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STORMWATER POLLUTION PREVENTION PLAN
For
FIELDBROOK COMMONS
Prepared For •�-��-° ''
Northwest Regional Office
3190 160th Avenue SE
Bellevue, WA 98008-5452
425-649-7000
Owner Developer Operator/Contractor
Fieldbrook Commons, LLC Fieldbrook Commons, LLC Maher A. Joudi, P.E. �
9675 SE 36th Street Suite 105 9675 SE 36th Street Suite 105 620 7th Avenue
Mercer Island, Washington Mercer Island, Washington Kirkland, Washington 98033
( 98040 98040
Project Site Location
17040 108th Avenue SE, Renton, Washington
Certified Erosion and Sediment Control Lead
Justin Lagers
253.405.5587
SWPPP Prepared By
D.R. Strong Consulting Engineers, Inc.
620 7'h Avenue
Kirkland, Washington 98033
Maher A. Joudi, P.E., Senior Project Engineer
SWPPP Preparation Date
December 2, 2013
Approximate Project Construction Dates
Start Date: TBD
End Date: August TBD
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STORMWATER POLLUTION PREVENTION PLAN
TABLE OF CONTENTS
1.0 INTRODUCTION .......................................................................................................1
2.0 SITE DESCRIPTION .................................................................................................3
2.1 Existing Conditions............................................................................................3
2.2 Proposed Construction Activities.......................................................................3
3.0 CONSTRUCTION STORMWATER BMPS................................................................6
3.1 The 12 BMP Elements.......................................................................................6
3.1.1 Element#1 — Mark Clearing Limits.............................................................6
3.1.2 Element#2 — Establish Construction Access .............................................6
3.1.3 Element#3 — Control Flow Rates...............................................................7
3.1.4 Element#4 — Install Sediment Controls .....................................................7
3.1.5 Element#5 — Stabilize Soils.......................................................................9
3.1.6 Element#6 — Protect Slopes......................................................................9
3.1.7 Element#7 — Protect Drain Inlets.............................................................10
3.1.8 Element#8 — Stabilize Channels and Outlets ..........................................10
3.1.9 Element#9 — Control Pollutants...............................................................11
3.1.10 Element#10 — Control Dewatering...........................................................12
' 3.1.11 Element#11 — Maintain BMPs .................................................................12
3.1.12 Element#12 — Manage the Project..........................................................12
3.2 Site Specific BMPs..........................................................................................15
3.3 Additional Advanced BMPs .............................................................................15
4.0 CONSTRUCTION PHASING AND BMP IMPLEMENTATION................................16
5.0 POLLUTION PREVENTION TEAM.........................................................................17
5.1 Roles and Responsibilities ..............................................................................17
5.2 Team Members ...............................................................................................17
6.0 SITE INSPECTIONS AND MONITORING...............................................................18
6.1 Site Inspection.................................................................................................18
6.1.1 Site Inspection Frequency........................................................................18
6.1.2 Site Inspection Documentation.................................................................18
6.2 Stormwater Quality Monitoring ........................................................................19
6.2.1 Turbidity Sampling .........................................................................................19
6.2.2 pH Sampling ..................................................................................................19
6.2.3 Temperature Monitoring ...........................................................................20
7.0 REPORTING AND RECORDKEEPING ..................................................................21
7.1 Recordkeeping ................................................................................................21
7.1.1 Site Log Book...........................................................................................21
7.1.2 Records Retention....................................................................................21
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7.1.3 Access to Plans and Records...................................................................21
7.1.4 Updating the SWPPP...............................................................................21
7.2 Reporting.................................................................. .......22
................................
7.2.1 Discharge Monitoring Reports..................................................................22
7.2.2 Notification of Noncompliance..................................................................22
7.2.3 Permit Application and Changes ..............................................................22
Appendices
AppendixA— Site Plans ................................................................................................23
Appendix B — Construction BMPs..................................................................................24
Appendix C —Alternative BMPs.....................................................................................25
Appendix D — General Permit........................................................................................26
Appendix E — Site Inspection Forms (And Site Log) ......................................................27
Appendix F — Engineering Calculations .........................................................................34
Appendix A Site Plans
• Vicinity map (with all discharge points)
• Site plan with TESC measures
Appendix B Construction BMPs
• Possibly reference in BMPs, but likely it will be a consolidated list so that
the applicant can photocopy from the list from the SWMM.
� Appendix C Alternative Construction BMP list
• List of BMPs not selected, but can be referenced if needed in each of the
12 elements
Appendix D General Permit
Appendix E Site Log and Inspection Forms
Appendix F Engineering Calculations
• Flows, ponds, etc...
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1 .0 INTRODUCTION
This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as par�t of the
NPDES stormwater permit requirements for the Fieldbrook Commons 162-unit
apartment complex project located in Renton, Washington. The site is located at 17040
108th Avenue SE, Renton, Washington. The proposed development consists of the
construction of a 162-unit apartment complex, associated walkways, driveways,
parking, drive aisles, stormwater detention facilities, and landscaping on 10.80 acres.
Construction activities will include, grading, roadway construction, utility installation and
building construction. The purpose of this SWPPP is to describe the proposed
construction activities and all temporary and permanent erosion and sediment control
(TESC) measures, pollution prevention measures, inspection/monitoring activities, and
recordkeeping that will be implemented during the proposed construction project. The
objectives of the SWPPP are to:
1. Implement Best Management Practices (BMPs) to prevent erosion and
sedimentation, and to identify, reduce, eliminate or prevent stormwater
contamination and water pollution from construction activity.
2. Prevent violations of surFace water quality, ground water quality, or sediment
management standards.
3. Prevent, during the construction phase, adverse water quality impacts
including impacts on beneficial uses of the receiving water by controlling peak
flow rates and volumes of stormwater runoff at the Permittee's outfalls and
downstream of the outfalls.
This SWPPP was prepared using the Ecology SWPPP Template downloaded from the
Ecology website on July 2, 2005. This SWPPP was prepared based on the
requirements set forth in the Construction Stormwater General Permit, Stormwater
Management Manual for Western Washington (SWMMWW 2005) and in the
Stormwater Management Manual for Eastern VVashington (SWMMEW 2004). The
report is divided into seven main sections with several appendices that include
stormwater related reference materials. The topics presented in the each of the main
' sections are:
• Section 1 — INTRODUCTION. This section provides a summary
description of the project, and the organization of the SWPPP document.
• Section 2 — SITE DESCRIPTION. This section provides a detailed
description of the existing site conditions, proposed construction activities,
and calculated stormwater flow rates for existing conditions and post—
construction conditions.
• Section 3 — CONSTRUCTION BMPs. This section provides a detailed
description of the BMPs to be implemented based on the 12 required
elements of the SWPPP (SWMMEW 2004).
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• Section 4 — CONSTRUCTION PHASING AND BMP IMPLEMENTATION.
This section provides a description of the timing of the BMP
implementation in relation to the project schedule.
• Section 5 — POLLUTION PREVENTION TEAM. This section identiiies the
appropriate contact names (emergency and non-emergency), monitoring
personnel, and the onsite temporary erosion and sedimentation control
inspector
• Section 6 — INSPECTION AND MONITORING. This section provides a
description of the inspection and monitoring requirements such as the
parameters of concern to be monitored, sample locations, sample
frequencies, and sampling methods for all stormwater discharge locations
from the site.
� Section 7 — RECORDKEEPING. This section describes the requirements
for documentation of the BMP implementation, site inspections, monitoring
results, and changes to the implementation of certain BMPs due to site
factors experienced during construction.
Supporting documentation and standard forms are provided in the following
Appendices:
Appendix A— Site plans
Appendix B — Construction BMPs
Appendix C —Alternative Construction BMP list
Appendix D — General Permit
Appendix E — Site Log and Inspection Forms
Appendix F — Engineering Calculations
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2.0 SITE DESCRIPTION
2.1 Existing Conditions
Total existing Site area is approximately 470,481 s.f. (10.80 ac) (Parcel Numbers
292305-9168, 292305-9022, and 292305-9023) (Project). Total proposed Project area
is 323,719 s.f. (7.43 ac) which includes 7,066 s.f. (0.16 ac) for the right-of-way frontage
improvements on 108t" Avenue SE and SE 172"d Street. The Parcels are currently
undeveloped and are heavily forested with moderate underbrush.
The predeveloped Site is contained within two Threshold Discharge Areas (TDAs), TDA
West and TDA East. TDA West has three Natural Discharge Areas (NDAs), NDA 1,
NDA 2 and NDA 3. Runoff from NDA 1 discharges at the Site's southwestern property
corner and heads south through the conveyance system in 108th Avenue SE. It
eventually crosses 108th in a westerly direction into a stream through the Springbrook
Project. Runoff from NDA 2 discharges at the Site's southern property line and heads
south through the conveyance system in 109th Place SE. It eventually is collected in
the conveyance system within Benson Drive S and converges with the path of NDA 1.
Runoff from NDA 3 sheet flows to the east across the southeastern property corner of
parcel number 292305-9023. It sheet flows across adjacent developed properties and
into SE 173rd Street before converging with the downstream path of NDA 2.
TDA East has two Natural Discharge Areas, NDA 1 and NDA 2. Runoff from NDA 1
sheet flows to the east and exits the Site near the northeast corner as sheet flow. The
runoff is eventually collected in Soos Creek. Runoff from NDA 2 sheet flows to the east
and exits the Site near the southeast property corner of parcel number 292305-9023. It
reaches a closed depression and o�erflows to the east where it converges with the
downstream path of NDA 1.
For the purpose of hydrologic calculations, the entire Site is modeled as till forest.
2.2 Proposed Construction Activities
The applicant has gained approval to construct a 162-unit apartment complex on 10.80
acres (Project). The developable area (Project Area) is approximately 7.43 acres
(includes frontage improvements on 108th Avenue SE and SE 172nd Street). The
building areas, associated walkways, driveways, parking and drive aisles will total
approximately 203,000 s.f. (includes bypass areas). The remainder of the Project Area
will consist of residential landscaping and other pervious surfaces.
Per Section 5.2.1 of the 2009 King County Surface Water Design Manual (Manual),
projects are required to mitigate for impervious surface by use of Flow Control Best
Management Practices (BMP's). The Project falls within the "Large Lot Low
Impervious" category, as the proposed impervious is approximately 42.5% of the total
Site area. However, to meet the intent of the Manual, we have analyzed the impervious
surface percentage based upon the developable area as approximately three acres of
the site is encumbered by sensitive areas. With 4.54 of the 7.43 developable area
categorized as impervious (61.1%), it would be prudent to analyze the Project as "Large
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Lot High Impervious". The Project is therefore required to mitigate for an impervious
area equal to 20% of the total [developable] lot area or 40% of the proposed impervious
area, whichever is less; 64,750 s.f, and 79,105 s.f., respectively.
Projects are required to first analyze the feasibility of dispersal and infiltration before
choosing another method. The Site's location and on site wetlands lend portions of the
Site to dispersion. Per the geotechnical report dated December 13, 2011 the site is not
suitable for infiltration.
The Project proposes to utilize basic dispersion for Buildings H, K and L (16,585 s.f.) as
depicted on the storm drainage plans. Flow to each 50-foot gravel trench will not
exceed 0.50 cfs per Figure C.2.1.D of the Manual. (Rational Method Calculations in
Section V). The project will utilize limited infiltration, by drywells, for buildings C, D, E,
G, J, M, N and the Recreation Building (44,080 s.f.) and pervious concrete in a portion
of the walkways (4,705 s.f.). These areas will be modeled as 50% grass, 50%
impervious.
The Project is located within a Conservation Flow Control and Basic Water Quality
Area. However as a multifamily development, it shall be required to adhere to the
Enhanced Water Quality Treatment criteria. Runoff will be collected and conveyed to
two wetvault facilities located in the western and eastern portions of the Site,
respectively. Each facility will be followed by a StormFilter media filtration system to
accommodate the Enhanced Water Quality Treatment requirements.
The following summarizes details regarding site areas:
• Total site developable area: 7.43 acres
• Percent impervious area before construction: 6.7 %
• Percent impervious area after construction: 61.1 %
• Disturbed area during construction: 7.43 acres
• Disturbed area that is characterized as impervious
(i.e., access roads, staging, parking): 0.78 acres
TDA West
• 2-year stormwater runoff peak flow prior to construction (existing): 0.107 cfs
• 10-year stormwater runoff peak flow prior to construction (existing): 0.187 cfs
• 2-year stormwater runoff peak flow during construction: 0.190 cfs
• 10-year stormwater runoff peak flow during construction: 0.353 cfs
• 2-year stormwater runoff peak flow after construction: 0.072 cfs
• 10-year stormwater runoff peak flow after construction: 0.187 cfs
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TDA East
• 2-year stormvvater runoff peak flow prior to construction {existing): 0.100 cfs
• 10-year stormwater runoff peak flow prior to construction (existing): 0.173 cfs
• 2-year stormwater runoff peak flow during construction: 0.177 cfs
• 10-year stormwater runoff peak flow during construction: 0.328 cfs
• 2-year stormwater runoff peak flow after construction: 0.050 cfs
• 10-year stormwater runoff peak flow after construction: 0.155 cfs
All stormwater flow calculations are provided in Appendix F.
