Stormwater Pollution Prevention PlanL
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STORM WATER POLLUTION
PREVENTION PLAN
Prepared for:
TAHOMA TERRA
Tahoma Terra, LLC
P.O. Box 627
Rainier, WA 98576
(3f 0) 448-3083
KPFF Consulting Engineers
4200 Sixth A~~~nue SE, Suite 309
Lacey, WA 98503
(360) 292-7230
July 16, 2006
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~ Tahoma Terra LLC
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Stormwater Pollution Prevention Plan
For
Tahoma Terra
Prepared For
Tahoma Terra LLC
PO Box 627
Rainier, WA 98576
360-446-3083
Developer Operator/Contractor
Tahoma Terra LLC Tahoma Terra LLC
Project Site Location
City of Yelm, Thurston County, WA
Certified Erosion and Sediment Control Lead
Tony Bloom
SWPPP Prepared By
KPFF Consulting Engineers
SWPPP Preparation Date
July 2006
Approximate Project Construction Dates
07/2006-09/2008
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~ Contents
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U 1.0 Introduction ...............................................................................................................................1
~ 2.0 Site Description ........................................................................................................................3
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2.1 Existing Conditions ...........................................................................................................3
~ 2.2 Proposed Construction Activities ......................................................................................4
3.0 Construction Stormwater BMPs
...............................................................................................7
r1~ 3.1 The 12 BMP Elements .......................................................................................................7
~ 3.1.1 Element #1 -Mark Clearing Limits ................................................................7
3.1.2 Element #2 -Establish Construction Access .............................:.....................7
r1 3.1.3 Element #3 -Control Flow Rates ....................................................................8
~J 3.1.4 Element #4 -Install Sediment Controls ..........................................................8
3.1.5 Element #5 -Stabilize Soils ..........................................................................10
3.1.6 Element #6 -Protect Slopes ......................................................................... 11
3.1.7 Element #7 -Protect Drain Inlets ..................................................................11
3.1.8 Element #8 -Stabilize Channels and Outlets ................................................12
~ 3.1.9 Element #9 -Control Pollutants ....................................................................12
v 3.1.10 Element #10 -Control Dewatering ...............................................................14
3.1.11 Element #11 -Maintain BMPs ......................................................................15
~ 3.1.12 Element #12 -Manage the Project ............15
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3.2 Site Specific BMPs ..........................................................................................................18
3.3 Additional Advanced BMPs ............................................................................................18
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4.0 Construction Phasing and BMP Implementation ...................................................................19
~ 5.0 Pollution Prevention Team ......................................................................................................21
U 5.1 Roles and Responsibilities ...............................................................................................21
5.2 Team Members ................................................................................................................21
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~ 6.0 Site Inspections and Monitoring .............................................................................................23
6.1 Site Inspection ......................................................................................::.........................23
~ 6.1.1 Site Ins ection Fre uenc
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~ 6.1.2 Site Inspection Documentation ......................................................................24
6.2 Stormwater Quality Monitoring ......................................................................................24
~ 6.2.1 Turbidity _
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rl 7.0 Reporting and Recordkeeping ................................................................................................27
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~--~ 7.1 Recordkee in
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r--1 7.1.1 Site Log Book ................................................................................................27
' 7.1.2 Records Retention ................. ...................................27
7.1.3 Access to Plans and Records ..........................................................................27
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~ 7.1.4 Updating the SWPPP .....................................................................................28
7.2 Reporting .........................................................................................................................28
n 7.2.1 Discharge Monitoring Reports .......................................................................28
7.2.2 Notification of Noncompliance ......................................................................28
7.2.3 Permit Application and Changes ...................................................................28
Appendix A -Site Plans .........................................................................................................33
Appendix B -Construction BMPs .........................................................................................35
r-~ Appendix C -Alternative BMPs ............................................................................................36
~ Appendix D -General Permit ................................................................................................39
Appendix E -Site Inspection Forms (and Site Log) ..............................................................40
Appendix F -Engineering Calculations .................................................................................49
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Appendix A Site plans ,
r-1 ^ Vicinity map
^ 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
r1 ^ List of BMPs not selected, but can be referenced if needed in each of the 12 elements
~j Appendix D General Permit
Appendix E Site Log and Inspection Forms
'-! Appendix F Engineering Calculations (if necessary)
U Flows, ponds, etc...
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Tahoma Terra Stormwater Pollution Prevention Plan
1.0 Int--------- -------- - ------------
roduchon
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This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the
NPDES stormwater permit requirements for the Tahoma Terra development project in
Yelm, Washington. The site is located on the west side of Yelm, near the Nisqualty Palley Golf
Course and in an area known as the Southwest Yelm Annexation Area. The existing site was
~ a dairy farm and consists majorly of grazed pasture. The proposed development will consist
~ of 544 single family residential lots, a neighborhood commercial center with estimated
100,000 sf of floor area, multifamily area with about 226 townhouses/condominiums units,
additional multifamily area with 18 unit and a network of open space/recreation
improvements, associated stormwater detention retention facilities, and landscaping.
~ Construction activities will include grading, excavation, services/utilities installation and
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Tahoma Blvd extension. The purpose of this SWPPP is to describe the proposed
n 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
n objectives of the SWPPP are to:
u 1. Implement Best Management Practices (BMPs) to prevent erosion
r~ and sedimentation, and to identify, reduce, eliminate or prevent
stormwater contamination and water pollution from construction
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activity.
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U 2. Prevent violations of surface water quality, ground water quality, or
sediment management standards.
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u 3. Prevent, during the construction phase, adverse water quality impacts
including impacts on beneficial uses of the receiving water by
n controlling peak flow rates and volumes of stormwater runoff at the
u Permittee's outfalls and downstream of the outfalls.
This SWPPP was prepared using the Ecology SWPPP Template downloaded from the
~J 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). The report is divided into seven main sections with
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the each of the main sections are:
presented in
Section 1 -INTRODUCTION. This section provides a summary
description of the project, and the organization of the SWPPP document.
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Tahoma Terra Stormwater Pollution Prevention Plan
~ ' Section 2 -SITE DESCRIPTION. This section provides a detailed
n description of the existing site conditions, proposed construction activities,
e and calculated stormwater flow rates for existing conditions and post-
construction conditions.
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~ ° 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.
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^ Section 4 -CONSTRUCTION PHASING AND BMP
n IMPLEMENTATION. This section provides a description of the timing
U of the BMP implementation in relation to the project schedule.
~`! Section 5 -POLLUTION PREVENTION TEAM. This section identifies
~1 the appropriate contact names (emergency and non-emergency),
monitoring personnel, and the onsite temporary erosion and sedimentation
`~ control inspector
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' Section 6 -INSPECTION AND MONITORING. This section provides a
n description of the inspection and monitoring requirements such as the
v parameters of concern to be monitored, sample locations, sample
frequencies, and sampling methods for all stormwater discharge locations
n from the site.
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n Section 7 - RECORDKEEPING. This section describes the requirements
for documentation of the BMP implementation, site inspections,
u 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:
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Appendix A
Appendix B
~ Appendix C
~ Appendix D
Appendix E
~ Appendix F
Site plans
Construction BMPs
Alternative Construction BMP list
General Permit
Site Log and Inspection Forms
Engineering Calculations
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2.0 Site Description
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r,f 2.1 Existing Conditions
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~-~, The proposed site is located in the western portion of the City of Yelm, Thurston County,
- Washington. A site vicinity map and coordinates are provided in Appendix A. The site is 180
~ acres in size and is currently unoccupied. The site is bisected by Thompson Creek. The site
~ topography east of Thompson Creek is relatively flat with no distinguishing features. Site
u topography west of Thompson Creek generally consists of gently slopping, rolling terrain over
the central portion of the site. Steep slopes lie immediately west of Thompson Creek except in
r-7 the central part of it. Moderately steep to steep slopes occupy the southern fringes of the site, and
slopping terrain is characteristic of the northern fringes of the site. Site vegetation consists of
uncropped pasture grasses. On-site soils are generally well drained and formed in glacial
n outwash. On-site soils consist of a combination of Nisqually loamy fine sand, Everett gravelly
v sandy loam, Yelm fine sandy loam and Mukilteo muck (drained). Slow ground water seepage
was encountered in three of the test pits at depth below 40 feet.
LJ Runoff from the site generally contains and infiltrates to groundwater within the site, and no
significant off-site drainage was observed. It was determined that there is a single linear wetland
on the site that starts in the south end of the property and extends along both sides of the creek to
~.J the main entry road that connects the east pasture to the west pasture and via a bridge across
Thompson Creek. The delineated wetland buffer will remain undisturbed. Thompson Creek is
not listed as a polluted water of the state under the State's Clean Water Act Section 303(d) list
and most likely to be considered Type 4 stream. There is no evidence of unstable soils anywhere
on-site.
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Tahoma Terra Stormwater Pollution Prevention Plan
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Tahoma Terra Stormwater Pollution Prevention Plan
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2.2 Proposed Construction Activities
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n The proposal is to grade 180 acres for future 544-lot single-family residential subdivision, a
neighborhood commercial center with estimated 100,000 sf of gross floor area, a 226-unit
townhouse/condominium community, a separate 18-unit townhouse community adjacent to golf
~} course, network of open space/recreational improvements and associated landscaping, and to
extend Tahoma Blvd.
~ Construction activities will include TESC installation, site wide grading, excavation for drainage
i...l facilities, street base construction, construction of Tahoma Blvd extension with Thompson Creek
crossing culverts replacement, extension of underground utilities including water and sanitary
sewer with associated trench excavation. The schedule and phasing of BMPs during construction
U is provided in Section 4.0. Each completed phase will be stabilized prior to beginning of
construction activities on each next phase. The only impervious surface constructed during this
n project will be extension of Tahoma Blvd, which will add about 5 acres of impervious surface
U for site with 180 acres of total area.
~ A wetpond and an infiltration pond will be constructed south of Tahoma Blvd and will handle
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runoff from residential subdivision's part located north of Tahoma Blvd along with major part of
proposed Tahoma Blvd extension itself. This runoff will be intercepted by street side catch
basins and conveyed into above described ponds through a system of storm pipes. After
completion of grading for future townhouse/condominium community another wetpond, located
in that area will be build, which will handle runoff from entire future residential subdivision,
multi-family area and Tahoma Blvd as well.
~ Stormwater runoff volumes were calculated using the Stormshed modeling software. The
~ sedimentation traps that will be used during construction were designed using the 2-year storm
event. These traps will be used as an additional safety margin to other proposed BMPs to reduce
r-~ chances of unlikely release to Thompson Creek and adjacent wetland. The only on-site area,
u{ which able potentially generate appreciative runoff during construction due to the relatively
shallow till layer is located in the NW quadrant of the project site and is surrounded by highly ••
permeable soils (characteristic of majority of on-site soils), which would by itself effectively
~~ preclude runoff from leaving the site during construction.
n All stormwater flow calculations are provided in Appendix F.
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Tahoma Terra Stormwater Pollution Prevention Plan
The following summarizes details regarding site areas:
° Total site area: 180 acres
° Percent impervious area before construction: 1 %
° Percent impervious area after construction: 2.7
° Disturbed area during construction: 138 acres
° Disturbed area that is characterized as impervious (i
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access roads, staging, parking):
5 acres
° 2-year Stormwater runoff peak flow prior to construction
(existing): 6.50 cfs
° 10-year Stormwater runoff peak flow prior to construction
(existing): 19.02 cfs
° 2-year stormwater runoff peak flow during construction: 13.75 cfs
° 10-year Stormwater runoff peak flow during construction: 29.29 cfs
° 2-year Stormwater runoff peak flow after construction: 7.25 cfs
° 10-year Stormwater runoff peak flow after construction: 20.14 cfs
All Stormwater flow calculations are provided in Appendix F.
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Tahoma Terra Stormwater Pollution Prevention Plan
3.0 Construction Stormwater BMPs
r-, 3.1 The 12 BMP Elements
~ 3.1.1 Element #1-Mark Clearing Limits
n 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
n field and on the plans. In general, natural vegetation and native topsoil shall be retained in an
~j undisturbed state to the maximum extent possible. The BMPs relevant to marking the clearing
limits that will be applied for this project include:
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v Preserving Natural Vegetation (BMP C101)
'~ Buffer Zones (BMP C 102)
High Visibility Plastic or Metal Fence (BMP C103) or
v Stake and Wire Fence (BMP C 104)
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 relat_ecLt~e~tablishiiig_constr_uction-access--thaz~vll-be used oir~hs-prajee
include:
Stabilized Construction Entrance BMP C 105
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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 ineffective or inappropriate
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Tahoma Terra Stormwater Pollution Prevention Plan
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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
u failing.
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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:
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~ Sediment Trap (BMP C240)
n Five sediments traps will be used in an area to be graded west of Thompson Creek. The sediment
v traps were sized for 2-year storm event based on 2,080 sf of surface per 1 cfs of flow. Each
sediment trap will serve drainage basin 3 ac or less in size.
v Temporary Sediment Pond (BMP C241)
A single temporary sediment pond will be used during construction in proposed commercial
~i center area east of Thompson Creek.
`~ Alternate flow control BMPs are included in Appendix C as a quick reference tool for the onsite
~ The project site is located west of the Cascade Mountain Crest. As such, the project must
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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
*~ m~vate~diseharge-requirements-(e.-g: disclrarg~to~ombine sewer sys ems .
inspector in the event the BMPs) 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.
~ 3.1.4 Element #4 -Install Sediment Controls
'~ All Stormwater runoff from disturbed areas shall pass through an appropriate sediment removal
J 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:
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Tahoma Terra Stormwater Pollution Prevention Plan
Silt Fence (BMP C233)
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Sediment Trap (BMP C240)
Storm Drain Inlet Protection (BMP C220).
Alternate sediment control BMPs are included in Appendix C as a quick reference tool for the
onsite inspector in the event the BMPs) 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-~ip~ sediment c~ntr~t~ a~~e4uiredto_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
L! maximized to reduce the need for end-of-pipe sedimentation controls.
^ Temporary Sediment Pond (BMP C241)
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Tahoma Terra Stormwater Pollution Prevention Plan
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The single temporarily sediment pond will be used during grading stage in future
~ commercial area east of Thompson Creek. It was sized for 2-year event.
~r 3.1.5 Element #5 -Stabilize Soils
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`~ 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)
Mulching (BMP C121)
~ Plastic Covering (BMP C123)
Surface Roughening (BMP C130)
Dust Control (BMP C 140)
~ Early application of gravel base on areas to be paved
Materials on Hand (BMP C150) may also be applicable.
Alternate soil stabilization BMPs are included in Appendix C as a quick reference tool for the
onsite inspector in the event the BMPs) 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 Apri130). 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
~°~asts-ln-general; eut-acrd 'Ir s a i ize as soon as posse e an soi stockpiles
,--t 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.
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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:
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Temporary and Permanent Seeding (BMP C120)
,--i Surface Roughening (BMP C130))
Interceptor Dike and Swale (BMP C200)
u Check Dams (BMP C207)
~ Materials on Hand (BMP C 150)
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~ Alternate slope protection BMPs are included in Appendix C as a quick reference tool for the
~( onsite inspector in the event the BMPs) 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
~l 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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~ 3.1.7 Element #7 -Protect Drain Inlets
~ There are no storm drain inlets near the site that could potentially receive surface runoff from the
L( construction site, except inlets on existing part of Tahoma Blvd, which will be protected with
catch basin filters for duration of construction activities.
~ 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
u 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 nroiect:
`~ Drop Inlet Protection
L( • Excavated Drop Inlet Protection
• Catch Basin Filters
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,~ Culvert Inlet Protection
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• Culvert Inlet Sediment Trap
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
,J Control Lead shall implement one or more of the alternative BMP inlet protection options listed
in Appendix C.
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3.1.8 Element #8 -Stabilize Channels and Outlets
~ No temporarily conveyance channels will be used on this project.Where site runoff is to be
conveyed in channels, or discharged to a stream or some other natural drainage point, efforts will
~ betaken to prevent downstream erosion. The specific BMPs for channel and outlet stabilization
~ that shall be used on this project include:
~ • Outlet Protection (BMP C209)
• Materials on Hand (BMP C150)
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~ Alternate channel and outlet stabilization BMPs are included in Appendix C as a quick reference
tool for the onsite inspector in the event the BMPs) 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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~ 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 1 A, 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
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~ 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
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Tahoma Terra Stormwater Pollution Prevention Plan
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 implemented 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.
~ Chemical storage:
,--I ° Any chemicals stored in the construction areas will conform to the
~ appropriate source control BMPs listed in Volume IV of the Ecology
stormwater manual. In Western WA, all chemicals shall have cover,
~ containment, and protection provided on site, per BMP C153 for Material
Delivery, Storage and Containment in SWMMWW 2005
r, ° Application of agricultural chemicals, including fertilizers and pesticides,
,J shall be conducted in a manner and at application rates that will not result
in loss of chemical to stormwater runoff. Manufacturers'
~ recommendations for application procedures and rates shall be followed.
Excavation and tunneling spoils dewatering waste:
^ Dewatering BMPs and BMPs sp~cific_tn the Px~~~man~~~lin
(including handling of contaminated soils) are discussed under Element
10.
Demolition:
'J Dust released from demolished sidewalks, buildings, or structures will be
controlled using Dust Control measures (BMP C 140).
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Tahoma Terra Stormwater Pollution Prevention Plan
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).
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 C 151).
Sanitary wastewater:
Portable sanitation facilities will be firmly secured, regularly maintained,
and emptied when necessary.
• Wheel wash or tire bath wastewater shall be discharged to a separate on-
site treatment system or to the sanitary sewer as part of Wheel Wash
implementation (BMP C106).
Solid Waste:
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Solid waste will be stored in secure, clearly marked containers.
Other BMPs will be administered as necessary to address any additional
pollutant sources on site.
The project 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
U
There will be no dewatering as part of this construction project.
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Alternate dewatering 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
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during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix
n 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
~J failing.
~ 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 BMP's specifications. Visual
,--I monitoring of the BMPs will be conducted at least once every calendar week and within 24 hours
~ of any rainfall event that causes a discharge from the site. If the site becomes inactive, and is
temporarily stabilized, the inspection frequency will be reduced to once every month.
n
U 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
U or vegetation shall be permanently stabilized.
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LJ 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.
n Emphasize erosion control rather than sediment control.
u
° Minimize the extent and duration of the area exposed.
u 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 listed below:
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As this project site is located west of the Cascade Mountain Crest, the project will be managed
~, according to the following key project components:
u
Phasing of Construction
n
u 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.
U
• Revegetation of exposed areas and maintenance of that vegetation shall be
n an integral part of the clearing activities during each phase of construction,
u per the Scheduling BMP (C 162).
n Seasonal Work Limitations
u
~ ^ From October 1 through Apri130, clearing, grading, and other soil
i
U 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:
i
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^ Site conditions including existing vegetative coverage, slope, soil
,~ type, and proximity to receiving waters; and
~J
^ Limitations on activities and the extent of disturbed areas; and
~ ^ Proposed erosion and sediment control measures.
n, ^ Based on the information provided and/or local weather conditions, the
~j local permitting authority may expand or restrict the seasonal limitation on
site disturbance.
u ^ The following activities are exempt from the seasonal clearing and grading
limitations:
n
~--~ ^ Routine maintenance and necessary repair of erosion and sediment
control BMPs; ,
^ Routine maintenance nfnuhlir f~~~~or-~x-i-stin~u~il-i-~
structures that do not expose the soil or result in the removal of the
n vegetative cover to soil; and
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^ Activities where there is 100 percent infiltration of surface water
n runoff within the site in approved and installed erosion and
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sediment control facilities.
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Coordination with Utilities and Other Jurisdictions
u ' Care has been taken to coordinate with utilities, other construction
projects, and the local jurisdiction in preparing this SWPPP and
~ scheduling the construction work.
u
Inspection and Monitoring
n
u 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:
r-,
`~ ^ Assess the site conditions and construction activities that could
r-, impact the quality of Stormwater, and
~ ^ Assess the effectiveness of erosion and sediment control measures
,~ used to control the quality of Stormwater discharges.
u
^ A Certified Erosion and Sediment Control Lead shall be on-site or on-call
n at all times.
v
® Whenever inspection and/or monitoring reveals that the BMPs identified
s-} in this SWPPP are inadequate, due to the actual discharge of or potential
L j to discharge a significant amount of any pollutant, appropriate BMPs or
design changes shall be implemented as soon as possible.
n
Maintaining an Updated Construction SWPPP
'-' • This SWPPP shall be retained on-site or within reasonable access to the
u 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.
U
n ° 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
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identified. Revisions to the SWPPP shall be completed within seven (7)
days following the inspection.
3.2 Site Specific BMPs
Site specific BMPs are shown on the TESL Plan Sheets and Details in Appendix A. These site
specific plan sheets will be updated annually.
3.3 Additional Advanced BMPs
None will be implemented
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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 is 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.
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 Apri130.
