equipment Company (OEC) who

manufactures pre-engineered (modular) treatment equipment and experienced with PFAS

water treatment for surface water. OEC will engineer and manufacture the system and

support start-up and commissioning of the installed treatment system.

The TWTS Conex enclosures will be installed behind the Recreational Pond berm and

southeast of the weir structure outfall as depicted in Figure 1. To protect against syphoning

of Recreational Pond, a vented high point will be provided in the effluent discharge line



Figure 1 TWTS System Location



Figure 2 TWTS Conceptual Diagram

2.1.1 Recreational Pond Water Intake and TWTS Feed Pump

Water will be drawn from the Recreational Pond via a submerged suction pump, which will

be mounted to a floating or temporary dock in a portion of the pond selected to maximize

usable volume and minimize exposure to damage and erosion. The intake will be submerged

and screened to prevent entry of floating debris, but off the bottom to minimize entrainment

of sediments. The screen will be sized to have a low intake velocity to reduce the likelihood

of collecting debris and adequately protect the pump. The screen will be accessible from the

floating or fixed dock for maintenance and cleaning if necessary. Water will be transferred

from the pump via flexible suction hose and high density polyethylene (HDPE) pipe to the

TWTS. The above ground line between the pond and the enclosure will be protected from

freezing. The pump will supply up to five-hundred (500) gpm to the TWTS. The pump will

be driven by a variable frequency drive (VFD) to maintain a flow processing rate under

variable TWTS back pressure. The pump will be controlled on/off by maintaining a target



level in the pond that is below the overflow level. A level transducer will be installed in the

pond to monitor and document the water level during system operation and control the

TWTS.

2.1.2 Pre-Treatment Enclosure

The first Conex enclosure will house the pre-treatment system. Pre-treatment is required to

remove solids that may enter the TWTS and prematurely foul the treatment media. The pre-

treatment system will consist of 1 centrifugal separator and bag filtration. The centrifugal

separator will be a carbon steel separator manufactured by Rosedale as shown in Figure 3.

The separator shall be designed for 500 gpm with less than 15 pounds per square inch (psi)

pressure drop. The separator shall remove solids contained in the pond water via centrifugal

action. The separation systems have a timed solenoid valve that opens and flushes out the

accumulated solids automatically. Flush water will be returned to the Recreational Pond.

Figure 3 Pretreatment Separator



Following the separator, the water will enter a second filtration system. The filtration system

consists of Rosedale multi-bag, two stage, No. 2 size bag filtration system constructed of

carbon steel. Each stage will have 6 filters in order to process 500 gallons per minute. The

first stage will have coarse bag filters (approximately 25 micron). The second stage will have

fine bag filters (approximately 10 micron). Figure 4 shows a Rosedale multiple bag filter

housing that could serve as either the coarse or fine filtration. The bag filter housings will

have pressure gauges and pressure transmitters located on the inlets and outlets, to

continuously monitor operating pressure during system operation. The pressure transmitter

will continuously document differential pressure at the control system and notify operations

staff when high differential pressure occurs indicating the bags will require change out.

Figure 4 Multi Bag Filter Skid



2.1.3 Treatment System Enclosures

After pre-treatment, process water will be divided into two streams and process forward flow

will be sent to two identical and independent treatment system enclosures installed in

parallel. Each independent treatment system will be configured with two (2) total treatment

trains housed in a single Conex enclosure for a total of four (4) treatment trains running in

parallel within two (2) Conex enclosures.

Each treatment train shall contain GAC pretreatment, primary ion exchange and polishing

ion exchange. The GAC pretreatment system will be comprised of two (2) GAC vessels,

running in parallel, for the removal of organic compounds that could impact the long term

performance of the ion exchange media for PFOS/PFOA removal. Each GAC vessel will be

approximately five (5) foot diameter, and contain approximately 2,500 lbs. of carbon.

Between the two (2) Conex enclosures there will be a total of four (4) GAC treatment vessels,

each containing approximately 2,500 pounds of GAC media. The GAC vessels will initially be

filled with 8x30 Calgon Filtrasorb 300 granular activated carbon media. When GAC is

exhausted and requires to be replaced during system operation, it will be profiled and

properly disposed at a landfill following incineration. Each GAC vessel will have an air vent,

drain and inlet/outlet valves, sample ports and pressure gauges in order to monitor their

performance and control their operation. Provisions will be made to allow for manually

backwashing the vessels if premature fouling occurs. If backwashing is performed backwash

water would be returned to the Recreational Pond away from the pump intake and in a

manner that does not disturb the pond or cause erosion.

In each enclosure after passing through the two GAC pretreatment vessels, the flow will

then be directed into the primary ion-exchange resin treatment vessels (two located within

each Conex enclosure) followed by the polishing ion exchange resin treatment vessels (two

located within each Conex enclosure) for the removal of PFOS/PFOA from the water. Each

vessel will contain approximately 70 cubic feet of Purolite® PFA694 ion-exchange media (or



equal). The eight ion exchange vessels will contain a total media volume of 560 cubic feet.

Four (4) ion-exchange treatment vessels will be installed in each parallel Conex enclosure.

Each vessel will be approximately five (5) foot diameter and have six (6) foot sidewalls. With

this configuration, there will be four (4) total treatment trains running in parallel (two

within each Conex enclosure). A manifold or flexible hoses with quick disconnects will be

provided to allow bypass of the primary vessels when they are exhausted and swapping the

primary and polishing vessels when media is replaced. The manifold will be equipped with

pressure gauges and sample ports to allow for monitoring the performance of each skid. Each

individual ion exchange vessel will have isolation valves to be able to service each unit

independently. Each ion exchange vessel will have an air vent, drain and inlet/outlet valves,

sample ports and pressure gauges in order to monitor their performance and control their

operation. During system operation when ion exchange media becomes exhausted and

requires to be replaced, it will be profiled and properly disposed at a landfill following

incineration.

The treated water will be combined and will exit both Conex treatment enclosures via a

single effluent line. The two effluent lines (one from each enclosure) will then be combined

and a single effluent flow meter will be installed to monitor the overall flow rate (gpm) and

total gallons treated. Discharge control valves are installed downstream of the flow meter

that will divert treated effluent either back to the Recreational pond (e.g. recycle) or direct

treated water adjacent to the outfall structure located adjacent to the overflow weir. Each

gravity discharge line will have a constructed high point and be vented.

2.1.4 General TWTS System Requirements and Controls

The treatment systems will contain sample ports on the influent (raw water), after each

pretreatment stage, and after each GAC and each ion exchange media stage as well as the

combined treated effluent. Intra-process monitoring is important to evaluate each process

stage and confirm breakthrough of PFOS/PFOA on the primary ion exchange media. Once



breakthrough of PFOS/PFOA are detected on the primary ion exchange at concentrations

exceeding one-half the HAL (35 ppt) the resin in the primary vessels will be replaced.

Following media replacement, the polishing vessels will then become the primary vessels and

the newly serviced primary vessels will become the polishing vessels. Water samples will be

collected approximately on a weekly basis during the first month and monthly thereafter.

More frequent sampling will be performed if raw water quality changes or observed or if

treatment system performance warrants more frequent monitoring. The sampling schedule

will be adjusted appropriately to ensure that ion exchange media change outs are conducted

in advance of PFAS breakthrough in the polishing effluent to ensure that the systems are

serviced in a timely manner to meet treatment objectives.

Pressure gauges and pressure transducers will be installed on the influent and effluent of

each treatment stage to monitor for pressure differentials, which could indicate the need for

system servicing or backwashing. The treatment system will have automated controls that

will allow local monitoring of system performance from a single location.

The controls will include a programmable logic controller (PLC) with a touch screen panel,

similar to one shown in Figure 5. A cellular modem with a static IP address will be installed

to allow for remote access and monitoring of the system on computers and smart phones.

Access will be password protected and secure. The control system will monitor; equipment

run status, system flows, system pressures, pond level, and alarms. If an alarm occurs the

system will be equipped with an alarm dialer or alarm management system that can be

custom configured to notify operations personnel of an alarm. Operations personnel will be

available to address any operations and maintenance concerns, 24 hours/day, 7 days a week.



Figure 5 Typical Control Panel

2.1.5 Conex Enclosures

Each Conex enclosure will be approximately eight (8) feet wide by forty (40) feet long by

nine (9) feet high. The enclosure will be insulated and will have electric heaters to protect

the systems from freezing. The enclosures will be constructed with interior lighting,

ventilation, personnel doors, fire extinguishers and double doors to allow for access to the

systems for servicing. These containers are not considered “confined space” under OSHA.

The systems and controls will come pre-fabricated within each Conex enclosure, minimizing

on-site time required for the erection of the systems and start-up.

The Conex enclosures will be installed on a level, gravel laydown pad that will be

constructed prior to delivery to the site. The Conex enclosure will arrive at the site via

flatbed truck and will be offloaded at the site using a crane. Interconnecting piping and

electrical for the treatment systems will then be constructed once the Conex enclosures are

situated on the laydown pad. A Conex enclosure similar to the enclosures envisioned at

SANGB is shown in Figure 6.



Figure 6 Typical Conex Enclosed TWTS

2.1.6 TWTS Electrical Service

Because of the remote location of the Recreational Pond and TWTS, no local, secondary

electrical power is readily available. Site reconnaissance has confirmed that high voltage

power (13,200 volts) is available at a nearby substation operated by SANGB. A temporary

high voltage electrical service will be installed through a combination of new and existing

spare underground raceways between the substation and the TWTS. At the TWTS area a

300 kVA, 3 phase, 460 volt, pad mounted transformer will be installed. The electrical service

will have a main fused service switch, a manual transfer switch, and all necessary secondary

distribution equipment and low voltage transformers to power the supply pump, equipment,

heat tracing, heaters, lighting, instrumentation and system controls needed to operate and

maintain the TWTS. The manual transfer switch will allow for connection of a temporary

generator to power the TWTS if an extended power outage occurs.

2.1.7 Interconnecting Process Piping

As discussed herein the TWTS will be mobilized as pre-engineered fabricated skids to reduce

construction field effort. Field fabrication and assembly of interconnecting process piping



will be required. Interconnecting piping will be comprised of PVC Pipe, HDPE Pipe, and

Suction Rated Flexible Hose. All exterior piping not subject to submergence or fully

drainable will also be insulated and heat traced for freeze protection.

2.1.8 TWTS Effluent Outfall The TWTS will be able to discharge treated water to both the existing outfall and recirculate

treated effluent back to the Recreational Pond via a central return line. The treated effluent

will normally be diverted to the existing overflow weir. The 8-inch HDPE line will be a

gravity return. It will discharge treated effluent to a temporary outfall structure situated

directly upstream of the existing overflow weir. Dam Safety flow curves were prepared by

BWS and submitted to NYSDEC to document estimated hydraulic impacts to the existing

overflow weir as a result of the temporarily outfall structure. These calculations are included

in Attachment 4. NYSDEC reviewed the temporary outfall drawings and calculations and

confirmed that the proposed outfall structure hydraulic impact is within acceptable limits

and no dam safety permit would be required. The temporary outfall structure will be a pre-

cast concrete chamber, equipped with an overflow installed at the same elevation as the

existing weir. The outfall structure will dissipate energy before flowing over the existing

weir. A 3-foot wide overflow spill way will be used to convey treated water to the existing

outfall weir. The temporary structure will be designed to resist buoyant forces.

2.1.9 Weather Protection Plan

A separate Weather Protection Plan will be submitted prior to mobilization. In general the

treatment systems will be housed in an insulated/heated enclosure, designed to protect the

system from freezing. Process piping (e.g., influent suction line, effluent piping and,

interconnecting Conex enclosure process lines) that are external from the enclosures shall be

placed on ground surface, insulated and heat traced to protect against freezing. The gravity

effluent lines will be sloped to fully drain so they do not require freeze protection. If a loss

of power occurs, the PLC based control system shall be provided with an uninterruptable



power supply (UPS) and configured to notify operations staff of a loss of power condition. In

addition, each enclosure should be equipped with a temperature transmitter and

automatically notify staff of a potential freezing condition. If an extended power outage

occurs during cold weather operations staff will need to either drain the system, provide

temporary heat and power to protect the system from freezing or mobilize a generator to

temporarily power the system. Additional specific weather protection details will be

submitted in a follow-up submittal.