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3.0 CONSTRUCTION STORMWATER BMPS
3.1 The 12 BMP Elements
3.'i.1 Element#1 — Mark Clearing Limits
To protect adjacent properties and to reduce the area of soil exposed to construction,
the limits of construction will be clearly marked before land-disturbing activities begin.
Trees that are to be preserved, as well as all sensitive areas and their buffers, shall be
clearly delineated, both in the field and on the plans. In general, natural vegetation and
native topsoil shall be retained in an undisturbed state to the maximum extent possible.
The BMPs relevant to marking the clearing limits that will be applied for this project
include:
� High Visibility Plastic or Metal Fence (BMP C103)
The plastic fence will be placed around the perimeter of the developable area of the
Site. BMP will be implemented at the start of construction.
Alternate BMPs for marking clearing limits are included in Appendix C as a quick
reference tool for the onsite inspector in the event the BMP(s) listed above are deemed
ineffective or inappropriate during construction to satisfy the requirements set forth in
the General NPDES Permit (Appendix D). To avoid potential erosion and sediment
control issues that may cause a violation(s) of the NPDES Construction Stormwater
permit (as provided in Appendix D), the Certified Erosion and Sediment Control Lead
will promptly initiate the implementation of one or more of the alternative BMPs listed in
Appendix C after the first sign that existing BMPs are ineffective or failing.
3.1.2 Element#2 — Establish Construction Access
Construction access or activities occurring on unpaved areas shall be minimized, yet
where necessary, access points shall be stabilized to minimize the tracking of sediment
onto public roads, and wheel washing, street sweeping, and street cleaning shall be
employed to prevent sediment from entering state waters. All wash wastewater shall be
controlled on site. The specific BMPs related to establishing construction access that
will be used on this project include:
• Stabilized Construction Entrance (BMP C105)
• Construction Road/Parking Area Stabilization (BMP C107)
A Stabilized Construction Entrance will be placed at the intersection of the proposed
drive aisle and SE 172nd Street. Another Stabilized Construction Entrance will be
placed at the existing edge of pavement of SE 172"d Street. This BMP will be
implemented at the start of construction.
Construction Road and Parking Area Stabilization will occur along the road into the site
and in staging areas where parking of equipment will occur. This will occur as the
project goes along. These designated are shown on the plan sheet. Also, the existing
gravel driveway, located onsite, will be utilized as a staging area during construction.
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Alternate construction access BMPs are included in Appendix C as a quick reference
tool for the onsite inspector in the event the BMP(s) listed above are deemed inefifective
or inappropriate during construction to satisfy the requirements set forth in the General
NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues
that may cause a violation(s) of the NPDES Construction Stormwater permit (as
provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly
initiate the implementation of one or more of the alternative BMPs listed in Appendix C
after the first sign that existing BMPs are ineffective or failing.
3.1.3 Element#3 — Control Flow Rates
In order to protect the properties and waterways downstream of the project site,
stormwater discharges from the site will be controlled. The specific BMPs for flow
control that shall be used on this project include:
• Detention Vaults
• Sediment Traps
Two detention vaults will be installed onsite. The vaults will be constructed and used as
a sedimentation device during construction.
Sediment Traps will be implemented at the start of construction. They will discharge to
specific monitor points as shown on the plan sheet.
Alternate flow control BMPs are included in Appendix C as a quick reference tool for the
onsite inspector in the event the BMP(s) listed above are deemed ineffective or
inappropriate during construction to satisfy the requirements set forth in the General
NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues
that may cause a violation(s) of the NPDES Construction Stormwater permit (as
provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly
initiate the implementation of one or more of the alternative BMPs listed in Appendix C
after the first sign that existing BMPs are ineffective or failing.
The project site is located west of the Cascade Mountain Crest. As such, the project
must comply with Minimum Requirement 7 (Ecology 2005).
In general, discharge rates of stormwater from the site will be controlled where
increases in impervious area or soil compaction during construction could lead to
downstream erosion, or where necessary to meet local agency stormwater discharge
requirements (e.g. discharge to combined sewer systems).
3.1.4 Element#4— Install Sediment Controls
All stormwater runoff from disturbed areas shall pass through an appropriate sediment
removal BMP before leaving the construction site or prior to being discharged to an
infiltration facility. The specific BMPs to be used for controlling sediment on this project
include:
• Silt Fence (BMP C233)
• Storm Drain Inlet Protection (BMP C220)
• Interceptor Swale (BMP C200)
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a Detention Vaults
• Sediment Traps
Silt fence will be installed around the perimeter of the Site in areas where runoff could
sheet-flow offsite. This BMP will be installed at the start of construction.
Storm Drain Inlet Protection will be installed on all newly constructed catch basins
throughout the site as well as the existing catch basins in 108t" Avenue SE and SE
172"d Street. The existing catch basin protection will be installed at the start of
construction, and protection for the newly constructed catch basins will occur as they
are installed.
The interceptor swales and sediment traps will be installed during site grading. I'
The detention vaults will be installed and used for sedimentation at the commencement
of construction.
Alternate sediment control BMPs are included in Appendix C as a quick reference tool ,
fior the onsite inspector in the event the BMP(s) listed above are deemed ineffective or
inappropriate during construction to satisfy the requirements set forth in the General
NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues
that may cause a violation(s) of the NPDES Construction Stormwater permit (as
provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly
initiate the implementation of one or more of the alternative BMPs listed in Appendix C
after the first sign that existing BMPs are ineffective or failing.
In addition, sediment will be removed from paved areas in and adjacent to construction
work areas manually or using mechanical sweepers, as needed, to minimize tracking of
sediments on vehicle tires away from the site and to minimize washoff of sediments
from adjacent streets in runoff.
Whenever possible, sediment laden water shall be discharged into onsite, relatively
level, vegetated areas (BMP C240 paragraph 5, page 4-102).
In some cases, sediment discharge in concentrated runoff can be controlled using
permanent stormwater BMPs (e.g., infiltration swales, ponds, trenches). Sediment
loads can limit the effectiveness of some permanent stormwater BMPs, such as those
used for infiltration or biofiltration; however, those BMPs designed to remove solids by
settling (wet ponds or detention ponds) can be used during the construction phase.
When permanent stormwater BMPs will be used to control sediment discharge during
construction, the structure will be protected from excessive sedimentation with adequate
erosion and sediment control BMPs. Any accumulated sediment shall be removed after
construction is complete and the permanent stormwater BMP will be restabilized with
vegetation per applicable design requirements once the remainder of the site has been
stabilized.
The following BMPs will be implemented as end-of-pipe sediment controls as required
to meet permitted turbidity limits in the site discharge{s). Prior to the implementation of
these technologies, sediment sources and erosion control and soil stabilization BMP
efforts will be maximized to reduce the need for end-of-pipe sedimentation controls.
• Construction Stormwater Filtration (BMP C251)
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• Construction Stormwater Chemical Treatment (BMP C 250) (implemented
only with prior written approval from Ecology).
3.1.5 Element#5 — Stabilize Soils
Exposed and unworked soils shall be stabilized with the application of effective BMPs to
prevent erosion throughout the life of the project. The specific BMPs for soil
stabilization that shall be used on this project include:
• Temporary and Permanent Seeding (BMP C120)
• Plastic Coverin BMP C123
9 � )
• Dust Control (BMP C140)
Permanent Seeding will occur as grading is completed. All stabilized sections will be
seeded and vegetated.
Plastic Covering will occur throughout the site as deemed necessary by the contractor
and CESCL.
Dust Control will occur throughout the site as deemed necessary by the contractor and
CESCL.
Alternate soil stabilization BMPs are included in Appendix C as a quick reference tool
for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or
inappropriate during construction to satisfy the requirements set forth in the General
NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues
that may cause a violation(s) of the NPDES Construction Stormwater permit (as
provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly
initiate the implementation of one or more of the alternative BMPs listed in Appendix C
after the first sign that existing BMPs are ineffective or failing.
The project site is located west of the Cascade Mountain Crest. As such, no soils shall
remain exposed and unworked for more than 7 days during the dry season (May 1 to
September 30) and 2 days during the wet season (October 1 to April 30). Regardless of
the time of year, all soils shall be stabilized at the end of the shift before a holiday or
weekend if needed based on weather forecasts.
In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles
will be temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized
from erosion, protected with sediment trapping measures, and where possible, be
located away from storm drain inlets, waterways, and drainage channels.
3.1.6 Element#6 — Protect Slopes
All cut and fill slopes will be designed, constructed, and protected in a manner than
minimizes erosion. The following specific BMPs will be used to protect slopes for this
project:
• Temporary and Permanent Seeding (BMP C120)
• Check Dams (BMP C207)
Permanent Seeding will occur throughout the site as slopes are stabilized.
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Checks Dams will be installed every 50' as shown on the plan.
Alternate slope protection BMPs are included in Appendix C as a quick reference tool
for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or
inappropriate during construction to satisfy the requirements set forth in the General
NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues
that may cause a violation(s) of the NPDES Construction Stormwater permit (as
provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly
initiate the implementation of one or more of the alternative BMPs listed in Appendix C
after the first sign that existing BMPs are ineffective or failing.
3.1.7 Element#7 — Protect Drain Inlets
All storm drain inlets and culverts made operable during construction shall be protected
to prevent unfiltered or untreated water from entering the drainage conveyance system.
However, the first priority is to keep all access roads clean of sediment and keep street
wash water separate from entering storm drains until treatment can be provided. Storm
Drain Inlet Protection (BMP C220) will be implemented for all drainage inlets and
culverts that could potentially be impacted by sediment-laden runoff on and near the
project site. The following inlet protection measures will be applied on this project:
Drop Inlet Protection
• Catch Basin Filters
There are several existing catch basins which will require a filter in 108t" Avenue SE
and SE 172"d Street.
If the BMP options listed above are deemed ineffective or inappropriate during
construction to satisfy the requirements set forth in the General NPDES Permit
(Appendix D), or if no BMPs are listed above but deemed necessary during
construction, the Certified Erosion and Sediment Control Lead shall implement one or
more of the alternative BMP inlet protection options listed in Appendix C.
3.1.8 Element#8 — Stabilize Channels and Outlets
Where site runoff is to be conveyed in channels, or discharged to a stream or some
other natural drainage point, efforts will be taken to prevent downstream erosion. The
specific BMPs for channel and outlet stabilization that shall be used on fihis project
include:
• No BMPs implemented
The project will not discharge to any outlets or channels; therefore no BMP's are
required.
Alternate channel and outlet stabilization BMPs are included in Appendix C as a quick
reference tool for the onsite inspector in the event the BMP(s) listed above are deemed
ineffective or inappropriate during construction to satisfy the requirements set forth in
the General NPDES Permit (Appendix D). To avoid potential erosion and sediment
control issues that may cause a violation(s) of the NPDES Construction Stormwater
permit (as provided in Appendix D), the Certified Erosion and Sediment Control Lead
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will promptly initiate the implementation of one or more of the alternative BMPs listed in
Appendix C after the first sign that existing BMPs are ineffective or failing.
The project site is located west of the Cascade Mountain Crest. As such, all temporary
on-site conveyance channels shall be designed, constructed, and stabilized to prevent
erosion from the expected peak 10 minute velocity of flow from a Type 1A, 10-year, 24-
hour recurrence interval storm for the developed condition. Alternatively, the 10-year, 1-
hour peak flow rate indicated by an approved continuous runoff simulation model,
increased by a factor of 1.6, shall be used. Stabilization, including armoring material,
adequate to prevent erosion of outlets, adjacent streambanks, slopes, and downstream
reaches shall be provided at the outlets of all conveyance systems.
3.1.9 Element#9 — Control Pollutants
All pollutants, including waste materials and demolition debris, that occur onsite shall be
handled and disposed of in a manner that does not cause contamination of stormwater.
Good housekeeping and preventative measures will be taken to ensure that the site will
be kept clean, well-organized, and free of debris. If required, BMPs to be implemenfied
to control specific sources of pollutants are discussed below.
Vehicles, construction equipment, and/or petroleum product storage/dispensing:
• All vehicles, equipment, and petroleum product storage/dispensing areas
will be inspected regularly to detect any leaks or spills, and to identify
maintenance needs to prevent leaks or spills.
• On-site fueling tanks and petroleum product storage containers shall
include secondary containment.
• Spill prevention measures, such as drip pans, will be used when
conducting maintenance and repair of vehicles or equipment.
• In order to perform emergency repairs on site, temporary plastic will be
placed beneath and, if raining, over the vehicle.
• Contaminated surfaces shall be cleaned immediately following any
discharge or spill incident.
Demolition:
• Dust released from demolished sidewalks, buildings, or strucfiures will be
controlled using Dust Control measures (BMP C140).