^ Estimate of Construction start date: 07 / 2006
^ Estimate of Construction finish date: 09 / 2008
° Mobilize equipment on site: 07 / 2006
^ Mobilize and store all ESC and soil stabilization products
(store materials on hand BMP C150): 07 / 2006
^ Install ESC measures: 07 / 2006
° Install stabilized,construction entrance: 07 / 2006
^ Begin clearing and grubbing: ~ 07 / 2006
° Temporary erosion control measures (hydroseeding) 08 / 2006
^ Excavate and install new utilities and services (Phase 1): 08 / 2006
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^ Complete Phase 1 utility construction 10 / 2006
^ Begin implementing soil stabilization and sediment
control BMPs throughout the site in preparation for wet
season: 09 / 2006
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° Wet Season starts: 10 / 2006
° Implement Element #12 BMPs and mana
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minimize soil disturbance during the wet season 10 / 2006
° Dry Season starts: OS / 2007
° Site grading begins(Phase 2): OS/ 2007
Excavate and install new utilities and services (Phase 2): 07 / 2007
° Site grading ends (Phase 2): 08 / 2007
° Permanent erosion control measures (hydroseeding): 09 / 2007
° Wet Season starts: 10 / 2007
° Implement Element #12 BMPs and mana
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minimize soil disturbance during the wet season 10 / 2007
• Dry Season starts: OS / 2008
° Site grading begins(Phase 3): OS/ 2008
Excavate and install new utilities and services (Phase 3): 07 / 2008
° Site grading ends: 08 / 2008
Permanent erosion control measures (hydroseeding): 09 / 2008
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5.0 Pollution Prevention Team
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~ 5.1 Roles and Responsibilities
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The pollution prevention team consists of personnel responsible for implementation of the
n SWPPP, including the following:
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• Certified Erosion and Sediment Control Lead (CESCL) -primary
'-1 contractor contact, responsible for site inspections (BMPs, visual
u monitoring, sampling, etc.); to be called upon in case of failure of any
ESC measures.
n
u Resident Engineer -For projects with engineered structures only
(sediment ponds/traps, sand filters, etc.): site representative for the owner
r' that is the project's supervising engineer responsible for inspections and
u issuing instructions and drawings to the contractor's site supervisor or
representative
n
'--' ^ Emergency Ecology Contact -individual to be contacted at Ecology in
case of emergency.
~ ° Emergency Owner Contact -individual that is the site owner or
r ~ representative of the site owner to be contacted in the case of an
U emergency.
,--, • Non-Emergency Ecology Contact -individual that is the site owner or
representative of the site owner than can be contacted if required.
u
n Monitoring Personnel -personnel responsible for conducting water
quality monitoring; for most sites this person is also the Certified Erosion
and Sediment Control Lead.
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5.2 Team Members
Names and contact information for those identified as members of the pollution nreventinn team
are provided in the following table:
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Title Name(s) Phone Number
Certified Erosion and Sediment Control
Lead (CESCL) Tony Bloom 360.446.2972
Resident Engineer Mark Steepy 360.292.7230
Emergency Ecology Contact Charles Gilman 360.407.7451
Emergency Owner Contact Doug Bloom 360.446.3083
Non-Emergency Ecology Contact Doug Bloom 360.446.3083
Monitoring Personnel Tony Bloom 360.446.2972
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6.0 Site Inspections and Monitoring
U 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:
u
r-, A record of the implementation of the SWPPP and other permit
~ requirements;
~ • Site inspections; and,
u
• Stormwater quality monitoring.
r,
,J 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 maybe separated and included in a separate site log book.
u 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.
n
~ 6.1 Site Inspection
~--~ All BMPs will be inspected, maintained, and repaired as needed to assure continued performance
~ of their intended function. Site inspections will be conducted by a person who is knowledgeable
in the principles and practices of erosion and sediment control. The onsite inspector will have
the skills to assess the potential for water quality impacts as a result of the type of construction
~ activities occurring on site, and the knowledge of the appropriate and effective ESC measures
~ needed to control the quality of Stormwater discharges.
,~ All BMPs will be inspected, maintained, and repaired as needed to assure continued performance
~i 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
r-i Section 5 of this SWPPP.
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Site inspection will occur in all areas disturbed by construction activities and at all stormwater
n 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
e ectiveness o t e 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
U 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.
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6.1.1 Site Inspection Frequency
Site inspections will be conducted at least once a week and within 24 hours following any
rainfall event which causes a discharge of Stormwater 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
v The site inspector will record each site inspection using the site log inspection forms provided in
Appendix E. The site inspection log forms maybe separated from this SWPPP document, but
~ will be maintained on-site or within reasonable access to the site and be made available upon
request to Ecology or the local jurisdiction.
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6.2 Stormwater Quality Monitoring
n
The construction site is more than five acres in size, does not discharge to an impaired water
u body, and is therefore a subject to the general water quality monitoring requirements set forth in
n the 2005 Construction Stormwater General Permit (Appendix D).
v~
Conduct weekly: site inspection, sampling wlturbidity meter. Conduct weekly pH sampling as
r~ outlined below only if significant concrete work will occur.
~ 6.2.1 Turbidity Sampling
~ Monitoring requirements for the proposed project will include either turbidity or water
LJ transparency sampling to monitor site discharges for water quality compliance with the 2005
Construction Stormwater General Permit (Appendix D). Sampling will be conducted at all
~' discharge points at least once per calendar week.
u
~ Turbidity or transparency monitoring will follow the analytical methodologies described in
Section S4 of the 2005 Construction Stormwater General Permit (Appendix D). The key
LI benchmark values that require action are 25 NTU for turbidity (equivalent to 32 cm
r~ transparency) and 250 NTU for turbidity (equivalent to 6, cm transparency). If the 25 NTU
u benchmark for turbidity (equivalent to 32 cm transparency) is exceeded, the following steps will
be conducted:
1. Ensure all BMPs specified in this SWPPP are installed and functionin as
mene.
n
2. Assess whether additional BMPs should be implemented, and document
revisions to the SWPPP as necessary.
n
u 3. Sample discharge location daily until the analysis results are less than 25
NTU (turbidity) or greater than 32 cm (transparency).
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If the turbidity is greater than 25 NTU (or transparency is less than 32 cm) but less than 250
NTU (transparency greater than 6 cm) for more than 3 days, additional treatment BMPs will be
implemented within 24 hours of the third consecutive sample that exceeded the benchmark
value. Additional treatment BMPs to be considered will include, but are not limited to, off-site
treatment, infiltration, filtration and chemical treatment.
If the 250 NTU benchmark for turbidity (or less than 6 cm transparency) is exceeded at any time,
the following steps will be conducted:
Notify Ecology by phone within 24 hours of analysis (see Section 5.0 of
this SWPPP for contact information).
2. Continue daily sampling until the turbidity is less than 25 NTU (or
transparency is greater than 32 cm).
3. Initiate additional treatment BMPs such as off-site treatment, infiltration,
filtration and chemical treatment within 24 hours of the first 250 NTU
exceedance.
4. Implement additional treatment BMPs as soon as possible, but within 7
days of the first 250 NTU exceedance.
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
Stormwater runoff will be monitored for pH starting on the first day of any activity that includes
more than 40 yards of poured or recycled concrete, or after the application of "Engineered Soils"
such as, Portland cement treated base, cement kiln dust, or fly ash. This does not include
fertilizers. For concrete work, pH>monitoring will start the first day°°concrete is p~oured~and
continue witil'~=weeks after the last°pour~ For engineered soils, the pH monitoring period begins
when engineered soils are first exposed to precipitation and continue until the area is fully
stabilized.
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Stormwater samples will be collected daily from all points of discharge from the site and
easuredforpH-usirrg~c~l~bra p me er, p es i , or wi e range pH indicator paper. If
n the measured pH is 8.5 or greater, the following steps will be conducted:
L~
1. Prevent the high pH water from entering storm drains or surface water.
2. Adjust or neutralize the high pH water if necessary using appropriate
technology such as COZ sparging (liquid or dry ice).
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Tahoma Terra Stormwater Pollution Prevention Plan
3. Contact Ecology if chemical treatment other than C02 sparging is planned.
6.2.2 plrI Samp'g
None required, as no discharge expected. Follow procedures above only if discharge will occur.
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7.0 Reporting and Recordkeeping
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n 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:
~,
u ° A record of the implementation of the SWPPP and other permit
n requirements;
U
^ Site inspections; and,
n
Lj ° Stormwater quality monitoring.
n
u For convenience, the inspection form and water quality monitoring forms included in this
SWPPP include the required information for the site log book.
U A separate site log be maintained incorporating the example forms provided in this
SWPPP Template document.
7.1.2 Records Retention
~ Records of all monitoring information (site log book, inspection reports/checklists, etc.), this
U
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.
U
7.1.3 Access to Plans and Records
The SWPPP, General Permit, Notice of Authorization letter, and Site Log Book will be retained
~n ~;re~r~vith~~-~-~a~anable-accP~c +~ +~P c,*~ ~}}-be-grade-iriui~di=a~ely a~e-up
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.
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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.
7.2 Reporting
7.2.1 Discharge Monitoring Reports
Discharge Monitoring Report (DMR) forms will not be submitted to Ecology because water
quality sampling is not being conducted at the site.
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
SS.F:
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.
n
7.2.3 Permit Application and Changes
n 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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'~i Appendix A -Site Plans
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PROJ NO SCALE
. ~ rte..' Consulfing Engineers
711 Court A, Suite 202
Tocoma, Washington 98402
(253) 396-0150 Fax (253) 396-0162
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TAHOMA TERRA
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Appendix B -Construction BMPs
The following includes a list of the BMPs to be implemented on the site.
Preserving Natural Vegetation (BMP C 101)
Buffer Zones (BMP C 102)
High Visibility Plastic or Metal Fence (BMP C103) or
Stake and Wire Fence (BMP C 104)
Stabilized Construction Entrance (BMP C 105)
Silt Fence (BMP C233)
Sediment Trap (BMP C240)
Storm Drain Inlet Protection (BMP C220).
Temporary Sediment Pond (BMP C241)
Temporary and Permanent Seeding (BMP C120)
Mulching (BMP C121)
Plastic Covering (BMP C123)
Surface Roughening (BMP C130)
Dust Control (BMP C140)
Early application of gravel base on areas to be paved
Materials on Hand (BMP C150) may also be applicable.
Interceptor Dike and Swale (BMP C200)
Check Dams (BMP C207)
Outlet Protection (BMP C209)
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4.1 Source Control BMPs
BMP C101: Preserving Natural Vegetation
Purpose The purpose of preserving natural vegetation is to reduce erosion wherever
practicable. Limiting site disturbance is the single most effective method
for reducing erosion. For example, conifers can hold up to about 50
percent of all rain that falls during a storm. Up to 20-30 percent of this rain
may never reach the ground but is taken up by the tree or evaporates.
Another benefit is that the rain held in the tree can be released slowly to the
ground after the storm.
Conditions of Use Natural vegetation should be preserved on steep slopes, near
perennial and intermittent watercourses or swales, and on building
sites in wooded areas.
• As required by local governments.
~ Design and Natural vegetation can be preserved in natural clumps or as individual
`
~ Installation trees, shrubs and vines.
- Specifications
~ The preservation of individual plants is more difficult because heavy
~ equipment is generally used to remove unwanted vegetation. The points
to remember when attempting to save individual plants are:
~ Is the plant worth saving? Consider the location, species, size, age,
~ vigor, and the work involved. Local governments may also have
ordinances to save natural vegetation and trees.
`~ Fence or clearly mark areas around trees that are to be saved. It is
~I preferable to keep ground disturbance away from the trees at least as
far out as the dripline.
,_j Plants need protection from three kinds of injuries:
~ Construction Equipment -This injury can be above or below the
u ground level. Damage results from scarring, cutting of roots, and
compaction of the soil. Placing a fenced buffer zone around plants to
r~ be saved prior to construction can prevent construction equipment
~ injuries.
• Grade Changes -Changing the natural ground level will alter grades,
'~ which affects the plant's ability to obtain the necessary air, water, and
,J minerals. Minor fills usually do not cause prohlemc alrhn„g~
sensitivity between species does vary and should be checked. Trees
`~ can tolerate fill of 6 inches or less. For shrubs and other plants, the fill
~ should be less.
When there are major changes in grade, it may become necessary to
~ supply air to the roots of plants. This can be done by placing a layer of
`-~ gravel and a the system over the roots before the fill is made. A the
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`~ 4-2 Volume 11 -Construction Stormwater Pollution Prevention February 2005
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system protects a tree from a raised grade. The the system should be
~ laid out on the original grade leading from a dry well around the tree
~ trunk. The system should then be covered with small stones to allow
air to circulate over the root area.
'~, Lowering the natural ground level can seriously damage trees and
~J shrubs. The highest percentage of the plant roots are in the upper 12
inches of the soil and cuts of only 2-3 inches can cause serious injury.
'~ To protect the roots it may be necessary to terrace the immediate area
Ll around the plants to be saved. If roots are exposed, construction of
retaining walls may be needed to keep the soil in place. Plants can
'~ also be preserved by leaving them on an undisturbed, gently sloping
v mound. To increase the chances for survival, it is best to limit grade
changes and other soil disturbances to areas outside the dripline of the
'~1 plant.
'-~ Excavations -Protect trees and other plants when excavating for
`~ drainfields, power, water, and sewer lines. Where possible, the
trenches should be routed around trees and large shrubs. When this is
v
not possible, it is best to tunnel under them. This can be done with
hand tools or with power augers. If it is not possible to route the
`~ trench around plants to be saved, then the following should be
~ observed:
~ Cut as few roots as possible. When you have to cut, cut clean. Paint
u
cut root ends with a wood dressing like asphalt base paint.
Backfill the trench as soon as possible.
n
`~
Tunnel beneath root systems as close to the center of the main trunk to
preserve most of the important feeder roots.
~~ Some problems that can be encountered with a few specific trees are:
~J
• Maple, Dogwood, Red alder, Western hemlock, Western red cedar,
'~ and Douglas fir do not readily adjust to changes in environment and
v special care should be taken to protect these trees.
~ • The windthrow hazard of Pacific silver fir and madronna is high, while
that of Western hemlock is moderate. The danger of windthrow
`J increases where dense stands have been thinned. Other species (unless
n they are on shallow, wet soils less than 20 inches deep) have a low
windthrow hazard.
v
• o onwoo s, map es, an wi ows ave water-seeking roots. These
n can cause trouble in sewer lines and infiltration fields. On the other
~ hand, they thrive in high moisture conditions that other trees would
not.
`~ Thinning operations in pure or mixed stands of Grand fir, Pacific silver
~J fir, Noble fir, Sitka spruce, Western red cedar, Western hemlock,
'--~ February 2005 Volume l1-Construction Stormwater Pollution Prevention 4-3
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Pacific dogwood, and Red alder can cause serious disease problems.
Disease can become established through damaged limbs, trunks, roots,
and freshly cut stumps. Diseased and weakened trees are also
susceptible to insect attack.
Maintenance Inspect flagged and/or fenced areas regularly to make sure flagging or
Standards fencing has not been removed or damaged. If the flagging or fencing
has been damaged or visibility reduced, it shall be repaired or
replaced immediately and visibility restored.
• If tree roots have been exposed or injured, "prune" cleanly with an
appropriate pruning saw or Topers directly above the damaged roots
and recover with native soils. Treatment of sap flowing trees (fir,
hemlock, pine, soft maples) is not advised as sap forms a natural
healing barrier.
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BMP C102: Buffer Zones
Purpose An undisturbed area or strip of natural vegetation or an established
suitable planting that will provide a living filter to reduce soil erosion and
runoff velocities.
Conditions of Use Natural buffer zones are used along streams, wetlands and other bodies of
water that need protection from erosion and sedimentation. Vegetative
buffer zones can be used to protect natural swales and can be incorporated
into the natural landscaping of an area.
Critical-areas buffer zones should not be used as sediment treatment areas.
These areas shall remain completely undisturbed. The local permitting
authority may expand the buffer widths temporarily to allow the use of the
expanded area for removal of sediment.
Design and Preserving natural vegetation or plantings in clumps, blocks, or strips
Installation is generally the easiest and most successful method.
Specifications Leave all unstable steep slopes in natural vegetation.
• Mark clearing limits and keep all equipment and construction debris
out of the natural areas. Steel construction fencing is the most
effective method in protecting sensitive areas and buffers.
Alternatively, wire-backed silt fence on steel posts is marginally
effective. Flagging alone is typically not effective.
• Keep all excavations outside the dripline of trees and shrubs.
• Do not push debris or extra soil into the buffer zone area because it
will cause damage from burying and smothering.
• Vegetative buffer zones for streams, lakes or other waterways shall be
established by the local permitting authority or other state or federal
permits or approvals.
Maintenance Inspect the area frequently to make sure flagging remains in place
Standards and the area remains undisturbed.
February 2005 Volume 11 -Construction Stormwater Pollution Prevention
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~ BMP C103: High Visibility Plastic or Metal Fence
'~ Purpose Fencing is intended to: (1) restrict clearing to approved limits; (2) prevent
~J disturbance of sensitive areas, their buffers, and other areas required to be
left undisturbed; (3) limit construction traffic to designated construction
'~ entrances or roads; and, (4) protect areas where marking with survey tape
~J may not provide adequate protection.
r~ Conditions of Use To establish clearing limits, plastic or metal fence may be used:
• At the boundary of sensitive areas, their buffers, and other areas
required to be left uncleared.
n
• As necessary to control vehicle access to and on the site.
~ Design and High visibility plastic fence shall be composed of ahigh-density
~ Installation polyethylene material and shall be at least four feet in height. Posts
Specifications for the fencing shall be steel or wood and placed every 6 feet on
~ center (maximum) or as needed to ensure rigidity. The fencing shall
~ be fastened to the post every six inches with a polyethylene tie. On
long continuous lengths of fencing, a tension wire or rope shall be
~ used as a top stringer to prevent sagging between posts. The fence
u color shall be high visibility orange. The fence tensile strength shall
be 3601bs./ft. using the ASTM D4595 testing method.
~ Metal fences shall be designed and installed according to the
u manufacturer's specifications.
,-~ Metal fences shall be at least 3 feet high and must be highly visible.
~J Fences shall not be wired or stapled to trees.
n Maintenance If the fence has been damaged or visibility reduced, it shall be
~j Standards repaired or replaced immediately and visibility restored.
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Volume 11 -Construction StormwaterPol/ution Prevention February 2005
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BMP C104: Stake and Wire Fence
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Purpose
Fencing is intended to: (1) restrict clearing to approved limits; (2) prevent
disturbance of sensitive areas, their buffers, and other areas required to be
~ left undisturbed; (3) limit construction traffic to designated construction
entrances or roads; and, (4) protect any areas where marking with survey
tape may not provide adequate protection.
Conditions of Use To establish clearing limits, stake or wire fence may be used:
U
• At the boundary of sensitive areas, their buffers, and other areas
r-~
l required to be left uncleared.
u As necessary, to control vehicle access to and on the site.
Design and See Figure 4.1 for details.
Installation
Specifications More substantial fencing shall be used if the fence does not prevent
•
n encroachment into those areas that are not to be disturbed.
~
U Maintenance If the fence has been damaged or visibility reduced, it shall be
Standards repaired or replaced immediately and visibility restored.
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Survey Flagging Baling Wire Do Not Nail or Staple
Wire to Trees
3' MIN,
10'-20'
Metal
Fence Post
IIII III IIII IIII-III-II IIII III I III-I11 I II IIII ,;
12 MIN.
Figure 4.1 -Stake and Wire Fence
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February 2005 Volume 11 -Construction Stormwater Pollution Prevention 4-7
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BMP C105: Stabilized Construction Entrance
Purpose Construction entrances are stabilized to reduce the amount of sediment
transported onto paved roads by vehicles or equipment by constructing a
stabilized pad of quarry spalls at entrances to construction sites.
Conditions of Use Construction entrances shall be stabilized wherever traffic will be leaving
a construction site and traveling on paved roads or other paved areas
within 1,000 feet of the site.
On large commercial, highway, and road projects, the designer should
include enough extra materials in the contract to allow for additional
stabilized entrances not shown in the initial Construction SWPPP. It is
difficult to determine exactly where access to these projects will take
place; additional materials will enable the contractor to install them where
needed.
Design and See Figure 4.2 for details. Note: the 100' minimum length of the
Installation entrance shall be reduced to the maximum practicable size when the
Specifications size or configuration of the site does not allow the full length (100').
• A separation geotextile shall be placed under the spalls to prevent
fine sediment from pumping up into the rock pad. The geotextile
shall meet the following standards:
Grab Tensile Strength (ASTM D4751) 200 psi min.
Grab Tensile Elongation (ASTM D4632) 30% max.
Mullen Burst Strength (ASTM D3786-80a) 400 psi min.
AOS (ASTM D4751) 20-45 (U.S. standard sieve size)
Consider early installation of the first lift of asphalt in areas that will
paved; this can be used as a stabilized entrance. Also consider the
installation of excess concrete as a stabilized entrance. During large
concrete pours, excess concrete is often available for this purpose.
~ Hog fuel (wood-based mulch) may be substituted for or combined with
~ quarry spalls in areas that will not be used for permanent roads. Hog
fuel is generally less effective at stabilizing construction entrances and
~ should be used only at sites where the amount of traffic is very limited.
~ Hog fuel is not recommended for entrance stabilization in urban areas.
The effectiveness of hog fuel is highly variable and it generally
,~ requires more maintenance than quarry spalls. The inspector may at
~ any time require the use of quarry spalls if the hog fuel is not
nrPVP bbl
fuel is being carried onto pavement. Hog fuel is prohibited in
permanent roadbeds because organics in the subgrade soils cause
`-~ degradation of the subgrade support over time.
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• Fencing (see BMPs C103 and C104) shall be installed as necessary to
restrict traffic to the construction entrance.
4-~s Volume Il -Construction Stormwater Pollution Prevention February 2005
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• Whenever possible, the entrance shall be constructed on a firm,
compacted subgrade. This can substantially increase the effectiveness
of the pad and reduce the need for maintenance.
Maintenance Quarry spans (or hog fuel) shall be added if the pad is no longer in
Standards accordance with the specifications.
• If the entrance is not preventing sediment from being tracked onto
pavement, then alternative measures to keep the streets free of
sediment shall be used. This may include street sweeping, an increase
in the dimensions of the entrance, or the installation of a wheel wash.