2.1.10 TWTS System Commissioning and Start-up

After the TWTS is constructed, the treatment system be commissioned and started up in

accordance with the individual equipment O&M manuals, and the TWTS system supplier

O&M manual.

Following system commissioning, initial samples will be collected from the influent, GAC

pretreatment effluent, primary ion exchange media effluent, and overall effluent and sent to

the approved analytical laboratory for analysis of PFOS/PFOA and other applicable SPDES

parameters. After confirmation that effluent quality is acceptable, effluent will be diverted to

its normal discharge at the new outfall structure and over the existing overflow weir.

Following startup, sampling will be performed as needed to monitor system performance.

2.2 RECREATIONAL POND STORAGE

In order to reduce discharge of untreated stormwater off site, the existing Recreational Pond

will be lowered approximately 2-feet to create approximately 1.86 million gallons of storage

capacity. This stored water will allow treatment and eventual discharge as described in

Section 2.1. As previously indicated the existing Recreational Pond is approximately 2.5 acres

and the pond depth to the top of sediment is believed to range between 3 to 8.3 feet deep

with an average pond depth of approximately 5.5 feet deep. The Recreational Pond has an

average of approximately 1.8 feet of sediment in the bottom based on 2017 soundings

completed by Aqua Survey, Inc.



Stormwater storage will be created by operating the TWTS and lowering the water level in

the pond. See the Stormwater Review Technical Memorandum issued 17 June 2019 included

as Attachment 5 for additional information. This storage approach does not require

modifications to the existing Recreational Pond outfall structure, which would take

significant time to evaluate and implement modifications that allow for raising the pond

level and increasing storage.

If the volume created by lowering the pond water level were determined to be insufficient or

if the estimated volumes are impacted by either increased groundwater infiltration or

sediments in the bottom of the pond, modifications to the outfall structure may be required

to increase storage by increasing the weir elevation. The modifications to the pond outfall

structure (if required) would raise the wet weather pool elevation while maintaining the dry

weather pool elevation through pumping of stored water to the TWTS. In order to evaluate

the optimal storage capacity and ensure stability of the stormwater system, a complete

geotechnical investigation and modeling of the facility-wide and of site stormwater

conveyance system would be necessary. This effort would be completed as part of the

CERCLA process and implemented, if necessary, as part of the final selected remedy. All

future modifications to the outfall structure will be coordinated by the NGB with the NY

DOT and NYNJPA, the lessee and owner of the outfall, and the NYDEC who regulates the

outfall structure.

2.2.1 Stormwater Condition Assessment

Limited stormwater condition assessments have been performed based on the minimal

stormwater flow dataset and information available for the existing stormwater system to

determine statistical returns and anticipated performance metrics for the proposed TWTS.

Since the weir outfall structure is not being substantially modified as part of the interim

mitigation a more robust analysis is not necessary at this time to support TWTS



implementation. However, data collection is on-going and a more in depth analysis will be

prepared as part of the CERCLA process to determine the appropriate final remedy.

The stormwater condition assessment will be a critical component to determining the final

remedy and will determine the feasibility of temporarily retaining stormwater in the

Recreational Pond above the existing dry water elevation by constraining flow through the

existing outlet structure. Weir stability, earthen embankment stability, and pond area

stability all depend on the results and findings of the stormwater condition, and require

supporting information from a geotechnical investigation, structural investigation, and

engineering assessment to fully quantify the ability to control the system utilizing structural

modifications to the outlet structure.

The stormwater condition assessment will additionally determine up to what storm event, or

series of events, will be able to be retained in the pond without overflow of the outlet

structure. It will consider continuous withdraw from the pond to the TWTS to a specified

maximum drawdown elevation, as well as event based stormwater runoff in determining

inflow into the pond and staged elevations if modifications to the weir are determined to be

necessary.

2.2.2 Outlet Structure

The existing outlet structure consists of a trapezoidal shaped broad crested weir built into an

earthen berm with wing walls on both the upstream and downstream sides. Dry weather

flow through the weir is continuous due to suspected groundwater influence and the

combined flow from the four outfalls previously described. It is reported that these water

sources provide a near constant flow depth of less than one inch to flow over the structure as

shown in Figure 7. A rock lined channel is downstream of the outlet structure as shown in

Figure 8. As discussed, BWS will install a temporary outfall structure just upstream of the

weir. The proposed temporary outfall structure will be a pre-cast concrete chamber,

equipped with an overflow installed at the same elevation as the existing weir. The outfall



structure will dissipate energy before flowing over the existing weir. A 3-foot wide overflow

spill way will be used to convey treated water to the existing outfall weir.

Figure 7 Existing Outlet Structure (Upstream)

Figure 8 Downstream of Outlet Structure



2.2.3 Other Activities

As previously discussed, the TWTS is just one of several initiatives being undertaken by the Air

National Guard (ANG) to mitigate PFAS from being discharged to the Recreational Pond. Other

ANG activities not part of this current project include stormwater drainage monitoring, sampling

and modeling of PFAS contributions into the pond, and collection of data that will allow for

evaluating long term strategies to mitigate or remediate PFAS from stormwater discharges.

The results of these studies will likely be completed prior to considering potential, modifications

such as drainage infrastructure modifications, or outfall structure modifications that could

be considered to increase storage volume by raising the water level. Any further

modifications would be evaluating through the CERCLA process.

This TWTS is being installed as an interim mitigation system, in order to reduce the

contamination level in the recreational pond outfall, while the site proceeds through the

CERCLA process. The site is currently at the Site Investigation (SI) phase within the

CERCLA process. The next phase in the CERCLA process is the remedial investigation phase.

During that phase a complete CSM and risk assessment are completed. Following the

CERLCA process a feasibility study, in which remedy alternative are evaluated for

consideration, will be undertaken. After remedy evaluation, a final remedy is chosen and

will be implemented as, required under the CERCLA process, to achieve New York state

and/or federal cleanup standards once those standards are properly promulgated.



3.0 AREAS OF ENVIRONMENTAL CONCERN

The only known or suspected contamination with the work area is the PFOS and PFOA

contaminants contained in the stormwater and groundwater. The presence of this

contamination is not expected to impact construction activities.



4.0 PERMITS

The proposed work will include electrical construction, installation of TWTS, modifications

to the existing Recreational Pond outlet structure, and earth disturbance activities associated

with establishing site access and construction of the proposed features.

The NYNJPA TAA process will require design and application submittal from SANGB and a

licensed engineer in the State of New York.

4.1 ELECTRICAL

All work associated with the electrical interconnection will follow all applicable codes and

regulations, however, no permits are expected to be obtained to complete the electrical

connection. Work will be performed by licensed electricians familiar with the type of work.

4.2 SPDES PERMIT

The ANG currently holds an expired discharge permit and is coordinating the continued use

of this SPDES Permit, with the New York State Department of Environmental Conservation

(NYSDEC). The system will be operated in and monitored in accordance with the

requirements set forth in the permit. In addition to the existing SPDES permit, PFAS

compounds will be monitored as discussed in Section 2.1 of this Plan.

4.3 STORMWATER AND EARTH DISTURBANCE

Prior to excavation or earth disturbance work Dig Safely New York will be contacted to

acquire state required utility clearances. Additionally, it is expected SANGB and NYNJPA

will require dig permitting to perform all earth disturbance activities.

Although a separate Stormwater Pollution Prevention Plan and SPDES permit for discharges

related to construction activities are not required for construction sites disturbing less than

one acre, an Environmental Protection Plan (EPP) will be prepared to depict the locations

and purpose of erosion and sediment control devices as well as depict the construction

activities and site development plan.



5.0 SITE MANAGEMENT ACTIVITIES

5.1 ENVIRONMENTAL PROTECTION PLAN

The EPP will be implemented by BWS personnel and involve the installation of a stabilized

construction entrance, silt fence, and disturbance area mulch and seed. Inspection of the site

will be completed monthly and after every significant rain event. A log of site inspections,

findings, and corrective actions will be kept on site.

5.2 SPILL CONTINGENCY PLAN

The nature of the work includes the potential for the spilling of small quantities of

construction equipment related fluids and TWTS operational fluids. BWS on site personnel

and contractors will be trained in the response for construction and TWTS operation related

spills and maintain adequate spill kits containing booms, absorbent pads, and containment on

site at all times. Spills will be recorded and reported in accordance with Federal, State, and

Local requirements. A detailed spill control plan is provided in the EPP.

5.3 MANAGEMENT OF EXCAVATED SOILS

Soils will only be excavated while installing the electrical conduit to the TWTS. No

contaminated soils are expected to be encountered and no off-site disposal of soils will be

performed. Any excess soils will be placed below the TWTS gravel pad in support of leveling

off that area.

Electrical Service raceways will be bedded in sand. No trenching is anticipated to be greater

than 4-feet deep. However, if deeper trenching was required, workers will not enter an

unsupported trench deeper than 4 feet and all other applicable OSHA and HASP

requirements will be maintained.

5.4 DEWATERING

Due to the shallow groundwater condition expected at the site, dewatering of the trench

excavations is anticipated. Excavation dewatering fluids will be directed to the Recreational



Pond after passing through a sedimentation device such as a filter bag or settling tank to

remove any fines or silts and discharged to the Recreational Pond in a manner that will not

cause erosion or disturb the pond sediments.

5.5 DUST CONTROL

Dust will be policed on site by maintaining stable, dust free work surfaces such as gravel pads

and adding erosion controls to areas as soon as earth disturbances are complete.

5.6 AIR MONITORING

No air monitoring is required for this mitigation activity.

5.7 SECURITY

The TWTS location is installed in a secure area but in a remote location. Access to the job

site will be controlled with locked perimeter entry gates. All TWTS Conex enclosures are

lockable and secure. No additional local security fencing or security measures are anticipated.

However, additional temporary fencing or video surveillance around the TWTS enclosures

could be provided if deemed necessary following construction.



6.0 TRAINING PROCEDURES

The TWTS Equipment Supplier (Onion Equipment Company, Inc.) is responsible for

leadings commissioning, start-up and training of the Pre-engineered TWTS. BWS personnel

will assist with commissioning, start-up and have hands-on training on system operations

and provide initial operation of the system. BWS will also perform all required system

monitoring as part of the Start-up and operations.

Hazard communication and documentation will be provided in accordance with Federal,

State, and Local requirements. All personnel entering the work areas will be provided with

site specific training and hazard communication.

Upon turnover of the TWTS, BWS will provide training to the future TWTS operator.



7.0 DOCUMENTATION AND REPORTING

A Completion Report will be prepared for the facility following completion of the final

maintenance period at that facility. The final Completion Report will contain: an executive

summary, a summary for completed work, schedule, a signed or certified statement by the

contractor that the system complied with all relevant standards during the project execution,

as-builts, warranties, certifications, testing, samples and analyses results, validation, and

points of contact for completed work.