• Storm drain inlets vulnerable to stormwater discharge carrying dust, soil,
or debris will be protected using Storm Drain Inlet Protection (BMP C220
as described above for Element 7).
• Process water and slurry resulting from sawcutting and surfacing
operations will be prevented from entering the waters of the State by
implementing Sawcutting and SurFacing Pollution Prevention measures
(BMP C152).
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� Stormwater Poliution Prevention Plan
Concrete and grout:
• Process water and slurry resulting from concrete work will be prevented
from entering the waters of the State by implementing Concrete Handling
measures (BMP C151).
Sanitary wastewater:
• Portable sanitation facilities will be firmly secured, regularly maintained,
and emptied when necessary.
Solid Waste:
• Solid waste will be stored in secure, clearly marked containers.
Other:
• Other BMPs will be administered as necessary to address any additional
pollutant sources on site.
The facility does not require a Spill Prevention, Control, and Countermeasure (SPCC)
Plan under the Federal regulations of the Clean Water Act (CWA).
3.1.10 Element#10 — Control Dewatering
There will be no dewatering as part of this construction project.
3.1.11 Element#11 — Maintain BMPs
All temporary and permanent erosion and sediment control BMPs shall be maintained
and repaired as needed to assure continued performance of their intended function.
Maintenance and repair shall be conducted in accordance with each particular BMPs
specifications (attached). Visual monitoring of the BMPs will be conducted at least once
every calendar week and within 24 hours of any stormwater or non-stormwater
discharge from the site. If the site becomes inactive, and is temporarily stabilized, the
inspection frequency will be reduced to once every month.
All temporary erosion and sediment control BMPs shall be removed within 30 days after
the final site stabilization is achieved or after the temporary BMPs are no longer
needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil
resulting from removal of BMPs or vegetation shall be permanently stabilized.
3.1.12 Element#12— Manage the Project
Erosion and sediment control BMPs for this project have been designed based on the
following principles:
• Design the project to fit the existing topography, soils, and drainage
patterns.
• Emphasize erosion control rather than sediment control.
• Minimize the extent and duration of the area exposed.
• Keep runoff velocities low.
• Retain sediment on site.
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• Thoroughly monitor site and maintain all ESC measures.
• Schedule major earthwork during the dry season.
In addition, project management will incorporate the key components lisied below:
(West Response) As this project site is located west of the Cascade Mountain Crest, the
project will be managed according to the following key project components:
Phasing of Construction
• The construction project is being phased to the extent practicable in order
to prevent soil erosion, and, to the maximum extent possible, the transport
of sediment from the site during construction.
• Revegetation of exposed areas and maintenance of that vegetation shall
be an integral part of the clearing activities during each phase of
construction, per the Scheduling BMP (C 162).
Seasonal Work Limitations
• From October 1 through April 30, clearing, grading, and other soil
disturbing activities shall only be permitted if shown to the satisfaction of
the local permitting authority that silt-laden runoff will be prevented from
leaving the site through a combination of the following:
o Site conditions including existing vegetative coverage, slope, soil type,
and proximity to receiving waters; and
o Limitations on activities and the extent of disturbed areas; and
o Proposed erosion and sediment control measures.
• Based on the information provided and/or local weather conditions, the
local permitting authority may expand or restrict fihe seasonal limitation on
site disturbance.
• The following activities are exempt from the seasonal clearing and grading
limitations.
o Routine maintenance and necessary repair of erosion and sediment
control BMPs;
o Routine maintenance of public facilities or existing utility structures that
do not expose the soil or result in the removal of the vegetative cover
to soil; and
o Activities where there is 100 percent infiltration of surface water runoff
within the site in approved and installed erosion and sediment control
facilities.
Coordination with Utilities and Other Jurisdictions
• Care has been taken to coordinate with utilities, other construction
projects, and the local jurisdiction in preparing this SWPPP and
scheduling the construction work.
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Inspection and Monitoring
• All BMPs shall be inspected, maintained, and repaired as needed to
assure continued performance of their intended function. Site inspections
shall be conducted by a person who is knowledgeable in the principles
and practices of erosion and sediment control. This person has the
necessary skills to:
o Assess the site conditions and construction activities that could impact
the quality of stormwater, and
o Assess the effectiveness of erosion and sediment control measures
used to control the quality of stormwater discharges.
• A Certified Erosion and Sediment Control Lead shall be on-site or on-call
at all times.
• Whenever inspection and/or monitoring reveals that the BMPs identified in
this SWPPP are inadequate, due to the actual discharge of or potential to
discharge a significant amount of any pollutant, appropriate BMPs or
design changes shall be implemented as soon as possible.
Maintaining an Updated Construction SWPPP
• This SWPPP shall be retained on-site or within reasonable access to the
site.
• The SWPPP shall be modified whenever there is a change in the design,
construction, operation, or maintenance at the construction site that has,
or could have, a significant effect on the discharge of pollutants to waters
of the state.
• The SWPPP shall be modified if, during inspections or investigations
conducted by the owner/operator, or the applicable local or state
regulatory authority, it is determined that the SWPPP is ineffective in
; eliminating or significantly minimizing pollutants in stormwater discharges
from the site. The SWPPP shall be modified as necessary to include
additional or modified BMPs designed to correct problems identified.
Revisions to the SWPPP shall be completed within seven (7) days
following the inspection.
If the BMP(s) listed above are deemed ineffective or inappropriate during construction to
satisfy the requirements set forth in the General NPDES Permit (Appendix D). To avoid
potential erosion and sediment control issues that may cause a violation(s) of the
NPDES Construction Stormwater permit (as provided in Appendix D), the Certified
Erosion and Sediment Control Lead will promptly initiate the implementation of one or
more of the alternative BMPs listed in Appendix C after the first sign that existing BMPs
are ineffective or failing.
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3.2 Site Specific BMP�
Site specific BMPs are shown on the TESC Plan Sheets and Details in Appendix A.
These site specific plan sheets will be updated annually.
3.3 Addi�ional Advanced �MPs
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4.0 CONSTRUCTION PHASING AND BMP IMPLEMENTATION
The BMP implementation schedule will be driven by the construction schedule. The
following provides a sequential list of the proposed construction schedule milestones
and the corresponding BMP implementation schedule. The list contains key milestones
such as wet season construction.
The BMP implementation schedule listed below is keyed to proposed phases of the
construction project, and reflects differences in BMP installations and inspections that
relate to wet season construction. The project site is located west of the Cascade
Mountain Crest. As such, the dry season is considered to be from May 1 to September
30 and the wet season is considered to be from October 1 to April 30.
• Estimate of Construction start date: TBD
• Estimate of Construction finish date: TBD
• Mobilize equipment on site: TBD
• Mobilize and store all ESC and soil stabilization products: TBD
• Install ESC measures: TBD
• Install stabilized construction entrance: TBD
• Begin clearing and grubbing: TBD
• Begin Site Grading: TBD
• Begin implementing soil stabilization and
sediment control BMPs throughout the site: TBD
• End Site Grading: TBD
• Begin Utility Construction: TBD
• End Utility Construction: TBD
• Begin Paving and Sidewalk Installation: TBD
• Permanent erosion control measures (hydroseeding): TBD
• End Paving and Sidewalk Installation: TBD
• Final landscaping and planting begins: TBD
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5.0 POLLUTION PREVENTION TEAM
5.1 Roles and Responsibilities
The pollution prevention team consists of personnel responsible for implementation of
the SWPPP, including the following:
� Certified Erosion and Sediment Control Lead (CESCL) — primary
contractor contact, responsible for site inspections (BMPs, visual
monitoring, sampling, etc.); to be called upon in case of failure of any ESC
measures.
• Resident Engineer — For projects with engineered structures only
(sediment ponds/traps, sand filters, etc.): site representative for the owner
that is the project's supervising engineer responsible for inspections and
issuing instructions and drawings to the contractor's site supervisor or
representative
• Emergency Ecology Contact — individual to be contacted at Ecology in
case of emergency
• Emergency Owner Contact — individual that is the site owner or
representative of the site owner to be contacted in the case of an
emergency.
• Non-Emergency Ecology Contact — individual that is the site owner or
representative of the site owner than can be contacted if required.
o Monitoring Personnel — personnel responsible for conducting water quality
monitoring; for most sites this person is also the Certified Erosion and
Sediment Control Lead.
5.2 Team Members
Names and contact information for those identified as members of the pollution
prevention team are provided in the following table.
Title Name(s) Phone Number
�
i Certified Erosion and Sediment Control Justin Lagers 253.4Q5.5587
� Lead(CESCL)
� Resident Engineer MaherA.Joudi 425.827.3063
Emergency Ecology Contact NW Regional Office 425.649.7000
Emergency Owner Contact Justin Lagers 253.405.5587
Non-Emergency Ecology Contact Ken Waldo 425.649.7279
Monitoring Personnel TBD
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6.0 SITE INSPECTIONS AND MONITORING
Monitoring includes visual inspection, monitoring for water quality parameters of
concern, and documentation of the inspection and monitoring findings in a site log book.
A site log book will be maintained for all on-site construction activities and will include:
• A record of the implementation of the SWPPP and other permit
requirements;
• Site inspections; and,
• Stormwater quality monitoring.
For convenience, the inspection form and water quality monitoring forms included in this
SWPPP include the required information for the site log book. This SWPPP may
function as the site log book if desired, or the forms may be separated and included in a
separate site log book. However, if separated, the site log book but must be maintained
on-site or within reasonable access to the site and be made available upon request to
Ecology or the local jurisdiction.
6.1 Site Inspection
All BMPs will be inspected, maintained, and repaired as needed to assure continued
perFormance of their intended function. The inspector will be a Certified Erosion and
Sediment Control Lead (CESCL) per BMP C160. The name and contact information for
the CESCL is provided in Section 5 of this SWPPP.
Site inspection will occur in all areas disturbed by construction acti�ities and at all
stormwater discharge points. Stormwater will be examined for the presence of
suspended sediment, turbidity, discoloration, and oily sheen. The site inspector will
evaluate and document the effectiveness of the installed BMPs and determine if it is
necessary to repair or replace any of the BMPs to improve the quality of stormwater
discharges. All maintenance and repairs will be documented in the site log book or
forms provided in this document. All new BMPs or design changes will be documented
in the SWPPP as soon as possible.
6.1.1 Site Inspection Frequency
Site inspections will be conducted at least once a week and within 24 hours following
any discharge from the site. For sites with temporary stabilization measures, the site
inspection frequency can be reduced to once every month.
6.1.2 Site Inspection Documentation
The site inspector will record each site inspection using the site log inspection forms
provided in Appendix E. The site inspection log forms may be separated from this
SWPPP document, but will be maintained on-site or within reasonable access to the site
and be made a�ailable upon request to Ecology or the local jurisdiction.
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6.2 Stormwater Quality Monitoring
TDA West will discharge into an existing storm drainage system and TDA East will
discharge to an existing wetland. Before project discharge leaves TDA West, it enters a
detention vault which outlets into a Stormfilter Manhole before entering the zxisting
conveyance system located near the intersection of 108t" Avenue SE and SE 172na
Street. Before project discharge leaves TDA East, it enters a detention vault which
outlets into a Stormfilter Manhole before entering an existing wetland located on the
eastern portion of the Site. This will be sufficient in accommodating water quality
requirements. Testing at the outlets will still occur as necessary.
6.2.1 Turbidity Sampling
Sampling and monitoring will be conducted during the enfiire consfruction phase of the
project. Samples will be collected daily at the downstream catch basin for both the
pond and vault. If there is no flow in this catch basin, the attempt to sample will be
recorded in the site log book and reported to Ecology in the monthly Discharge
Monitoring Report (DMR) as "No Discharge". Samples will be analyzed for turbidity
using the EPA 180.1 analytical method.
The key benchmark turbidity value is 25 nephelometric turbidity units (NTU) for the
downstream receiving water body. If the 25 NTU benchmark is exceeded in any sample
collected from the tested catch basins, the following steps will be conducted:
1. Ensure all BMPs specified in this SWPPP are installed and functioning as
intended.
2. Assess whether additional BMPs should be implemented, and document
modified BMPs in the SWPPP as necessary.
3. Sample discharge daily until the discharge is 25 NTU or lower.
If the turbidity exceeds 250 NTU at any time, the following steps will be conducted:
1. Notify Ecology by phone within 24 hours of analysis (see Section 5.0 of this
SWPPP for contact information).
2. Continue sampling daily until the discharge is 25 NTU or lower Initiate
additional treatment BMPs such as off-site treatment, infiltration, filtration and
chemical treatment within 24 hours, and implement those additional treatment
BMPs as soon as possible, but within a minimum of 7 days.
3. Describe inspection results and remedial actions taken in the site log book ,
and in monthly discharge monitoring reports as described in Section 7.0 of
this SWPPP.
6.2.2 pH Sampling
Sampling and monitoring for pH will occur during the phase of construction when
concrete pouring will be conducted until fully cured (3 weeks from last pour) and
discharges are documented to be below pH 8.5. Samples will be collected weekly at
the sedimentation pond prior to discharge to surface water. Samples will be analyzed
for pH using a calibrated pH meter and recorded in the site log book.