• Any sediment that is tracked onto pavement shall be removed by
shoveling or street sweeping. The sediment collected by sweeping
shall be removed or stabilized on site. The pavement shall not be
cleaned by washing down the street, except when sweeping is
ineffective and there is a threat to public safety. If it is necessary to
wash the streets, the construction of a small sump shall be considered.
The sediment would then be washed into the sump where it can be
controlled.
• Any quarry spans that are loosened from the pad, which end up on the
roadway shall be removed immediately.
• If vehicles are entering or exiting the site at points other than the
construction entrance(s), fencing (see B]VIl's C103 and C104) shall be
installed to control traffic.
• Upon project completion and site stabilization, all construction
accesses intended as permanent access for maintenance shall be
permanently stabilized.
Driveway shalt meet the
regwrements of the
permitting agency
It is recommended that
the entrance 6e
crowned so that runoff
Poyd drains off the pad
~°o.
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Install driveway culvert
if there is a roadside
ditch present
4'-t3" quarry spans
Geotexhle I
12' mm thickness ~- •~ \ ~~
Provide full width of
ingress/egress area
Figure 4.2 -Stabilized Construction Entrance
February 2005 Volume /1- Construction Stormwater Pollution Prevention
4-9
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BMP C120: Temporary and Permanent Seeding
Purpose Seeding is intended to reduce erosion by stabilizing exposed soils. A
well-established vegetative cover is one of the most effective methods of
reducing erosion.
~ Conditions of Use Seeding may be used throughout the project on disturbed areas that
have reached final grade or that will remain unworked for more than
n 30 days.
i
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Channels that will be vegetated should be installed before major
earthwork and hydroseeded with a Bonded Fiber Matrix. The
vegetation should be well established (i.e., 75 percent cover) before
water is allowed to flow in the ditch. With channels that will have
high flows, erosion control blankets should be installed over the
'~I hydroseed. If vegetation cannot be established from seed before water
~..J is allowed in the ditch, sod should be installed in the bottom of the
ditch over hydromulch and blankets.
• Retention/detentionpnnds should be seeded as required.
• Mulch is required at all times because it protects seeds from heat,
moisture loss, and transport due to runoff.
• All disturbed areas shall be reviewed in late August to early September
and all seeding should be completed by the end of September.
Otherwise, vegetation will not establish itself enough to provide more
v than average protection.
,~ At final site stabilization, all disturbed areas not otherwise vegetated or
stabilized shall be seeded and mulched. Final stabilization means the
completion of all soil disturbing activities at the site and the
,~ establishment of a permanent vegetative cover, or equivalent
~ permanent stabilization measures (such as pavement, riprap, gabions
or geotextiles) which will prevent erosion.
~ Design and Seeding should be done during those seasons most conducive to
'--~ Installation growth and will vary with the climate conditions of the region.
Specifications Local experience should be used to determine the appropriate
'~ seeding periods.
'~ The optimum seeding windows for western Washington are April 1
through June 30 and September 1 through October 1. Seeding that
n occurs between July 1 and August 30 will require irrigation unti175
u percent grass cover i~ P~t~hl;shPd Seedi=ng *~~* ^~^~~~~ ~~~~
October 1 and March 30 will require a mulch or plastic cover until
n 75 percent grass cover is established.
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• To prevent seed from being washed away, confirm that all required
surface water control measures have been installed.
reoruary 1vv5 Volume 11 -Construction Stormwater Pollution Prevention
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~ The seedbed should be firm and rough. All soil should be roughened
,-~ no matter what the slope. If compaction is required for engineering
`~ purposes, slopes must be track walked before seeding. Backblading or
smoothing of slopes greater than 4:1 is not allowed if they are to be
,~ seeded.
,J New and more effective restoration-based landscape practices rely on
deeper incorporation than that provided by a simple single-pass
r( rototilling treatment. Wherever practical the subgrade should be
Lj initially ripped to improve long-term permeability, infiltration, and
water inflow qualities. At a minimum, permanent areas shall use soil
~ amendments to achieve organic matter and permeability performance
defined i
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so
an
scape systems. For systems that are
deeper than 8 inches the rototilling process should be done in multiple
r-~ lifts, or the prepared soil system shall be prepared properly and then
Lj placed to achieve the specified depth.
• Organic matter is the most appropriate form of "fertilizer" because it
'~ provides nutrients (including nitrogen, phosphorus, and potassium) in
v the least water-soluble form. A natural system typically releases 2-10
percent of its nutrients annually. Chemical fertilizers have since been
'~ formulated to simulate what organic matter does naturally.
~ In general, 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer
n can be used at a rate of 90 pounds per acre. Slow-release fertilizers
should always be used because they are more efficient and have fewer
`~ environmental impacts. It is recommended that areas being seeded for
final landscaping conduct soil tests to determine the exact type and
i
'~ quant
ty of fertilizer needed. This will prevent the over-application of
fertilizer. Fertilizer should not be added to the hydromulch machine
~ and agitated more than 20 minutes before it is to be used. If agitated
too much, the slow-release coating is destroyed.
• There are numerous products available on the market that take the
~ place of chemical fertilizers. These include several with seaweed
~ extracts that are beneficial to soil microbes and organisms. If 100
percent cottonseed meal is used as the mulch in hydroseed, chemical
~ fertilizer may not be necessary. Cottonseed meal is a good source of
v
long-term, slow-release, available nitrogen.
• Hydroseed applications shall include a minimum of 1,500 pounds per
'~ acre of mulch with 3 percent tackifier. Mulch may be made up of 100
~I percent: cottonseed meal; fibers made of wo~d_ recvolerl rellnlneP
hemp, and kenaf; compost; or blends of these. Tackifier shall be plant-
~ based, such as guar or alpha plantago, or chemical-based such as
,J polyacrylamide or polymers. Any mulch or tackifier product used
shall be installed per manufacturer's instructions. Generally, mulches
n come in 40-50 pound bags. Seed and fertilizer are added at time of
v application.
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4-14 Volume 11 -Construction Stom7waterPollution Prevention February 2005
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`J Mulch is always required for seeding. Mulch can be applied on top of
,--1 the seed or simultaneously by hydroseeding.
• On steep slopes, Bonded Fiber Matrix (BFM) or Mechanically Bonded
Fiber Matrix (MBFM) products should be used. BFM/MBFM
~ products are applied at a minimum rate of 3,000 pounds per acre of
~ mulch with approximately 10 percent tackifier. Application is made
so that a minimum of 95 percent soil coverage is achieved. Numerous
products are available commercially and should be installed per
manufacturer's instructions. Most products require 24-36 hours to
cure before a rainfall and cannot be installed on wet or saturated soils.
,-~ Generally, these products come in 40-50 pound bags and include all
necessary ingredients except for seed and fertilizer.
BFMs and MBFMs have some advantages over blankets:
n
• No surface preparation required;
• Can be installed via helicopter in remote areas;
• On slopes steeper than 2.5:1, blanket installers may need to be roped
and harnessed for safety;
~ They are at least $1,000 per acre cheaper installed.
In most cases, the shear strength of blankets is not a factor when used on
'~ slopes, only when used in channels. BFMs and MBFMs are good
alternatives to blankets in most situations where vegetation establishment
is the goal.
• When installing seed via hydroseeding operations, only about 1/3 of
the seed actually ends up in contact with the soil surface. This reduces
~ the ability to establish a good stand of grass quickly. One way to
overcome this is to increase seed quantities by up to 50 percent.
v
• Vegetation establishment can also be enhanced by dividing the
,--1 hydromulch operation into two phases:
~I 1. Phase 1-Install all seed and fertilizer with 25-30 percent mulch
and tackifier onto soil in the first lift;
n
2. Phase 2- Install the rest of the mulch and tackifier over the first lift.
An alternative is to install the mulch, seed, fertilizer, and tackifier in one
1~ lift. Then, spread or blow straw over the top of the hydromulch at a rate of
u about 800-1000 bounds 1701' aC1'P Nnlrl CtYa Sz, in~lara xx~i~}-i-a-.°it'mida~
tackifier. Both of these approaches will increase cost moderately but will
`~ greatly improve and enhance vegetative establishment. The increased cost
i.J may be offset by the reduced need for:
1. Irrigation
~ 2. Reapplication of mulch
u 3. Repair of failed slope surfaces
n
~J
f-e6ruary 2005 Volume ll -Construction Stormwater Pollution Prevention
4-15
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The seedbed should be firm and rough. All soil should be roughened
,-~ no matter what the slope. If compaction is required for engineering
purposes, slopes must be track walked before seeding. Backblading or
smoothing of slopes greater than 4:1 is not allowed if they are to be
,~ seeded.
LJ New and more effective restoration-based landscape practices rely on
deeper incorporation than that provided by a simple single-pass
rototilling treatment. Wherever practical the subgrade should be
~ initially ripped to improve long-term permeability, infiltration, and
water inflow qualities. At a minimum, permanent areas shall use soil
amendments to achieve organic matter and permeability performance
~ defined in engineered soil/landscape systems. For systems that are
deeper than 8 inches the rototilling process should be done in multiple
~ lifts, or the prepared soil system shall be prepared properly and then
~ placed to achieve the specified depth.
• Organic matter is the most appropriate form of "fertilizer" because it
id
i
i
prov
es nutr
ents (
ncluding nitrogen, phosphorus, and potassium) in
~ the least water-soluble form. A natural system typically releases 2-10
percent of its nutrients annually. Chemical fertilizers have since been
'~ formulated to simulate what organic matter does naturally.
~ •
In general, 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer
n can be used at a rate of 90 pounds per acre. Slow-release fertilizers
~ should always be used because they are more efficient and have fewer
environmental impacts. It is recommended that areas being seeded for
~ final landscaping conduct soil tests to determine the exact type and
'J quantity of fertilizer needed. This will prevent the over-application of
fertilizer. Fertilizer should not be added to the hydromulch machine
and agitated more than 20 minutes before it is to be used. If agitated
~ too much, the slow-release coating is destroyed.
• There are numerous products available on the market that take the
~ place of chemical fertilizers. These include several with seaweed
extracts that are beneficial to soil microbes and organisms. If 100
percent cottonseed meal is used as the mulch in hydroseed, chemical
~ fertilizer may not be necessary. Cottonseed meal is a good source of
~ long-term, slow-release, available nitrogen.
• Hydroseed applications shall include a minimum of 1,500 pounds per
`~ acre of mulch with 3 percent tackifier. Mulch may be made up of 100
~J percent: cottonseed meal; fibers made of w~n~g~o~
hemp, and kenaf; compost; or blends of these. Tackifier shall be plant-
~i based, such as guar or alpha plantago, or chemical-based such as
v polyacrylamide or polymers. Any mulch or tackifier product used
shall be installed per manufacturer's instructions. Generally, mulches
~ come in 40-50 pound bags. Seed and fertilizer are added at time of
~ application.
~- ~ ~ volume ll -Construction Stormwater Pollution Prevention February 2005
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v
• Mulch is always required for seeding. Mulch can be applied on top of
~ the seed or simultaneously by hydroseeding.
~ On steep slopes, Bonded Fiber Matrix (BFM) or Mechanically Bonded
Fiber Matrix (MBFM) products should be used. BFM/MBFM
~ products are applied at a minimum rate of 3,000 pounds per acre of
,J mulch with approximately 10 percent tackifier. Application is made
so that a minimum of 95 percent soil coverage is achieved. Numerous
~ products are available commercially and should be installed per
~ manufacturer's instructions. Most products require 24-36 hours to
cure before a rainfall and cannot be installed on wet or saturated soils.
c-~ Generally, these products come in 40-50 pound bags and include all
~ necessary ingredients except for seed and fertilizer.
BFMs and MBFMs have some advantages over blankets:
Lj No surface preparation required;
• Can be installed via helicopter in remote areas;
• On slopes steeper than 2.5:1, blanket installers may need to be roped
U and harnessed for safety;
~ They are at least $1,000 per acre cheaper installed.
In most cases, the shear strength of blankets is not a factor when used on
~? slopes, only when used in channels. BFMs and MBFMs are good
u alternatives to blankets in most situations where vegetation establishment
is the goal.
r~
~
When installing seed via hydroseeding operations, only about 1/3 of
the seed actually ends up in contact with the soil surface. This reduces
the ability to establish a good stand of grass quickly. One way to
overcome this is to increase seed quantities by up to 50 percent.
• Vegetation establishment can also be enhanced by dividing the
r-~ hydromulch operation into two phases:
~„~ 1. Phase 1-Install all seed and fertilizer with 25-30 percent mulch
and tackifier onto soil in the first lift;
2. Phase 2- Install the rest of the mulch and tackifier over the first lift.
An alternative is to install the mulch, seed, fertilizer, and tackifier in one
lift. Then, spread or blow straw over the top of the hydromulch at a rate of
U about 800-1000 pounder a~rP u~t~ ctra~x~ in nlor~a .,~tn_u ~c0.r~,,•.,7
tackifier. Both of these approaches will increase cost moderately but will
'~ greatly improve and enhance vegetative establishment. The increased cost
,_.J may be offset by the reduced need for:
1. Irrigation
n 2. Reapplication of mulch
~ 3. Repair of failed slope surfaces
reuruary wvo volume ll -Construction Stormwater Pollution Prevention
4-75
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`J This technique works with standard hydromulch (1,500 pounds per acre
~ minimum) and BFM/MBFMs (3,000 pounds per acre minimum).
'--~ Areas to be permanently landscaped shall provide a healthy topsoil
~ that reduces the need for fertilizers, improves overall topsoil quality,
'J provides for better vegetal health and vitality, improves hydrologic
characteristics, and reduces the need for irrigation. This can be
'-1 accomplished in a number of ways:
~-l Recent research has shown that the best method to improve till soils is
to amend these soils with compost. The optimum mixture is
`~
J approximately two parts soil to one part compost. This equates to 4
i
h
nc
es of compost mixed to a depth of 12 inches in till soils. Increasing
the concentration of compost beyond this level can have negative
rl, effects on vegetal health, while decreasing the concentrations can
,J reduce the benefits of amended soils. Please note: The compost should
meet specifications for Grade A quality compost in Ecology
'~ Publication 94-038.
u
Other soils, such as gravel or cobble outwash soils, may require
different approaches. Organics and fines easily migrate through the
~ loose structure of these soils. Therefore, the importation of at least 6
inches of quality topsoil, underlain by some type of filter fabric to
n prevent the migration of fines, may be more appropriate for these soils.
~ Areas that already have good topsoil, such as undisturbed areas, do not
r-, require soil amendments.
• Areas that will be seeded only and not landscaped may need compost
or meal-based mulch included in the hydroseed in order to establish
~I vegetation. Native topsoil should be re-installed on the disturbed soil
U surface before application.
r-~ Seed that is installed as a temporary measure may be installed by hand
if it will be covered by straw, mulch, or topsoil. Seed that is installed
as a permanent measure may be installed by hand on small areas
r-~ (usually less than I acre) that will be covered with mulch, topsoil, or
~ erosion blankets. The seed mixes listed below include recommended
mixes for both temporary and permanent seeding. These mixes, with
n the exception of the wetland mix, shall be applied at a rate of 120
~ pounds per acre. This rate can be reduced if soil amendments or slow-
ase e i izers are use oca supp iers or the local conservation
~ district should be consulted for their recommendations because the
~ appropriate mix depends on a variety of factors, including location,
exposure, soil type, slope, and expected foot traffic. Alternative seed
~ mixes approved by the local authority may be used.
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Table 4.1 represents the standard mix for those areas where just a
temporary vegetative cover is required.
Table 4.1
Tem ora Erosion Control Seed Mix
Wei ht % Puri % Germination
Chewings or annual blue grass 40 98 90
Festuca rubra var commutata or Poa anna
Perennial rye - 50 98 90
Lolium erenne
Redtop or colonial bentgrass 5 92 85
A ostis alba or A ostis tenuts
White dutch clover 5 98 90
Tri olium re ens
Table 4.2 provides just one recommended possibility for landscaping seed.
Table 4.2
Landscaping Seed Mix
Wei ht % Puri % Germination
Perennial rye blend 70 98 90
Lolium erenne
Chewings and red fescue blend 30 98 90
Festuca rubra var. commutata
or Festuca rubra
This turf seed mix in Table 4.3 is for dry situations where there is no need
for much water. The advantage is that this mix requires very little
maintenance.
Table 4.3
Low-Growing Turf Seed Mix
Wei ht % Puri % Germination
Dwarf tall fescue (several varieties) 45 98 90
Festuca arundinacea var.
Dwarf perennial rye (Barclay) 30 98 90
Lolium erenne var barcl
Red fescue 20 98 90
Festuca rubra
Colonial bentgrass 5 98 90
A ostis tenuts
Table 4.4 presents a mix recommended for bioswales and other
intermittently wet areas.
Table 4.4
Bioswale Seed Mix*
Wei ht % Puri % Germination
a or mea ow escue 75-80 98 90
Festuca arundinacea or Festuca elatTOr
Seaside/Creeping bentgrass 10-15 92 85
A rostis alustris
Redtop bentgrass 5-10 90 80
A ostis alba orA rostis i antea
,~ ~ ~.,.
~~<~uy«u ~~ ~u~s~rr~~, l~rc. nyuroseeatng cTutae wetlands J'eed Mix
t-eoruary 2005 Volume 11-Construction Stormwater Pollution Prevention
4-17
`J The seed mix shown in Table 4.5 is a recommended low-growing,
,~ relatively non-invasive seed mix appropriate for very wet areas that are
not regulated wetlands. Other mixes may be appropriate, depending on
the soil type and hydrology of the area. Recent research suggests that
~ bentgrass (agrostis sp.) should be emphasized in wet-area seed mixes.
J Apply this mixture at a rate of 60 pounds per acre.
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Wet Area Seed Mix*
Wei ht % Puri % Germination
Tall or meadow fescue 60-70 98 90
Festuca arundinacea or
Festuca elatior
Seaside/Creeping bentgrass 10-15 98 85
A rostis alustris
Meadow foxtail 10-15 90 80
Ale ocurus ratensis
Alsike clover 1-6 98 90
Tri olium h bridum
Redtop bentgrass 1-6 92 85
A ostis alba
Modtfied Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix
The meadow seed mix in Table 4.6 is recommended for areas that will be
maintained infrequently or not at all and where colonization by native
plants is desirable. Likely applications include rural road and utility right-
of-way. Seeding should take place in September or very early October in
order to obtain adequate establishment prior to the winter months. The
appropriateness of clover in the mix may need to be considered, as this can
be a fairly invasive species. If the soil is amended, the addition of clover
may not be necessary.
Table 4.6
Meadow Seed Mix
Wei ht % Puri % Germination
Redtop or Oregon bentgrass 20 92 85
A ostis alba or A rostis ore onensis
Red fescue 70 98 90
Festuca rubra
White dutch clover 10 98 90
Tri olium re ens
n Maintenance Any seeded areas that fail to establish at least 80 percent cover (100
L~ Standards percent cover for areas that receive sheet or concentrated flowsl shall
be reseeded. If reseeding is ineffective, an alternate method, such as
r-~ sodding, mulching, or nets blankets, shall be used. If winter weather
~ prevents adequate grass growth, this time limit may be relaxed at the
discretion of the local authority when sensitive areas would otherwise
r-~ be protected.
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`~ After adequate cover is achieved, any areas that experience erosion
,--~ shall be reseeded and protected by mulch. If the erosion problem is
J drainage related, the problem shall be fixed and the eroded area
reseeded and protected by mulch.
~ Seeded areas shall be supplied with adequate moisture, but not watered
~ to the extent that it causes runoff.
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BMP C121: Mulching
Purpose The purpose of mulching soils is to provide immediate temporary
protection from erosion. Mulch also enhances plant establishment by
conserving moisture, holding fertilizer, seed, and topsoil in place, and
moderating soil temperatures. There is an enormous variety of mulches
that can be used. Only the most common types are discussed in this
section.
Conditions of Use As a temporary cover measure, mulch should be used:
• On disturbed areas that require cover measures for less than 30 days.
• As a cover for seed during the wet season and during the hot summer
months.
• During the wet season on slopes steeper than 3H:1 V with more than 10
feet of vertical relief.
• Mulch may be applied at any time of the year and must be refreshed
periodically.
Design and For mulch materials, application rates, and specifications, see Table 4.7.
Installation Note: Thicknesses may be increased for disturbed areas in or near
Specifications sensitive areas or other areas highly susceptible to erosion.
Mulch used within the ordinary high-water mark of surface waters should
be selected to minimize potential flotation of organic matter. Composted
organic materials have higher specific gravities (densities) than straw,
wood, or chipped material.
Maintenance The thickness of the cover must be maintained.
Standards ~y areas that experience erosion shall be remulched and/or protected
with a net or blanket. If the erosion problem is drainage related, then
the problem shall be fixed and the eroded area remulched.
4-LU Volume 11 -Construction Stormwater Pollution Prevention February 2005
Table 4.7
Mulch Standards and Guidelines
Mulch Application
Material Quali Standards Rates Remarks
Straw Air-dried; free from 2"-3" thick; 5
r-1 undesirable seed and bales per 1000 sf
J coarse material. or 2-3 tons per
acre
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Cost-effective protection when applied with adequate
thickness. Hand-application generally requires greater
thickness than blown straw. The thickness of straw may be
reduced by half when used in conjunction with seeding. In
windy areas straw must be held in place by crimping, using a
tackifier, or covering with netting. Blown straw always has
to beheld in place with a tackifier as even light winds will
blow it away. Straw, however, has several deficiencies that
should be considered when selecting mulch materials. It
often introduces and/or encourages the propagation of weed
species and it has no significant long-term benefits. Straw
should be used only if mulches with long-tenrn benefits are
unavailable locally. It should also not be used within the
ordinary high-water elevation of surface waters (due to
flotation).