ATTACHMENT 1

Site Location Map

ATTACHMENT 2

Outfall 010 – Stormwater Quality and Flow Data from DMR Records

Attachment 2 - Outfall 010 Storm water Quality and Flow Data

1 of 1

Month 2016 2017 2018January No Data 3,570,320 4,865,070 February 1,898,560 No Data No DataMarch 1,769,890 1,481,170 10,659,100 April 1,808,240 6,001,870 9,587,740 May 6,906,790 5,405,350 No DataJune No Data 5,580,890 4,696,920 July 303,598 1,411,670 3,801,720 August No Data No Data No DataSeptember 616,100 No Data 6,553,550 October 46,115 3,538,927 No DataNovember 2,191,550 No Data 4,348,690 December 1,151,190 No Data 6,139,710 Minimum 46,115 1,411,670 3,801,720 Average 1,854,670 3,855,742 6,331,563 Maximum 6,906,790 6,001,870 10,659,100 1Flow Data source - Flow Data & Outfall 010 DMR Records in PWS Attachment G

MonthBOD, 5 day

(mg/L)pH

(s.u.)Oil & Grease

(mg/L)Glycol (mg/L)

January-18 7.8 7.0 <5.2 <5March-18 21 7.4 <5 9.6

April-18 <6 7.2 <5 <5June-18 <4 7.2 <5 <5July-18 <6 7.5 <5 <5

September-18 <6 7.2 <5 <5November-18 <6 7.1 <5 <5December-18 <6 7.1 <5 <5

2Sample results - Outfall 010 DMR Records in PWS Attachment G

Date Analyte

Upstream outfall 010

RP-SW-20 (ppt)

Downstream Outfall 010 - RP-SW-21

(ppt) Average (ppt)PFOS 601 607 604PFOA 63 79 71PFOS+PFOA 664 686 675PFOS NS 322 322PFOA NS 36 36PFOS+PFOA NS 358 358

3Sample result source - Wood Environment & Infrastructure Services, Inc. Abbreviationsppt - Parts per Trillion mg/L - milligrams per liter SU - standard unit

10/18/2017

5/18/2018

Recreation Pond - PFOS & PFOA Surface Water Sample Results (3)

Estimated Maximum Daily Flow During the MonthGallons per Day (GPD) (1)

SPDES Sample Results (2)

ATTACHMENT 3

Outfall 010 Recreation Pond and Outfall 002 Storm Drain Water Quality Sample Results

Parameter Result Units Parameter Result UnitsPerfluoroheptanoic Acid (PFHpA) 35 ng/L Perfluoroheptanoic Acid (PFHpA) 36 ng/LPerfluorooctaoic Acid (PFOA) 46 ng/L Perfluorooctaoic Acid (PFOA) 50 ng/LPerfluorononanoic Acid (PFNA) 14 ng/L Perfluorononanoic Acid (PFNA) 13 ng/LPerfluorobutanesulfonic Acid (PFBS) 17 ng/L Perfluorobutanesulfonic Acid (PFBS) 11 ng/LPerfluorhexanesulfonic Acid (PFHxS) 120 ng/L Perfluorhexanesulfonic Acid (PFHxS) 94 ng/LPerfluoroocatnesulfonic Acid (PFOS) 490 ng/L Perfluoroocatnesulfonic Acid (PFOS) 380 ng/LTotal PFOA/PFOS 536 ng/L Total PFOA/PFOS 430 ng/L

TSS 1.79 J mg/LT. Alkalinity 164 mg/L Note: Current Health Advisory is 70 parts per trillion for PFOA/PFOS Bicarbonate Alk. 164 mg/L Individually or Combined.Carbonate Alk. 4.0 U mg/LBOD 3.05 mg/LO/G HEM 4.0 U mg/LBTEX No Detections NASVOCS No Detections NAGlycols No Detections NAN as No3 0.090 U mg/LP as PO4 0.30 U mg/LTOC 2.9 mg/L

BOD - Biochemical Oxygen DemandBTEX - Benzene, toluene, ethylebenzene and xylenes mg/L - milligrams per liter or parts per millionng/L - nanograms per liter or parts per trillionNO3 - NitratePO4 - PhospateSVOC - Semi-volatile Organic CompoundsTOC - Total Organic CarbonTSS - total suspended solidsA full list of SVOCs and glyclols is available on request

SANG-EFF010-04042019

Stewart ANG Sample Results

Sample Date 04/04/2019

SANG-RPOND-04042019

ATTACHMENT 4

Recreation Pond Outfall Stage Discharge Curves

23 August 2019

CALCULATION COVER SHEET

PROJECT: Stewart ANGB

WORK ORDER NO. 15254.002.037.0003

CALC NO. 1

SHEET 1 of_7__

SUBJECT: Recreation Pond – Stage Discharge Curves

DISCIPLINE (Civil, Mech. Process, Elect.): Civil

PREPARED BY: H. Nathanson DATE:08/20/2019

CALCULATION STATUS ISSUED FOR REVIEW

FINAL

CONFIRMED

SUPERCEDED

VOIDED

COMPUTER PROGRAMS USED:

Yes No DESCRIPTION/VERSION: Microsoft Excel 2013

REFERENCE SPECIFICATIONS:

REFERENCE DRAWINGS:

SOURCES OF DATA: 1. HydroCAD Software Solutions LLC. HydroCAD Stormwater Modeling System: Owner’s Manual Version 10. HydroCAD

Software Solutions LLC, 2011. 2. Weston Solutions, Inc. (August 12, 2019). Temporary Water Treatment System (TWTS) Outfall Alternatives.

SUMMARY OF RESULTS: Weston Solutions, Inc. (WESTON) performed an analysis to determine the hydraulic impacts associated with placement of a precast outfall structure against the existing weir in Recreation Pond, to facilitate a Temporary Water Treatment System (TWTS). The precast outfall would behave as a six inch (6”) tall, five foot (5’) wide obstruction on the weir crest. WESTON’S analysis of the hydraulic impacts associated with partially obstructing the existing weir in Recreation Pond indicated that the restriction will increase the stage height to achieve the same discharge flowrate as that over the unrestricted weir. WESTON estimates that the restricted weir will have an increased stage height (head) over the unrestricted weir of approximately three to four inches (3 to 4”), dependent on actual flow. For example, at a discharge rate of 500 CFS, the TWTS restricted weir indicates an increased stage height (head) over the weir of approximately three-and-a-half inches (3.5”). Based on limited available flow data, weir flows have peaked at approximately 400 CFS in response to a 1.69" rain event, with a peak precipitation rate of 1.1 in/hr. WESTON’S calculations estimate the unrestricted weir capacity is in excess of 900 CFS with a maximum height of six feet (6’) with one foot (1’) of freeboard. Based on the calculated capacity compared to the available storm response data, the increase in stage height (e.g. approximately 4”) is expected to have de minimus impacts on the performance and safety of the existing weir structure. Please note that WESTON has not been provided design data for the existing weir, and it should it be made available, WESTON may utilize this data to further evaluate the findings.

RECORD OF REVISIONS NO. REASON FOR REVISION TOTAL NO.

OF SHEETS LAST SHEET

NO. BY CHECKED APPROVED/

ACCEPTED DATE

0 Issued for Review 7 HN CS AB 8/20/19 1 Response to Comments 7 HN CS AB 8/23/19

SHEET 2 OF 7 _

CLIENT/SUBJECT Stewart ANGB W.O. NO 15254.002.037 .

TASK DESCRIPTION Recreation Pond – Stage Discharge Curves TASK NO 0003 .

PREPARED BY H. Nathanson DEPT 2118 DATE 8/19/2019 . APPROVED BY

MATH CHECK BY C. Sembera DEPT 2118 DATE 8/19/2019 .

METHOD REV. BY A. Brown DEPT 2118 DATE 8/20/2019 .DEPT_ DATE_

File Name: 2-Stewart_ANGB_Rec_Pond_Stage Discharge Curve.docx Print date: 08/23/19 11:19 AM

Objective:

Determine the increase in relative stage height associated with placement of a precast outfall structure

against the existing weir in Recreation Pond, in conjunction with a temporary water treatment system

(TWTS).

References:

HydroCAD Software Solutions LLC. HydroCAD Stormwater Modeling System: Owner’s Manual Version 10. HydroCAD Software Solutions LLC, 2011.

Weston Solutions, Inc. (August 12, 2019). Temporary Water Treatment System (TWTS) Outfall Alternatives.

Attachments:

Attachment A – Stage Discharge Curve Temporary Water Treatment System Outfall Alternative 1.

Attachment B – Sheet C-5: Outfall Structure Plans and Sections.

SHEET 3 OF 7 _







Assumptions:

• The weir is asymmetrical, and therefore divided into rectangular and half-v sections, which are

then summed, to determine the flow through the weir.

• A half-v weir is equivalent to half of a triangular or v-notch weir.

• The base of the existing weir is 15.5 feet long, and comprised of rectangles and right triangles.

• The existing weir has one foot (1’) of freeboard, and flows will not exceed a stage height over six

feet (6’) above the weir.

• A weir coefficient value of 2.95 corresponds to the rectangular portions of the weir.

• A weir coefficient value of 0.593 corresponds to the half-v portions of the weir, and represents a

90 degree angle.

• Approach velocity is negligible.

• The precast outfall partially blocks the weir and is expected to behave as a six inch (6”) tall, five

foot (5’) wide obstruction on the weir crest.

Discussion:

Weston Solutions, Inc. (WESTON) performed an analysis to determine the hydraulic impacts associated

with placement of a precast outfall structure against the existing weir in Recreation Pond to facilitate the

TWTS. The precast structure would extend five feet (5’) along the length and six inches (6”) above the

existing weir crest (Attachment B). The analysis compared the flows over the existing unrestricted weir to

those over an obstructed weir to determine the difference in head at varying stage levels.

Analysis:

Adding a partial obstruction to the existing weir would result in an asymmetrical weir; therefore flows

over the weir were calculated by dividing the opening into rectangular and half-v sections (HydroCAD

Software Solutions LLC, page 93). This methodology was utilized for both the unrestricted and TWTS

restricted weir for consistency in comparison. Figure 1 below shows the divided cross-sections of either

scenario, in which V represents a half-v weir and R designates a rectangular weir.

SHEET 4 OF 7 _







Figure 1 - Cross-sections of Asymmetrical Weirs

The total flow (QT) over the weir, in cubic feet per second (cfs), is represented by the summation of flows

over each divided section, as designated in Equation 1:

Equation 1:

𝑄𝑄𝑇𝑇 = ∑𝑄𝑄𝑉𝑉𝑉𝑉 + 𝑄𝑄𝑅𝑅𝑉𝑉

The flow for a triangular weir and rectangular weir are calculated by Equation 2 and Equation 3,

respectfully.

Equation 2:

𝑄𝑄𝑉𝑉 =12𝐶𝐶1 �

815

tan𝜃𝜃2�

(𝐻𝐻5 2⁄ )�2𝑔𝑔 Equation 3:

𝑄𝑄𝑅𝑅 = 𝐶𝐶2𝑏𝑏𝐻𝐻32�

Where:

• C1 = Triangular weir coefficient; 0.593 for 90° • H = water surface elevation upstream of weir crest (ft) • g = gravitational constant (32.2 ft/sec) • b = weir length (ft) • C2 = Rectangular weir coefficient; 2.95 average

These equations were applied to each cross-sectional weir area to obtain a flow, which was summed for

various stage heights above the weir crest (H).

SHEET 5 OF 7 _







For the unrestricted weir, total flow is calculated using:

𝑄𝑄𝑉𝑉1 =12

(0.593) �8

15tan

1.572 � (𝐻𝐻5 2⁄ )�2(32.3)

𝑄𝑄𝑅𝑅1 = (2.95)(15.5′)𝐻𝐻32�

𝑄𝑄𝑇𝑇 = 2𝑄𝑄𝑉𝑉1 + 𝑄𝑄𝑅𝑅1

For the TWTS restricted weir, total flow is calculated using:

𝑄𝑄𝑉𝑉1 =12

(0.593) �8

15tan

1.572 � (𝐻𝐻5 2⁄ )�2(32.3)

𝑄𝑄𝑅𝑅1 = (2.95)(15.5′ − 5′)𝐻𝐻32�

𝑄𝑄𝑉𝑉2 = 12

(0.593) � 815

tan 1.572� (𝐻𝐻 − 0.5)5 2⁄ �2(32.3) for values of H above six inches (6”)1

𝑄𝑄𝑅𝑅2 = (2.95)(5′)(𝐻𝐻 − 0.5)3 2� for values of H above six inches (6”)1

𝑄𝑄𝑇𝑇 = 𝑄𝑄𝑉𝑉1 + 𝑄𝑄𝑅𝑅1 + 𝑄𝑄𝑅𝑅2 + 𝑄𝑄𝑉𝑉2

The resultant stage discharge curves for both scenarios are depicted in Figure 2.