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The key benchmark pH value for stormwater is a maximum of 8.5. If a pH greater than
8.5 is measured in the sedimentation trap/pond(s) that has the potential to discharge to
surface water, the following steps will be conducted:
1. Prevent (detain) all discharges from leaving the site and entering surFace
waters or storm drains if the pH is greater than 8.5
2. Implement CO2 sparging or dry ice treatment in accordance with Ecology
BMP C252.
Describe inspection results and remedial acfiions that are taken in the site log book and
in monthly discharge monitoring repor�s as described in Secfiion 7.0 of this SWPPP.
6.2.3 Temperature Monitoring
No temperature monitoring is required i`or this construction site.
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7.0 REPORTING AND RECORDKEEPING
7.1 Recordkeeping
7.1.1 Site Log Book
A site log book will be maintained for all on-site construction activities and will include:
• A record of the implementation of the SWPPP and other permit
requirements;
• Site inspections; and,
• Stormwater quality monitoring.
For convenience, the inspection form and water quality monitoring forms included in this
SV1lPPP include the required information for the site log book.
7.1.2 Records Retention
Records of all monitoring information (site log book, inspection reports/checklists, etc.),
this Stormwater Pollution Prevention Plan, and any other documentation of compliance
with permit requirements will be retained during the life of the construction project and
for a minimum of three years following the termination of permit coverage in accordance
with permit condition SS.C.
7.1.3 Access to Plans and Records
The SWPPP, General Permit, Notice of Authorization letter, and Site Log Book will be
retained on site or within reasonable access to the site and will be made immediately
available upon request to Ecology or the local jurisdiction. A copy of this SWPPP will be
provided to Ecology within 14 days of receipt of a written request for the SWPPP from
Ecology. Any other information requested by Ecology will be submitted within a
reasonable time. A copy of the SWPPP or access to the SWPPP will be provided to the
public when requested in writing in accordance with permit condition SS.G.
7.1.4 Updating the SWPPP
In accordance with Conditions S3, S4.B, and S9.B.3 of the General Permit, this SWPPP
will be modified if the SWPPP is ineffective in eliminating or significantly minimizing
pollutants in stormwater discharges from the site or there has been a change in design,
construction, operation, or maintenance at the site that has a significant effect on the
discharge, or potential for discharge, of pollutants to the waters of the State. The
SWPPP will be modified within seven days of determination based on inspection(s) that
additional or modified BMPs are necessary to correct problems identified, and an
updated timeline for BMP implementation will be prepared.
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7.2 Reporting
7.2.1 Discharge Monitoring Reports
Water quality sampling results will be submitted to Ecology monthly on Discharge
Monitoring Report (DMR) forms in accordance with permit condition SS.B. If there was
no discharge during a given monitoring period, the form will be submitted with the words
"no discharge" entered in place of the monitoring results. If a benchmark was
exceeded, a brief summary of inspection results and remedial actions taken will be
included. If sampling could not be performed during a monitoring period, a DMR will be
submitted with an explanation of why sampling could not be perFormed.
7.2.2 Notification of Noncompliance
If any of the terms and conditions of the permit are not met, and it causes a threat to
human health or the environment, the following steps will be taken in accordance with
permit section S5.F:
1. Ecology will be immediately notified of the failure to comply.
2. Immediate action will be taken to control the noncompliance issue and to
correct the problem. If applicable, sampling and analysis of any
noncompliance will be repeated immediately and the results submitted to
Ecology within five (5) days of becoming aware of the violation.
3. A detailed written report describing the noncompliance will be submitted to
Ecology within five (5) days, unless requested earlier by Ecology.
Any time turbidity sampling indicates turbidity is 250 nephelometric turbidity units (NTU)
or greater or water transparency is 6 centimeters or less, the Ecology regional office will
be notified by phone within 24 hours of analysis as required by permit condition SS.A
(see Section 5.0 of this SWPPP for contact information).
In accordance with permit condition S4.F.6.b, the Ecology regional office will be notified
if chemical treatment other than CO2 sparging is planned for adjustment of high pH
water (see Section 5.0 of this SWPPP for contact information).
7.2.3 Permit Application and Changes
In accordance with permit condition S2.A, a complete application form will be submitted
to Ecology and the appropriate local jurisdiction (if applicable) to be covered by the
General Permit.
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APPENDIX A - SITE PLANS
I''�i
�
�
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APPENDIX B - CONSTRUCTION �MPS
High Visibility Plastic or Metal Fence (BMP C103) �
Sfiabilized Construction Entrance (BMP C105)
Construction Road/Parking Area Stabilization (BMP C107) II
Temporary and Permanent Seeding (BMP C120) �
Plastic Covering (BMP C123)
Dust Control (BMP C140)
Nlaterials on Hand (BMP C150)
Interceptor Swale (BMP C200)
Check Dams (BMP C207)
Storm Drain Inlet Protection (BMP C220)
Silt Fence (BMP C233)
Sediment Trap
Detention Vault
�2013 D. R.STRONG Consulting Engineers Inc. Page 24 of 56
Stormwater Pollution Prevention Plan Fieldbrook COCY�IYIOCIS December 2, 2013
.
Stormwater Pollution Prevention Plan
APPENDIX C - ALTERNATIVE BMPS
The following includes a list of possible alternative BMPs for each of the 12 elements
not described in the main SWPPP text. This list can be referenced in the event a BMP
ior a specific element is not functioning as designed and an alternative BMP needs to
be implemented.
Rlone Proposed
t��2013 D. R. STRONG Consulting Engineers Inc. Page 25 of 55
Storm��vater Pollution Prevention Plan Fieldbrook Commons December 2,2013
�
APPENDIX D - GENERAL PERMIT
���2013 D. R.STRONG Conswting Engineer�Inc. Page 26 of 56 ,
Storm�^�ater Pollution Prevention Plan Fieldbrook COr(1111011� Decemb2r 2,2013 I
�
APPENDIX E - SITE INSPECTION FORMS (AND SITE LOG)
The results of each inspection shall be summarized in an inspection report or checklist
that is entered into or attached to the site log book. It is suggested that the inspection
report or checklist be included in this appendix to keep monitoring and inspection
information in one document, but this is optional. However, it is mandatory that this
SWPPP and the site inspection forms be kept onsite at all times during consfiruction,
and that inspections be perFormed and documented as outlined below.
At a minimum, each inspection report or checklist shall include:
a. Inspection date/times
b. Weather information: general conditions during inspecfion, approximate
amount of precipitation since the last inspection, and approximate amount
of precipitation within the last 24 hours.
c. A summary or list of all BMPs that have been implemented, including
observations of all erosion/sediment control structures or practices.
d. The following shall be noted:
i. locations of BMPs inspected,
ii. locations of BMPs that need maintenance,
iii. the reason maintenance is needed,
iv. locations of BMPs that failed to operate as designed or intended, and
v. locations where additional or different BMPs are needed, and the
reason(s) why
e. A description of stormwater discharged from the site. The presence of
suspended sediment, turbid water, discoloration, and/or oil sheen shall be
noted, as applicable.
f. A description of any water quality monitoring performed during inspection,
and the results of that monitoring.
g. General comments and notes, including a brief description of any BMP
repairs, maintenance or installations made as a result of the inspection.
h. A statement that, in the judgment of the person conducting the site
inspection, the site is either in compliance or out of compliance with the
terms and conditions of the SWPPP and the NPDES permit. If the site
inspection indicates that the site is out of compliance, the inspection report
shall include a summary of the remedial actions required to bring the site
back into compliance, as well as a schedule of implementation.
i. Name, title, and signature of person conducting the site inspection; and
the following statement: "I certify under penalty of law that this report is
true, accurate, and complete, to the best of my knowledge and belief'.
��2013 D. R.STRONG Consulting Engineers Inc. Page 27 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
.
1Nhen the site inspection indicates that the site is not in compliance with any terms and
conditions of the NPDES permit, the Permittee shall take immediate action(s) to: stop,
contain, and clean up the unauthorized discharges, or otherwise stop the
noncompliance; correct the problem(s); implement appropriate Best Management
Practices (BMPs), and/or conduct maintenance of existing BMPs; and achieve
compliance with all applicable standards and permit conditions. In addition, if the
noncompliance causes a threat to human health or the environment, the Permittee shall
comply with the Noncompliance Notification requirements in Special Condition SS.F of
the permit.
�
O 2013 D.R.STRONG Consulting Engineers Inc. Page 28 of 56
Stormwater Pollution Prevention Plan Fieldbrook Commons December 2,2013
__ _ _ —�
, � �
SITE INSPECTION FORM
General Information
Project Name:
Inspector Name: Title:
CESCL# :
Date: Time:
Inspection Type: ❑ After a rain event
❑ Weekly
❑ Turbidity/transparency benchmark exceedance I
❑ Other
Weather
Precipitation Since last inspection In last 24 hours
Description of General Site Conditions:
Inspection of BMPs
Element 1: Mark Clearing Limits
BMP:
Location Inspected Functioning ProblemlCorrective Action
Y N Y N NIP
BM P:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
Element 2: Establish Construction Access
BM P:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
Element 3: Control Flow Rates
BM P:
Location Inspected Functioning ProblemlCorrective Action
Y N Y N NIP
O 2013 D. R.STRONG Consulting Engineers Inc. Page 29 of 56
5tormwater Poilution Prevention Plan Fieldbrook Commons December 2,2013
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Aciion
Element 4: Install Sediment Controls
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP ProblemlCorrective Action
i
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
Element 5: Stabilize Soils
BMP:
Inspected Functioning
Location Y N � Y � N NIP Problem/Corrective Action
�
BMP:
Inspected Functioning
Location Y N Y N NIP ProblemlCorrective Action
��2013 D.R.STRONG Consulting Engineers Inc. Page 30 of 56
Stormvdater Poliution Prevention Plan Fieldbrook Commons December 2,2013
�
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
i
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
�
Element 6: Protect Slopes
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
I
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
Element 7: Protect Orain lnlets
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
I
I
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
�
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
�-2013 D. R.STRONG Consuliing Engineers Inc. Page 31 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2.2013
�
Element 8: Stabilize Channels and Outlets
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP ProblemlCorrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP ProblemlCorrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP ProblemlCorrective Action
Element 9: Confrol Po!lutants
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
�
Element 10: Contro!Dewatering
BM P:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
�
�
BMP:
Location Inspected Functioning Problem/Corrective Action
Y N Y N NIP
r�2013 D. R.STRONG Consuiting Engineers Inc. Page 32 of 56
Stormwater Pollution Prevention Plan Fieldbrook Commons December 2. 2013
BMP:
Inspected Functioning
Location Y N Y N NIP Problem/Corrective Action
Stormwater Discharges From the Site
Observed? Problem/Corrective Action
Y ON
Location
Turbidity
Discoloration
Sheen
Location
Turbidity
Discoloration
Sheen
Water Quality Monitoring
Was any water quality monitoring conducted? ❑ Yes ❑ No
If water quality monitoring was conducted, record results here:
If water quality monitoring indicated turbidity 250 NTU or greater; or transparency 6 cm or less, I'
was Ecology notified by phone within 24 hrs?
❑ Yes ❑ No
If Ecology was notified, indicate the date, time, contact name and phone number below: ,
Date:
Time:
Contact Name:
Phone#:
General Comments and Notes
Include BMP repairs, maintenance, or installations made as a result of the inspection.
Were Photos Taken? ❑ Yes ❑ No
If photos taken, describe photos below:
O 2013 D.R.STRONG Consulting Engineers Inc. Page 33 of 56
Stormwater Pollution Prevention Plan Fieidbrook Commons December 2, 2013
r
APPENDIX F - ENGINEERING CALCULATIONS
� 2013 D. R. STRONG Consulting Engineers Inc. Page 34 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
.
EXISTING SITE HYDROLOGY
FLOW CONTROL AND WQ►TER (�UALITY F'ACILITY ANALYSIS AND DESIGN
The continuous simulation model, the King County Runoff Time Series, KCRTS, was
used to analyze the pre and post developed runoff rates. Per Table 3.2.2.b of the
Manual, the soil type is modeled as "Till" for the Alderwood gravelly sandy loam SCS
classification as shown in Figure 4. Soils. Results of the KCRTS analysis are included
in this section.
EXISTING SITE HYDROLO�'t
Modeling input — TDA West
�Lznd Use Summary o I I.s.�-y.�--�r��.
Area ?