Hydromulch No growth Approx. 25-30 Shall be applied with hydromulcher. Shall not be used
inhibiting factors. ]bs per 1000 sf without seed and tackifier unless the application rate is at
or 1500 - 2000 least doubled. Fibers longer than about 3/<-1 inch clog
lbs per acre hydromulch equipment. Fibers should be kept to less than 3/4
inch.
Composted No visible water or 2" thick min.; More effective control can be obtained by increasing
Mulch and dust during approx. 100 tons thickness to 3". Excellent mulch for protecting final grades
Compost handling. Must be per acre (approx. until landscaping because it can be directly seeded or tilled
purchased from 800 lbs per yard) into soil as an amendment. Composted mulch has a coarser
supplier with Solid size gradation than compost. It is more stable and practical
Waste Handling to use in wet azeas and during rainy weather conditions
Permit (unless .
exempt).
Chipped Site Average size shall 2" minimum This is acost-effective way to dispose of debris from
Vegetation be several inches. thickness clearing and grubbing, and it eliminates the problems
Gradations from associated with burning. Generally, it should not be used on
fines to 6 inches in
length for texture slopes above approx. 10% because of its tendency to be
, transported by runoff. It is not recommended within 200
variation, and feet of surface waters. If seeding is expected shortly after
interlocking mulch, the decomposition of the chipped vegetation may tie
properties. up nutrients important to grass establishment.
Wood-based No visible water or 2" thick; approx. This material is often called "hog or hogged fuel
" It is
Mulch dust during 100 tons per acre .
usable as a material for Stabilized Construction Entrances
handling. Must be (approx. 8001bs. (BMP C 105) and as a mulch. The use of mulch ultimately
purchased from a per cubic yard) improves the organic matter in the soil. Special caution is
supplier with a Solid advised regarding the source and composition of wood-
Waste Handling based mulches. Its preparation typically does not provide
Permit or one any weed seed control, so evidence of residual ve
etati
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waste regulations. should be monitored and prevented (or minimized).
February 2005 Volume ll -Construction Stormwater Pollution Prevention 4-21
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'-~ BMP C123: Plastic Covering
J Purpose Plastic covering provides immediate, short-term erosion protection to
slopes and disturbed areas.
J Conditions of • Plastic covering may be used on disturbed areas that require cover
Use measures for less than 30 days, except as stated below.
'~ Plastic is particularly useful for protecting cut and fill slopes and
~ stockpiles. Note: The relatively rapid breakdown of most polyethylene
sheeting makes it unsuitable for long-term (greater than six months)
^I applications.
• Clear plastic sheeting can be used over newly-seeded areas to create a
greenhouse effect and encourage grass growth if the hydroseed was
v installed too late in the season to establish 75 percent grass cover, or if
the wet season started earlier than normal. Clear plastic should not be
used for this purpose during the summer months because the resulting
high temperatures can kill the grass.
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• Due to rapid runoff caused by plastic sheeting, this method shall not be
~ used upslope of areas that might be adversely impacted by
~ concentrated runoff. Such areas include steep andlor unstable slopes.
• While plastic is inexpensive to purchase, the added cost of installation
,
maintenance, removal, and disposal make this an expensive material,
up to $1.50-2.00 per square yard.
• Whenever plastic is used to protect slopes, water collection measures
must be installed at the base of the slope. These measures include
plastic-covered berms, channels, and pipes used to covey clean
rainwater away from bare soil and disturbed areas. At no time is clean
runoff from a plastic covered slope to be mixed with dirty runoff from
a project.
~ Other uses for plastic include:
u 1. Temporary ditch liner;
~ 2. Pond liner in temporary sediment pond;
~j 3. Liner for bermed temporary fuel storage area if plastic is not
reactive to the type of fuel being stored;
n 4. Emergency slope protection durin hea
g vy rains; and,
emporary rampipe "elephant trunk") used to direct water.
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• Plastic slope cover must be installed as follows:
1. Run plastic up and down slope, not across slope;
2. Plastic may be installed perpendicular to a slope if the slope length
is less than 10 feet;
3. Minimum of 8-inch overlap at seams;
4. On long or wide slopes, or slopes subject to wind, all seams should
be taped;
5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench
at the top of the slope and backfill with soil to keep water from
flowing underneath;
6. Place sand filled burlap or geotextile bags every 3 to 6 feet along
seams and pound a wooden stake through each to hold them in
place;
7. Inspect plastic for rips, tears, and open seams regularly and repair
immediately. This prevents high velocity runoff from contacting
bare soil which causes extreme erosion;
8. Sandbags may be lowered into place tied to ropes. However, all
sandbags must be staked in place.
• Plastic sheeting shall have a minimum thickness of 0.06 millimeters.
• If erosion at the toe of a slope is likely, a gravel berm, riprap, or other
suitable protection shall be installed at the toe of the slope in order to
reduce the velocity of runoff.
Maintenance Torn sheets must be replaced and open seams repaired.
Standards
• If the plastic begins to deteriorate due to ultraviolet radiation, it must
be completely removed and replaced.
• When the plastic is no longer needed, it shall be completely removed.
• Dispose of old tires appropriately.
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~ BMP C130: SurFace Roughening
,~ Purpose Surface roughening aids in the establishment of vegetative cover, reduces
runoff vel
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ncreases infiltration, and provides for sediment trapping
through the provision of a rough soil surface. Horizontal depressions are
~ created by operating a tiller or other suitable equipment on the contour or
~ by leaving slopes in a roughened condition by not fine grading them.
Conditions for All slopes steeper than 3:1 and greater than 5 vertical feet require
~ Use surface roughening.
~J
Areas with grades steeper than 3:1 should be roughened to a depth of 2
~ to 4 inches prior to seeding.
~ Areas that will not be stabilized immediately may be roughened to
reduce runoff velocity until seeding takes place.
~ Slopes with a stable rock face do not require roughening.
~ Slopes where mowing is planned should not be excessively roughened.
'-' Design and There are different methods for achieving a roughened soil surface on a
Install
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on slope, and the selection of an appropriate method depends upon the type of
Specifications slope. Roughening methods include stair-step grading
groovin
cont
`~ ,
g,
our
furrows, and tracking. See Figure 4.6 for tracking and contour furrows
~
~ .
Factors to be considered in choosing a method are slope steepness, mowing
requirements, and whether the slope is formed by cutting or filling.
~ Disturbed areas that will not require mowing may be stair-step graded
U ,
grooved, or left rough after filling.
• Stair-step grading is particularly appropriate in soils containing large
~ amounts of soft rock. Each "step" catches material that sloughs from
i
u above, and provides a level site where vegetation can become
established. Stairs should be wide enough to work with standard earth
n moving equipment. Stair steps must be on contour or gullies will form
on the slope.
• Areas that will be mowed (these areas should have slopes less steep
n than 3:1) may have small furrows left by disking, harrowing, raking, or
`j seed-planting machinery operated on the contour.
'~ • Graded areas with slopes greater than 3:1 but less than 2:1 should be
roughened before seeding. This can be accomplished in a variety of
Li ways, including "track walking," or driving a crawler tractor up and
down the slope, leaving a pattern of cleat imprints arallel t 1
p osope
`-! contours.
U .~r~r~rin~~_doiie~~ _uperatil`lg~,glji an own e s ope to
leave horizontal depressions in the soil.
~ Maintenance
Areas that are graded in this manner should be seeded as quickly as
Standards possible.
~ Regular inspections should be made of the area. If rills appear, they
~ should be re-graded and re-seeded immediately.
~ 4-36
Volume 11 -Construction Stormwater Pollution Prevention February 2005
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~ mss'- ~-~ ~ ~?. Fem.
\\ \\ Q ~_~ ~-+1 ~
~- ~ ~ Cam. ~ ~, a
cam- ~' 8 ~`~-~. 8 C"
Contour Furrows
50'
(15m
~j\//\/\
~~~\~\
Grooves Will Catch Seed,
Fertilizer, Mulch, Rainfall
and Decrease Runoff.
Figure 4.6 -Surface Roughening by Tracking and Contour Furrows
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Volume 11 -Construction Stormwater Pollution Prevention
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4-37
'TRACKING' with machinery up and down ~~ ~ ~.
the slope provides grooves that will catch \\\\~ ~~,
seed, rainfall and reduce runoff. \\\\\
.\ ~ \ ~~
Maximum 1
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v BMP C140: Dust Control
~ Purpose Dust control prevents wind transport of dust from disturbed soil surfaces
'--~ onto roadways, drainage ways, and surface waters.
Conditions of Use In areas (including roadways) subject to surface and air movement of
~l dust where on-site and off-site impacts to roadways, drainage ways, or
surface waters are likely.
~ D
i
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, es
gn an egetate or mulch areas that will not receive vehicle traffic. In areas
Installation where planting, mulching, or paving is impractical, apply gravel or
r~ Specifications landscaping rock.
'J Limit dust generation by clearing only those areas where immediate
activity will take place, leaving the remaining area(s) in the original
J condition, if stable. Maintain the original ground cover as long as
practical.
~ Construct natural or artificial windbreaks or windscreens. These may
~ be designed as enclosures for small dust sources.
- • Sprinkle the site with water until surface is wet. Repeat as needed. To
`
1 prevent carryout of mud onto street, refer to Stabilized Construction
E
ntrance (BMP C 105).
~ Irrigation water can be used for dust control. Irrigation systems should
be installed as a first step on sites where dust control is a concern.
• Spray exposed soil areas with a dust palliative, following the
~ manufacturer's instructions and cautions regarding handling and
~ application. Used oil is prohibited from use as a dust suppressant.
Local governments may approve other dust palliatives such as calcium
~ chloride or PAM.
~ PAM (BMP C126) added to water at a rate of 0.5 lbs. per 1,000
gallons of water per acre and applied from a water truck is more
~! effective than water alone. This is due to the increased infiltration of
~ water into the soil and reduced evaporation. In addition, small soil
-' particles are bonded together and are not as easily transported by wind.
'
? Adding PAM may actually reduce the quantity of water needed for
~1 dust control, especially in eastern Washington. Since the wholesale
cost of PAM is about $ 4.00 per pound, this is an extremely cost-
`~ effective dust control method.
`J TPohnic}u~s tha~can-be-used~or-unpaved-roads-and~lots ino
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• Lower speed limits. High vehicle speed increases the amount of dust
stirred up from unpaved roads and lots.
• Upgrade the road surface strength by improving particle size, shape,
and mineral types that make up the surface and base materials.
Volume /l -Construction Stormwater Pollution Prevention February 2005
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v Add surface gravel to reduce the source of dust emission. Limit the
amount of fine particles (those smaller than .075 mm) to 10 to 20
rl percent.
'J Use geotextile fabrics to increase the strength of new roads or roads
~ undergoing reconstruction.
Lf Encourage the use of alternate, paved routes, if available.
• Restrict use by tracked vehicles and heavy trucks to prevent damage to
~ road surface and base.
`~ Apply chemical dust suppressants using the admix method, blending
n the product with the top few inches of surface material. Suppressants
J may also be applied as surface treatments.
• Pave unpaved permanent roads and other trafficked areas.
~ Use vacuum street sweepers.
~l
• Remove mud and other dirt promptly so it does not dry and then turn
~ into dust.
• Limit dust-causing work on windy days.
rl Contact your local Air Pollution Control Authority for guidance and
training on other dust control measures. Compliance with the local Air
Pollution Control Authority constitutes compliance with this BMP.
n
Maintenance Respray area as necessary to keep dust to a minimum.
u Standards
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BMP C150: Materials On Hand
n Purpose Quantities of erosion prevention and sediment control materials can be
~ kept on the project site at all times to be used for emergency situations
such as unexpected heavy summer rains. Having these materials on-site
~l reduces the time needed to implement BMPs when inspections indicate
that existing BMPs are not meeting the Construction SWPPP
requirements. In addition, contractors can save money by buying some
r-~ materials in bulk and storing them at their office or yard.
J Conditions of Use Construction projects of any size or type can benefit from having
materials on hand. A small commercial development project could
have a roll of plastic and some gravel available for immediate
protection of bare soil and temporary berm construction. A large
earthwork project, such as highway construction, might have several
`~
~ tons of straw, several rolls of plastic, flexible pipe, sandbags,
il
f
"
"
, geotext
e
abric and steel
T
posts.
~ • Materials are stockpiled and readily available before any site clearing,
grubbing, or earthwork begins. A large contractor or developer could
`-~ keep a stockpile of materials that are available to be used on several
~ projects.
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Installation
Specifications
• If storage space at the project site is at a premium, the contractor could
maintain the materials at their office or yard. The office or yard must
be less than an hour from the project site.
Depending on project type, size, complexity, and length, materials and
quantities will vary. A good minimum that will cover numerous situations
includes:
Material Measure Quantit
Clear Plastic, 6 mil 100 foot roll 1-2
Drain i e, 6 or 8 inch diameter 25 foot section 4-6
Sandba s, filled each 25-50
Straw Bales for mulchin , a rox. 50# each 10-20
ua Sails ton 2.4
Washed Gravel cubic and 2-4
Geotextile Fabric 100 foot roll 1-2
Catch Basin Inserts each 2-4
Steel "T" Posts each 12-24
~-i Maintenance All mater;als_with the-exception-ef-the-quarry--spal}s; stee " ost ,
Standards and gravel should be kept covered and out of both sun and rain.
n
• Re-stock materials used as needed.
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4.2 Runoff Conveyance and Treatment BMPs
`~l BMP C200: Interceptor Dike and Swale
'-~ Purpose Provide a ridge of compacted soil, or a ridge with an upslope swale, at the
~ top or base of a disturbed slope or along the perimeter of a disturbed
LJ construction area to convey stormwater. Use the dike and/or swale to
intercept the runoff from unprotected areas and direct it to areas where
~ erosion can be controlled. This can prevent storm runoff from entering the
work area or sediment-laden runoff from leaving the construction site.
Conditions of Use Where the runoff from an exposed site or disturbed slope must be conveyed
~ to an erosion control facility which can safely convey the stormwater.
~ Locate upslope of a construction site to prevent runoff from entering
disturbed area.
• When placed horizontally across a disturbed slope, it reduces the
amount and velocity of runoff flowing down the slope.
r--~ Locate downslope to collect runoff from a disturbed area and direct it
~. ~
to a sediment basin.
Design and Dike and/or swale and channel must be stabilized with temporary or
r"1 Installation permanent vegetation or other channel protection during construction.
~J Specifications Channel requires a positive grade for drainage; steeper grades require
channel protection and check dams.
n
• Review construction for areas where overtopping may occur.
~ Can be used at top of new fill before vegetation is established.
n
May be used as a permanent diversion channel to carry the runoff.
~ Sub-basin tributary area should be one acre or less.
~ Design capacity for the peak flow from a 10-year, 24-hour storm,
~ assuming a Type lA rainfall distribution, for temporary facilities.
Alternatively, use 1.6 times the 10-year, 1-hour flow indicated by an
~ approved continuous runoff model. For facilities that will also serve
`
~ on a permanent basis, consult the local government's drainage
- requirements.
n Interceptor dikes shall meet the following criteria:
U Top Width 2 feet minimum.
Height 1.5 feet minimum on berm.
'-' Side Slope 2:1 or flatter.
~J Grade Depends on topo~raph~. however_ dike cvctPm minimum-iv
0.5%, maximum is 1%.
`~~ Compaction Minimum of 90 percent ASTM D698 standard proctor.
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Horizontal Spacing of Interceptor Dikes:
~ Average Slope Slope Percent Flowpath Length
20H:1 V or less 3-5% 300 feet
v (10 to 20)H:1V 5-10% 200 feet
~ (4 to 10)H:1 V 10-25% 100 feet
(2 to 4)H:l V 25-50% 50 feet
~ Stabilization depends on velocity and reach
r~ Slopes <5% Seed and mulch applied within 5 days of dike
~ construction (see BMP C121, Mulching).
Slopes 5 - 40% Dependent on runoff velocities and dike materials.
,--~ Stabilization should be done immediately using either
~ sod or riprap or other measures to avoid erosion.
The upslope side of the dike shall provide positive drainage to the dike
~ outlet. No erosion shall occur at the outlet. Provide energy dissipation
'J measures as necessary. Sediment-laden runoff must be released
through a sediment trapping facility.
'~ Minimize construction traffic over temporary dikes. Use temporary
~ cross culverts for channel crossing.
Interceptor swales shall meet the following criteria:
n
~ Bottom Width 2 feet minimum; the bottom shall be level.
Depth 1-foot minimum.
~ Side Slope 2:1 or flatter.
v Grade Maximum 5 percent, with positive drainage to a
suitable outlet (such as a sediment pond).
~ Stabilization Seed as per BMP C120, Temporary and Permanent
~ Seeding, or BMP C202, Channel Lining, 12 inches
thick of riprap pressed into the bank and extending
~-, at least 8 inches vertical from the bottom.
• Inspect diversion dikes and interceptor swales once a week and after
u every rainfall. Immediately remove sediment from the flow area.
~ Damage caused by construction traffic or other activity must be
U repaired before the end of each working day.
Check outlets and make timely repairs as needed to avoid gully formation. When
n the area below the temporary diversion dike is permanently stabilized, remove the
u dike and fill and stabilize the channel to blend with the natural surface.
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Purpose Construction of small dams across a swale or ditch reduces the velocity of
concentrated flow and dissipates energy at the check dam.
'~ Conditions of Use Where temporary channels or permanent channels are not yet vegetated,
~ channel lining is infeasible, and velocity checks are required.
• Check dams may not be placed in streams unless approved by the State
~' Department of Fish and Wildlife. Check dams may not be placed in
U wetlands without approval from a permitting agency.
,~ Check dams shall not be placed below the expected backwater from
U any salmonid bearing water between October 1 and May 31 to ensure
that there is no loss of high flow refuge habitat for overwintering
~ juvenile sahnonids and emergent salmonid fry.
U Design and Whatever material is used, the dam should form a triangle when viewed
Installation from the side. This prevents undercutting as water flows over the face of
r-1 Specifications the dam rather than falling directly onto the ditch bottom.
U Check dams in association with sumps work more effectively at slowing
flow and retaining sediment than just a check dam alone. A deep sump
~, should be provided immediately upstream of the check dam.
~ In some cases, if carefully located and designed, check dams can
~ remain as permanent installations with very minor regrading. They
~ may be left as either spillways, in which case accumulated sediment
would be graded and seeded, or as check dams to prevent further
,--~ sediment from leaving the site.
U Check dams can be constructed of either rock orpea-gravel filled bags.
Numerous new products are also available for this purpose. They tend
'~ to be re-usable, quick and easy to install, effective, and cost efficient.
U Check dams should be placed perpendicular to the flow of water.
n The maximum spacing between the dams shall be such that the toe of
~ the upstream dam is at the same elevation as the top of the downstream
dam.
'~ Keep the maximum height at 2 feet at the center of the dam.
~ Keep the center of the check dam at least 12 inches lower than the
,~ outer edges at natural ground elevation.
~J Keep the side slopes of the check dam at 2:1 or flatter.
• Key the stone into the ditch banks and extend it beyond the abutments
n a minimum of 18 inches to avoid washouts from overflow around the
dam.
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~I Use filter fabric foundation under a rock or sand bag check dam. If a
blanket ditch liner is used, this is not necessary. Apiece of organic or
synthetic blanket cut to fit will also work for this purpose.
• Rock check dams shall be constructed of appropriately sized rock.
The rock must be placed by hand or by mechanical means (no
d
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k
ump
ng o
roc
to form dam) to achieve complete coverage of the
ditch or swale and to ensure that the center of the dam is lower than
the edges. The rock used must be large enough to stay in place given
th
d d
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es
gn flow through the channel.
• In the case of grass-lined ditches and swales, all check dams and
r~ accumulated sediment shall be removed when the grass has matured
U sufficiently to protect the ditch or swale -unless the slope of the Swale
is greater than 4 percent. The area beneath the check dams shall be
seeded and mulched immediately after dam removal.
~I • Ensure that channel appurtenances, such as culvert entrances below
- check dams, are not subject to damage or blockage from displaced
'
! stones. Figure 4.13 depicts a typical rock check dam.
~J
Maintenance Check dams shall be monitored for performance and sediment
n Standards accumulation during and after each runoff producing rainfall. Sediment
u shall be removed when it reaches one half the sump depth.
• Anticipate submergence and deposition above the check dam and
n erosion from high flows around the edges of the dam.
~ If significant erosion occurs between dams, install a protective riprap
liner in that portion of the channel.
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View Looking llpst~eam_
NOTE:
Key stone into channel banks and
extend it beyond the abutments a
minimum of 18" (0.5m) to prevent
flow around dam.
12"(150mm) ~ti~~~A ~~a,~~
a oo
A
Spacing Between Check Dams
'L' =the distance such that points 'A' and
'B' are of equal elevation.
L'
~~POINT'A'
POINT ' B'
NOT TO SCALE
Figure 4.13 -Check Dams
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Section A - A
FLOW
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BMP C220: Storm Drain Inlet Protection
Purpose To prevent coarse sediment from entering drainage systems prior to
permanent stabilization of the disturbed area.
Conditions of Use Where storm drain inlets are to be made operational before permanent
stabilization of the disturbed drainage area. Protection should be provided
for all storm drain inlets downslope and within 500 feet of a disturbed or
construction area, unless the runoff that enters the catch basin will be
conveyed to a sediment pond or trap. Inlet protection may be used
anywhere to protect the drainage system. It is likely that the drainage
system will still require cleaning.
Table 4.9 lists several options for inlet protection. All of the methods for
storm drain inlet protection are prone to plugging and require a high
frequency of maintenance. Drainage areas should be limited to 1 acre or
less. Emergency overflows may be required where stormwater ponding
would cause a hazard. If an emergency overflow is provided, additional
end-of--pipe treatment may be required.