1 Flow is obstructed in this portion of the weir until the stage height exceeds six inches (6”). Therefore the stage height above these potions of the weir is equivalent to the original stage height less six inches (6”).

SHEET 6 OF 7 _







Figure 2 - Stage Discharge Curves for the Unrestricted Weir and TWTS Restricted Weir

Conclusion:

WESTON’S analysis of the hydraulic impacts associated with partially obstructing the existing weir in

Recreation Pond indicated that the restriction will increase the stage height to achieve the same discharge

flowrate as that over the unrestricted weir. WESTON estimates that the restricted weir will have an

increased stage height (head) over the unrestricted weir of approximately three to four inches (3 to 4”),

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

0 100 200 300 400 500 600 700 800 900 1000

Stag

e He

ight

(fee

t)

Discharge (cfs)

Unrestricted Weir TWTS Restricted Weir

SHEET 7 OF 7 _







dependent on actual flow. For example, at a discharge rate of 500 CFS, the TWTS restricted weir

indicates an increased stage height (head) over the weir of approximately three-and-a-half inches (3.5”).

Based on limited available flow data we have reviewed from the fall of 2017, WESTON understands that

weir flows have peaked at approximately 400 CFS in response to a 1.69" rain event, with a peak

precipitation rate of 1.1 in/hr, (i.e. an intense storm event). WESTON’S calculations estimate the

unrestricted weir capacity is in excess of 900 CFS with a maximum height of six feet (6’) with one foot

(1’) of freeboard. Based on the calculated capacity compared to the available storm response data, the

increase in stage height (e.g. approximately 4”) is expected to have de minimus impacts on the

performance and safety of the existing weir structure.

WESTON has not been provided design data for the existing weir. Should NYDEC or the Dam Safety

Section provide applicable information for the existing weir, WESTON may utilize this data to further

evaluate the findings.

Limitations:

Conclusions stated or referenced in this analysis are limited by several assumptions made. WESTON has

not been provided design data for the existing weir. The weir data utilized was based on field

measurements and assumes that the weir is consistently leveled and sloped; any variations in the

construction of the weir were not accounted for. The weir coefficients selected represent average values,

and actual conditions may vary.

The representation of the stage discharge curve is for comparison purposes only and does not take in to

account, among other parameters, tail water, velocity, and bed slope conditions.

ATTACHMENT A

WEIR STAGE CALCULATIONS

QV1

QR1

QT

C1 0.593

Ɵ 1.570796 radians (90 degrees)

g 32.2 ft/sec

b 15.5 ft

C2 2.95

Water Surface

Elevation (H) ft 2*QV1 QR1 QT

0 0 0 0

0.1 0.008026 1.445951 1.45397741

0.2 0.045402 4.089768 4.13516995

0.3 0.125112 7.513384 7.63849633

0.4 0.25683 11.56761 11.824442

0.5 0.448664 16.16623 16.6148929

0.6 0.707741 21.25106 21.9588008

0.7 1.040498 26.7794 27.8198943

0.8 1.452852 32.71815 34.1709985

0.9 1.950305 39.04069 40.9909948

1 2.538028 45.725 48.2630277

1.1 3.220906 52.75246 55.9733692

1.2 4.003589 60.10707 64.1106623

1.3 4.890517 67.77488 72.6653943

1.4 5.885948 75.74357 81.6295178

1.5 6.993982 84.00219 90.9961707

1.6 8.218571 92.54089 100.759464

1.7 9.56354 101.3508 110.91432

1.8 11.03259 110.4237 121.456338

1.9 12.62933 119.7524 132.381701

2 14.35725 129.3298 143.687083

2.1 16.21977 139.1498 155.369589

2.2 18.2202 149.2065 167.426694

2.3 20.36179 159.4944 179.8562

2.4 22.64772 170.0085 192.656196

1/2 of a v‐notch weir

Sharp Crested ‐ assumed approach

velocity negligable

=QV1+QR1+QR2+QV2

Unrestricted Weir Flow Calculations

Water Surface

Elevation (H) ft 2*QV1 QR1 QT

Unrestricted Weir Flow Calculations

2.5 25.08109 180.7439 205.825021

2.6 27.66494 191.6963 219.361242

2.7 30.40225 202.8614 233.263626

2.8 33.29595 214.2352 247.531118

2.9 36.34891 225.8139 262.162827

3 39.56394 237.5941 277.158006

3.1 42.94381 249.5722 292.516039

3.2 46.49126 261.7452 308.236431

3.3 50.20896 274.1098 324.318796

3.4 54.09955 286.6633 340.762845

3.5 58.16563 299.4027 357.568381

3.6 62.40977 312.3255 374.735289

3.7 66.83449 325.429 392.263531

3.8 71.44229 338.7109 410.153137

3.9 76.23561 352.1686 428.404204

4 81.21689 365.8 447.016886

4.1 86.38851 379.6029 465.991393

4.2 91.75285 393.5751 485.327986

4.3 97.31225 407.7147 505.026971

4.4 103.069 422.0197 525.0887

4.5 109.0254 436.4882 545.513565

4.6 115.1837 451.1183 566.301993

4.7 121.5461 465.9084 587.45445

4.8 128.1148 480.8566 608.971431

4.9 134.8921 495.9614 630.853463

5 141.8801 511.221 653.101102

5.1 149.0808 526.6341 675.71493

5.2 156.4965 542.199 698.695552

5.3 164.1293 557.9143 722.043599

5.4 171.9811 573.7786 745.759722

5.5 180.0541 589.7905 769.844593

5.6 188.3503 605.9486 794.298902

5.7 196.8718 622.2516 819.123357

5.8 205.6205 638.6982 844.318684

5.9 214.5984 655.2873 869.885623

6 223.8074 672.0175 895.824931

QV1

QV2

QR1

QR2

QT

C1 0.593

Ɵ 1.570796 radians (90 degrees)

g 32.2 ft/sec

b1 15.5 ft

b2 5 ft

C2 2.95

Water Surface

Elevation (H) ft QV1 QR1 QR2 QV2 QT

0 0 0 0 0 0

0.1 0.004013 0.979516 0 0 0.983528

0.2 0.022701 2.770488 0 0 2.793189

0.3 0.062556 5.089712 0 0 5.152268

0.4 0.128415 7.836124 0 0 7.964539

0.5 0.224332 10.95132 0 0 11.17565

0.6 0.353871 14.39588 0.466436 0.004013 15.2202

0.7 0.520249 18.14088 1.31928 0.022701 20.00311

0.8 0.726426 22.16391 2.423672 0.062556 25.37656

0.9 0.975153 26.44692 3.731488 0.128415 31.28197

1 1.269014 30.975 5.214913 0.224332 37.68326

1.1 1.610453 35.73554 6.855181 0.353871 44.55504

1.2 2.001794 40.71769 8.638515 0.520249 51.87825

1.3 2.445258 45.91201 10.55424 0.726426 59.63794

1.4 2.942974 51.31016 12.59377 0.975153 67.82206

1.5 3.496991 56.90471 14.75 1.269014 76.42071

1.6 4.109286 62.68899 17.01692 1.610453 85.42565

1.7 4.78177 68.65698 19.38938 2.001794 94.82992

1.8 5.516297 74.80318 21.86286 2.445258 104.6276

TWTS Restricted Weir Flow Calculations

1/2 of a v‐notch weir

1/2 of a v‐notch weir (Partially Obstructed)

Sharp Crested ‐ assumed approach velocity negligable

Sharp Crested ‐ assumed approach velocity negligable

(Partially Obstructed)

=QV1+QR1+QR2+QV2

Water Surface

Elevation (H) ft QV1 QR1 QR2 QV2 QT

TWTS Restricted Weir Flow Calculations

1.9 6.314666 81.12257 24.43341 2.942974 114.8136

2 7.178626 87.61053 27.09748 3.496991 125.3836

2.1 8.109883 94.26278 29.8519 4.109286 136.3339

2.2 9.110098 101.0754 32.6938 4.78177 147.661

2.3 10.18089 108.0446 35.62056 5.516297 159.3624

2.4 11.32386 115.167 38.6298 6.314666 171.4354

2.5 12.54054 122.4394 41.7193 7.178626 183.8779

2.6 13.83247 129.8588 44.88704 8.109883 196.6882

2.7 15.20113 137.4222 48.13113 9.110098 209.8646

2.8 16.64798 145.127 51.44981 10.18089 223.4057

2.9 18.17445 152.9707 54.84144 11.32386 237.3105

3 19.78197 160.9508 58.30449 12.54054 251.5778

3.1 21.47191 169.0651 61.83752 13.83247 266.2069

3.2 23.24563 177.3112 65.43915 15.20113 281.1972

3.3 25.10448 185.6873 69.10812 16.64798 296.5479

3.4 27.04977 194.1913 72.8432 18.17445 312.2587

3.5 29.08282 202.8212 76.64325 19.78197 328.3292

3.6 31.20489 211.5753 80.50717 21.47191 344.7593

3.7 33.41725 220.4519 84.43393 23.24563 361.5487

3.8 35.72114 229.4493 88.42253 25.10448 378.6974

3.9 38.1178 238.5658 92.47203 27.04977 396.2054

4 40.60844 247.8 96.58153 29.08282 414.0728

4.1 43.19426 257.1503 100.7502 31.20489 432.2996

4.2 45.87643 266.6154 104.9771 33.41725 450.8862

4.3 48.65612 276.1938 109.2616 35.72114 469.8327

4.4 51.5345 285.8843 113.6028 38.1178 489.1394

4.5 54.51269 295.6855 118 40.60844 508.8067

4.6 57.59184 305.5963 122.4525 43.19426 528.8349

4.7 60.77305 315.6153 126.9597 45.87643 549.2245

4.8 64.05742 325.7416 131.5209 48.65612 569.976

4.9 67.44606 335.9738 136.1354 51.5345 591.0898

5 70.94003 346.311 140.8026 54.51269 612.5664

5.1 74.54041 356.7521 145.522 57.59184 634.4064

5.2 78.24827 367.2961 150.293 60.77305 656.6104

5.3 82.06463 377.942 155.115 64.05742 679.1791

5.4 85.99056 388.6887 159.9875 67.44606 702.1129

5.5 90.02706 399.5355 164.91 70.94003 725.4126

5.6 94.17517 410.4813 169.882 74.54041 749.0788

5.7 98.4359 421.5253 174.9029 78.24827 773.1123

5.8 102.8102 432.6665 179.9724 82.06463 797.5138

5.9 107.2992 443.9043 185.0899 85.99056 822.2839

6 111.9037 455.2377 190.255 90.02706 847.4234

ATTACHMENT B

SHEET C-5: OUTFALL STRUCTURE PLANS AND SECTIONS

PROGRESS PRINT

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INSTALLATION NOTES: : 1. DIVERT FLOW TO WEST SIDE OF EXISTING WEIR DIVERT FLOW TO WEST SIDE OF EXISTING WEIR WITH SAND BAGS IN ORDER TO SET TEMPORARY PRE-CAST STRUCTURE. 2. SET TEMPORARY OUTFALL STRUCTURE AT EAST SET TEMPORARY OUTFALL STRUCTURE AT EAST END OF HORIZONTAL TRAPEZOID WEIR. 3. RELOCATE 8"-12" RIPRAP AS REQUIRED TO SET RELOCATE 8"-12" RIPRAP AS REQUIRED TO SET PRECAST STRUCTURE AND INSTALL TEMPORARY EFFLUENT LINE AT REQUIRED ELEVATIONS. 4. SET STRUCTURE OVERFLOW TO MATCH EXISTING SET STRUCTURE OVERFLOW TO MATCH EXISTING OUTFALL ELEVATION. SET STRUCTURE ON COMPACTED LEVEL STONE BASE (NYSDOT OPEN GRADED SUBBASE 2) OR APPROVED EQUAL. 5. ANCHOR 8" DROP TO OUTFALL STRUCTURE WALL. ANCHOR 8" DROP TO OUTFALL STRUCTURE WALL. ARMOR SUBMERGED RUN WITH EXCESS RIPRAP.