I
Till Forest� 3.85 acres
Till Pasture 0.00 acres,
Till Grass 0.00 acres''
Oulvrash Forest 0.00 acres'�
Oulwash Pasture O.OD acres
Outwash Grass 0.00 acres
Wetland 0.00 acres
Impervious 0.00 acresi
Total –,
3.85 acres,
�-
�Scale Factor: 1.00 Hourly Reduced
Time Series: predev »
Compute Time Series I
` Modify User Input I
��— File for computed Time Series[.TSF]
Modeling results —TDA West
Flow Frequencl �nal��sis
Time Series File:prede�.tsf
Project Location:Sea-Tac
---Annual Peak Flow Ra�es--- ----�lo�-; �r�Uuency �nalysis-----
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.243 2 2/09/Ol 18:00 0.311 1 100.00 0. 99C
0. 066 7 1/06/02 3:00 0.243 2 25.00 0.960
0. 180 4 2/28/03 3: 00 0. 187 3 10.00 0. 900
0.006 8 3/24/04 20:00 0.180 4 5.00 0.800
0. 107 6 1/05/05 8:00 0.157 5 3. 00 0. 66r
0. 187 3 1/18/06 21:00 0. 107 6 2 . 00 0.50C
0.157 5 11/24/06 4:00 0.066 7 1.30 0.231
0.311 1 1/09/08 9:00 0.006 8 1. 10 0.091
Computed Peaks 0. 288 50. 00 0. 980
�2013 D. R. STRONG Consulting Engineers Inc. Page 35 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2,2013
Modeling inpufi —TDA East
�Land U>e Summary �i �-`"�'
Area J
Till Forestl 3.58 acres
Till Pasture 0.00 acresl'I
Till Grassi 0.00 acresl
Ouiwash Forest 0.00 acres'
Outwash Pasturei 0.00 acresi
Outwash Grassl 0.00 acresi
Wetland' 0.00 acresi
Impervious 0.00 acres�
--�
Total--
3.58 acresl
Scale Factor: 1.00 Hourly Reduced
Time Series: predev »
Compute Time Series I
Modify User Input I
_. ----------__- ------__ ___--
r--
File far computed Time Series[.TSF�
I
Modeling results —TDA East
Flow Frequenc�i Analys=s
Time Series File:predev.tsf
Project Location:Sea-Tac
---Annual Peak Flow Ra�es--- �loc,r Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.226 2 2/09/Ol 18:00 0.289 1 100. 00 0. °�0
0.061 7 1/06/02 3:00 0. 226 2 25.00 0. 96u
0.167 4 2/28/03 3:00 0. 173 3 10.00 0.90�
0.006 8 3/24/04 20:00 0. 167 4 5.00 0.80G
0.100 6 1/05/05 8:00 0.146 5 3.00 0. 66;
0.173 3 1/18/06 21:00 0.100 6 2 . 00 0.5G0
0.146 5 11/24/06 4:00 0.061 7 1. 30 0.231
0.289 1 1/09/08 9:00 0. 006 8 1. 10 O.OS1
Computed Peaks 0.268 50. 0� 0. 98C
��2013 D. R. STRONG Consulting Engireers Inc. Page 35 of 55
Stormv��ater Pollutien Prevention Plan Fieldbrook Commons December 2. 2013
c
DEVELOPED HYDRO�OGY
Soil type
The soil types are unchanged from pre-developed condifiions.
Land covers
KCRTS was used to model the developed peak runoff from the Sifie. The portions of fihe
Site within the proposed clearing limits tributary to the proposed detention pond were
modeled as "Till Grass" and Impervious as appropriate. Results of the KCRTS analysis
are included in this section.
Area Breakdown
TDA West
Predev
Forest 167866 3.854
RD In
Impervious (Actual) 97533 2.239
Impervious(Input) 82142.5 1.886 Flow Control BMP Reduction
Till Grass(Actual) 54603 1.254
Till Grass (Input) 69993.5 1.607 Flow Control BMP Increase
Bypass
Impervious 5052 0.116
Till Grass 10678 0.245
TDA East
Predev
Forest 155853 3.578
RD In
Impervious (Actual) 100425 2.305
Impervious(Input) 83407.5 1.915 Flo�v Control BMP Reduction
Till Grass (Actual) 51240 1.176
Till Grass (Input) 68257.5 1.567 Flow Control BMP Increase
Bypass
Impervious 0 0.000
Till Grass 4188 0.096
., 2013 D. R.STRONG Consulting Engineers Inc. Page 37 of 56
Stormvdater Pollution Prevention Plan Fieldbrook Commons December 2,2013
Modeling input—TDA West
{�Land Use Sum�ar� � � � ' ��-�"`=
-Area - -- ?
i
Tili Forest 0.00 acres�
Till Pasture� 0.00 acresl
Tili Grass 1.61 acres
Outwash Forest� 0.00 acres;
Outwash Pasture 0.00 acres�
Outwash Grass O.UO acres
i '
Wetland O.OD acres
� Impervious 1.89 acresll
Total-----
� 3.49 acres
� Scale Factar: 1.00 Hourly Reduced
� Time Series: rdin »I
� Compute Time Series
� . _ - —I
� Modify User input I
� File far computed Time Series[.TSF]
Modeling results —TDA West
Flow Frequency Analysis
Time Series File:rdin.ts-
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency �nalysis------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0. 601 6 2/09/Ol 2:00 1.23 1 100. 00 0. 990
0.476 8 1/05/02 16:00 0.726 2 25. 00 0. 960
0.725 3 2/27/03 7:00 0.725 3 10. 00 0. 900
0.500 7 8/26/04 2:00 0. 636 4 5. 00 0.8CG
0.605 5 10/28/04 16:00 0. 605 5 3.00 0. 667
0. 636 4 1/18/06 16:00 0. 601 6 2.00 0.500
0.726 2 10/26/06 0:00 0.500 7 1.30 0.231
1.23 1 1/09/08 6:00 0. 476 8 1. 10 0. 091
Computed Peaks 1 .06 50. 00 0. 980
���2013 D. R.STRONG Consulting Engineers Inc. Page 38 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Cornmons December 2, 2013
Modeling input — TDA East
{r�Land Use Summary � � � (����'"
Area ?�
Till Forestl 3.58 acres'�
Till Pasture 0.00 acres
Tiil Grass 0.00 acres
Outwash Forest� 0.00 acres
Ouiwash Pasture� 0.00 acres
Ouiwash Grass� 0.00 acres
WeHandl 0.00 acres
Impervious 0.00 acres
Total --�
I 3.58 acres�
t—
Scale Factor: 1.00 Hourly Reduced
Time Series: predev »
Compute Time Series I
Modity User Input (
� File(or compuied Time Series[.TSF]
Modeling results —TDA East
Flow Frequency �r_alysis
Time Series File:rdin.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----F�oe� Freq��iency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS} Period
0. 604 6 2/09/O1 2:00 1.24 1 100.00 0. 990
0.481 8 1/05/02 16:00 0.736 2 25.00 0. 960
0.729 3 2/27/03 7:00 0.729 3 10.00 0.900
0.506 7 8/26/04 2 :00 0. 640 4 5.00 0.800
0. 613 5 10/28/09 16:00 0. 613 5 3.00 0. 66�
0. 640 4 1/18/06 16:00 0. 604 6 2.00 0.5CC
0.736 2 10/26/06 0:00 0.506 7 1.30 0.231
1.24 1 1/09/08 6:00 0.481 8 1.10 0.0°1
Comouted Peaks 1 . 07 50. 00 0 . 980
�2013 D.R.STRONG Consulting Engineers Inc. Page 39 of 56
Stormwater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
�YPASS AREA HY�ROLOGY
Modeling input —TDA 1Nest
�C,Land Use Surt:mary .... � . l� ��
A.rea— --- ?
Till Forest 0•�0 acres
Till Pasture 0.00 acres,'
',
Till Grass 0.25 acresi
Ouiwash Forest 0.00 acresl
Ouiwash Pasture 0.00 acresl
Outwash Grass 0.00 acres
Wetland 0.00 acres
� Impervious 0.12 acres
' Total
0.37 acres
i Scale Factor: 1.00 Hourly Reduced
Time Series: bypass »
Compute Time Series I
j Modify User Input I
,f File for camputed Time Series�.TSF]
Modeling results —TDA West
Flow Frequency Analysis
Time Series File:bypass.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flcw Rate Rank Time of Peak - - Peaks - - Rank Return Prob
;CFS) (CFS) Period
0.050 4 2/09/O1 2: 00 0. 107 1 100.00 0. 990
0.036 7 1/05/02 16:00 0.061 2 25.00 0. 960
0. 061 2 2/27/03 7:00 0. 052 3 10.00 0. 900
G.034 8 8/26/09 2:00 0. 050 4 5. 00 0.800
0.042 6 10/28/09 16:00 0. 049 5 3. 00 0. 667
G.052 3 1/18/06 16:00 0. 042 6 2. 00 0.500
�� . 049 5 11/24/06 3:00 0.036 7 1. 30 0.231
0 . 107 1 1/09/08 6:00 0.034 8 1. 10 0.091
Ccmputed Peaks 0.092 50. 00 0. 980
The flow control facility is designed to compensate for uncontrolled bypass. The 100-
year discharge from the bypass areas is 0.107 cfs, which is less than the 0.4 cfs
threshold. There should be no adverse downstream impacts to the downstream
drainage system created by the runoff from the bypass.
The onsite bypass areas satisfy all the requirements set forth in the Manual, Section 1.2
with the exception of TDA East as it pertains to convergence with the downstream path
of the facility within a quarter mile. This is further detailed in �he following section.
�J 2013 D. R.STRONG Consulting Engineers Inc. Page 40 of 56
Stormwater Pollution Prevention Plan Fieldbrook Commons December 2. 2013
Modeling input—TDA East
�Land Use Summary wy�; o ''
Area-- i �
Till Forest' O.OU acresl
Till Pasture 0.00 acres
Till Grass, 0.10 acres
Outwash Forestl 0.00 acres
Ouiwash Pasture 0.00 acres �
Ouhvash Grass 0.00 acres,
Wetland 0.00 acres�
Impervious O.DO acres�
I Total —
I
L0 10 acre I
Scale Factor: 1.00 Hourly Reduced
Time Series: bypass » E
Compute Time Series �
Modity User Input I
j� File for computed Time Series[.TSFJ '
�
Modeling results —TDA East
Flow Frequency Analysis
Time Series File:bypass.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.009 3 2/09/Ol 2:00 0.020 1 100.00 0. 990
0.004 7 1/05/02 16:00 0. 011 2 25.00 0. 960
0.011 2 2/27/03 7:00 0.009 3 10.00 0. 900
0.002 8 3/24/04 19:00 0.009 4 5. 00 0.800
0.004 6 1/05/05 8:00 0.008 5 3.00 0. 667
0. 009 4 1/18/06 16:00 0. 004 6 2.00 0.500 '
0. 008 5 11/24/06 3:00 0. 004 7 1.30 0.231 ''
0.020 1 1/09/08 6:00 0. 002 8 1. 10 0.091
Computed Peaks 0. 017 50. 00 0. 980
The flow control facility is designed to compensate for uncontrolled bypass. The 100-
year discharge from the bypass areas is 0.02 cfs, which is less than the 0.4 cfs
threshold. There should be no adverse downstream impacts to the downstream
drainage system created by the runoff from the bypass.
The onsite bypass areas satisfy all the requirements set forth in the Manual, Section 1.2
with the exception of TDA East as it pertains to convergence with the downstream pafih
of the facility within a quarter mile. This is further detailed in the following section.
��2013 D. R.STRONG Consulting Engineers Inc. Page 41 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2,2013
PERFORMANCE STANDARDS
The Project is located in a Conservation Flow Control Area and will therefore adhere to
Level 2 Flow Control Standards, forested conditions. Two defiention vaults will provide
flow control as required. The Project is required to "match developed discharge
durations to predeveloped durations for the range of predeveloped discharge rates
firom 50% of the two-year peak flow up to the full 50-year peak flow. Also match
developed peak discharge rates to predeveloped peak discharge rates for the 2 and the
10 year return periods. Assum(ing) historic conditions as the predeveloped condition."
(KCSWDM, Sec. 1.2).