Table 4.9
Storm Drain Inlet Protetion
Applicable for
Type of Inlet Emergency Paved/ Earthen
Protection Overflow Surfaces Conditions of Use
Dro Inlet Protection
Excavated drop inlet Yes, Earthen Applicable for heavy flows. Easy
protection temporary to maintain. Large area
flooding will Requirement: 30' X 30'/acre
occur
Block and gravel drop Yes Paved or Earthen Applicable for heavy concentrated
inlet protection flows. Will not pond.
Gravel and wire drop No Applicable for heavy concentrated
inlet protection flows. Will pond. Can withstand
traffic.
Catch basin filters Yes Paved or Earthen Fre uent maintenance re uired.
Curb Inlet Protection
Curb inlet protection Small capacity Paved Used for sturdy, more compact
with a wooden weir overflow installation.
Block and gravel curb Yes Paved Sturdy, but limited filtration.
inlet protection
Culvert Inlet Protection
Culvert inlet sediment 18 month expected life.
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4-82 Volume 11-Construction Stormwater Pollution Prevention February 2005
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Design and Excavated Drop Inlet Protection - An excavated impoundment around the
Installation storm drain. Sediment settles out of the stormwater prior to entering the
Specifications storm drain.
• Depth 1-2 ft as measured from the crest of the inlet structure.
+J Side Slopes of excavation no steeper than 2:1.
• Minimum volume of excavation 35 cubic yards.
~ Shape basin to fit site with longest dimension oriented toward the
•
longest inflow area.
r~ Install provisions for draining to prevent standing water problems.
u l Clear the area of all debris.
• Grade the approach to the inlet uniformly.
• Drill weep holes into the side of the inlet.
• Protect weep holes with screen wire and washed aggregate.
• Seal weep holes when removing structure and stabilizing area.
• It may be necessary to build a temporary dike to the down slope side
of the structure to prevent bypass flow.
U
Block and Gravel Filter - A barrier formed around the storm drain inlet
with standard concrete blocks and gravel. See Figure 4.14.
~ Height 1 to 2 feet above inlet.
~ Recess the first row 2 inches into the ground for stability.
~ Support subsequent courses by placing a 2x4 through the block
opening.
• Do not use mortar.
rt Lay some blocks in the bottom row on their side for dewatering the
iJ pool.
• Place hardware cloth or comparable wire mesh with %2-inch openings
r' over all block openings.
~ Place gravel just below the top of blocks on slopes of 2:1 or flatter.
• An alternative design is a gravel donut.
~1
• Inlet slope of 3:1.
• Outlet slope of 2:1.
~ 1-foot wide level stone area between the structure and the inlet.
• Outlet slope use gravel %2- to 3/4-inch at a minimum thickness of 1-foot.
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Plan View
Drain _
Grate
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Concrete
Block
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Section A - A
Gravel Backfill ~
Drop Inlet
Wire Screen or
Filter Fabric
Ponding Height
~ ,~~
Notes
1 Drop inlet sediment barners are to be used for small, nearly level drainage areas (less than 5%)
2 Excavate a basin of sufficient size adfacent to the drop inlet
n 3 The top of the structure (pondmg height) must be well below the ground elevation downslope to prevent
lJ runoff from bypassing the inlet A temporary dike may be necessary on the dowslope side of the structure
Figure 4.14 -Block and Gravel Filter
~ Gravel and Wire Mesh Filter - A gravel barrier placed over the top of the
inlet. This structure does not provide an overflow.
:-, Hardware cloth or comparable wire mesh with %2-inch openings.
v Coarse aggregate.
,--r Height 1-foot or more, 18 inches wider than inlet on all sides.
Lj Place wire mesh over the drop inlet so that the wire extends a
minimum of 1-foot beyond each side of the inlet structure.
~
~ If more than one stri of mesh is necessa
p ry, overlap the strips.
• Place coarse aggregate over the wire mesh.
~ The depth of the gravel should be at least 12 inches over the entire
~I inlet opening and extend at least 18 inches on all sides.
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4-84 Volume 11 -Construction Sto-mwater Pollution Prevention February 2005
Concrete Block
Overflow
~ Water
,~ °~~
II~I~Water
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~ catchbasin Filters -Inserts should be designed by the manufacturer for
~ use at construction sites. The limited sediment storage capacity increases
the amount of inspection and maintenance required, which may be daily
for heavy sediment loads. The maintenance requirements can be reduced
by combining a catchbasin filter with another type of inlet protection.
~ This type of inlet protection provides flow bypass without overflow and
~J therefore may be a better method for inlets located along active rights-of-
way.
• 5 cubic feet of storage.
• Dewatering provisions.
~ High-flow bypass that will not clog under normal use at a construction
site.
r~ The catchbasin filter is inserted in the catchbasin just below the
grating.
Curb Inlet Protection with Wooden Weir -Barrier formed around a curb
inlet with a wooden frame and gravel.
• Wire mesh with %2-inch openings.
~ Extra strength filter cloth.
~ • Construct a frame.
Attach the wire and filter fabric to the frame.
rl • Pile coarse washed aggregate against wire/fabric.
Place weight on frame anchors.
•
Block and Gravel Curb Inlet Protection -Barrier formed around an inlet
~ with concrete blocks and gravel. See Figure 4.14.
~ Wire mesh with''/z-inch openings.
• Place two concrete blocks on their sides abutting the curb at either side
of the inlet opening. These are spacer blocks.
~ Place a 2x4 stud through the outer holes of each spacer block to align
•
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the front blocks.
,J Place blocks on their sides across the front of the inlet and abutting the
spacer blocks.
~ Place wire mesh over the outside vertical face.
•
u • Pile coarse aggregate against the wire to the top of the barrier.
`-` Curb and Gutter Sediment Barrier -Sandbag or rock berm (riprap and
~..1 aggreaate) 3 fe~high_and ~ feet w;r~P ;,, a l,~r~P~t,.r~o_shape: fee-Fgur
4.16.
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• Construct a horseshoe shaped berm, faced with coarse aggregate if
using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet.
• Construct a horseshoe shaped sedimentation trap on the outside of the
berm sized to sediment trap standards for protecting a culvert inlet.
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Maintenance Catch basin filters should be inspected frequently, especially after
Standards storm events. If the insert becomes clogged, it should be cleaned or
replaced.
• For systems using stone filters: If the stone filter becomes clogged
with sediment, the stones must be pulled away from the inlet and
cleaned or replaced. Since cleaning of gravel at a construction site
may be difficult, an alternative approach would be to use the clogged
stone as fill and put fresh stone around the inlet.
• Do not wash sediment into storm drains while cleaning. Spread all
excavated material evenly over the surrounding land area or stockpile
and stabilize as appropriate.
4-86 Volume 11 - Construction Stormwater Pollution Prevention February 2005
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Plan View
r- Back of Sidewalk A
Catch Basm
Back of Curb
Curb Inlet
Wire Screen
Filter Fabric
Section A ' A (20mm)n
'/." Drain Gravel
(20mm)
2x4 Wood Stud
Concrete Block
A -~ `Concrete Block
Pondmg Height
~~Concrete Block
(100x50 Timber Stud)
NOTES
~,-~Ise~lockartd-gravel-typesediment-barrier-when-curb rrr is oca a in gen y s oping street segment
where water can pond and allow sediment to separate from runoff
2 Barrier shall allow for overflow from severe storm event
3 Inspect barriers and remove sediment after each storm event Sediment and gravel must be removed
from the traveled way immediately
Figure 4.15 -Block and Gravel Curb Inlet Protection
February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-87
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Back of Sidewalk
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~;`,~~ _ ~ ~; ~ ~tacKea i igntry
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NOTES•
1. Place curb type sediment barriers on gently sloping street segments, where water can pond and allow
sediment to separate from runoff.
2. Sandbags of either burlap or woven ' geotexhle' fabric, are filled with gravel, layered and packed tightly.
3 Leave a one sandbag gap in the top row to provede a spillway for overflow
4. Inspect bamers and remove sediment after each storm event. Sediment and gravel must be removed from
the traveled way immediately.
Fiqure 4.16 -Curb and Gutter Barrier
4-88 Volume 11-Construction Stormwater Pollution Prevention
February 2005
Burlap Sacks to Catch Basin
___ _ Overlap onto Curb
'' ~ Curb Inlet
~;
j ,~ -- _~,1 Back of Curb
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~ BMP C209: Outlet Protection
~
~ Purpose Outlet protection prevents scour at conveyance outlets and minimizes the
potential for downstream erosion by reducing the velocity of concentrated
stormwater flows.
U Conditions of use Outlet protection is required at the outlets of all ponds, pipes, ditches, or
other conveyances, and where runoff is conveyed to a natural or manmade
~ drainage feature such as a stream, wetland, lake, or ditch.
-- Design and
Installation The receiving channel at the outlet of a culvert shall be protected from
,
i
Specifications erosion by rock lining a minimum of 6 feet downstream and extending up
~ the channel sides a minimum of 1-foot above the maximum tailwater
elevation or 1-foot above the crown, whichever is higher. For large pipes
n (more than 18 inches in diameter), the outlet protection lining of the
~s channel is lengthened to four times the diameter of the culvert.
~ • Standard wingwalls, and tapered outlets and paved channels should
also be considered when appropriate for permanent culvert outlet
'~ protection. (See WSDOT Hydraulic Manual, available through
n
WSDOT Engineering Publications).
U Organic or synthetic erosion blankets, with or without vegetation, are
usually more effective than rock, cheaper, and easier to install.
r-i Materials can be chosen using manufacturer product specifications.
U ASTM test results are available for most products and the designer can
choose the correct material for the expected flow.
`~ With low flows, vegetation (including sod) can be effective.
`~ The following guidelines shall be used for riprap outlet protection:
~ 1. If the discharge velocity at the outlet is less than 5 fps (pipe slope
,J less than 1 percent), use 2-inch to 8-inch riprap. Minimum
thickness is 1-foot.
r-, 2. For 5 to 10 fps discharge velocity at the outlet (pipe slope less than
~ 3 percent), use 24-inch to 4-foot riprap. Minimum thickness is 2
feet.
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U 3. For outlets at the base of steep slope pipes (pipe slope greater than
10 percent), an engineered energy dissipater shall be used.
`-' Filter fabric or erosion control blankets should always be used under
U riprap to prevent scour and channel erosion.
~ • New pipe outfalls can provide an opportunity for low-cost fish habitat
`~ improvements. For example, an alcove of low-velocity water can be
created by constructing the pipe outfall and associated energy
dissipater back from the stream edge and digging a channel, over-
widened to the upstream side, from the outfall. Overwintering juvenile
~ and migrating adult salmonids may use the alcove as shelter during
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high flows. Bank stabilization, bioengineering, and habitat features
may be required for disturbed areas. See Volume V for more
information on outfall system design.
Maintenance . Inspect and repair as needed.
Standards
• Add rock as needed to maintain the intended function.
• Clean energy dissipater if sediment builds up.
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February 2005 Volume 11 - Construction Stormwater Pollution Prevention
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BMP C233: Silt Fence
Purpose Use of a silt fence reduces the transport of coarse sediment from a
construction site by providing a temporary physical barrier to sediment
and reducing the runoff velocities of overland flow. See Figure 4.19 for
details on silt fence construction.
Conditions of Use Silt fence may be used downslope of all disturbed areas.
• Silt fence is not intended to treat concentrated flows, nor is it intended
to treat substantial amounts of overland flow. Any concentrated flows
must be conveyed through the drainage system to a sediment pond.
The only circumstance in which overland flow can be treated solely by
a silt fence, rather than by a sediment pond, is when the area draining
to the fence is one acre or less and flow rates are less than 0.5 cfs.
• Silt fences should not be constructed in streams or used in V-shaped
ditches. They are not an adequate method of silt control for anything
deeper than sheet or overland flow.
Filter fabric
I ~ ~ 6' max-~; ~ ~ Minimum 4"x4" trench '~~
~ I Backftll trench with native soil /
Post spacing may be increased or 3/4"-1.5" washed gravel
to 8' if wire backing is used
2"x2" wood posts, steel fence
posts, or equivalent
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rigure 4.~y - gut rence
~ Design and Drainage area of 1 acre or less or in combination with sediment basin
Installation in a larger site.
Specifications
n, • Maximum slope steepness (normal (perpendicular) to fence line) 1:1.
u Maximum sheet or overland_fln~ath 1~ ~ h~ ± ~n th~fense-of-1-00 feet.
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• No flows greater than 0.5 cfs.
• The geotextile used shall meet the following standards. All geotextile
properties listed below are minimum average roll values (i.e., the test
result for any sampled roll in a lot shall meet or exceed the values
shown in Table 4.10):
Volume 11 -Construction Stormwater Pollution Prevention February 2005
2"x2" by 14 Ga. wire or
equivalent, if standard
strength fabric used
~J
Joints in filter fabric shall be spliced at
posts Use staples, wire nngs or
equivalent to attach fabric to posts
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Table 4.10
Geotextile Standards
Polymeric Mesh AOS 0.60 mm maximum for slit film wovens (#30 sieve). 0.30
(ASTM D4751) mm maximum for all other geotextile types (#50 sieve).
0.15 mm minimum for all fabric types (#100 sieve).
Water Permittivity 0.02 sec' minimum
(ASTM D4491)
Grab Tensile Strength 1801bs. Minimum for extra strength fabric.
(ASTM D4632) 1001bs minimum for standard strength fabric.
Grab Tensile Strength 30% maximum
(ASTM D4632)
Ultraviolet Resistance 70% minimum
(ASTM D4355)
• Standard strength fabrics shall be supported with wire mesh, chicken
wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the
strength of the fabric. Silt fence materials are available that have
synthetic mesh backing attached.
• Filter fabric material shall contain ultraviolet ray inhibitors and
stabilizers to provide a minimum of six months of expected usable
construction life at a temperature range of 0°F. to 120°F.
• 100 percent biodegradable silt fence is available that is strong, long
n lasting, and can be left in place after the project is completed, if
Lj permitted by local regulations.
• Standard Notes for construction plans and specifications follow. Refer
~ to Figure 4.19 for standard silt fence details.
~ The contractor shall install and maintain temporary silt fences at the
,~ locations shown in the Plans. The silt fences shall be constructed in
~ the areas of clearing, grading, or drainage prior to starting those
activities. A silt fence shall not be considered temporary if the silt
,--f fence must function beyond the life of the contract. The silt fence
shall prevent soil carried by runoff water from going beneath, through,
or over the top of the silt fence, but shall allow the water to pass
~ through the fence.
,~ The minimum height of the top of silt fence shall be 2 feet and the
maximum height shall be 2% feet above the original ground surface.
The geotextile shall be sewn together at the point of manufacture, or at
an annrnvPri lnratii1on_.apa~ d~t~r~ll~n~~-b„~ 4hL~~-,-ilgii "~.zL~i_tv_f~rrrl_gE6texttl
lengths as required. All sewn seams shall be located at a support post.
Alternati
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wo sect
ons o
s
t fence can be overlapped, provided
~ the Contractor can demonstrate, to the satisfaction of the Engineer, that
the overlap is long enough and that the adjacent fence sections are
`~ close enough together to prevent silt laden water from escaping
LI through the fence at the overlap.
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The geotextile shall be attached on the up-slope side of the posts and
support system with staples, wire, or in accordance with the
manufacturer's recommendations. The geotextile shall be attached to
h
t
e posts in a manner that reduces the potential for geotextile tearing at
the staples, wire, or other connection device. Silt fence back-up
~`` support for the geotextile in the form of a wire or plastic mesh is
~1 dependent on the properties of the geotextile selected for use. If wire
or plastic back-up mesh is used, the mesh shall be fastened securely to
~ the up-slope of the posts with the geotextile being up-slope of the
mesh back-up support.
The geotextile at the bottom of the fence shall be buried in a trench to
a minimum depth of 4 inches below the ground surface. The trench
shall be backfilled and the soil tamped in place over the buried portion
of the geotextile, such that no flow can pass beneath the fence and
scouring can not occur. When wire or polymeric back-up support
~-- ~ mesh is used, the wire or polymeric mesh shall extend into the trench a
minimum of 3 inches.
The fence posts shall be placed or driven a minimum of 18 inches. A
minimum depth of 12 inches is allowed if topsoil or other soft
subgrade soil is not present and a minimum depth of 18 inches cannot
be reached. Fence post depths shall be increased by 6 inches if the
fence is located on slopes of 3:1 or steeper and the slope is
,~ perpendicular to the fence. If required post depths cannot be obtained,
~
`~ the posts shall be adequately secured by bracing or guying to prevent
overturning of the fence due to sediment loading.
Silt fences shall be located on contour as much as possible, except at
h
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ence, where the fence shall be turned uphill such that
the silt fence captures the runoff water and prevents water from
~1 flowing around the end of the fence.
u If the fence must cross contours, with the exception of the ends of the
fence, gravel check dams placed perpendicular to the back of the fence
shall be used to minimize concentrated flow and erosion along the
back of the fence. The gravel check dams shall be approximately 1-
foot deep at the back of the fence. It shall be continued perpendicular
~ to the fence at the same elevation until the top of the check dam
u intercepts the ground surface behind the fence. The gravel check dams
shall consist of crushed surfacing base course, gravel backfill for
`~ walls, or shoulder ballast. The gravel check dams shall be located
y eery 10 feet along the fence_where the fen~P must crass-contours.
The slope of the fence line where contours must be crossed shall not
'~
i be steeper than 3:1.
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Wood, steel or equivalent posts shall be used. Wood posts shall have
minimum dimensions of 2 inches by 2 inches by 3 feet minimum
length, and shall be free of defects such as knots, splits, or gouges.
4-96 Volume 11 -Construction Stormwater Pollution Prevention February 2005
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~J Steel posts shall consist of either size No. 6 rebar or larger, ASTM A
120 steel pipe with a minimum diameter of 1-inch, U, T, L, or C shape
'~
~ steel posts with a minimum weight of 1.35 lbs./ft. or other steel posts
h
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, av
ng equivalent strength and bending resistance to the post sizes
listed. The spacing of the support posts shall be a maximum of 6 feet.
~
'~ Fence back-up support, if used, shall consist of steel wire with a
maximum mesh spacing of 2 inches, or a prefabricated polymeric
mesh. The strength of the wire or polymeric mesh shall be equivalent
to or greater than 180 lbs. grab tensile strength. The polymeric mesh
must be as resistant to ultraviolet radiation as the geotextile it supports.
~ • Silt fence installation using the slicing method specification details
,~ follow. Refer to Figure 4.20 for slicing method details.
The base of both end posts must be at least 2 to 4 inches above the top
~ of the silt fence fabric on the middle posts for ditch checks to drain
~ properly. Use a hand level or string level, if necessary, to mark base
points before installation.
r--r
~
Install posts 3 to 4 feet apart in critical retention areas and 6 to 7 feet
apart in standard applications.
~ Install posts 24 inches deep on the downstream side of the silt fence
Lj ,
and as close as possible to the fabric, enabling posts to support the
fabric from upstream water pressure.
r' Install posts with the nipples facing away from the silt fence fabric.
Attach the fabric to each post with three ties, all spaced within the top
n 8 inches of the fabric. Attach each tie diagonally 45 degrees through
the fabric, with each puncture at least 1 inch vertically apart. In
addition, each tie should be positioned to hang on a post nipple when
~ tightening to prevent sagging.
~l Wrap approximately 6 inches of fabric around the end posts and secure
with 3 ties.
n
No more than 24 inches of a 36-inch fabric is allowed above ground
level.
~ The rope lock system must be used in all ditch check applications.
v The installation should be checked and corrected for any deviation
before compaction. Use aflat-bladed shovel to tuck fabric dee er inter
p
`~ the ground if necessary.
~.,ompacuon is vitally nnportant for effective resu ts. ompact t e soil
,~ immediately next to the silt fence fabric with the front wheel of the
~ tractor, skid steer, or roller exerting at least 60 pounds per square inch.
`~ Compact the upstream side first and then each side twice for a total of
~ four trips.
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~.J Any damage shall be repaired immediately.
Maintenance If concentrated flows are evident uphill of the fence, they must be
~ Standards intercepted and conveyed to a sediment pond.
'~ It is important to check the uphill side of the fence for signs of the
fence clogging and acting as a barrier to flow and then causing
channelization of flows parallel to the fence. If this occurs, replace the
fence or remove the trapped sediment.
~ Sediment deposits shall either be removed when the deposit reaches
Lj approximately one-third the height of the silt fence, or a second silt
fence shall be installed.
'~ If the filter fabric (geotextile) has deteriorated due to ultraviolet
>_J _ breakdown, it shall be replaced.
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Parading height POST SPRGtNG:
max. 24- T max, en open runs
`' Ma1C On POblltlg a1`Oal
Attach laDAc to
uPstraala aide of Post ;
i
i
1 i:~ow-..
•~
- WWe ever e.eh sIW w
POSr nePTN:
alit tens 2 to i times ~ As much betew ground
anN drHCe exbru~ r
f
b
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sa
s
r
c above ground
tw p.e.i. or groater ~
J toox eempeeel,q~ t
O
OX eompsetlan
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~
~~i~~~~rr ~ ~~~ ~~~ ~~~ ~~~
~\%f ~i ~i ~~~ ~i~~~~
~
~~ii~
~ i
i
~i~~~~i~°i~~`i ~~~%~~~~~~~ ~~
~~ i~!i~'' \/ ~O~f \~
. ii ii
a
~ No more than 24° of a 36" fabnc
is allowed above ground.
Roe of s7t fence
~ ~! OPTration
(
tJ __
(~ Fatxlc
above
U O ~ gmtnd
`~' ~t z,~~q~.6~~
~
~~ `F~ ~~li
I ~
.