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APPROX. 4'x6'x2' I.D. PRE-CAST STRUCTURE

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±12" ROCKSIN CHANNEL (LEVEL W/WEIR)

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±12" ROCKSIN CHANNEL (LEVEL W/WEIR)

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STAIR

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WEIR

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8" FROM TWTS

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EXISTING FLOW METER

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APPROXIMATE BOTTOM OF CHANNEL

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UNKNOWN BELOW GRADE

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SPILLWAY

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PRECAST STRUCTURE

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SPILLWAY

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RECREATIONAL POND

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STREAM FLOW

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PIPE SUPPORT

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8" TREATED EFFLUENT AS LOW AS POSSIBLE

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FABRICATED SPILLWAY LEVEL W/WEIR

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6" ABOVE EXISTING WEIR (MAX.)

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FABRICATED SPILLWAY LEVEL W/WEIR

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FLANGE/LIP AND BOLTED WATER TIGHT SEAL TO INSIDE FACE ON THREE SIDES

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KOR-N-SEAL BOOT (TYP)

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OUTFALL WEIR

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PRECAST CONCRETE STRUCTURE IN ACCORDANCE WITH ASTM C913

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FABRICATED SPILLWAY NOT SHOWN

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MATCH TOP OF EXISTING WEIR

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APPR.

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NO.

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DATE

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REVISION

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REVISION

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PROJ. MGR.

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APPROVED

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APPROVED

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CHECKED

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DES. ENG.

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PROJ. ENG.

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DATE

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CLIENT APPROVALS

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DATE

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SHT.

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OF

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DRAWN

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SCALE

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DATE

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W.O. NO.

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DWG. NO.

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REV. NO.

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USACE OMAHA DISTRICT

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PFOS/PFOA INTERIM MITIGATION

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STEWART AIR NATIONAL GUARD BASE

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NEW YORK

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G:\ACADPROJ\15254002037 USACE Stewart ANG\

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15254.002.037.0003

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AS SHOWN

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D.ZIEGLER

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7/19/19

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AB

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BF

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RW

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AB

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ANCHORAGE

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ALASKA

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NO.

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DATE

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PORT AUTHORITY OF NY & NJ - TENNANT ALTERATION APPLICATION - #SWF-TAA S-0078

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0

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AKB

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S

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W

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Y

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R

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K

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NOT VALID UNLESS SIGNED AND DATED

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Information shown on this plan is not necessarily complete or correct.

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Date:

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20-Aug-19

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SECTION

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A

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3/16"=1'-0"

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C-5

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LIMITATIONS NOTE: : THESE DRAWINGS ARE PART OF A LARGER DESIGN PACKAGE AND MAY NOT BE USED WITHOUT REVIEWING THE DOCUMENT IN ITS ENTIRETY. THESE DRAWINGS HAVE BEEN PREPARED TO CONVEY THE INTENDED SITE DEVELOPMENT AND INTERACTIONS WITH EXISTING INFRASTRUCTURE ONLY. SITE CONDITIONS HAVE NOT BEEN CONFIRMED AND MAY DIFFER FROM THOSE DEPICTED HERE. ALL CHANGES TO THE PLANS AND SYSTEMS DEPICTED IN THIS DRAWING PACKAGE MUST BE CONVEYED TO THE ENGINEER FOR REVIEW AND CONCURRENCE

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SECTION

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B

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1/2"=1'-0"

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C-5

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A

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B

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C-5

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C-5

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VIEW FROM DOWNSTREAM LOOKING NORTH

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OUTFALL STRUCTURE ENLARGED PLAN SCALE: 1/2"=1'-0"

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SECTION

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C

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1/2"=1'-0"

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C-5

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C

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C-5

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OUTFALL STRUCTURE PLAN

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1

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3/16"=1'-0"

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C-2

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OUTFALL STRUCTURE PLANS

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& SECTIONS

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Stewart ANG.dwg

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C-5

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0

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8

ATTACHMENT 5

Stormwater Review Technical Memorandum 17 June 2019

Technical Memo - Stormwater Review and Analysis - Final - Stormwater Review and

Analysis Page 1 of 4

June 17, 2019

TECHNICAL MEMORANDUM

TO: Michelle Lordemann, Project Manager, USACE

Cc: PFOS/PFOA Interim Mitigation Project Delivery Team Members

From: Adam Brown, P.E Date: June 17, 2019

NY License No. 097396

RE: PFOS/PFOA Interim Mitigation Project

Stormwater Review and Analysis

INTRODUCTION

Weston Solutions, Inc. (WESTON) has reviewed and analyzed available stormwater and survey data for

the Recreation Pond, including draft and progress datasets provided by the John Wood Group (Wood), to

better characterize the Pond’s response to storm events and determine its ability to be utilized for storing

stormwater runoff for treatment prior to discharge. The project Performance Work Statement defines the

objective of these analyses stating, “Measures are to be implemented to limit overflow during storm events,”

which can be achieved by, “…raising the height of the outfall weir structure, approximately three feet.”

This Technical Memorandum is supported by two calculation packages that analyze both the stormwater

flows experienced by Recreation Pond and the Pond’s storage capacity, and are and included as the

following attachments:

Attachment A - Recreation Pond Water Retention Analysis

Attachment B - Pond Storage Volume Analysis

BOTTOM LINE UP FRONT

WESTON recommends artificially reducing the pond elevation by two feet, and maintaining this elevation

between storm events through artificial drawdown via pumping stormwater to the treatment plant for

discharge. WESTON does not recommend making modifications to the weir at this time. WESTON

considered the following facts, either determined by our analysis or presentation by others, in our review:

https://westonsolutions.sharepoint.com/Support/Marketing/Logos/Forms/AllItems.aspx?PageView=Shared&InitialTabId=Ribbon.WebPartPage&VisibilityContext=WSSWebPartPage#InplviewHashb24a7dc2-201b-46a5-aa76-eddf158357ab=PageView%3DShared-InitialTabId%3DRibbon.WebPartPage-VisibilityContext%3DWSSWebPartPage-FilterField1%3DLogo-FilterValue1%3DBlue%2520Weston

PFOS/PFOA Interim Mitigation Project


Technical Memo - Stormwater Review and Analysis -

Final Page 2 of 4

June 7, 2019

1. There are roughly five-million gallons of water storage within the pond below the existing weir

elevation, without dredging sediment.

2. Raising the weir discharge elevation or drawing down the Pond will result in the additional storage

of approximately one-million gallons of storage per foot raised or lowered. Therefore, a three foot

increase in weir elevation would result in roughly three-million gallons of additional storage in

Recreation Pond.

3. A total flow volume of three-million gallons equates to a 0.44 inch rainfall event in the Pond’s

drainage area. For approximately every 0.13 inches of rainfall, one-million gallons of runoff can

be expected, after considering an initial depression storage of 0.05 inches.

4. Two feet of draw-down should result in approximately 1.86 million gallons of additional storage,

without requiring modifications to the existing weir.

5. During a 24-hour period, the proposed treatment plant is preliminarily designed to withdraw

approximately 720,000 gallons of water from the Pond, treat it, and ultimately discharge it to the

downstream watercourses beyond the weir.

6. A majority of the Pond’s water surface area will remain with up to three feet of drawdown.

Drawdown beyond that will cause areas of the Pond to become dry.

7. The Pond depth, away from the shoreline, ranges from 3.0 to 8.3 feet deep, as measured from the

weir to the top of soft sediments on the Pond’s bottom.

ANALYSIS DISCUSSION

A full discussion of each analysis and its sources of data are presented in the two aforementioned

attachments. A high level summary of these analyses is discussed below.

The storm analysis and relationships developed in Attachment A demonstrated that no extreme storm events

were experienced within the Pond’s drainage area during the approximate two month period of previously

monitored data. The largest event experienced during the period of monitoring consisted of 1.7 inches over

a period of four hours. This modest storm event resulted in the production of 13-million gallons of

stormwater flow to Recreation Pond, over a course of 48 hours, before returning to base-flow rates. A

relationship developed as part of this analysis determined that the difference between two-million and three-

million gallons stormwater flow is only the difference between a 0.31 inch and 0.44 inch storm event,

respectively.

Attachment 2 determined that roughly six-million gallons of water storage could be available within the

Recreation Pond if it were to be dredged of its soft sediments. The dredging or excavation of loose

sediments introduces challenges associated with habitat destruction, sedimentation, erosion, and increasing

hydrodynamic forces on the inlet pipes. Furthermore, any alteration of the Pond’s elevation that would




Technical Memo - Stormwater Review and Analysis -

Final Page 3 of 4

June 7, 2019

result in reducing the tail water depth of the inlet pipes to less than six inches would require additional

armament, and energy dissipation devices, to avoid advanced scour and redeposition of the Pond’s

sediments. This potential exists both within the Recreation Pond, and in the case of changing Pond outlet

dynamics, in the downstream waterbodies. The analysis also established that the Pond water elevation could

be lowered by slightly less than three feet before significant portions of the Pond would be rendered dry.

However, lowering the Pond by this quantity would expose the inlet pipe at the outfalls, and would require

additional stabilization.

A reduction of Pond’s dry water depth by two feet is not expected to have significant impacts on

sedimentation and erosion in the Pond. This reduction is expected to result in an additional storage volume

of 1.86 million gallons. This storage volume, coupled with the a 500 gallon per minute pumping rate to the

treatment plant, is equivalent to a 0.4 inch storm event within a 24-hour period, without the need for

operational contingencies or monitoring of the weir structure. This strategy provides nearly the same 24-

period storage capacity as raising the weir structure by three feet without artificial drawdown or pumping.




Technical Memo - Stormwater Review and Analysis - Final - Stormwater Review and

Analysis Page 4 of 4

June 17, 2019

RECOMMENDATION

From the established relationship between rainfall and stormwater flow to Recreation Pond, it is apparent

that creating a storage feature at the confluence of this large drainage area will require daily weather

monitoring and operation. A failure in management, unexpectedly large storm event, or human error could

result in overtopping of any weir modifications made to raise the dry-weather Pond elevation, and

potentially the berm itself, with the potential consequence for a catastrophic collapse of both. Given the

magnitudes of unknowns and diminishing returns with regards to storm event protection, modifications to

the weir structure are not recommended without a more in depth analysis and monitoring of the drainage

area. Prior to making modifications, it is highly recommended that a storm response model, calibrated to

actual events, be generated to predict potential exceedances of storage capacity.

Reducing the dry weather pond elevation by two feet, via drawdown, is therefore recommended.

LIMITATIONS

Analysis limitations to this technical memo are discussed in more detail within each of the attachments.

The overarching concept is that there is a limited dataset available for the basis of this recommendation.

Due to this, a somewhat conservative approach was made to maintain a stable environment within the Pond,

as well as prevent detrimental impacts to the berm and/or weir structure. As more information is made

available, and observations are made in the field, a more aggressive approach may be determined, if it

should be deemed necessary.

Attachments:

Attachment A - Recreation Pond Water Retention Analysis

Attachment B - Pond Storage Volume Analysis


ATTACHMENT A



WORK ORDER NO. 15254.002.037.0003

CALC NO.