FL.OW CONTROL SYSTEM
TDA West
P.�tenti:;n/Detention Facility
Type of Facility: Detention Vault
Facility Length: 61. 00 ft
Facility Width: 00. 75 ft
Facility Area: 3706. sq. ft
Effective Storage Depth: 11.00 ft
Stage 0 Elevation: 403. 00 ft
Storage Volume: 40763. cu. ft
Riser Head: 11. 00 ft
Riser Diameter: 12.00 inches
DIu__�ber of orifices: 2
Full Head Pipe
Orifice # Height Diameter Discharge Diameter
(ft) (in) (CFS) (in)
1 0.00 0.80 0.058
2 7.50 1. 65 0. 138 4.0
Top Notch Weir: None
Outflow Rating Curve: None
:tage Elevation Storage Discharge Percolation
;=t) (ft) (cu. ft) (ac-ft) (cfs) (cfs)
0.00 403.00 0. 0.000 0.000 0.00
,�. Ol 403.01 37. 0.001 0.002 0.00
�. 02 403.02 74. 0.002 0.002 0.00
,�. 03 403.03 111. 0. 003 0.003 0.00
0. 04 403.04 148. 0. 003 0.004 0.00
0. 05 403.05 185. 0. 004 0.004 0.00
0. 06 403.06 222. 0. 005 0.004 0.00
0. 07 403.07 259. 0. 006 0.004 0.00
0.25 403.25 926. 0.021 0.009 0.00
0. 44 403.44 1631. 0.037 0.012 0.00
0. 63 403. 63 2335. 0.054 0.014 0. 00
0. 81 403.81 3002 . 0.069 0.016 0. 00
"_. 00 404.00 3706. 0.085 0.017 0.00
-. 19 404. 19 4410. 0.101 0.019 0.00
1.37 404.37 5077. 0. 117 0.020 0. 00
1. 56 404 .56 5781. 0. 133 0.022 0.00
1. 74 404 .74 6448 . 0. 148 0.023 0.00
1. 93 404 . 93 7152. 0. 164 0.024 0.00
2. 12 405 . 12 7856. 0. 180 0.025 0. 00
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Stormtivater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
2 . 30 405.30 8523. 0. 196 0 .026 0.00
2.49 405.49 9227. 0.212 0.027 0.00
2. 68 405.68 9931. 0.228 0.028 0. 00
2.86 405.86 10598. 0.243 0.029 0. 00
3.05 406.05 11303. 0.259 0.030 0.00
3.24 406.24 12007. 0.276 0.031 0.00
3. 42 406.42 12674. 0.291 0.032 0.00
3. 61 406. 61 13378. 0.307 0.033 0.00
3.80 406.80 14082. 0.323 0.034 0.00
3. 98 406.98 14749. 0.339 0.035 0.00
4. 17 407.17 15453. 0.355 0.035 0.00
4.35 407.35 16120. 0.370 0.036 0.00
4 . 54 407.54 16824. 0.386 0.037 0.00
4 . 73 407.73 17528. 0.402 0.038 0. 00
4 . 91 407. 91 18195. 0.418 0.038 0. 00
5. 10 408.10 18899. 0.434 0.039 0.00
5.29 408.29 19603. 0.450 0.040 0.00
5. 47 408.47 20270. 0 .465 0.041 0.00
5. 66 408. 66 20975. 0 .482 0.041 0.00
5. 85 408.85 21679. 0.498 0.042 0. 00
6.03 409.03 22346. 0.513 0.043 0.00
6.22 409.22 23050. 0.529 0.043 0.00
6.41 409.41 23754. 0.545 0.044 0. 00
6. 59 409.59 24421. 0.561 0.045 0.00
6. 78 409.78 25125. 0.577 0.045 0.00
6. 96 409.96 25792. 0.592 0.046 0. 00
7 .15 410.15 26496. 0. 608 0.046 0. 00
7.34 410.34 27200. 0.624 0.047 0. 00
7.50 410.50 27793. 0.638 0.048 0.00
7.52 410.52 27867. 0.640 0.048 0. 00
7.53 410.53 27904. 0.641 0.050 O.00
7.55 410.55 27978. 0. 642 0.053 O.00
7.57 410.57 28053. 0.644 0.057 0. 00
7 .59 410.59 28127. 0. 646 0.062 0.00
7. 60 410. 60 28164. 0. 647 0.068 0. 00
7. 62 410. 62 28238. 0. 648 0.074 0. 00
7. 64 410. 64 28312. 0. 650 0.075 0. 00
7.82 410.82 28979. 0. 665 0.091 0. 00
8.01 411.01 29683. 0. 681 0.102 0. 00
8.20 411 .20 30387. 0. 698 0.111 0.00
8.38 411.38 31054. 0.713 0. 120 0.00
8.57 411 .57 31758. 0.729 0. 127 0. 00
8.76 411.76 32462. 0.745 0.134 0.00
8. 94 411. 94 33129. 0.761 0.141 0.00
9. 13 412 .13 33833. 0.777 0.147 0. 00
9.32 412.32 34538. 0.793 0. 152 0. 00
9.50 412.50 35205. 0.808 0. 158 0. 00
9. 69 412. 69 35909. 0 .824 0. 163 0.00
9. 87 412 . 87 36576. 0 .840 0.168 0.00
10. 06 413. 06 37280. 0.856 0.173 0.00
10.25 413.25 37984 . 0.872 0. 178 0.00
10.43 413.43 38651 . 0.887 0. 183 0.00
10. 62 413.62 39355 . 0. 903 0. 187 0.00
10.81 413.81 40059. 0. 920 0. 191 0.00
G 2013 D. R.STRONG Consulting Engineers Inc. Page 43 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2. 2013
10. 99 413. 99 40726. 0. 935 0.196 0.00
11.00 414.00 40763. 0. 936 0.196 0.00
11. 10 414. 10 41134. 0. 944 0.506 0.00
11.20 414.20 41504. 0. 953 1.070 0.00
11.30 414.30 41875. 0. 961 1.800 0. 00
11. 40 414.40 42246. 0. 970 2 . 600 0. 00
11.50 414 .50 42616. 0.978 2.880 0. 00
11. 60 414 . 60 42987. 0.987 3.140 0.00
11. 70 414 .70 43357. 0. 995 3.370 0.00
11. 80 414 . 80 43728. 1.004 3.600 0.00
11. 90 414 .90 44098. 1.012 3.800 0.00
12.00 415.00 44469. 1.021 4.000 0.00
12. 10 415.10 44890. 1.029 4.190 0.00
12.20 415.20 45210. 1. 038 4.360 0.00
12.30 415.30 45581. 1.046 4 .530 0. 00
12. 40 415.40 45951 . 1.055 4 .700 0. 00
12.50 415.50 46322 . 1.063 4.860 0. 00
12. 60 415. 60 46692. 1.072 5.010 0.00
12.70 415.70 47063. 1.080 5.160 0.00
12.80 415.80 47434. 1.089 5.310 0.00
12. 90 415.90 47804. 1. 097 5.450 0.00
Hyd Inflow Outflow Peak Storage
Stage Elev (Cu-Ft) (Ac-Ft)
1 1.23 0.76 11. 14 414. 14 41300. 0. 948
2 0. 60 0. 19 10. 66 413. 66 39510. 0. 907
3 0.73 0. 16 9. 68 412. 68 35865. 0.823
4 0. 60 0. 15 9.22 412.22 34171. 0.784
5 0. 64 0.08 7. 69 410. 69 28503. 0. 654
6 0.48 0.04 6. 41 409.41 23739. 0.545
7 0.37 0.05 7. 00 410.00 25922. 0.595 ',
8 0.50 0. 03 3. 84 406.84 14215 . 0 .326
Hyd R/D Facility Tributary Reservoir POC Outflow �
Outflow Inflow Inflow Target Calc
1 0.76 0.11 ******** ******* 0.80
2 0. 19 0. 05 ******** 0.24 0.22
3 0. 16 0. 06 ******** ******* 0. 19
4 0. 15 0.05 ******** ******* 0. 17
5 0.08 0.05 ******** ******* 0.09
6 0.04 0.04 ******** ******* 0. 07
7 0.05 0.03 ******** ******* 0. 07
8 0.03 0.03 ******** ******* 0.06
Route Time Series through Faciiity
Inflow Time Series File:rdin.tsf
Outflow Time Series File:rdout
POC Time Series File:dsout
Inflow/Outflow Analysis
' Peak Inflow Discharge: 1.23 CFS at 6:00 on Jan 9 in Year 8
Peak Outflow Discharge: 0.759 CFS at 10:00 on Jan 9 in Year 8
Peak Reservoir Stage: 11. 14 Ft
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Stormwater Pollution Prevention Plan Fieldbrook Commons December 2,2013
Peak Reservoir Elev: 414. 14 Ft
Peak Reservoir Storage: 41300. Cu-Ft
. 0. 948 Ac-Ft
Add Time Series:bypass.tsf
Peak Summed Discharge: 0.796 CFS at 10:00 on Jan 9 in Year 8
Point of Compliance File:dsout.tsf
Flow Frequency Analysis
Time Series File:rdout.ts-
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flo��r Frequer_cy �na-_ysis------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) (ft) Period
0.193 2 2/09/Ol 21:00 0.759 11. 14 1 100.00 0. 9°0
0.044 7 1/07/02 4:00 0. 193 10. 90 2 25. 00 0. 9E0
0. 163 3 3/06/03 22:00 0. 163 9. 68 3 10.00 0. 900
0.034 8 8/26/04 8:00 0. 149 9.22 4 5.00 0.800
0.046 6 1/08/OS 5: 00 0. 080 7 .70 5 3.00 0. 667
0.080 5 1/19/06 5: 00 0.046 7 .00 6 2.00 0. 500
0. 149 4 11/24/06 8: 00 0.044 6.41 7 1.30 0.231
0.759 1 1/09/08 10:00 0. 034 3.84 8 1. 10 0. 0°1
Computed Peaks 0.570 11 .11 50. 00 0. 980
Flow Frequency Analys�s
Time Series File:dsout.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.224 2 2/09/O1 18:00 0. 796 1 100.00 0.990
0.072 6 1/05/02 16:00 0.224 2 25.00 0. 960
0. 187 3 3/06/03 19:00 0. 187 3 10.00 0. 900
0.063 8 8/26/04 2:00 0. 173 4 5.00 0.800
0.068 7 1/05/05 8:00 0.092 5 3.00 0. 667
0.092 5 1/19/06 3:00 0. 072 6 2.00 0.500
0. 173 4 11/24/06 6:00 0.068 7 1.30 0.231
0.796 1 1/09/08 10:00 0.063 8 1. 10 0.091
Computed Peaks 0. 605 50.00 0. 980
Flow Duration from Time Series File:rdout.tsf
Cutoff Count Frequency CDF Exceedence Probability
CFS ° ° ° -
0 0 0
0.003 29967 48.870 48.870 51. 130 0.511E+00
0. 008 7142 11.647 60.517 39. 483 0.395E+00
0. 014 5765 9.402 69. 918 30.082 0.301E+00
0.019 5642 9.201 79.119 20.881 0.209E+00
0.024 4637 7.562 86.681 13.319 0. 133E+00
0.030 3305 5.390 92.071 7 .929 0.793E-01
0.035 1812 2. 955 95. 026 4 .974 0. 497E-01
0.041 1331 2.171 97 . 197 2.803 0. 280E-01
0. 046 1230 2.006 99.203 0.797 0. 797E-02
0.052 189 0.308 99.511 0.489 0. 489E-02
0.057 18 0.029 99.540 0. 460 0. 460E-02
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Stormwater Pollution Prevention Plan Fieldbrook Commons December 2,2013 I
C. 062 14 0.023 99.503 0. 437 0. 437E-02
0. 068 6 0.010 99.573 0. 427 0. 427E-02
0 . 073 8 0.013 99.586 0.414 0. 414E-02
0 . 079 35 0.057 99.643 0.357 0. 357E-02
0 . 084 19 0.031 99.674 0.326 0.326E-02
0.090 16 0.026 99.700 0.300 0.300E-02
0.095 20 0.033 99.733 0.267 0.267E-02
0. 100 20 0.033 99.765 0.235 0.235E-02
0. 106 14 0.023 99.788 0.212 0.212E-02
0 . 111 13 0.021 99.809 0 . 191 0. 191E-02
0 , 117 8 0.013 99.822 0. 178 0. 178E-02
C. 122 7 0.011 99.834 0. 166 0. 166E-02
C . 127 9 0.015 99.848 0. 152 0. 152E-02
C. 133 11 0.018 99.866 0. 134 0. 134E-02
0 . 138 11 0.018 99.884 0.116 0. 116E-02
0 . 144 9 0.015 99.899 0. 101 O. 101E-02
0 . 149 10 0.016 99. 915 0.085 0.848E-03
0. 155 9 0.015 99. 930 0.070 0. 701E-03
0. 160 6 0.010 99. 940 0.060 0. 603E-03
0. 165 12 0.020 99.959 0. 041 0.408E-03
;��. 171 7 0.011 99.971 0.029 0.294E-03
J . 176 3 0.005 99. 976 0.024 0.245E-03
u. 182 3 0.005 99. 980 0.020 0. 196E-03
0. 187 5 0.008 99.989 0.011 0. 114E-03
0. 192 4 0.007 99. 995 0.005 0. 489E-04
F1ow Duration from Time Series File:dsout.tsf
Cutoff Count Frequency CDF Exceedence Probability
CFS ° ° ° -
0 0 �
0.003 30024 48.963 48.963 51.037 0.510E+00
0.009 7829 12.767 61.730 38.270 0.383E+00
0.016 6111 9. 966 71.696 28.304 0.283E+00
C�. 022 5669 9.245 80.941 19.059 0. 191E+00
0. 028 4718 7 . 694 88.635 11.365 0. 114E+00
0 . 035 2630 4 .289 92.924 7.076 0.708E-01
0 . 041 1780 2 . 903 95.827 4. 173 0.417E-01
0 . 047 1274 2 .078 97.904 2. 096 0.210E-01
0 . 053 749 1.221 99.126 0. 874 0.874E-02
0 . 060 158 0.258 99.384 0. 616 0. 616E-02
0 . 066 50 0.082 99.465 0.535 0.535E-02
u . 072 34 0.055 99.521 0.479 0. 479E-02
0.078 23 0.038 99.558 0.442 0. 442E-02
J.085 32 0.052 99.610 0.390 0.390E-02
��.091 29 0.047 99.658 0.342 0. 342E-02
�. 097 22 0.036 99. 693 0.307 0. 307E-02
C . 103 21 0.034 99.728 0.272 0.272E-02
C . 110 22 0.036 99.764 0.236 0.236E-02
0 . 116 14 0.023 99.786 0.214 0.214E-02
0 . 122 11 0.018 99.804 0. 196 0. 196E-02
0 . 129 11 0.018 99.822 0. 178 0. 178E-02
0 . 135 8 0.013 99.835 0.165 0.165E-02
0 . 141 7 0.011 99.847 0. 153 0. 153E-02
0. 147 13 0.021 99.868 0. 132 0. 132E-02
0 . 154 11 0.018 99. 886 0. 114 0. 114E-02
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Stormwater Pollution Prevention Plan Fieldbrook Commons December 2. 2013
0. 160 9 0.015 99.901 0. 099 0. 995E-03
0. 166 9 0.015 99.915 0.085 0.848E-03
0. 172 9 0.015 99. 930 0.070 0.701E-03
0. 179 10 0.016 99. 946 0.054 0.538E-03
0. 185 8 0.013 99. 959 0.041 0. 408E-03
0. 191 9 0.015 99.974 0.026 0.261E-03
0. 198 2 0.003 99.977 0.023 0.228E-03
r,204 3 0.005 99.982 0.018 0. 179E-03
,�.210 4 0.007 99.989 0.011 0. 114E-03
��.216 5 0.008 99. 997 0.003 0.326E-04
0.223 1 0.002 99. 998 0.002 0. 163E-04
��uration Comparison Anaylsis
Base File: predev.tsf
New File: dsout.tsf
C�i�off Units: Discharge in CrS
-----Fraction of Time Check cf Tole�ance-------
rutc=f Base New oCnange Probability Base Netia oChange
0 . 053 � 0. 95E-02 0.87E-02 -8.2 � 0.95E-02 0. 053 0.052 -1.7
U .068 � 0. 63E-02 0.52E-02 -18 .0 � 0. 63E-02 0. 068 0.059 -12 . 9 '
0 .082 � 0. 49E-02 0.41E-02 -16.8 I 0.49E-02 0.082 0.070 -14 .8
0,097 � 0. 37E-02 0.31E-02 -16. 4 � 0.37E-02 0. 097 0.087 -10 .2
u. 112 � 0. 29E-02 0.23E-02 -19. 9 I 0.29E-02 0. 112 0.101 -9. 4
0. 126 � 0. 22E-02 0. 18E-02 -�6. 9 � 0.22E-02 0. 126 0. 114 -9. 9
0. 141 � 0. 15E-02 0.15E-02 3.3 I 0.15E-02 0. 141 0. 142 0. 8
0. 155 � O. 10E-02 0.11E-02 8 . 1 � O.10E-02 0. 155 0. 159 2 . 6
0. 170 � 0. 62E-03 0.75E-03 21 . 1 � 0.62E-03 0. 170 0. 175 3.2
0. 184 � 0.34E-03 0.41E-03 19.0 � 0.34E-03 0. 184 0 . 188 1.7
0. 199 � 0.23E-03 0.21E-03 -7. 1 � 0.23E-03 0. 199 0. 198 -0.7
��; . 214 � 0. 16E-03 0.65E-04 -60.0 I 0.16E-03 0.214 0.205 -4 . 1
U .228 � 0. 11E-03 O.00E+00 -100.0 � 0.11E-03 0.228 0.210 -7 .8
C .243 � 0. 16E-04 O.00E+00 -100.0 � 0.16E-04 0.243 0.224 -7 . 9
I1a:�,_mum positive excursion = 0.008 cf s ( 4. 9 0)
o��curring at 0. 158 cfs on the Base Data:predev.tsf
a�id at 0. 166 cfs on the New Data:dsout.tsf
:::ximum negative excursion = 0.011 cTs (-15. 3%)
cccurring at 0.074 cfs on the Base Data:predev.tsf
and at 0 . 06? cfs o_� �he tde��i ^ata:dsoat.tsf
���2013 D. R. STRONG Consulting Engineers Inc. Page 47 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
I�c<�:�a-ri�F,�y<r�.:�-KCFrs . . _-'�� ns+�� r ���<>s �� ��'.'. ' -<'e:����� ,..-_�..- l�o'[�.I�.r3..�
Retum Pariod �
2 5 10 20 5� 100 �'
c r�ut.pks in Sea-T�c �
• dsc�dpks '
� prW-:pKs �
R � �
p � 4
10� o
N � _
•
V � 00
m o
A
r
O
10�
1 O-3
1 2 5 70 20 30 40 50 60 70 80 90 95 98 99
Cumulative Proba6iliry
Peaks Plot
�j v.�:�e n�,ana�a�-0y,�,-Rcars 3, ,_,_. � ;.,.•+w' .,. s. d.." ,j. � .�I C'I.tsJ
a _ _
N
O O'_- ,
f�OLld�Jf :
dsouLdur .�
�^__`._� ��I�JE�.G'Uf �
H p� l.
O �
c' R � ��a♦
�- ��h ?
i
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o �
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LL
v �`''�
a � `\�
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u
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0
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0
0
o� '—��''—�—�
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o �
_�A�
a
0
i o o � � �
�� � ,
70-5 10j 10-� 10�� 30-� I . I 10°
Prab2tifty Erce2dence
Duration Curve �
�;2013 D. R. STRONG Consulting Engineers Inc. Page 48 of 56
Storm�^!ater Pollution Prevention Plan Fieidbrook Commons Dec2mber 2, 2013
TDA East
Retention/Detention Facility
Type of Facility: Ce��en�io:z �,%ault
Facility Length: 68 . 50 it
Facility Width: 68. 00 ft
Facility Area: 4658 . scr. _�
Effective Storage Depth: 8. 50 ft
Stage 0 Elevation: 415. 00 ft
Storage Volume: 39593. cu. ft
Riser Head: 8.50 ft
Riser Diameter: 12.00 inches
Number of orifices: 2
Full Head Fip�
Orifice # Height Diameter Discharge DidITte�a�
(ft) (in) (CFS) (ini
1 0.00 0.87 0.060
2 5.50 1. 60 0. 120 4 . J
Top Notch Weir: None
Outflow Rating Curve: None
Stage Elevation S�o��ce Disc�ar�e Percolaticr
(ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs}
0. 00 415.00 0. 0.000 0.000 0.00
0.01 415.01 47. 0.001 0.002 0.00
0.02 415.02 93. 0.002 0.003 0.00
0.03 415.03 140. 0.003 0.003 0. 00
0. 04 415.04 186. 0.004 0. 004 0. 00
0.05 415.05 233. 0.005 0. 005 0. 00
0.06 415.06 280. 0.006 0.005 0. 00
0.07 415.07 326. 0.007 0.006 0.00
0.22 415.22 1025. 0.024 0.010 0.00
0.36 415.36 1677. 0.038 0.012 0.00
0.50 415.50 2329. 0.053 0.015 0.00
0. 65 415. 65 3028. 0.070 0.017 0.00
0.79 415.79 3680. 0.084 0.018 0.00
0. 94 415. 94 4379. 0. 101 0.020 0. 00
1.08 416.08 5031. 0. 115 0. 021 0. 00
1.23 416.23 5729. 0.132 0. 023 0. 00
1.37 416.37 6382. 0. 146 0. 024 0. 00
1.51 416.51 7034. 0. 161 0.025 0.00
1. 66 416. 66 7732. 0. 178 0.026 0.00
1. 80 416.80 8384. 0. 192 0.028 0.00
1. 95 416.95 9083. 0.209 0.029 0.00
2. 09 417.09 9735. 0.223 0.030 0. 00
2 .23 417.23 10387. 0.238 0.031 0. 00
2 . 38 417.38 11086. 0.255 0.032 0. 00
2 . 52 417.52 11738. 0.269 0.033 0. 00
2. 67 417. 67 12937. 0.286 0. 034 0. 00
2.81 417 .81 13089. 0.300 0.034 0. 00
2. 95 417 . 95 13741. 0.315 0.035 0. 00
3. 10 418 . 10 14440. 0.331 0.036 0.00
3.24 418 .24 15092. 0.346 0.037 0.00
3.39 418 .39 15791. 0.363 0.038 0. 00
3.53 418.53 16443. 0. 377 0.039 0. 00
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Stormwater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
3 . 67 418 . 67 17095. 0.392 0. 039 0.00
3 . 82 418.82 17794. 0.408 0.040 0.00
3 . 96 418.96 18446. 0.423 0.041 0.00
4 . 11 419.11 19144. 0.439 0.042 0.00
4 .25 419.25 19797 . 0. 454 0.042 0. 00
4 .39 419.39 20449. 0. 469 0.043 0.00
4 . 54 419.54 21147. 0. 485 0.044 0.00
4 . 68 419. 68 21799. 0.500 0. 044 0.00
4 . 83 419.83 22498. 0.516 0. 045 0. 00
4 . 97 419.97 23150. 0.531 0. 046 0. 00
5. 11 420.11 23802. 0.546 0. 046 0.00
5. 26 420.26 24501. 0.562 0. 047 0.00
5. 40 420.40 25153. 0.577 0.048 0.00
� . 50 420.50 25619. 0 .588 0.048 0.00
� . 52 420.52 25712. 0 .590 0.049 0.00
5 .53 420.53 25759. 0.591 0.050 0.00
5 . 55 420.55 25852. 0.593 0.053 0.00
5 . 57 420.57 25945. 0.596 0.057 0.00
5 . 58 420.58 25992 . 0.597 0. 062 0.00
5 . 60 420. 60 26085. 0.599 0.067 0.00
5. 62 420. 62 26178. 0. 601 0. 072 0.00
5. 63 420. 63 26225. 0. 602 0. 074 0. 00
5.78 420.78 26923 . 0. 618 0. 086 0.00
5. 92 420. 92 27575. 0. 633 0. 095 0.00
6. 07 421.07 28274. 0. 649 0.103 0.00
6.21 421.21 28926. 0. 664 0.110 0.00
6. 35 421.35 29578. 0.679 0. 116 0. 00
6. 50 421.50 30277. 0.695 0. 122 0.00
6. 64 421. 64 30929. 0.710 0. 127 0.00
6. 79 421.79 31628. 0.726 0. 132 0.00
0. 93 421. 93 32280. 0.741 0. 137 0. 00
7 . 07 422 .07 32932 . 0.756 0. 142 0. 00
i .22 422.22 33631. 0.772 0. 146 0. 00
7 .36 422.36 34283. 0.787 0. 150 0. 00
7 .51 422 .51 34982. 0. 803 0. 155 0. 00
7 . 65 422 . 05 35634. 0. 818 0. 159 0.00
"? .79 422.79 36286. 0. 833 0. 162 0. 00
�% . 94 422. 94 36985. 0. 849 0. 166 0.00
8 .08 423.08 37637. 0.864 0. 170 0.00
8.23 423.23 38335. 0.880 0. 174 0. 00
R . 37 423.37 38987. 0.895 0. 177 0. 00
? . 50 423.50 39593. 0. 909 0. 180 0. 00
� . 60 423.60 40059. 0. 920 0. 490 0. 00
� .70 423.70 40525. 0. 930 1. 060 0. 00
� .80 423.80 40990. 0. 941 1. 790 0. 00
8 . 90 423. 90 41456. 0. 952 2 . 580 0. 00
G. 00 424 .00 41922. 0. 962 2. 870 0. 00
9. 10 424 .10 42388. 0. 973 3. 120 0. 00
� .20 424.20 42854. 0. 984 3.360 0.00
9.30 424.30 43319. 0. 994 3.580 0.00 �
9. 40 424.40 43785. 1.005 3.790 0. 00
9.50 424.50 44251. 1.016 3. 980 0.00
9. 60 424.60 44717. 1.027 4. 170 0.00
9.70 424 .70 45183. 1 .037 4 . 350 0. 00
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Stormwater Pollution Prevention Plan Fieldbrook Commons December 2,2013
9. 80 424 .80 45648. 1.0�8 4 .520 0.00
9. 90 424. 90 46114. 1.059 4 .690 0.00
10. 00 425.00 46580. 1.069 4 .840 0. 00
10. 10 425.10 47046. 1.080 5.000 0. 00
10.20 425.20 47512. 1.091 5. 150 0. 00
10.30 425 .30 47977. 1. 101 5 .290 0. 00
10. 40 425 . 40 48443. 1. 112 � . 430 0. 00
Hyd Inflow Outflo:a Peak Storage
Stage Elev (Cu-Ft) (Ac-Ft)
1 1.24 0.79 8. 65 423. 65 40303. 0. 925