~ ~,~~.r~~~''c~ ~~'
y
, ~ ~~
~ ~~~
i 200-33
ma
(
/
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Set Fence
Pou
efstalled
after
compaction
Fiorta>ntal chisel poklt S6ctrlg blade
{7fi mm wig} (18 mm w(dth) ^
Completed ~lSta®atlon
Vibratory plow is not acceptable because of hollzontai compaction
Figure 4.20 -Silt Fence Installation by Slicing Method
4-98 Volume Il - Construction Stormwater Pollution Prevention February 2005
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BMP C240: Sediment Trap
Purpose A sediment trap is a small temporary ponding area with a gravel outlet
used to collect and store sediment from sites cleared and/or graded during
construction. Sediment traps, along with other perimeter controls, shall be
installed before any land disturbance takes place in the drainage area.
Conditions of Use Prior to leaving a construction site, stormwater runoff must pass through a
~ sediment pond or trap or other appropriate sediment removal best
~ management practice. Non-engineered sediment traps may be used on-site
prior to an engineered sediment trap or sediment pond to provide
,--~ additional sediment removal capacity.
It is intended for use on sites where the tributary drainage area is less than
3 acres, with no unusual drainage features, and a projected build-out time
~ of six months or less. The sediment trap is a temporary measure (with a
~ design life of approximately 6 months) and shall be maintained until the
site area is permanently protected against erosion by vegetation and/or
~
I structures.
~J
Sediment traps and ponds are only effective in removing sediment down
to about the medium silt size fraction. Runoff with sediment of finer
grades (fine silt and clay) will pass through untreated, emphasizing the
need to control erosion to the maximum extent first.
~ Whenever possible, sediment-laden water shall be discharged into onsite
'J ,
relatively level, vegetated areas (see BMP C234 -Vegetated Strip). This
is the only way to effectively remove fine particles from runoff unless
n
~ chemical treatment or filtration is used. This can be particularly useful
after initial treatment in a sediment trap or pond. The areas of release
must be evaluated on a site-by-site basis in order to determine appropriate
U locations for and methods of releasing runoff. Vegetated wetlands shall
not be used for this purpose. Frequently, it may be possible to pump water
from the collection point at the downhill end of the site to an upslope
r? vegetated area. Pumping shall only augment the treatment system, not
~ replace it, because of the possibility of pump failure or runoff volume in
excess of pump capacity.
~-,
~ All projects that are constructing permanent facilities for runoff quantity
control should use the rough-graded or final-graded permanent facilities
n for traps and ponds. This includes combined facilities and infiltration
facilities. When permanent facilities are used as temporary sedimentation
aci rties, t e su ace area requirement of a sediment trap or pond must be
s-~ met. If the surface area requirements are larger than the surface area of
~ the permanent facility, then the trap or pond shall be enlarged to comply
with the surface area requirement. The permanent pond shall also be
,~ divided into two cells as required for sediment ponds.
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er apermanent control structure or the temporary control structure
(described in BMP C241, Temporary Sediment Pond) can be used. If a
permanent control structure is used, it may be advisable to partially restrict
the lower orifice with gravel to increase residence time while still allowing
dewatering of the pond. A shut-off valve may be added to the control
structure to allow complete retention of stormwater in emergency
situations. In this case, an emergency overflow weir must be added.
r'1 A skimmer may be used for the sediment trap outlet if approved by the
~ Local Permitting Authority.
~ Design and See Figures 4.22 and 4.23 for details.
U Installation
Specifications • If permanent runoff control facilities are part of the project, they
should be used for sediment retention.
~ • To determine the sediment trap geometry, first calculate the design
surface area (SA) of the trap, measured at the invert of the weir. Use
the following equation:
~ SA = FS(QZIVs)
~ where
f
~;
Qa = Design inflow based on the peak discharge from the
developed 2-year runoff event from the contributing
n drainage area as computed in the hydrologic analysis. The
;J 10-year peak flow shall be used if the project size, expected
timing and duration of construction, or downstream
~ conditions warrant a higher level of protection. If no
~ hydrologic analysis is required, the Rational Method may
be used.
`~ Vs = The settling velocity of the soil particle of interest. The
U 0.02 mm (medium silt) particle with an assumed density of
~ 2.65 g/cm3 has been selected as the particle of interest and
has a settling velocity (VS) of 0.00096 ft/sec.
u
- FS = A safety factor of 2 to account for non-ideal settling.
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Therefore, the equation for computing surface area becomes:
~---,
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SA = 2 x Qz/0.00096 or
2080 square feet per cfs of inflow
Note: Even if permanent facilities are used, they must still have a
surface area that is at least as large as that derived from the above
formula. If they do not, the pond must be enlarged.
• To aid in determining sediment depth, all sediment traps shall have a
staff gauge with a prominent mark 1-foot above the bottom of the trap
Volume 11-Construction Storrnwater Pollution Prevention
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Maintenance • Sediment shall be removed from the trap when it reaches 1-foot in
Standards depth.
• Any damage to the pond embankments or slopes shall be repaired.
• Sediment traps may not be feasible on utility projects due to the
limited work space or the short-term nature of the work. Portable
tanks may be used in place of sediment traps for utility projects.
Surface area determined 4' Min.
at top of weir ~---~ -L
_ L 1' Min. Overflow
~ - -
T 1' Min. ~ T[-
~G 3.5'-5'
Flat Bottom t 1.5 Min. ~
1
Note: Trap may be formed by berm or by
partial or complete excavation
,~•' - 1 5" 2"-4" Rock RipRap
Washed gravel
Geotextile
Discharge to stabilized
conveyance, outlet, or
level spreader
Figure 4.22 Cross Section of Sediment Trap
6' Mln.
1' Min. depth overflow spillway
-~ ~. -i
Native sod or ' -~ ~ ~ _ ~ a ~ ~= Min. 1' depth
compacted backfill ~~ ~ ~ -'~:~. . " I-~ ~ ~- 2"-4"' rock
Geotextile ~ ~ ~_~ ~ ~-~ ~ ~_~ I ~-~ ~-~ ~ ~=~ ~ ~_~ ~ I-~ ~ ~- ~ Min. 1' depth 3/4"-1.5"
-~ ~ ~_~ ~ ~=~ ~ ~-~ ~ ~-~ ~ ~-~ ~ ~_~ ~ ~-~ ~ ~_~ ~ washed gravel
Figure 4.23 Sediment Trap Outlet
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4-104 Volume /l -Construction Stormwater Pollution Prevention February 2005
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S
di
: emporary
e
ment Pond
Purpose Sediment ponds remove sediment from runoff originating from disturbed
'
} areas of the site. Sediment ponds are typically designed to remove
- sediment no smaller than medium silt (0.02 mm). Consequently, they
usually reduce turbidity only slightly.
~ Conditions of Use Prior to leaving a construction site, stormwater runoff must pass through a
sediment pond or other appropriate sediment removal best management
n practice.
~J A sediment pond shall be used where the contributing drainage area is 3
acres or more. Ponds must be used in conjunction with erosion control
~ practices to reduce the amount of sediment flowing into the basin.
~ Design and • Sediment basins must be installed only on sites where failure of the
Installation structure would not result in loss of life, damage to homes or
Specifications buildings, or interruption of use or service of public roads or utilities.
Also, sediment traps and ponds are attractive to children and can be
very dangerous. Compliance with local ordinances regarding health
d
f
an
sa
ety must be addressed. If fencing of the pond is required, the
type of fence and its location shall be shown on the ESC plan.
r-~ Structures having a maximum storage capacity at the top of the dam of
3
~ 10 acre-ft (435,600 ft
) or more are subject to the Washington Dam
Safety Regulations (Chapter 173-175 WAC).
~ See Figure 4.24, Figure 4.25, and Figure 4.26 for details.
~ If permanent runoff control facilities are part of the project, they
should be used for sediment retention. The surface area requirements
`~ of the sediment basin must be met. This may require enlarging the
~ permanent basin to comply with the surface area requirements. If a
permanent control structure is used, it may be advisable to partially
r? restrict the lower orifice with gravel to increase residence time while
~,i still allowing dewatering of the basin.
r-, Use of infiltration facilities for sedimentation basins during
construction tends to clog the soils and reduce their capacity to
~ infiltrate. If infiltration facilities are to be used, the sides and bottom
of the facility must only be rough excavated to a minimum of 2 feet
n above final grade. Final grading of the infiltration facility shall occur
u only when all contributing drainage areas are fully stabilized. The
infiltration pretreatment facility should be fully constructed and used
r' with the sedimentation basin to help prevent clogging.
~ ~ He ermining on eome ry
n Obtain the discharge from the hydrologic calculations of the peak flow
U for the 2-year runoff event (QZ). The 10-year peak flow shall be used
if the project size, expected timing and duration of construction, or
n downstream conditions warrant a higher level of protection. If no
hydrologic analysis is required, the Rational Method may be used.
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Determine the required surface area at the top of the riser pipe with the
equation:
SA = 2 x QZ/0.00096 or
'--~ 2080 square feet per cfs of inflow
See BMP C240 for more information on the derivation of the surface
~ area calculation.
- The basic geometry of the pond can now be determined using the
`
? following design criteria:
~ Required surface area SA (from Step 2 above) at top of riser.
r-~ Minimum 3.5-foot depth from top of riser to bottom of pond.
II
~__1 Maximum 3:1 interior side slopes and maximum 2:1 exterior slopes.
The interior slopes can be increased to a maximum of 2:1 if fencing is
provided at or above the maximum water surface.
• One foot of freeboard between the top of the riser and the crest of the
emergency spillway.
~ Flat bottom.
U
• Minimum 1-foot deep spillway.
~ Length-to-width ratio between 3:1 and 6:1.
U
Sizing of Discharge Mechanisms.
n The outlet for the basin consists of a combination of principal and
~ emergency spillways. These outlets must pass the peak runoff expected
~ from the contributing drainage area fora 100-year storm. If, due to site
n conditions and basin geometry, a separate emergency spill-way is not
~ feasible, the principal spillway must pass the entire peak runoff expected
from the 100-year storm. However, an attempt to provide a separate
`~ emergency spillway should always be made. The runoff calculations
should be based on the site conditions during construction. The flow
h
t
rough the dewatering orifice cannot be utilized when calculating the
100-year storm elevation because of its potential to become clogged;
n therefore, available spillway storage must begin at the principal spillway
LJ riser crest.
- The principal spillway designed by the procedures contained in this
`
! standard will result in some reduction in the peak rate of runoff.
t_,_} However, the riser outlet design will not adequately control the basin
discharge to the predevelopment discharge limitations as stated in
n Minimum Requirement #7: Flow Control. However, if the basin for a
permanent stormwater detention pond is used for a te~11n~~
sedimentation basin, the control structure for the permanent pond can be
r-~ used to maintain predevelopment discharge limitations. The size of the
~ basin, the expected life of the construction project, the anticipated
downstream effects and the anticipated weather conditions during
,-~ construction, should be considered to determine the need of additional
~ discharge control. See Figure 4.28 for riser inflow curves.
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Key divider into slope
- ---- -- to prevent flow----
arouri&i~
The pond length shall be 3 to 6
times the maximum pond width
~Pon'tl length
Stlt fence or --'
equivalent divider
I t FUFdd IS ~ i~etali
Emergency overflow
j ~ spillway
/ _ ~~j ` . ~ y//
s.--
iserpip ~ ~` v'~~De
'k~ ~~a
f Discharge to stabilized
' conveyance, outlet, or
` \ ~~ 1 level spreader
1
Note Pond may be formed by berm or ~~~~~
by partial or complete excavation ~
Figure 4.24 -Sediment Pond Plan View
Riser pipe
(principal spillway) Crest of
open at top with 6' min Width
trash rack emergejnc spillway
ii-''~~~ Dewatenng device ~ -~-- __:___ +' a~V Embankment compacted 95%
II~~. _~~:-__-,~ ervious materials such as
I ~yL (see user detail) \,,` _ _ - ravel or clean sand shall
- _ ~ not be used
Wire-backed silt fence f T ~ ~~~+~ ~~ Discharge to stabilized
staked haybales wrapped Dewatenng Concrete base conveyance outlet or
with filter fabnc, or orifice (see user detail) level spreader
equivalent divider
rlgure 4.z5 -Sediment Pond Cross Section
Polyethylene cap Provide adequate
strapping
Perforated polyethylene -
drainage tubing, diameter - Corrugated
mm 2" larger than = metal riser
dewatenng orifice = 3 5" min
Tubing shall comply Watertight
with ASTM F667 and - Dewatenng orrFice, schedule,
coupling 40 steel stub min
AASHTO M294 _ -~ j k weld
Diameteras percalculations
I L---r---~ -
16" min I Alternatively, metal stakes
Concrete base and wire may be used to
prevent flotation
~- 2X nserdia Min ---I
Figure 4.26 -Sediment Pond Riser
February 2005 Volume ll -Construction Stormwater Pollution Prevention 4-107
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72 54 48
/ / X
42
36
33
30
27
24
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d
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21
18
15
10
1 ~
0.1
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HEAD IN FEET (measured from crest of riser)
Q weir=9.739 DH3iz
Q orifice=3.782 D 2H t/2
Q in cfs, D and H in feet
Slope change occurs atweir-orifice transition
10
Figure 4.27 - Riser Inflow Curves
4-908 Volume 11 - Construction Stormwater Pollution Prevention February 2005
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way: Determine the required diameter for the principal
spillway (riser pipe). The diameter shall be the minimum necessary to
~ pass the pre-developed 10-year peak flow (Qlp). Use Figure 4.28 to
~J determine this diameter (h = 1-foot). Note: A permanent control structure
may be used instead of a temporary riser.
~
'~ Emergency Overflow Spillway: Determine the required size and design
of the emergency overflow spillway for the developed 100-year peak flow
,~ using the method contained in Volume III.
~ Dewatering Orifice: Determine the size of the dewatering orifice(s)
(minimum 1-inch diameter) using a modified version of the discharge
~ equation for a vertical orifice and a basic equation for the area of a circular
~j orifice. Determine the required area of the orifice with the following
equation:
n
~
A = AS(2h)os
°
0.6x3600Tg o s
v
where Ao = orifice area (square feet)
As = pond surface area (square feet)
n h = head of water above orifice (height of riser in feet)
u T = dewatering time (24 hours)
g = acceleration of gravity (32.2 feedsecond2)
'-~ Convert the required surface area to the required diameter D of the orifice:
~ D = 24x A° =13.54x A°
u ~
r-, The vertical, perforated tubing connected to the dewatering orifice must be
at least 2 inches larger in diameter than the orifice to improve flow
u characteristics. The size and number of perforations in the tubing should
~, be large enough so that the tubing does not restrict flow. The orifice
should control the flow rate.
u
• Additional Design Specifications
r--,
The pond shall be divided into two roughly equal volume cells by a
'-~ permeable divider that will reduce turbulence while allowing
s movement of water between cells. The divider shall be at least one-
half the height of the riser and a minimum of one foot below the top of
=-~' the~er: --W-irerba~k~~' '' ' r
tea; L= to ~=rout-high, extra-strength-frlter-fabr'
supported by treated 4"x4"s can be used as a divider. Alternatively,
`~ staked straw bales wrapped with filter fabric (geotextile) may be used.
v If the pond is more than 6 feet deep, a different mechanism must be
proposed. A riprap embankment is one acceptable method of
`~ separation for deeper ponds. Other designs that satisfy the intent of
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~ February 2005 Volume 11 -Construction Stormwater Pollution Prevention 4-109
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'--~ this provision are allowed as long as the divider is permeable,
~ structurally sound, and designed to prevent erosion under or around
the barrier.
~J
To aid in determining sediment depth, one-foot intervals shall be
~ prominently marked on the riser.
~ If an embankment of more than 6 feet is proposed, the pond must
comply with the criteria contained in Volume III regarding dam safety
'~ for detention BMPs.
'J The most common structural failure of sedimentation basins is caused
~ by piping. Piping refers to two phenomena: (1) water seeping through
fine-grained soil, eroding the soil grain by grain and forming pipes or
'--~ tunnels; and, (2) water under pressure flowing upward through a
~ granular soil with a head of sufficient magnitude to cause soil grains to
lose contact and capability for support.
The most critical construction sequences to prevent piping will be:
~ 1. Tight connections between riser and barrel and other pipe
~ connections.
,-, 2. Adequate anchoring of riser.
~ 3. Proper soil compaction of the embankment and riser footing.
4. Proper construction of anti-seep devices.
~ Maintenance Sediment shall be removed from the pond when it reaches 1-foot in
Standards depth.
~ e Any damage to the pond embankments or slopes shall be repaired.
~~
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Appendix C -Alternative BMPs
'-1
~` 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 for a specific
~ element is not functioning as designed and an alternative BMP needs to be implemented.
Element #1 -Mark Clearing Limits
~l
,J N/A
'~ Element #2 -Establish Construction Access
~J
Wheel Wash (BMP C106)
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'~ Water Bars (BMP C203) may also be applicable.
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'J Element #3 -Control Flow Rates
`~ Detention Pond or Vault
~J
~ Infiltration Trench
~ Element #4 -Install Sediment Controls
v
~ Straw Bale Barrier (BMP C230)
n Brush Barrier (BMP C231)
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Gravel Filter Berm (BMP C232)
n
u Vegetated Strip (BMP C234)
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Straw Wattles (BMP C235)
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Tahoma Terra Stormwater Pollution Prevention Plan
Portable Water Storage Tanks (e.g., Baker Tank) for Sedimentation.
Materials on Hand (BMP C150) may also be applicable
Detention Pond Or Vault
Advanced BMPs:
Element #5 -Stabilize Soils
Nets and Blankets (BMP C122)
~ Sodding (BMP C124)
Topsoiling (BMP C125)
~
J
Polyacrylamide for Soil Erosion Protection (C126)
v
Gradient Terraces (BMP C 131)
~ Element #6 -Protect Slopes
~ Gradient Terraces (BMP C 131)
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Grass-Lined Channels (BMP C201)
n
,~ Channel Lining (BMP C202)
~ Pipe Slope Drains (BMP C204)
u
Subsurface Drains (BMP C205)
n
~d Level Spreader (BMP C206)
'-' Check Dams (BMP C207)
v
Triangular Silt Dike (Geotextile-Encased Check Dam; BMP C208)
~f
~ Straw Wattles (BMP C235)
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Element #8 -Stabilize Channels and Outlets
`~
~j • Grass-Lined Channels (BMP C201)
'~ • Channel Lining (BMP C202)
• Level Spreader (BMP C206)
• Check Dams (BMP C207)
~ • Triangular Silt Dike (Geotextile-Encased Check Dam -BMP C208)
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Element #10 -Control Dewatering
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^ Concrete Handling (BMP C 151)
^ Temporary Sediment Pond (BMP C241)
^ Construction Stormwater Chemical Treatment (BMP C250)
^ Construction Stormwater Filtration (BMP C 251)
^ Infiltration
^ Use of a sedimentation bag, with outfall to a ditch or Swale for small
volumes of localized dewatering.
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Tahoma Terra Stormwater Pollution Prevention Plan
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Appendix D -General Permit
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`J Issuance Date: November 16, 2005
Effective Date: December 16, 2005
~ Expiration Date: December 16, 2010
~ CONSTR~JCTION S'I'®~WATER GENERAL PElaIVIIT
~
~1 National Pollutant Discharge Elimination System (NPDES) and State Waste
Discharge General Permit for Stormwater Discharges Associated With
~ Construction Activity
State of Washington
Department of Ecology
`~ Olympia, Washington 98504-7600
v
In compliance with the provisions of
~ The State of Washington Water Pollution Control Law
Chapter 90.48 Revised Code of Washington
'-~ and
The Federal Water Pollution Control Act
~! (The Clean Water Act)
Lj Title 33 United States Code, Section 1251 et seq.
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'~ Until this permit expires, is modified or revoked, Permittees that have properly obtained
coverage under this general permit are authorized to discharge in accordance with the special and
'~ general conditions which follow.
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David C. Peeler, Manager
~ Water Quality Program
Washington State Department of Ecology
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~ Page 2 of 46
`~ TABLE OF CONTENTS
~1
~j SUMMARY OF PERMIT REPORT SUBMITTALS .....................................................................3
SUMMARY OF REQUIRED ON SITE DOCUMENTATION .....................................................3
SPECIAL CONDITIONS
S 1. PERMIT COVERAGE ........................................................................................................4
J
S3. COMPLIANCE WITH STANDARDS ...............................................................................9
~! S4. MONITORING REQUIREMENTS ..................................................................................10
~
i S5. REPORTING AND RECORDKEEPING REQUIREMENTS ......................................... 15
S6. PERMIT FEES ................................................................................................................... 18
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S7. SOLID AND LIQUID WASTE DISPOSAL .................................................................... 18
u
S8. DISCHARGES TO 303(d) OR TMDL WATERBODIES ................................................ 18
L-1 S9. STORMWATER POLLUTION PREVENTION PLAN ................................................... 21
~? S 10. NOTICE OF TERMINATION .....
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.....................................................29
GENERAL CONDITIONS ...........................................................................................................30
~ G1. DISCHARGE VIOLATIONS ........................................................................................ ...30
u G2. SIGNATORY REQUIREMENTS .................................................................................. ...30
G3. RIGHT OF INSPECTION AND ENTRY ...................................................................... ...31
~ G4. GENERAL PERMIT MODIFICATION AND REVOCATION ................................... ...31
G5. REVOCATION OF COVERAGE UNDER THE PERMIT 31
.......................................... ...