1 SHEET 1 of_7__

SUBJECT: Recreation Pond – Precipitation vs. Volume Analysis


PREPARED BY: M. Mardenov DATE:06/17/19


FINAL

CONFIRMED

SUPERCEDED

VOIDED


Yes No DESCRIPTION/VERSION: PCSWMM 7.2


REFERENCE DRAWINGS:

SOURCES OF DATA:

1. HDR, Inc. (November 17, 2017). Melissa E. LaMacchia to Tony Palumbo. New York Air National Guard Base, Stewart International Airport, Newburgh, Orange County, New York, Recreation Pond Pre-Design Investigation [Letter].

2. John Wood Group, PLC (October 29, 2018). Preliminary Estimate of Rec Pond Base Flow and Storm Flow Treatment Stewart Air National Guard Base, Newburgh, Orange County, New York [Draft Memorandum].

3. John Wood Group, PLC (May 21, 2019). Rich Niles to Adam Brown. Rec Pond Flow Data [Email]. 4. New York State Department of Environmental Conservation (January 2015). New York State Stormwater

Management Design Manual. Albany, NY. Retrieved from https://www.dec.ny.gov/docs/water_pdf/swdm2015entire.pdf 5. PCSWMM Professional 2D, Version 7.2.

SUMMARY OF RESULTS:

Weston evaluated the data collected by HDR, developed a linear relationship and yielded a storm depth of 0.44 inches that can be retained within a 3.0 million gallon storage volume. WESTON also determined a water quality volume for Outfalls 02, 03, 14 per the requirements of the New York State Stormwater Manual. This water quality volume was compared to the observed flow and precipitation data collected by HDR on August 2nd, 2017, to determine an estimate for discharge associated with the unknown watershed contributing to Outfall 17K.

RECORD OF REVISIONS

NO. REASON FOR REVISION TOTAL NO. OF SHEETS

LAST SHEET NO.

BY CHECKED APPROVED/ ACCEPTED

DATE

0 Issued for Review 7 MM DB AB 6/07/2019

1 Final 7 AB HN AB 6/17/2019

https://www.dec.ny.gov/docs/water_pdf/swdm2015entire.pdf

SHEET 2 OF 7 _


TASK DESCRIPTION Recreation Pond – Precipitation vs. Volume Analysis TASK NO 0003 .

PREPARED BY M. Mardenov DEPT 2118 DATE 6/07/2019 . APPROVED BY

MATH CHECK BY D. Borger DEPT 2118 DATE 6/07/2019 .

METHOD REV. BY D. Borger DEPT 2118 DATE 6/07/2019 .DEPT_ DATE_

File Name: 2-Stewart_ANGB_Rec_Pond_Volume_Evaluation_Rev5_mm Print date: 06/17/19 11:24 PM

Objective:

Determine the relationship between stormwater discharge to Recreation Pond and rainfall event total

precipitation quantities. Additionally quantify storage requirements for runoff dictated by The New York

Department of Environmental Conservation.

References:

HDR, Inc. (November 17, 2017). Melissa E. LaMacchia to Tony Palumbo. New York Air National Guard

Base, Stewart International Airport, Newburgh, Orange County, New York, Recreation Pond Pre-

Design Investigation [Letter].

John Wood Group, PLC (October 29, 2018). Preliminary Estimate of Rec Pond Base Flow and Storm

Flow Treatment Stewart Air National Guard Base, Newburgh, Orange County, New York [Draft

Memorandum].

John Wood Group, PLC (May 21, 2019). Rich Niles to Adam Brown. Rec Pond Flow Data [Email].

New York State Department of Environmental Conservation (January 2015). New York State Stormwater

Management Design Manual. Albany, NY. Retrieved from


PCSWMM Professional 2D, Version 7.2.

Attachments:

Attachment A – Site Layout

Attachment B – PCSWMM Drainage Area Measurements

Assumptions:

The stormwater discharge flow is the summation of metered flow from Outfalls 02, 03, 14, and

17K. Additional flow from local contributors is considered negligible.

The stormwater flows were assumed to begin at the start of a precipitation event and end when the

last outfall (typically Outfall 17K) ceased discharging into Recreation Pond.


SHEET 3 OF 7 _







The calculated volumes do not include inflow associated from groundwater that may enter

Recreation Pond.

Inflow and infiltration from other sources in the collection system are included in the metered flow

data.

Linear relationship exists between precipitation depth and stormwater runoff volume for storms

events.

Discussion:

Weston Solutions, Inc. (Weston) performed an analysis to determine the relationship between stormwater

discharge and rainfall events. The analysis utilized metered flow data obtained from outfalls that

discharge to Recreation Pond (Outfalls 02, 03, 14, and 17K), and recorded precipitation depths, collected

during a previous study completed by HDR, Inc. (HDR, 2017). Weston generated a linear relationship

between the total summed outfall discharges produced from their respective storm events, from the data

collected during seven recorded storm events during the HDR study. The precipitation values were plotted

against the summation of the metered stormwater discharge volumes entering Recreation Pond (for

Outfalls 02, 03, 14, and 17K), for which the results are indicated in Figure 1.

This information was compared to a draft memorandum, dated October 29th, 2018 and prepared by the

John Wood Group, PLC (Wood, 2018), which also developed a ratio of outfall runoff volume per depth of

rainfall. However, this memorandum only utilized the data from two storm events (9/2/2017 and

9/6/2017), so the results differ slightly. Weston’s analysis described herein is an attempt to develop a

linear relationship using all of the observed precipitation and flow data collected by HDR, Inc. (HDR,

2017).

Weston also evaluated the Water Quality Volume (WQv) for the site. A WQv is a New York State

Department of Environmental Conservation ([NYSDEC], 2015) defined storage requirement intended to

SHEET 4 OF 7 _







identify the storage volume necessary to capture and treat runoff from 90 percent of the average annual

rainfall events that are to be expected to fall on the site. Weston calculated this value to provide a frame of

reference to the evaluated storms and established relationship.

The WQv was calculated for areas contributing to Outfalls 02, 03, and 14 based on aerial photography of

the contributing areas. Outfall 17K was not included in this calculation due to the unknown

characteristics, location, and size of the watershed contributing to this outfall. Instead, a ratio was

developed between the cumulative summed volumes of Outfalls 02, 03, and 14, and the cumulative

volume of Outfall 17K alone. The total WQv estimated from the cumulative discharge sum from Outfalls

02, 03, 14 and 17K was then determined.

Analysis:

The precipitation depths from the seven recorded storm events and their associated stormwater runoff

flow volumes from Outfalls 02, 03, 14 and 17K were plotted against one another. The results

demonstrated that a linear relationship was the best fit for the comparison of precipitation and summed

outfall discharge volumes (Figure 1 – Linear Relationship), and a trend line equation was developed using

Microsoft Excel’s best fit algorithms. A y-intercept of 0.05 inches was assigned to the equation to

represent depression storage within the watershed.

SHEET 5 OF 7 _







Figure 1 Linear Relationship

Utilizing this linear relationship, a storm precipitation depth can be calculated from a corresponding

stormwater volume that would discharge to Recreation Pond. Equation 1 (below) yields the total

precipitation determined from the linear regression equations of Figure 1.

An example below demonstrates that a given three MG discharge volume corresponds to a precipitation

depth of 0.44 inches as determined by the linear relationship.

Equation 1:

𝑦 = (1.3093 ∗ 10−7)𝑥 + 0.05

𝑦 = (1.3093 ∗ 10−7) ∗ (3,000,000 𝑔𝑎𝑙𝑙𝑜𝑛𝑠) + 0.05

𝑦 = 0.44 𝑖𝑛𝑐ℎ𝑒𝑠

Where:

y = the precipitation depth in inches.

x = the discharge volume in gallons.

The following equation (Equation 2) calculates the aforementioned WQv. This calculated WQv accounts

for runoff from Outfalls 02, 03, and 14. As previously discussed, Outfall 17K and the associated

y = 1E-07x + 0.05R² = 0.959

0

0.5

1

1.5

2

2.5

Pre

cip

itat

ion

(in

ches

)

Discharge Volume (gallons)

Linear Relationship

SHEET 6 OF 7 _







watershed was excluded from the Equation 2 calculation, due to the unknown characteristics of the

watershed.

Equation 2:

𝑊𝑄𝑣 = 𝑃 ∗ (0.05 + 0.009(𝐼)) ∗ 𝐴

12

𝑊𝑄𝑣 =(1.4 𝑖𝑛𝑐ℎ𝑒𝑠) ∗ (0.05 + 0.009(70.2 %)) ∗ (509.4 𝑎𝑐𝑟𝑒𝑠)

12

𝑊𝑄𝑣 = 40.5 acre-feet

𝑊𝑄𝑣 = 13.2 𝑀𝐺

Where:

P = the 90 percent rainfall event number from Figure 4.1 of the NYS SWDM in inches.

A = the contributing area in acres that was measured from Attachment A – Site Layout as well as

from measurements based on aerial imagery made in PCSWMM from Attachment B – PCSWMM

Drainage Area Measurements.

I = the percent impervious cover that was measured in PCSWMM.

Weston further evaluated the metered flow data to determine what portion of the total inflow to

Recreation Pond was from Outfall 17K to estimate the WQv for all four outfalls, rather than the three (3)

discussed above. Adding the observed stormwater volumes from Outfall 17K and comparing them to

Outfalls 02, 03, and 14, results in a total stormwater volume percent increase between 50 to 70 percent.

When this ratio is added to the WQv (Equation 2), it is expected that the water quality volume for all four

outfalls (02, 03, 14 and 17K) would result in a total calculated WQv range between 19.8 MG and 22.4

MG.

SHEET 7 OF 7 _







Conclusion:

Weston’s analysis of the previously collected data yielded a linear relationship (Equation 1) that predicts

storm depth given a discharge volume. An example calculation for a 3.0 MG discharge volume yields a

0.44 inch precipitation event.

Limitations:

Conclusions stated or referenced in this analysis are limited to the precipitation and flow metering data

provided by HDR, Inc. (HDR, 2017). The dataset was concise, but not complete with many data gaps and

interpretation was necessary to create complete storm responses. This interpretation can affect the total

runoff volumes calculated. For instance, the HDR report interpreted the duration of discharge over a

shorter period than interpreted by WESTON using the same dataset. Interpretations can vary for a number

of reasons depending on the analysis goals.

Additionally, the metered flow data and precipitation measurements occurred over a limited time spanning

from July 20, 2017 to September 11, 2017. Therefore, the data collection does not account for seasonal

variations or statistical normalization from data collection spanning multiple years. Variability in storm

duration and intensities also cause variation in final runoff volumes as compared to those describe herein.

An analysis relying on a small number of storm events (seven (7) storm events were utilized for this

analysis) inhibits the accuracy of the trends generated.

Lastly, the WQv calculation relies solely on precipitation and impervious area acreage, and does not

account for all watershed characteristics (e.g. conveyance routing, soil types, etc.). These characteristics

would normally be captured in a site wide conceptual model that, when calibrated, would allow more

accurate discharge predictions.

OUTFALL 010DISCHARGE POINT

OUTFALL 002

OUTFALL A

WEIR

RECREATIONPOND

17K OUTFALL

OUTFALL 003

0

OUTFALL A

OUTFALL 002

OUTFALL 003

17K OUTFALL

RECREATION POND

LEGEND

SCALE (ft)

400 ft

Recreation PondStewart International Airport - Air National Guard Base

Newburgh, NY

Site Layout

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OUTFALL 002

borgerd

Text Box

Outfall A = Outfall 14

PCSWMM Professional 2D Version 7.2 – Drainage Area Measurements for Outfalls 02, 03, and 14

mardenom

Text Box

Area = 509.4 acres Percent Impervious = 70.2%

ATTACHMENT B



WORK ORDER NO. 15254.002.037.0003

CALC NO.