2 0. 60 0.22 8. 51 423. 51 39652. 0. 910
3 0. 73 0. 15 7.37 422 . 37 34337. 0.788
4 0. 74 0. 15 7.22 422 .22 33609. 0.772
5 0. 64 0. 10 5. 96 420.96 27785. 0. 638
6 0.40 0.05 5. 45 420.45 25371. 0.582
7 0. 48 0.05 4.84 419.84 22532. 0.517
8 0.51 0.04 3.02 418.02 14077. 0.323
�yd R/D Facility Tributary Reservoir POC Outflow
Outflow Inflow Inflow Target Calc
1 0.79 0.02 ******** ******* 0.80
2 0.22 0.01 ******** 0.23 0.23
3 0. 15 0.01 ******** ******* 0. 15
4 0. 15 0.01 ******** ******* 0. 15
5 0. 10 0.01 ******** ******* 0. 10
6 0.05 0.00 ******** ******* 0.05
7 0. 05 0. 00 ******** ******* 0 . 05
8 0. 04 G, 00 ***x**x* �**>T** 0 . 04
Route Time Series through Facility
Inilow Time Series File:rdin.tsf
�utilcw Time Series File:rdout
PvC Time Series File:dsout
-r:floNr/Outflow Analysis
Peak Inflow Discharge: 1.24 CFS at 6:00 on Jan 9 in Year 8
Peak Outflow Discharge: 0.789 CFS at 10:00 on Jan 9 in Year 8
Peak Reservoir Stage: 8 . 65 Ft
Peak Reservoir Elev: 423 . 65 Ft
�=ea{ Reservoir Stcrage: 40303 . Cu-Ft
. 0. 925 Ac-Ft
Add Time Series:bypass.tsf
Peak Summed Discharge: 0.795 CFS at 10:00 on Jan 9 in Year 8
Pcint of Compliance File:dsout.tsf
Flow Frequency Analysis
iime Series File:rdout.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
�low Rate Rank Time of Peak - - Peaks - - Rank Return Prob
l,CFS} (CFS) (ft) Period
<�2013 D. R.STRONG Consulting Engineers Inc. Page 51 of 56
Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
0.220 2 2/09/O1 20: 00 0.789 8. 65 1 100. 00 0. 990
0.045 7 1/07/02 4:00 0.220 8.51 2 25.00 0. 960
0. 150 3 3/06/03 22:00 0. 150 7.37 3 10. 00 0. 900
0. 035 8 8/26/04 8:00 0.146 7.22 4 5. 00 0. 800
0 . 048 6 1/08/05 5:00 0.097 5. 96 5 3. 00 0. 667
0. 097 5 1/19/06 1:00 0. 048 5.45 6 2 . 00 0.500
0. 146 4 11/24/06 8:00 0.045 4.84 7 1. 30 0.231
0.789 1 1/09/08 10:00 0.035 3.02 8 1. 10 0.091
Computed Peaks 0.599 8. 62 50.00 0. 980
Floca Frequency Analysis
Time Series File:dsout.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS} Period
0.226 2 2/09/01 20:00 0. 795 1 100. 00 0.990
0.047 7 1/07/02 0:00 0.226 2 25. 00 0. 960
0. 155 3 3/06/03 22:00 0. 155 3 10.00 0. 900
0.036 8 8/26/04 6:00 0. 151 4 5.00 0.800
0.050 6 1/08/05 1:00 0. 102 5 3. 00 0. 667
0. 102 5 1/19/06 2:00 0. 050 6 2.00 0.500
0. 151 4 11/24/06 8:00 0. 047 7 1.30 0.231
0.795 1 1/09/08 10:00 0. 036 8 1. 10 0.091
Ccm.�uted Peaks 0. 605 50.00 0. 980
Flow Duration from Time Series File:rdout. tsf
Cutoff Count Frequency CDF Exceedence Probability
CFS ° ° °
o a o
0 . 003 31933 52.076 52.076 47. 924 0. 479E+00
0 . 009 6451 10.520 62.596 37.404 0.374E+00
0 . 016 6318 10.303 72 . 900 27 .100 0.271E+00
0 .022 6026 9.827 82 .727 17.273 0. 173E+00
0.028 4268 6.960 89. 687 10.313 0. 103E+00
0. 034 2439 3. 977 93. 664 6.336 0. 634E-01
0. 040 1920 3.131 96.796 3.205 0. 320E-01
0. 046 1370 2 .234 99.030 0. 970 0. 970E-02
G. 052 258 0.421 99.450 0.550 0. 550E-02
��.059 14 0.023 99.473 0.527 0. 527E-02
��.065 12 0.020 99.493 0.547 0. 507E-02
;;�. 071 8 0.013 99.506 0. 494 0. 494E-02
C%. 077 27 0.094 99.550 0.450 0. 450E-02
C . 083 35 0.057 99. 607 0.393 0.393E-02
C . 089 28 0.046 99.653 0.347 0. 347E-02
0 . 096 34 0.055 99.708 0.292 0.292E-02
0 . 102 23 0.038 99.746 0.254 0.254E-02
0 . 108 20 0.033 99.778 0.222 0.222E-02
0 . 114 18 0.029 99.808 0. 192 0. 192E-02
0. 120 11 0.018 99.826 0. 174 0. 174E-02
0. 126 15 0.024 99.850 0. 150 0. 150E-02
0. 132 13 0.021 99.871 0. 129 0. 129E-02
0. 139 12 0.020 99.891 0. 109 0. 109E-02
0. 145 16 0.026 99.917 0.083 0. 832E-03
Q . 151 16 0.025 99. 943 0.057 0. 571E-03
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Stormwater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
0. 157 5 0.008 99. 951 0.049 0. 489E-03
0. 163 13 0.021 99. 972 0.028 0.277E-03
0.169 4 0.007 99.979 0.021 0.212E-03
0. 176 6 0.010 99.989 0.011 0. 114E-03
0. 182 5 0.008 99.997 0.003 0. 326E-04
0. 188 0 0.000 99.997 0.003 0.326E-04
0. 194 1 0.002 99.998 0. 002 0.163E-04
0.200 0 0.000 99.998 0. 002 0.163E-04
0.206 0 0.000 99.998 0.002 0. 163E-04
0.213 0 0.000 99. 998 0.002 0. 163E-04
0.219 0 0.000 99. 998 0.002 0. 163E-04
Flow Duration from Tirne Series File:dsout.tsf
Cutoff Count Frequency CDF Exceedence Probab-l-t�;
CFS ° ° ° -
s o a
0.003 32010 52.202 52.202 47 .798 0. 478E+00
0.010 6496 10.594 62.795 37 .205 0.372E+00
0.016 6438 10.499 73.294 26.706 0.267E+00
0.022 5973 9.741 83.035 16. 965 0. 170E+00
0.029 4312 7. 032 90.067 9.933 0. 993E-C1
0.035 2455 4 . 004 94 .070 5.930 0.593E-C1
0.041 1705 2.780 96.851 3. 149 0.315E-01
0.048 1308 2.133 98 . 984 1.016 0. 102E-01
0.054 280 0.457 99.441 0.559 0. 559E-02
0.060 20 0.033 99.473 0.527 0.527E-02
0.067 11 0.018 99.491 0.509 0.509E-02
0.073 11 0.018 99.509 0. 491 0.491E-02
0.079 25 0.041 99.550 0. 450 0.450E-02
0.086 35 0.057 99.607 0.393 0.393E-02
0.092 27 0. 044 99. 651 0.349 0.349E-02
0. 098 32 0. 052 99.703 0.297 0.297E-02
0. 105 26 0.042 99.746 0.254 0.254E-02
0.111 20 0.033 99.778 0.222 0.222E-02
0.117 18 0.029 99.808 0.192 0. 192E-02
0.124 13 0.021 99.829 0.171 0. 171E-02
0. 130 12 0.020 99.848 0. 152 0. 152E-02
0. 137 15 0.024 99.873 0. 127 0. 127E-02
0. 143 13 0.021 99.894 0. 106 0. 106E-02
0. 149 14 0.023 99.917 0.083 0.832E-03
0.156 16 0. 026 99.943 0.057 0.571E-03
0.162 5 0. 008 99. 951 0.049 0.489E-03
0. 168 12 0. 020 99. 971 0.029 0.294E-03
0.175 5 0.008 99. 979 0.021 0.212E-03
0. 181 4 0.007 99. 985 0.015 0. 147E-03
0. 187 7 0.011 99. 997 0.003 0.326E-��=
0. 194 0 0.000 99. 997 0.003 0.326E-C�:
0.200 1 0.002 99. 998 0.002 0. 163E-U4
0.206 0 0.000 99. 998 0.002 0. 163E-04
0.213 0 0.000 99. 998 0.002 0. 163E-0=�
0.219 0 0. 000 99. 9°8 0.002 0. 163E-04
0.225 0 0. 000 �9. �9� :; . 002 �. _63�-0�'_
Duration Comparison Ana�•;lsis
Base File: predev.tsf
Neti,? File: dsout.tsf
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Storm�vater Pollution Prevention Plan Fieldbrook Commons December 2,2013
. , +
Cutoff Units : Discharge in CFS
-----Fraction of Time----- ---------Check of Tolerance-------
Cutoff Base New oChange Probability Base New oChange
0 .050 � 0. 94E-02 0. 61E-02 -34 . 9 � 0. 94E-02 0. 050 0.048 -3 . 6
0.063 I 0. 63E-02 0.52E-02 -17. 1 � 0. 63E-02 0. 063 0.050 -21. 5
0.077 � 0. 49E-02 0.47E-02 -3.7 � 0.49E-02 0. 077 0.073 -4 . 4
0 .090 � 0. 37E-02 0.36E-02 -1.8 � 0.37E-02 0.090 0.089 -1.2
0. 104 � 0.28E-02 0.26E-02 -8 .0 � 0.28E-02 0. 104 0. 100 -3. 4
0. 117 � 0.22E-02 0.19E-02 -12.5 � 0.22E-02 0. 117 0. 111 -5. 4
0 . 131 � 0. 15E-02 0. 15E-02 -2 .2 � 0. 15E-02 0. 131 0. 131 -0. 2
0 . 144 � O. 10E-02 0. 10E-02 1. 6 � 0.10E-02 0. 144 0. 145 0. 4
0 . 158 � 0. 62E-03 0.55E-03 -10.5 � 0. 62E-03 0. 158 0. 154 -2 . 1
0 . 171 � 0.34E-03 0.26E-03 -23. 8 � 0.34E-03 0. 171 0.166 -3.2
n . 185 � 0.23E-03 0.65E-04 -71 . 4 � 0.23E-03 0. 185 0.174 -6. 1
0. 198 � 0. 16E-03 0. 16E-04 -90.0 I 0. 16E-03 0.198 0. 179 -9.8
J .212 � 0. 98E-04 0.16E-04 -83.3 � 0. 98E-04 0.212 0.184 -13.3
;�� .225 � 0 . 16E-04 0.16E-04 0.0 � 0. 16E-04 0.225 0.226 0. 4
'�Iaximum positive excursion = 0.003 cfs ( 1.50)
�ccurring at 0.223 cfs on the Base Data:predev.tsf
and at 0.226 cfs on the New Data:dsout.tsf
P�iaximum negative excursion = 0. 016 cfs (-24 . 10)
occurring at 0. 068 cfs on the Base Data:predev.tsf
and at 0.052 cfs on the New Data:dsout.tsf
�Ceu;M-F'.owirt3uer�y-KCAiS Io',OO II �
Retum Period
2 5 10 20 50 700
o rCaB.pksinSea-Tac �
• dsout.pks
^ predev.pks
0
R �
� � w
10-� �
y c
LL GO
V s E
m �
, m
`m
L
�
� tO-2
I C
103
7 2 5 70 2� 30 d0 50 60 70 &0 90 95 98 99
Cumufeti�re Probatti�ty
Peaks Plot
�2013 D. R.STRONG Consulting Engineers Inc. Page 54 of 56
Storm�r�ater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
��?erd-ou�a�io�Ana�f'--KcaTs .� :3
I N -___
O
-� rda�d_d�r c
dsaitd�r a,
� °`1�, 1�r�2idur �
,-'�—v
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o `__�c� ��
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u> ! �,y
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o �
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i i �
]0-� 70-d 10-3 70-2 10-' 1p°
Probab:lity E:<cesderca
Duration Curve
�
.�,2013 D. R. STRONG Consul:ing Engineers Inc. Page 55 of 56
Stormvdater Pollution Prevention Plan Fieldbrook Commons December 2, 2013
�
WATER QUALITY TREATMENT SYSTEM
The Project is located in the Enhanced Water Quality Treatment area. A wetvauit
followed by a Stormfilter media filtration system will be utilized for each TDA.
�
TDA West �
A 96" Stormfilter manhole will be installed downstream of the detention facility with 11 I
ZPG cartridges. �
TDA East
A 72" Stormfilter manhole will be installed downstream of the detention facility with 7 �
ZPG cartridges.
�
�
�I
�
���2013 D. R. STRONG Consulting Engineers Inc. Page 56 of 56
StormvJater Pollution Prevention Plan Fieldbroo'�c Commons December 2, 2013