G6. REPORTING A CAUSE FOR MODIFICATION ......................................................... ...32
r--~ G7. COMPLIANCE WITH OTHER LAWS AND STATUTES .......................................... ...32
' G8. DUTY TO REAPPLY ...... ...32
G9. TRANSFER OF GENERAL PERMIT COVERAGE .................................................... ...32
n G10. REMOVED SUBSTANCES .............................................................................................33
'
~J G11. DUTY TO PROVIDE INFORMATION ...........................................................................33
G12. OTHER REQUIREMENTS OF 40 CFR ...........................................................................33
r--~ G13. ADDITIONAL MONITORING ........................................................................................33
G14. PENALTIES FOR VIOLATING PERMIT CONDITIONS .....33
r--~
G16. .....................................................................................
PROPERTY RIGHTS ........................................................................................................34
G17. DUTY TO COMPLY ...................................................................................................... ..34
~ G18. TOXIC POLLUTANTS ................................................................................................... ..34
G19. PENALTIES FOR TAMPERING ......................................................... 35
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G20.
..........................
REPORTING PLANNED CHANGES ..........................................................................
..
35
~ G21. ..
REPORTING OTHER INFORMATION ........................................................................ ..
..35
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G22. REPORTING ANTICIPATED NON-COMPLIANCE .....................................................35
G23. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT..........36
G24. APPEALS ..........................................................................................................................36
G25. SEVERABILITY ...............................................................................................................36
G26. BYPASS PROHIBITED ....................................................................................................36
APPENDIX A -DEFINITIONS ...................................................................................................39
APPENDIX B -ACRONYMS .....................................................................................................46
SUNIMARY OF PERMIT REPORT SUBMITTALS
Refer to the Special and General Conditions for additional submittal requirements.
Permit Submittal Frequency First Submittal Date
Section
SS.A High Turbidity/Transparency Phone As Necessary Within 24 hours
Reporting
SS.B Discharge Monitoring Report Monthly Within 15 days after the
applicable monitoring
period
SS.F Noncompliance Notification As necessary Immediately
SS.F Noncompliance Notification -Written As necessary Within 5 Days of non-
Report compliance
G2. Notice of Change in Authorization As necessary
G6. Permit Application for Substantive As necessary
Changes to the Discharge
G8. Application for Permit Renewal 1/permit cycle No later than 180 days
before expiration
G9. Notice of Permit Transfer As necessary
G20. Notice of Planned Changes As necessary
G22. Reporting Anticipated Non-compliance As necessary
SUMMARY OF REQUIRED ON SITE DOCUMENTATION
Permit Conditions Document Title
Conditions S2, SS Permit Covera e Letter
on i ions ons ruc ion ormwa er enera ermi
Conditions S4, SS Site Lo Book
Conditions S9, SS Stormwater Pollution Prevention Plan SWPPP
,-~ Page 4 of 46
`^1
`-j S1. PERMIT COVERAGE
SPECIAL. CONDITIONS
~ A. Permit Area
This general permit covers all areas of Washington State, except for federal and tribal
~ lands specified in S 1.D.3.
B. Operators Required to Seek Coverage Under this General Permit:
1. Operators of the following construction activities are required to seek coverage under
this permit:
~ a. Clearing, grading and/or excavation which results in the disturbance of one or
more acres, and discharges stormwater to surface waters of the state; and clearing,
~ grading and/or excavation on sites smaller than one acre which are part of a larger
common plan of development or sale, if the common plan of development or sale
`~ will ultimately disturb one acre or more, and discharges stormwater to surface
~ waters of the state.
~--~ i. This includes forest practices that are part of a construction activity that will
result in the disturbance of one or more acres, and discharges to surface waters
`~ of the state (i.e., forest practices which are preparing a site for construction
~ activities); and
`~1 b. Any size construction activity discharging stormwater to waters of the state which
~J the Department of Ecology (Ecology):
r1 i. Determines to be a significant contributor of pollutants to waters of the state of
v Washington, or
n ii. Reasonably expects to cause a violation of any water quality standard.
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,--, 2. Operators of the following activities are not required to seek coverage under this
~ permit, unless specifically required under Condition S1.B.l.b. (Significant
Contributor):
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I f a. Construction activities which discharge all stormwater and non-stormwater to
"-' lTYn7/N/) lA)ntON anr~ IIAVP nn n/11YIt onoirnn ~lon Fl L^4o 4........
rarg~ to-su~fac, ~~ ~~To~n
sewer system that drains to surface waters of the state;
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u b. Construction activities covered under an Erosivity Waiver (Condition S2.C);
`~ c. Routine maintenance that is performed to maintain the original line and grade,
~_.J hydraulic capacity, or original purpose of a facility.
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C. Authorized Discharges:
Page 5 of 46
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1. Stormwater Associated with Construction Activity. Subject to compliance with the
terms and conditions of this permit, Permittees are authorized to discharge
Stormwater associated with construction activity to surface waters of the state or to a
storm sewer system that drains to surface waters of the state.
2. Stormwater Associated with Construction Support Activity. This permit also
`~ authorizes Stormwater discharges from support activities related to the permitted
~1 construction site (e.g., off-site equipment staging yards, material storage areas,
borrow areas, etc.) provided:
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,~ a. The support activity is directly related to the permitted construction site that is
required to have an NPDES permit; and
b. The support activity is not a commercial operation serving multiple unrelated
construction projects, and does not operate beyond the completion of the
~ construction activity; and
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c. Appropriate controls and measures are identified in the Stormwater Pollution
r-, Prevention Plan (SWPPP)for the discharges from the support activity areas
.
3. Non-Stormwater Dischar es. The categories and sources of non-stormwater
r-t discharges identified below are conditionally authorized, provided the discharge is
~ consistent with the terms and conditions of this permit:
~ a. Discharges from fire fighting activities;
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b. Fire hydrant system flushing;
c. Potable water including uncontaminated water line flushing (de-chlorinated);
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d. Pipeline hydrostatic test water;
~---' e. Uncontaminated air conditioning or compressor condensate;
~' £ Uncontaminated ground water or spring water;
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g. Uncontaminated excavation de-watering (in accordance with S9.D.10)
~; h. Uncontaminated discharges from foundation or footing drains;
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i. Water used to control dust;
j. Routine external building wash down that does not use detergents; and
k. Landscape irrigation.
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----- ------
-- - - ----
`J All authorized non-stormwater discharges, except for discharges from fire fighting
,--~ activities, shall be adequately addressed in the SWPPP and comply with Special
~ Condition S3.
D. Limitations on Covera e
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~ The Director may require any discharger to apply for and obtain coverage under an
individual permit or another more specific general permit. Such alternative coverage
~ will be required when Ecology determines that this general permit does not provide
~ adequate assurance that water quality will be protected; or there is a reasonable potential
for the project to cause or contribute to a violation of water quality standards.
' The following stormwater discharges are not covered by this permit:
1. Post-construction stormwater discharges that originate from the site after construction
~ activities have been completed and the site has undergone final stabilization.
2. Nonpoint source silvicultural activities such as nursery operations, site preparation,
`~ reforestation and subsequent cultural treatment, thinning, prescribed burning, pest and
v fire control, harvesting operations, surface drainage, or road construction and
maintenance from which there is natural runoff as excluded in 40 CFR Subpart
`~ 122.27.
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3. Stormwater from any federal project or project on federal land or land within an
~t Indian Reservation except for the Puyallup Reservation. Within the Puyallup
~ Reservation, any project that discharges to surface water on land held in trust by the
federal government may be covered by this permit.
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4. Stormwater from any site covered under an existing NPDES individual permit in
which stormwater management and/or treatment requirements are included for all
~ stormwater discharges associated with construction activity.
i--~ 5. Where an applicable Total Maximum Daily Load (TMDL) specifically precludes or
r-, prohibits discharges from construction activity, the operator is not eligible for
coverage under this permit.
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S2. APPLICATION REQUIREMENTS
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u A. Permit Application Forms
1. Notice of Intent Form/Timeline
a. perators of new or previously unpermitted construction activities shall submit a
r! complete and accurate permit application form [Notice of Intent (NOI)] to
U Ecology. Applicants are encouraged to use Ecology's Internet-based electronic
NOI to apply for permit coverage.
~ b. The NOI shall be submitted on or before the date of the first public notice (see
Condition S2.B below) and at least 60 days prior to the discharge of stormwater
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from construction activities. The 30-day public comment period required by WAC
r~ 173-226-130(5) begins on the publication date of the second public notice. Unless
u Ecology responds to the complete application in writing, based on public
comments, or any other relevant factors, coverage under the general permit will
,~ automatically commence on the thirty-first day following receipt by Ecology of a
completed NOI, or the issuance date of this permit, whichever is later; unless a
later date is specified by Ecology in writing.
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c. Applicants that discharge to a storm sewer system operated by Seattle, King
County, Snohomish County, Tacoma, Pierce County, or Clark County shall also
,-~ submit a copy of the NOI to the appropriate jurisdiction.
u 2. Transfer of Covera e Form
~ Current coverage under this permit may be transferred to one or more new operators,
~ including operators of sites within a Common Plan of Development, by submitting
a Transfer of Coverage Form in accordance with Condition G9. Transfers do not
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require public notice.
U B. Public Notice
~ For new or previously unpermitted sites, the applicant shall publish a public notice at
~ least one time each week for two consecutive weeks, with a 7-day time span between
dates, in a newspaper that has general circulation in the county in which the construction
is to take place. The notice shall contain the following:
~ 1. A statement that "The applicant is seeking coverage under the Washington State
,~ Department of Ecology's Construction Stormwater NPDES and State Waste Discharge
General Permit";
rl 2. The name, address and location of the construction site;
~ 3. The name and address of the applicant;
'-I 4. The type of construction activity that will result in a discharge, (e.g., residential
U construction, commercial construction, etc.) and the number of acres to be disturbed;
n 5. The name of the receiving water(s) (i.e., the surface water(s) that the site will discharge
U to), or if the discharge is through a storm sewer system, the name of the operator of the
storm sewer; and
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U 6. The statement: "Any person desiring to present their views to the Department of
F^^~~ ~Lre~arding this-application; oiznterested i~he epa ent s action on this
~ application may notify the Department of Ecology in writing within 30 days of the last
~ date of publication of this notice. Comments can be submitted to: Department of
Ecology, P.O. Box 47696, Olympia, WA 98504-7696, Attn: Water Quality Program,
n Construction Stormwater".
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C. Erosivity Waiver
Operators may qualify for a waiver from the permit if the following conditions are met:
1. The site will result in the disturbance of less than 5 acres; and the site is not a portion
of a common plan of development or sale that will disturb 5 acres or greater.
2. Calculation of Erosivity "R"Factor and Regional Timeframe:
a. The project's rainfall erosivity factor ("R" Factor) must be less than 5 during the
period of construction activity, as calculated using the Texas A&M University
online rainfall erosivity calculator at: http://ei.tamu.edu/. The period of
construction activity begins at initial earth disturbance and ends with final
stabilization; and, in addition:
b. The entire period of construction activity must fall within the following
timeframes:
i. For sites west of the Cascades Crest: June 15 -September 15; or
ii. For sites east of the Cascades Crest, excluding the Central Basin: June 15 -
October 15; or
iii. For sites east of the Cascades Crest, within the Central Basin*: no additional
timeframe restrictions apply.
*Note: The Central Basin is defined as the portions of Eastern Washington
with mean annual precipitation of less than 12 inches.
3. Operators must submit a complete Erosivity Waiver Certification Form at least one
week prior to commencing land disturbing activities. Certification must include:
a. A statement that the operator will comply with applicable local stormwater
requirements; and
b. A statement that the operator will implement appropriate erosion and sediment
~ control BMPs to prevent violations of water quality standards.
~ 4. This waiver is not available for facilities declared a significant contributor of
,~ pollutants as defined in Condition S 1.B. l .b.
5~=~=~-~~~ ly-to 'vi w ~ me u es non-stormwater
,~ discharges listed in S l .C.3.
~ 6. If construction activity extends beyond the certified waiver period for any reason, the
,~ operator shall either:
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Page 9 of 46
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a. Recalculate the rainfall erosivity "R" factor using the original start date and a new
~ projected ending date and, if the "R" factor is still under 5 and the entire project
falls within the applicable regional timeframe in S2.C.2.b, complete and submit
an amended waiver certification form before the original waiver expires; or
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~ b. Submit a complete permit application to Ecology in accordance with Condition
S2.A and B before the end of the certified waiver period.
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,J S3. COMPLIANCE WITH STANDARDS
~ A. Discharges shall not cause or contribute to a violation of surface water quality standards
~ (Chapter 173-201A WAC), ground water quality standards (Chapter 173-200 WAC),
sediment management standards (Chapter 173-204 WAC), and human health-based
~ criteria in the National Toxics Rule (40 CFR Part 131.36). Discharges that are not in
~ compliance with these standards are not authorized.
,-, B. Prior to the discharge of stormwater and non-stormwater to waters of the state, the
Permittee shall apply all known, available, and reasonable methods of prevention,
~ control, and treatment (AKAR7). This includes the preparation and implementation of an
,~ adequate Stormwater Pollution Prevention Plan (SWPPP), with all appropriate best
management practices (BMPs) installed and maintained in accordance with the SWPPP
u and the terms and conditions of this permit.
`~ C. Compliance with water quality standards shall be presumed, unless discharge monitoring
~1 data or other site specific information demonstrates that a discharge causes or contributes
to a violation of water quality standards, when the Permittee is:
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u 1. In full compliance with all permit conditions, including planning, sampling,
monitoring, reporting, and recordkeeping conditions; and
~ 2. Fully implementing stormwater BMPs contained in stormwater management manuals
published or approved by Ecology, or BMPs that are demonstrably equivalent to
,~ BMPs contained in stormwater technical manuals published or approved by Ecology,
~ including the proper selection, implementation, and maintenance of all applicable and
appropriate BMPs for on-site pollution control.
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D. For sites that discharge to both surface water and ground water, all ground water
~ discharges are also subject to the terms and conditions of this permit. Permittees who
,~ discharge to ground water through an injection well shall comply with any applicable
requirements of the Underground Injection Control (UIC) regulations, Chapter 173-218
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S4. MONITORING REQUIREMENTS
'-1
The primary monitoring requirements are summarized in Table 3 (below):
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Table 3. Summary of Monitoring Requirements)
Size of Soil Disturbance Weekly Weekly Weekly Weekly
Site Sampling w/ Sampling w/ pH
Inspections Turbidity Meter Transparency sampling3
Tube
Sites which disturb less than 1 Required Not Required Not Required Not
acre Re uired
Sites which disturb 1 acre or Required Sampling Requir4 d -either Required
more, but less than 5 acres method
Sites which disturb 5 acres or Required Required Not Required5 Required
more
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A. Site Log Book
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The Pennittee shall maintain a site log book that contains a record of the
implementation of the SWPPP and other permit requirements including the installation
and maintenance of BMPs, site inspections, and stormwater monitoring.
`~, B. Site Inspections
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1. Site inspections shall include all areas disturbed by construction activities, all BMPs,
n and all stormwater discharge points. Stormwater shall be visually examined for the
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1 Additional monitoring requirements may apply for: 1) discharges to 303(d) listed waterbodies and waterbodies
n with applicable TMDLs for turbidity, fine sediment, high pH, or phosphorus -see Condition S8; and 2) sites
~ required to perform additional monitoring by Ecology order- see Condition G13.
2 Soil disturbance is calculated by adding together all areas affected by construction activity. Construction Activity
means clearing, grading, excavation, and any other activity which disturbs the surface of the land, including
U ingress/egress from the site.
rl 3 Beginning October 1, 2006, if construction activity involves significant concrete work or the use of engineered
soils, and stormwater from the affected area drains to a stormwater collection system or other surface water, the
D-e~mtte~ shatl-cenduet-~H-s"--~~accerdanee-with-Fondition~4-r`.
rl 4 Beginning October 1, 2008, sites with one or more acres, but less than 5 acres of soil disturbance, shall conduct
L-1 turbidity or transparency sampling in accordance with Condition S4.C.
~ 5 Beginning October 1, 2006, sites greater than or equal to 5 acres of soil disturbance shall conduct turbidity
U sampling using a turbidity meter in accordance with Condition S4.C.
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~ presence of suspended sediment, turbidity, discoloration, and oil sheen. Inspectors
~ shall evaluate the effectiveness of BMPs and determine if it is necessary to install,
~ maintain, or repair BMPs to improve the quality of stonnwater discharges.
Based on the results of the inspection, the Permittee shall correct the problems
'~ identified as follows:
'J a. Review the SWPPP for compliance with Condition S9 and make appropriate
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revisions within 7 days of the inspection; and
~j b. Fully implement and maintain appropriate source control and/or treatment BMPs
as soon as possible, but no later than 10 days of the inspection; and
~ c. Document BMP implementation and maintenance in the site log book.
2. The site inspections shall be conducted at least once every calendar week and within
`~
i 24 hours of any discharge from the site. The inspection frequency for temporarily
~ stabilized, inactive sites may be reduced to once every calendar month.
r-, 3. Site inspections shall be conducted by a person who is knowledgeable in the
~
`
' principles and practices of erosion and sediment control. The inspector shall have the
~ skills to:
'`"1 a. Assess the site conditions and construction activities that could impact the quality
~ of stormwater, and
b. Assess the effectiveness of erosion and sediment control measures used to control
the quality of stormwater discharges.
4. Beginning October 1, 2006, construction sites one acre or larger that discharge
~
~ stonnwater to surface waters of the state, shall have site inspections conducted by a
C
ertified Erosion and Sediment Control Lead (CESCL). The CESCL shall be
identified in the SWPPP and shall be present on-site or on-call at all times.
'~ Certification shall be obtained through an approved erosion and sediment control
v training program that meets the minimum training standards established by Ecology
(see BMP C 160 in the Manual).
~ 5. The inspector shall summarize the results of each inspection in an inspection report or
u checklist and be entered into, or attached to, the site log book. At a minimum, each
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inspection report or checklist shall include:
a. Inspection date and time.
~ b. Weather information; general conditions during inspection and approximate
~1 amount of precipitation since the last inspection, and within the last 24 hours.
c. A summary or list of all BMPs which have been implemented, including
'~ observations of all erosion/sedimentcnntrol structures or practices.
~ d. The following shall be noted:
`~ i. locations of BMPs inspected,
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~ 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 inspector shall note the
rl presence of suspended sediment, turbid water, discoloration, and/or oil sheen, as
v applicable.
,~ £ Any water quality monitoring performed during inspection.
~ g. General comments and notes, including a brief description of any BMP repairs,
maintenance or installations made as a result of the inspection.
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U 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
n the SWPPP and the 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
r~ implementation.
~ i. Name, title, and signature of the person conducting site inspection; and the
following statement: "I certify that this report is true, accurate, and complete, to
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est of my knowledge and belief
.
C. Turbidi /Transparency Sampling Requirements
n 1. Sampling MethodsBffective Dates
a. Beginning October 1, 2006, if construction activity will involve the disturbance
~ of 5 acres or more, the Permittee shall conduct turbidity sampling per Condition
u S4.C.
n b. Beginning October 1, 2008, if construction activity will involve greater than or
U equal to 1 acre, but less than 5 acres of soil disturbance, the Permittee shall
conduct transparency sampling or turbidity sampling per Condition S4.C.
~ 2. Sampling Frequency
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a. Sampling shall be conducted at least once every calendar week, when there is a
~ discharge of stormwater (or authorized non-stormwater) from the site. Samples
~ shall be representative of the flow and characteristics of the discharge.
,~ b. When there is no discharge during a calendar week, sampling is not required.
U c. Sampling is not required outside of normal working hours or during unsafe
conditions. If a Permittee is unable to sample during a monitoring period, the
'~ Discharge Monitoring Report (DMR) shall include a brief explanation.
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3. Sampling Locations
a. Sampling is required at all discharge points where stormwater (or authorized non-
stormwater) is discharged off-site.
b. All sampling point(s) shall be identified on the SWPPP site map and be clearly
marked in the field with a flag, tape, stake or other visible marker.
4. Sampling and Analysis Methods
a. Turbidity analysis shall be performed with a calibrated turbidity meter
(turbidimeter), either on-site or at an accredited lab. The results shall be recorded
in the site log book in Nephelometric Turbidity Units (NTU).
b. Transparency analysis shall be performed on-site withal 3/4 inch diameter, 60
centimeter (cm) long Transparency Tube. The results shall be recorded in the site
log book in centimeters (cm). Transparency Tubes are available from:
http://watermonitoringequip.com/~ages/stream html
Parameter
Units Analytical
Method Sampling
Fre uenc Benchmark
Value
Turbidity NTU SM2130 or Weekly, if 25 NTU
EPA 180.1 discharging
Transparency cm Manufacturer Weekly, if 31 cm
instructions, or discharging
Ecology
Guidance
5. Turbidity/Transparency Benchmark Values
The benchmark value for turbidity is 25 NTU (Nephelometric Turbidity Units); and
the benchmark value for transparency is 31 cm.
a. Turbidity 26 - 249 NTU, or Transparency 30 - 7 cm•
If discharge turbidity is greater than 25 NTU, but less than 250 NTU; or if
discharge transparency is less than 31 cm, but greater than 6 cm, the CESCL
shall:
i. Review the SWPPP for compliance with Condition S9 and make appropriate
revisions within 7 days of the discharge that exceeded the benchmark; and
~ ;;, F„ii~, imr~~am~nt and--m- ain~a-in~ppr-opr-iate~ource-eorrtro-l-and/or-treatmen
BMPs as soon as possible, but within 10 days of the discharge that
~ exceeded the benchmark; and
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iii. Document BMP implementation and maintenance in the site log book.