1 SHEET 1 of_12__

SUBJECT: Pond Storage Volume


PREPARED BY: A. Brown DATE:06/06/19


FINAL

CONFIRMED

SUPERCEDED

VOIDED


Yes No DESCRIPTION/VERSION:


REFERENCE DRAWINGS:

SOURCES OF DATA: 1. HDR, Inc. (November 17, 2017). Melissa E. LaMacchia to Tony Palumbo. New York Air National Guard Base, Stewart

International Airport, Newburgh, Orange County, New York, Recreation Pond Pre-Design Investigation [Letter]. 2. John Wood Group, PLC (October 29, 2018). Preliminary Estimate of Rec Pond Base Flow and Storm Flow Treatment

Stewart Air National Guard Base, Newburgh, Orange County, New York [Draft Memorandum]. SUMMARY OF RESULTS:

Weston evaluated the bathymetry data available for the Recreation Pond and determined a relationship of storage volume versus depth of artificial drawdown and/or raising the weird overflow elevation. One foot of drawdown or weir elevation increase results in roughly one million gallons of additional storage capacity. After three feet of drawdown, significant portions of the Pond will start to dry up, thereby reducing the increase in storage for every foot of additional drawdown.

RECORD OF REVISIONS

NO. REASON FOR REVISION TOTAL NO. OF SHEETS

LAST SHEET NO.

BY CHECKED APPROVED/ ACCEPTED

DATE

0 Issued for Review 12 AB HN/CS AB 6/6/2019

1 Final 12 AB HN AB 6/17/2019

SHEET 2 OF 12


TASK DESCRIPTION Pond Storage Volume TASK NO 0003 .

PREPARED BY A. Brown DEPT 2118 DATE 6/6/2019 . APPROVED BY


METHOD REV. BY H. Nathanson DEPT 2118 DATE 6/6/2019 .DEPT_ DATE_

File Name: Stewart ANG Pond Volume Analysis - Final Print date: 06/17/19 11:42 PM

Objective:

Determine the potential storage volume within the Recreation Pond at Stewart Air National Guard Base

(ANGB). Calculate the amount of artificially increased storage volume of the Pond via drawn down for

various drawdown depths as well as increase in dry weather storage by modifying the weir outlet

structure.

References:

Attachment A – Site Layout

Attachment B – Stewart Airport Pond Depth 1, July 2017, Sheet 1 of 1, ASI Project #: 37-133

Attachment C – Stewart Airport Pond Depth 2, July 2017, Sheet 1 of 1, ASI Project #: 37-133

HDR, Inc. (November 17, 2017). Melissa E. LaMacchia to Tony Palumbo. New York Air National

Guard Base, Stewart International Airport, Newburgh, Orange County, New York, Recreation

Pond Pre-Design Investigation [Letter].

John Wood Group, PLC (October 29, 2018). Preliminary Estimate of Rec Pond Base Flow and

Storm Flow Treatment Stewart Air National Guard Base, Newburgh, Orange County, New

York [Memorandum to Kerry Tull, from Rich Niles, James Barbis, and Sarah Dickert] (Not

attached)

Assumptions:

Elevation datum for all referenced reports (Wood Memorandum and Aqua Survey, Inc. (ASI)) is

NAD 88.

The Recreation Pond weir elevation is 376.24 feet NAD 88.

Recreation Pond can be divided into 39 equal areas (sectors) that comprise the total area of the

Pond.

The bathymetry elevations, shot by Aqua Survey, Inc. (ASI), represent an average depth within the

area of the corresponding sector.

SHEET 3 OF 12







Discussion:

The existing Recreation Pond (Pond), located at the southern edge of the Stewart Air National Guard Base

(ANGB), receives stormwater drainage from four (4) outfalls (Outfalls 02, 03, 14, and 17K) and local

overland flow. A trapezoidal weir, located at Outlet 10, controls outflow from the Pond. A site layout

indicating the locations of these items is included in Attachment A.

The following volumes will be calculated to determine the amount of storage the Recreation Pond can

provide, prior to discharging via Outfall 10 to the receiving watercourse:

1. Free Water Volume – the volume of water below the weir elevation;

2. Dredge Volume – the additional volume below the weir elevation that could be gained if soft

sediments at the bottom of the Pond were removed or dredged;

3. Gate Volume – volume of storage available if the discharge weir elevation was raised from its

current elevation, by modifying the weir using permanent or temporary structures, such as a sluice

gate or stop logs; and,

4. Additional Storage Volume – the volume of additional storage that could be obtained by

artificially drawing down water levels in the Pond to make room for additional flows.

To calculate the Free Water Volume and Dredge Volume, the total area of the pond was subdivided into

39 equal sectors. The depth of each sector was then determined via a bathymetry survey, completed by

ASI (HDR, Inc., 2017), by subtracting measured values from a reference elevation. In the case of the Free

Water Volume, depth was calculated by subtracting the elevation of the sediment (Pond bottom) at each

sector (shown in Attachment A) from the weir crest elevation. The Dredge Volume depth was calculated

SHEET 4 OF 12







by subtracting the elevation of the bottom of the soft sediment at each sector (Attachment B) from the

corresponding sector’s top of soft sediment, or Pond bottom (Attachment A).

To calculate the Gate Volume, the total Pond area was measured using aerial imagery, as exhibited in

Figure 1 below. The total Pond area (approximately 124,000 square feet) was then multiplied by an

increase in elevation that could be generated by weir modifications.

Figure 1 - Recreation Pond Area

To artificially increase the storage volume of Recreation Pond, one proposed method is to create a volume

of water could be drawn down to create airspace for new stormwater flows to enter the Pond. This would

be an intermediate measure, similar to the Free Water Volume, that would prevent the need to fully drain

the Pond. To calculate this Additional Storage Volume available, the height of the weir is “adjusted” by a

drawdown depth, and calculated in the same manner as the Free Water Volume at the reduced elevation.

SHEET 5 OF 12







The difference between the original Free Water Volume and the adjusted Free Water Volume represents

the Additional Storage Volume. This volume generally follows the trend of the Gate Volume until sectors

of the Pond no longer have water available, which are reflected as zero or negative volumes as the

artificial weir elevation exceeds the water depth.

Analysis:

Equation 1 – Free Water Volume:

𝐹𝑊𝑉 = 𝐴 × (𝐸𝑤 − 𝐸𝑠)

Where:

𝐹𝑊𝑉 = 𝐹𝑟𝑒𝑒 𝑊𝑎𝑡𝑒𝑟 𝑉𝑜𝑙𝑢𝑚𝑒 (𝑓𝑡3)

𝐴 = 𝑆𝑒𝑐𝑡𝑜𝑟 𝐴𝑟𝑒𝑎 = 𝑇𝑜𝑡𝑎𝑙 𝑃𝑜𝑛𝑑 𝐴𝑟𝑒𝑎

𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑆𝑒𝑐𝑡𝑜𝑟𝑠=

124,000 (𝑓𝑡2)

39= 3,179.5 (𝑓𝑡2 𝑝𝑒𝑟 𝑠𝑒𝑐𝑡𝑜𝑟)

𝐸𝑤 = 𝑊𝑒𝑖𝑟 𝐸𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 (𝑓𝑡)

𝐸𝑠 = 𝐸𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑇𝑜𝑝 𝑜𝑓 𝑆𝑒𝑑𝑖𝑚𝑒𝑛𝑡 𝑑𝑒𝑝𝑖𝑐𝑡𝑒𝑑 𝑖𝑛 𝐴𝑡𝑡𝑎𝑐ℎ𝑚𝑒𝑛𝑡 𝐵 (𝑓𝑡)

Example (Sector 2.2):

𝐹𝑊𝑉 = 𝐴 × (𝐸𝑤 − 𝐸𝑠) = 3,179.5 𝑓𝑡2 × (376.2 𝑓𝑡 − 368.0 𝑓𝑡) = 26,071.9 𝑓𝑡3

Please note that the calculations for all sectors are presented in Table 1. Summing the calculated

values for all 39 sectors resulted in a total Free Water Volume of 5,122,764 gallons.

Equation 2 – Dredge Volume:

𝐷𝑉 = 𝐴 × (𝐸𝑠 − 𝐸𝐵)

Where:

𝐷𝑉 = 𝐷𝑟𝑒𝑑𝑔𝑒 𝑉𝑜𝑙𝑢𝑚𝑒 (𝑓𝑡3)



124,000 (𝑓𝑡2)

39= 3,179.5 (𝑓𝑡2 𝑝𝑒𝑟 𝑠𝑒𝑐𝑡𝑜𝑟)

SHEET 6 OF 12







𝐸𝑠 = 𝐸𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑇𝑜𝑝 𝑜𝑓 𝑆𝑒𝑑𝑖𝑚𝑒𝑛𝑡 𝑑𝑒𝑝𝑖𝑐𝑡𝑒𝑑 𝑖𝑛 𝐴𝑡𝑡𝑎𝑐ℎ𝑚𝑒𝑛𝑡 𝐵 (𝑓𝑡)

𝐸𝐵 = 𝐸𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝐵𝑜𝑡𝑡𝑜𝑚 𝑜𝑓 𝑆𝑜𝑓𝑡 𝑆𝑒𝑑𝑖𝑚𝑒𝑛𝑡 𝑑𝑒𝑝𝑖𝑐𝑡𝑒𝑑 𝑖𝑛 𝐴𝑡𝑡𝑎𝑐ℎ𝑚𝑒𝑛𝑡 𝐶 (𝑓𝑡)

Example (Sector 2.2):

𝐹𝑊𝑉 = 𝐴 × (𝐸𝑆 − 𝐸𝐵) = 3,179.5 𝑓𝑡2 × (368.0 𝑓𝑡 − 364.9 𝑓𝑡) = 9,856.5 𝑓𝑡3

Please note that the calculations for all sectors are presented in Table 2. Summing the

calculated values for all 39 sectors resulted in a total Dredge Volume of 1,626,727 gallons.

Equation 3 – Gate Volume:

𝐺𝑉 = 𝐴𝑃 × 𝐻𝑤

Where:

𝐺𝑉 = 𝐺𝑎𝑡𝑒 𝑉𝑜𝑙𝑢𝑚𝑒 (𝑓𝑡3)

𝐴𝑝 = 𝑇𝑜𝑡𝑎𝑙 𝑃𝑜𝑛𝑑 𝐴𝑟𝑒𝑎 = 124,000 (𝑓𝑡2)

𝐻𝑤 = 𝐶ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑊𝑒𝑖𝑟 𝐻𝑒𝑖𝑔ℎ𝑡 (𝑓𝑡) = 𝑁𝑒𝑤 𝑊𝑒𝑖𝑟 𝐸𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 (𝑓𝑡) − 𝐸𝑊 (𝑓𝑡)

Example – One (1’) Foot Increase in Weir Elevation:

𝐺𝑉 = 𝐴 × 𝐻𝑤 = 124,000 𝑓𝑡2 × 1 𝑓𝑡 = 124,000 𝑓𝑡3 = 927,520 𝑔𝑎𝑙𝑙𝑜𝑛𝑠

Equation 4 – Additional Storage Volume:

𝐴𝑆𝑉 = 𝐴 × (𝐸𝑤 − 𝐷 − 𝐸𝑠)

Where:

𝐴𝑆𝑉 = 𝐴𝑑𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑆𝑡𝑜𝑟𝑎𝑔𝑒 𝑉𝑜𝑙𝑢𝑚𝑒 (𝑓𝑡3)



124,000 (𝑓𝑡2)

39= 3,179.5 (𝑓𝑡2 𝑝𝑒𝑟 𝑠𝑒𝑐𝑡𝑜𝑟)

𝐸𝑤 = 𝑊𝑒𝑖𝑟 𝐸𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 (𝑓𝑡)

SHEET 7 OF 12







𝐷 = 𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝐷𝑟𝑎𝑤𝑑𝑜𝑤𝑛 (𝑓𝑡)

𝐸𝑠 = 𝐸𝑙𝑒𝑣𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑇𝑜𝑝 𝑜𝑓 𝑆𝑒𝑑𝑖𝑚𝑒𝑛𝑡 𝑑𝑒𝑝𝑖𝑐𝑡𝑒𝑑 𝑖𝑛 𝐴𝑡𝑡𝑎𝑐ℎ𝑚𝑒𝑛𝑡 𝐴 (𝑓𝑡)

The total Additional Storage Volume is calculated at different depths for each sector as well as for the

entire Pond in Table 3.

SHEET 8 OF 12







Table 1 - Free Water Volume Calculations

Cross

Section

Node

FWV (cf) = Area (ft2) X (

Ew

Estimated Weir

Elevation

-

Es

Depth 1 - Top of

Sediment

)

1.1 13989.7 3179.5 376.2 371.8

1.2 17487.2 3179.5 376.2 370.7

1.3 23846.2 3179.5 376.2 368.7

1.4 20348.7 3179.5 376.2 369.8

2.1 13671.8 3179.5 376.2 371.9

2.2 26071.8 3179.5 376.2 368.0

2.3 26071.8 3179.5 376.2 368.0

2.4 26389.7 3179.5 376.2 367.9

3.1 15897.4 3179.5 376.2 371.2

3.2 24482.1 3179.5 376.2 368.5

3.3 20984.6 3179.5 376.2 369.6

3.4 22892.3 3179.5 376.2 369.0

3.5 14307.7 3179.5 376.2 371.7

4.1 19712.8 3179.5 376.2 370.0

4.2 14943.6 3179.5 376.2 371.5

4.3 18759.0 3179.5 376.2 370.3

4.4 25435.9 3179.5 376.2 368.2

4.5 15897.4 3179.5 376.2 371.2

5.1 19394.9 3179.5 376.2 370.1

5.2 16851.3 3179.5 376.2 370.9

6.1 11446.2 3179.5 376.2 372.6

6.2 14307.7 3179.5 376.2 371.7

6.3 18441.0 3179.5 376.2 370.4

6.4 18759.0 3179.5 376.2 370.3

6.5 15897.4 3179.5 376.2 371.2

7.1 12717.9 3179.5 376.2 372.2

7.2 13035.9 3179.5 376.2 372.1

7.3 18759.0 3179.5 376.2 370.3

7.4 17805.1 3179.5 376.2 370.6

7.5 15897.4 3179.5 376.2 371.2

8.1 15261.5 3179.5 376.2 371.4

8.2 12717.9 3179.5 376.2 372.2

8.3 17487.2 3179.5 376.2 370.7

8.4 13035.9 3179.5 376.2 372.1

9.1 12717.9 3179.5 376.2 372.2

9.2 11128.2 3179.5 376.2 372.7

9.3 19076.9 3179.5 376.2 370.2

9.4 9538.5 3179.5 376.2 373.2

9.5 19394.9 3179.5 376.2 370.1

Total : 684861.5 cubic feet

5122764 gallons

SHEET 9 OF 12







Table 2 - Dredge Volume Calculations

Cross

Section

Sector

DV = Area (ft2) X (

Es

Depth 1 -

Top of

Sediment

-

Eb

Depth 2 -

Bottom of

Pond

)

1.1 1271.8 3179.5 371.8 371.4

1.2 4769.2 3179.5 370.7 369.2

1.3 4769.2 3179.5 368.7 367.2

1.4 7948.7 3179.5 369.8 367.3

2.1 953.8 3179.5 371.9 371.6

2.2 9856.4 3179.5 368.0 364.9

2.3 12082.1 3179.5 368.0 364.2

2.4 4451.3 3179.5 367.9 366.5

3.1 6359.0 3179.5 371.2 369.2

3.2 7312.8 3179.5 368.5 366.2

3.3 9538.5 3179.5 369.6 366.6

3.4 6359.0 3179.5 369.0 367.0

3.5 317.9 3179.5 371.7 371.6

4.1 5723.1 3179.5 370.0 368.2

4.2 6359.0 3179.5 371.5 369.5

4.3 6041.0 3179.5 370.3 368.4

4.4 11128.2 3179.5 368.2 364.7

4.5 1589.7 3179.5 371.2 370.7

5.1 9538.5 3179.5 370.1 367.1

5.2 3179.5 3179.5 370.9 369.9

6.1 5087.2 3179.5 372.6 371.0

6.2 4451.3 3179.5 371.7 370.3

6.3 7630.8 3179.5 370.4 368.0

6.4 9856.4 3179.5 370.3 367.2

6.5 6359.0 3179.5 371.2 369.2

7.1 6359.0 3179.5 372.2 370.2

7.2 3179.5 3179.5 372.1 371.1

7.3 9856.4 3179.5 370.3 367.2

7.4 6359.0 3179.5 370.6 368.6

7.5 6359.0 3179.5 371.2 369.2

8.1 2543.6 3179.5 371.4 370.6

8.2 8902.6 3179.5 372.2 369.4

8.3 7630.8 3179.5 370.7 368.3

8.4 3497.4 3179.5 372.1 371.0

9.1 3179.5 3179.5 372.2 371.2

9.2 635.9 3179.5 372.7 372.5

9.3 4769.2 3179.5 370.2 368.7

9.4 953.8 3179.5 373.2 372.9

9.5 317.9 3179.5 370.1 370.0

Total : 217476.9

1,626,727.38

cubic feet

gallons

SHEET 10 OF 12







Table 3 - Storage Volume Calculations

Cross

Section

Sector

SV1 (cf) SV2 (cf) SV3 (cf) SV4 (cf) FWV (cf) = Area (ft2) X (

Ew

Estimated

Weir Elev.

-

Es

Depth 1 -

Top of

Sediment

)

Drawdown

(ft)1 ft 2 ft 3 ft 4 ft Total

1.1 10810.3 7630.8 4451.3 1271.8 13989.7 3179.5 376.2 371.8

1.2 14307.7 11128.2 7948.7 4769.2 17487.2 3179.5 376.2 370.7

1.3 20666.7 17487.2 14307.7 11128.2 23846.2 3179.5 376.2 368.7

1.4 17169.2 13989.7 10810.3 7630.8 20348.7 3179.5 376.2 369.8

2.1 10492.3 7312.8 4133.3 953.8 13671.8 3179.5 376.2 371.9

2.2 22892.3 19712.8 16533.3 13353.8 26071.8 3179.5 376.2 368.0

2.3 22892.3 19712.8 16533.3 13353.8 26071.8 3179.5 376.2 368.0

2.4 23210.3 20030.8 16851.3 13671.8 26389.7 3179.5 376.2 367.9

3.1 12717.9 9538.5 6359.0 3179.5 15897.4 3179.5 376.2 371.2

3.2 21302.6 18123.1 14943.6 11764.1 24482.1 3179.5 376.2 368.5

3.3 17805.1 14625.6 11446.2 8266.7 20984.6 3179.5 376.2 369.6

3.4 19712.8 16533.3 13353.8 10174.4 22892.3 3179.5 376.2 369.0

3.5 11128.2 7948.7 4769.2 1589.7 14307.7 3179.5 376.2 371.7

4.1 16533.3 13353.8 10174.4 6994.9 19712.8 3179.5 376.2 370.0

4.2 11764.1 8584.6 5405.1 2225.6 14943.6 3179.5 376.2 371.5

4.3 15579.5 12400.0 9220.5 6041.0 18759.0 3179.5 376.2 370.3

4.4 22256.4 19076.9 15897.4 12717.9 25435.9 3179.5 376.2 368.2

4.5 12717.9 9538.5 6359.0 3179.5 15897.4 3179.5 376.2 371.2

5.1 16215.4 13035.9 9856.4 6676.9 19394.9 3179.5 376.2 370.1

5.2 13671.8 10492.3 7312.8 4133.3 16851.3 3179.5 376.2 370.9

6.1 8266.7 5087.2 1907.7 0.0 11446.2 3179.5 376.2 372.6

6.2 11128.2 7948.7 4769.2 1589.7 14307.7 3179.5 376.2 371.7

6.3 15261.5 12082.1 8902.6 5723.1 18441.0 3179.5 376.2 370.4

6.4 15579.5 12400.0 9220.5 6041.0 18759.0 3179.5 376.2 370.3

6.5 12717.9 9538.5 6359.0 3179.5 15897.4 3179.5 376.2 371.2

7.1 9538.5 6359.0 3179.5 0.0 12717.9 3179.5 376.2 372.2

7.2 9856.4 6676.9 3497.4 317.9 13035.9 3179.5 376.2 372.1

7.3 15579.5 12400.0 9220.5 6041.0 18759.0 3179.5 376.2 370.3

7.4 14625.6 11446.2 8266.7 5087.2 17805.1 3179.5 376.2 370.6

7.5 12717.9 9538.5 6359.0 3179.5 15897.4 3179.5 376.2 371.2

8.1 12082.1 8902.6 5723.1 2543.6 15261.5 3179.5 376.2 371.4

8.2 9538.5 6359.0 3179.5 0.0 12717.9 3179.5 376.2 372.2

8.3 14307.7 11128.2 7948.7 4769.2 17487.2 3179.5 376.2 370.7

8.4 9856.4 6676.9 3497.4 317.9 13035.9 3179.5 376.2 372.1

9.1 9538.5 6359.0 3179.5 0.0 12717.9 3179.5 376.2 372.2

9.2 7948.7 4769.2 1589.7 0.0 11128.2 3179.5 376.2 372.7

9.3 15897.4 12717.9 9538.5 6359.0 19076.9 3179.5 376.2 370.2

9.4 6359.0 3179.5 0.0 0.0 9538.5 3179.5 376.2 373.2

9.5 16215.4 13035.9 9856.4 6676.9 19394.9 3179.5 376.2 370.1

Totals : 124000 248000 372000 489959 684862

927,520 1,855,040 2,782,560 3,664,893 5,122,764

cubic feet

gallons

SHEET 11 OF 12







Conclusion:

The storage available in Recreation Pond is approximately 5,122,000 gallons. An additional storage

volume of approximately 1,626,000 gallons could be gained by dredging the soft sediment material from

the Pond.

The storage in the pond can be increased by roughly one-million gallons per foot of additional structure

height installed in the weir outlet or foot of drawdown. The available storage in the Pond through artificial

drawdown alone is depicted in the below figure:

Figure 2 - Drawdown Storage Available

927,520

1,855,040

2,782,560

3,664,893

5,122,764

-

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

1 ft 2 ft 3 ft 4 ft Total

Drawdown Storage Available

SHEET 12 OF 12





METHOD REV. BY M. Mardenov DEPT 2118 DATE 6/6/2019 .DEPT_ DATE_


Limitations:

As previously mentioned, it is assumed that Recreation Pond can be divided into 39 equal sectors, and the

bathymetry elevation at each sector represents an average depth within that sector’s area. This averaging

may not fully encompass the changing topography and depth of the Pond at all locations, nor does it

account for sidewalls or shoreline characteristics. The varying geometry of the pond cannot be accounted

for without additional data, and so the calculation is as accurate as can reasonably be assumed. A more

completed bathymetry, with increased data collection in transition areas (shorelines), would increase the

accuracy of the analysis.

Additionally, a concise survey that encompasses both the land and bathymetry below the weir elevation

was not completed. Coupling two or more data sources may lead to errors in measurements used in

determining sizes and depths of the Pond. Additionally, the data sources that were used, while accurate,

have limited coverage and may not completely represent the Pond bottom due to the spacing of the

recorded bathymetry.

The values presented should be considered accurate up to a half order of magnitude. For instance, a value

of 3,000,000 may vary as much as 500,000 from actual values that could be calculated or measured given

a more complete dataset and survey.

OUTFALL 010DISCHARGE POINT

OUTFALL 002

OUTFALL A

WEIR

RECREATIONPOND

17K OUTFALL

OUTFALL 003

0

OUTFALL A

OUTFALL 002

OUTFALL 003

17K OUTFALL

RECREATION POND

LEGEND

SCALE (ft)

400 ft

Recreation PondStewart International Airport - Air National Guard Base

Newburgh, NY

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pfos and pfoa mitigation plan

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