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~ b. Turbidity 250 NTU or greater or Transparency 6 cm or less•
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`~ If discharge turbidity is greater than or equal to 250 NTU; or if discharge
transparency is less than or equal to 6 cm, the CESCL shall:
~I i. Notify Ecology by phone in accordance with Condition SS.A.; and
,--~ ii. Review the SWPPP for compliance with Condition S9 and make appropriate
~ revisions within 7 days of the discharge that exceeded the benchmark; and
iii. Fully implement and maintain appropriate source control and/or treatment
BMPs as soon as possible, but within 10 days of the discharge that
exceeded the benchmark;
n iv. Document BMP implementation and maintenance in the site log book; and
~ v. Continue to sample discharges daily until:
1. turbidity is 25 NTU (or lower); or
2. transparency is 31 cm (or greater); or
~ 3. the CESCL has demonstrated compliance with the water quality
~ standard for turbidity:
~ a. no more than 5 NTU over background turbidity, if background is
Lj less than 50 NTU, or
,~ b. no more than 10% over background turbidity, if background is 50
NTU or greater; or
4. the discharge stops or is eliminated.
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D. pH Monitoring: Sites with Significant Concrete Work or Engineered Soils
i-1 Beginning October 1, 2006, if construction activity will result in the disturbance of 1
- acre or more, and involves significant concrete work or the use of engineered soils, and
'
' stormwater from the affected area drains to surface waters of the state or to a storm
~i sewer system that drains to surface waters of the state, the Permittee shall conduct pH
monitoring as set forth below:
~ 1. For sites with significant concrete work, the pHmonitoringperiod shall commence
when the concrete is first exposed to precipitation and continue weekly until
r, stormwater pH is 8.5 or less.
« ~,
u a ~ignif_rc rk--me-an titer-tharrl-0Ofl-eul7i
~ e-yard~poure-d~a cre e
or recycled concrete.
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2. For sites with engineered soils, the pH monitoring period shall commence when the
soil amendments are first exposed to precipitation and shall continue until the area of
engineered soils is fully stabilized.
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Page 15 of 46
a. "En ineered soils" means soil amendments incl
g udmg, but not limited, to Portland
cement treated base (CTB), cement kiln dust (CKD), or fly ash.
~J 3. During the pH monitoring period, the Permittee shall obtain a representative sample
of stormwater and conduct pH analysis at least once per week.
4. The Permittee shall monitor pH in the sediment trap/pond(s) or other locations that
receive stormwater runoff from the area of significant concrete work or engineered
,--~ soils prior to discharge to surface waters.
5. The benchmark value for pH is 8.5 standard units. Any time sampling indicates that
pH is 8.5 or greater, the Permittee shall:
~ a. Prevent the high pH water (8.5 or above) from entering storm sewer systems or
surface waters; and
~ b. If necessary, adjust or neutralize the high pH water using an appropriate treatment
BMP such as COZ sparging or dry ice. The Permittee shall obtain written
~ approval from Ecology prior to using any form of chemical treatment other than
i COZ sparging or dry ice.
6. The Permittee shall perform pH analysis on-site with a calibrated pH meter, pH test
'~ kit, or wide range pH indicator paper. The Permittee shall record pH monitoring
v results in the site log book.
~ S5. REPORTING AND RECORDKEEPING REQUIREMENTS
u A. High Turbidity Phone Reporting
~ Any time sampling performed in accordance with Special Condition S4.C indicates
v turbidity is 250 NTU or greater (or transparency is 6 cm or less) the Permittee shall notify
the appropriate Ecology regional office by phone within 24 hours of analysis.
~ B. Discharge Monitoring Reports
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1. Permittees required to conduct water quality sampling in accordance with Special
r! Conditions S.4.C (Turbidity/Transparency), S4.D (pH) and/or S8 [303(d)/TMDL
U sampling] shall submit the results to Ecology monthly on Discharge Monitoring
Report (DMR) forms provided by Ecology.
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~
Permittees are authorized and encouraged to submit electronic DMRs using the "E-
DMRForm" on Ecology's Construction Stormwater web site:
http•//www ec wa / / /
,~ y. aov programs wq stormwater/construction/.
~ 2, ThP p~T orin ~ttee-sl-rall-s,.''....:+ T„` ~" r----- -' - - mai o e receive y
Ecology within 15 days following the end of each month. If there was no discharge
~ during a given monitoring period, the Permittee shall submit the form as required
~ with the words "no discharge" entered in place of the monitoring results. If the
Permittee is unable to submit discharge monitoring reports electronically, the
`~ Permittee may mail reports to the address listed below:
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~ Department of Ecology
Water Quality Program -Construction Stormwater
PO Box 47696
~ Olympia, Washington 98504-7696
~ C. Records Retention
~l
The Permittee shall retain records of all monitoring information (site log book, sampling
~ results, inspection reports/checklists, etc.), Stormwater Pollution Prevention Plan, and
~ any other documentation of compliance with permit requirements during the life of the
construction project and for a minimum of three years following the termination of
n permit coverage. Such information shall include all calibration and maintenance records,
and records of all data used to complete the application for this permit. This period of
'~ retention shall be extended during the course of any unresolved litigation regarding the
discharge of pollutants by the Permittee or when requested by Ecology.
Lj D. Recording of Results
~ For each measurement or sample taken, the Permittee shall record the following
information:
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1. Date, place, method, and time of sampling or measurement;
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~ 2. The individual who performed the sampling or measurement;
3. The dates the analyses were performed;
,J 4. The individual who performed the analyses;
~ 5. The analytical techniques or methods used; and
~ 6. The results of all analyses.
n E. Additional Monitoring_by the Permittee
~ If the Permittee monitors any pollutant more frequently than required by this permit using
~ test procedures specified by Condition S4 of this permit, the results of this monitoring
shall be included in the calculation and reporting of the data submitted in the Permittee's
`-~ DMR.
`-! F. Noncompliance Notification
~ In the event the Permittee is unable to comply with any of the terms and conditions of
n this permit which may cause a threat to human health or the environment, the Permittee
shall:
1. Immediately notify Ecology of the failure to comply.
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~ 2. Immediately take action to prevent the discharge/pollution, or otherwise stop or
correct the noncompliance, and, if applicable, repeat sampling and analysis of any
n noncompliance immediately and submit the results to Ecology within five (5) days
after becoming aware of the violation.
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3. Submit a detailed written report to Ecology within five (5) days, unless requested
earlier by Ecology. The report shall contain a description of the noncompliance,
including exact dates and times, and if the noncompliance has not been corrected, the
anticipated time it is expected to continue; and the steps taken or planned to reduce,
eliminate, and prevent reoccurrence of the noncompliance.
Compliance with these requirements does not relieve the Permittee from
responsibility to maintain continuous compliance with the terms and conditions of
this permit or the resulting liability for failure to comply.
G. Access to Plans and Records
1. The Permittee shall retain the following permit documentation (plans and records) on-
site, or within reasonable access to the site, for use by the operator; or on-site review
by Ecology or the local jurisdiction:
,~ a. General Permit;
~ b. Permit Coverage Letter;
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c. Stormwater Pollution Prevention Plan (SWPPP); and
~
~1 d. Site Log Book
2. The Permittee(s) shall address written requests for plans and records listed above
`~ (Condition SS.G.1) as follows:
a. A copy of plans and records shall be provided to Ecology within 14 days of
~? receipt of a written request from Ecology.
b. A copy of plans and records shall be provided to the public when requested in
n writing. Upon receiving a written request from the public for the Permittee's
~j plans and records, the Pertnittee shall either:
r-1 i. Provide a copy of the plans and records to the requestor within 14 days of a
receipt of the written request; or
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ii. Notify the requestor within 10 days of receipt of the written request of the
n location and times within normal business hours when the plans and records
v may be viewed, and provide access to the plans and records within 14 days of
receipt of the written request; or
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~ ~ iii. Within 14 days of receipt of the written request, the Permittee may submit a
copy of the plans and records to Ecology for viewing and/or copying by the
~ requestor at an Ecology office, or a mutually agreed upon location. If plans
and records are viewed and/or copied at a location other than at an Ecology
office, the Permittee will provide reasonable access to copying services for
~ which a reasonable fee may be charged. The Permittee shall notify the
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----
~ requestor within 10 days of receipt of the request where the plans and records
may be viewed andlor copied.
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S6. PERMIT FEES
~ The Permittee shall pay permit fees assessed by Ecology. Fees for stormwater discharges
covered under this permit shall be established by Chapter 173-224 WAC. Permit fees will
continue to be assessed until the permit is terminated in accordance with Special Condition
~ S 10 or revoked in accordance with General Condition G5.
~ S7. SOLID AND LIQUID WASTE DISPOSAL
`J Solid and liquid wastes generated by construction activity such as demolition debris,
,~ construction materials, contaminated materials, and waste materials from maintenance
~ activities, including liquids and solids from cleaning catch basins and other stormwater
facilities, shall be handled and disposed of in accordance with:
'~ 1. Special Condition S3, Compliance with Standards, and
2. WAC 173-216-110, and other applicable regulations.
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~ S8. DISCHARGES TO 303(D) OR TMDL WATERBODIES
~l A. Sampling and Numeric Effluent Limitations For Discharges to 303(dl listed Waterbodies
~j 1. 1.Permittees that discharge to water bodies listed as impaired by the State of
Washington under Section 303(d) of the Clean Water Act for turbidity, fine
`~ sediment, high pH, or phosphorus, shall conduct water quality sampling according
v to the requirements of this section.
,-, 2. All references and requirements associated with Section 303(d) of the Clean Water
' Act mean the most current listing by Ecology of impaired waters that exists on
~ November 16, 2005, or the date when the operator's complete permit application is
,-, received by Ecology, whichever is later.
u B. Discharges to 303(d)-Listed Waterbodies (Turbidity Fine Sediment or Phosphorus)
~ 1. Permittees which discharge to waterbodies on the 303(d) list for turbidity, fine
i__i sediment, or phosphorus shall conduct turbidity sampling at the following locations
to evaluate compliance with the water quality standard for turbidity:
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u a. Background turbidity shall be measured in the 303(d)-listed receiving water
`""~'
a or ou si e e area o m uence o t e
discharge; and
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U b. Discharge turbidity shall be measured at the point of discharge into the 303(d)
listed receiving waterbody, inside the area of influence of the discharge; or
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~J Alternatively, discharge turbidity may be measured at the point where the
discharge leaves the construction site, rather than in the receiving waterbody.
~ 2. Based on sampling, if the discharge turbidity exceeds the water quality standard for
turbidity (more than 5 NTU over background turbidity when the background
~ turbidity is 50 NTU or less, or more than a 10% increase in turbidity when the
~ background turbidity is more than 50 NTU), all future discharges shall comply with
a numeric effluent limit which is equal to the water quality standard for turbidity.
3. If a future discharge exceeds the water quality standard for turbidity, the Permittee
shall:
~ a. Review the SWPPP for compliance with Condition S9 and make appropriate
~ revisions within 7 days of the discharge that exceeded the standard;
~ b. Fully implement and maintain appropriate source control and/or treatment BMPs
~ as soon as possible, but within 10 days of the discharge that exceeded the
standard;
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c. Document BNIP implementation and maintenance in the site log book;
d. Notify the appropriate Ecology Regional Office by phone within 24 hours of
analysis;
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e. Continue to sample daily until discharge turbidity meets the water quality
n standard for turbidity.
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C. Discharges to waterbodies on the 303(d) list for High pH
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1. Permittees which discharge to waterbodies on the 303(d) list for high pH shall
conduct sampling at one of the following locations to evaluate compliance with the
~--, water quality standard for pH (in the range of 6.5 - 8.5):
u a. pH shall be measured at the point of discharge into the 303(d) listed waterbody,
inside the area of influence of the discharge; or
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~ b. Alternatively, pH may be measured at the point where the discharge leaves the
construction site, rather than in the receiving water.
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~ 2. Based on the sampling set forth above, if the pH exceeds the water quality standard
for pH (in the range of 6.5 - 8.5), all future discharges shall comply with a numeric
n effluent limit which is equal to the water quality standard for pH.
``~ excee s e wa er qua ity stan ar or pH, the Permittee shall:
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a. Review the SWPPP for compliance with Condition S9 and make appropriate
revisions within 7 days of the discharge that exceeded the water quality standard;
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b. Fully implement and maintain appropriate source control and/or treatment BMPs
as soon as possible, but within 10 days of the discharge that exceeded the
~ standards;
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c. Document BMP implementation and maintenance in the site log book;
Lj d. Notify the appropriate Ecology Regional Office by phone within 24 hours of
analysis; and
~ e. Continue to sample daily until discharge meets the water quality standard for pH
(in the range of 6.5 - 8.5) or the discharge stops or is eliminated.
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Parameter identified
in 303(d) listing Parameter/Units Analytical
Method Sampling
Frequency Water Quality
Standard
Turbidity Turbidity/NTU SM2130 or Weekly, if If background is 50
Fine Sediment EPA180.1 discharging NTU or less: 5 NTU
Phosphorus over background; or
If background is
more than 50 NTU:
10% over
background
High pH pH/Standard pH meter Weekly, if In the range of
Units discharging 6.5 - 8.5
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u D. Sampling and Limitations For Sites Discharging to Applicable TMDLs
,-, 1. Discharges to a waterbodies subject to an applicable Total Maximum Daily Load
(TMDL) for turbidity, fine sediment, high pH, or phosphorus, shall be consistent with
u the assumptions and requirements of the TMDL.
~ a. Where an applicable TMDL sets specific waste load allocations or requirements
~ for discharges covered by this permit, discharges shall be consistent with any
specific waste load allocations or requirements established by the applicable
'~~ TMDL.
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ii, e ermittee s a samp a isc arges weekly, or as otherwise specified by the
n TMDL, to evaluate compliance with the specific waste load allocations or
~ requirements.
iii. Analytical methods used to meet the monitoring requirements shall conform to
~ the latest revision of the Guidelines Establishing Test Procedures for the
u Analysis of Pollutants contained in 40 CFR Part 136. Turbidity and pH methods
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need not be accredited or registered unless conducted at a laboratory which must
otherwise be accredited or registered.
b. Where an applicable TMDL has established a general waste load allocation for
construction stormwater discharges, but no specific requirements have been
identified, compliance with Conditions S4 (Monitoring) and S9 (SWPPPs) will be
assumed to be consistent with the approved TMDL.
,~ c. Where an applicable TMDL has not specified a waste load allocation for
'~ construction stormwater discharges, but has not excluded these discharges,
compliance with Conditions S4 (Monitoring) and S9 (SWPPPs) will be assumed
~ to be consistent with the approved TMDL.
~l d. Where an applicable TMDL specifically precludes or prohibits discharges from
construction activity, the operator is not eligible for coverage under this permit.
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2. Applicable TMDL means a TMDL for turbidity, fine sediment, high pH, or
phosphorus, which has been completed and approved by EPA prior to November 16
,~ ,
2005, or prior to the date the operator's complete permit application is received by
U Ecology, whichever is later. TMDLs completed after the operator's complete permit
application is received by Ecology become applicable to the Permittee only if they are
,-, imposed through an administrative order by Ecology, or through a modification of
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permit coverage.
S9. STORMWATER POLLUTION PREVENTION PLAN
~ An adequate Stormwater Pollution Prevention Plan (SWPPP) for construction activity shall
be prepared and implemented in accordance with the requirements of this permit beginning
~ with initial soil disturbance and until final stabilization.
`J A. The SWPPP shall meet the following objectives•
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~ 1. To 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. To prevent violations of surface water quality, ground water quality, or sediment
'-' management standards.
3. To control peak volumetric flow rates and velocities of stormwater discharges.
~ B. General Requirements
'-' 1. The SWPPP shall include a narrative and drawings. All BMPs shall be clearly
~I referenced in the narrative and marked ~n the_dra
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The SWPPP narrative shall include documentation to explain and justify the pollution
prevention decisions made for the project. Documentation shall include:
a. Information about existing site conditions (topography, drainage, soils,
vegetation, etc.);
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b. Potential erosion problem areas;
c. The 12 elements of a SWPPP in S9.D.1-12, including BMPs used to address each
element;
'-1 d. Construction phasing/sequence and general BMP implementation schedule;
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e. The actions to be taken if BMP performance goals are not achieved; and
f. Engineering calculations for ponds and any other designed structures.
2. The Pennittee shall modify the SWPPP if, during inspections or investigations
'~ conducted by the owner/operator, or the applicable local or state regulatory authority,
,J it is determined that the SWPPP is, or would be, ineffective in eliminating or
significantly minimizing pollutants in stormwater discharges from the site. The
~ Permittee shall take the following actions:
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a. Review the SWPPP for compliance with Condition S9 and make appropriate
~ revisions within 7 days of the inspection or investigation;
'-~ b. Fully implement and maintain appropriate source control and/or treatment BMPs
as soon as possible, but no later than 10 days from the inspection or investigation;
and
c. Document BMP implementation and maintenance in the site log book
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3. The Permittee shall modify the SWPPP whenever there is a change in 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.
U C. Stormwater Best Management Practices BMPs,~
n BMPs shall be consistent with:
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~ 1. Stormwater Management Manual for Western Washington (most recent edition), for
sites west of the crest of the Cascade Mountains;
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`-' 2. Stormwater Management Manual for Eastern Washington (most recent edition)
for
,
sites east of the crest of the Cascade Mountains; or
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3. Other stormwater management guidance documents or manuals which provide an
~~ equivalent level of pollution prevention and are approved by Ecology; or
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ocumentation m the SWPPP that the BMPs selected provides an equivalent level of
~ pollution prevention, compared to the applicable Stormwater Management Manuals,
~ including:
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a. The technical basis for the selection of all stonnwater BMPs (scientific, technical
studies, and/or modeling) which support the performance claims for the BMPs
~ being selected; and
b. An assessment of how the selected BMP will satis AKART re uirements and
fy q
,--~ the applicable federal technology-based treatment requirements under 40 CFR
U part 125.3.
D. SWPPP -Narrative Contents and Requirements
v The Permittee shall include each of the 12 elements below in S9.D.1-12 in the narrative
of the SWPPP and ensure that they are implemented unless site conditions render the
r! element unnecessary and the exemption from that element is clearly justified in the
U S WPPP.
'~ 1. Preserve Vegetation/Mark Clearing Limits
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a. Prior to beginning land disturbing activities, including clearing and grading,
'~ clearly mark all clearing limits, sensitive areas and their buffers, and trees that are
u to be preserved within the construction area.
~ b. The duff layer, native top soil, and natural vegetation shall be retained in an
undisturbed state to the maximum degree practicable.
2. Establish Construction Access
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a. Construction vehicle access and exit shall be limited to one route, if possible.
b. Access points shall be stabilized with a pad of quarry spalls, crushed rock, or other
n equivalent BMP, to minimize the tracking of sediment onto public roads.
u c. Wheel wash or tire baths shall be located on site, if the stabilized construction
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entrance is not effective in preventing sediment from being tracked onto public
roads.
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d. If sediment is tracked off site, public roads shall be cleaned thoroughly at the end of
r-l each day, or more frequently during wet weather. Sediment shall be removed from
~ roads by shoveling or pickup sweeping and shall be transported to a controlled
sediment disposal area.
'V! e. Street washing is allowed only after sediment is removed in accordance with
u S9.D.2.d. Street wash wastewater shall be controlled by pumping back on site or
otherwise be prevented from discharging into systems tributary to waters of the
'~ state.
7 /"~___i.__1 T1 r
r--i a. Properties and waterways downstream from development sites shall be protected
U from erosion due to increases in the velocity and peak volumetric flow rate of
stormwater runoff from the project site, as required by local plan approval
~ authority.
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'J b. Where necessary to comply with S9.D.3.a., stormwater retention or detention
facilities shall be constructed as one of the first steps in grading. Detention
`~ facilities shall be functional prior to construction of site improvements (e.g.,
impervious surfaces).
,--~ c. If permanent infiltration ponds are used for flow control during construction, these
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facilities shall be protected from siltation during the construction phase.
4. Install Sediment Controls
~ j a. Stormwater runoff from disturbed areas shall pass through a sediment pond or other
appropriate sediment removal BMP, prior to leaving a construction site or prior to
r-~ discharge to an infiltration facility. Runoff from fully stabilized areas may be
~ discharged without a sediment removal BMP, but shall meet the flow control
performance standard of S9.D.3.a.
`~ b. Sediment control BMPs (sediment ponds, traps, filters, etc.) shall be constructed as
~-I one of the first steps in grading. These BMPs shall be functional before other land
disturbing activities take place.
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c. BMPs intended to trap sediment on site shall be located in a manner to avoid
interference with the movement of juvenile salmonids attempting to enter off-
,~ channel areas or drainages.
,~ 5. Stabilize Soils
r~ a. Exposed and unworked soils shall be stabilized by application of effective BMPs
~ that prevent erosion. Applicable BMPs include, but are not limited to: temporary
and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics
,--, and matting, soil application of polyacrylamide (PAM), the early application of
~ gravel base on areas to be paved, and dust control.
b. Depending on the geographic location of the project, no soils shall remain exposed
'~ and unworked for more than the time periods set forth below to prevent erosion:
~ West of the Cascade Mountains Crest
n During the dry season (May 1 - Sept. 30): 7 days
During the wet season (October 1 -April 30): 2 days
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East of the Cascade Mountains Crest, except for Central Basin*
~' During the dry season (July 1 -September 30): 10 days
~ During the wet season (October 1 -June 30): 5 days
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The Central Basin*, East of the Cascade Mountains Crest
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During the wet season (October 1 -June 30): 15 days
U *Note: The Central Basin is defined as the portions of Eastern Washington
with mean annual precipitation of less than 12 inches.
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~ The time period may be adjusted by a local jurisdiction, if the jurisdiction
can show that local precipitation data justify a different standard.
~ c. Soils shall be stabilized at the end of the shift before a holiday or weekend if needed
~ based on the weather forecast.
'~ d. Soil stockpiles shall be stabilized from erosion, protected with sediment trapping
measures, and where possible, be located away from storm drain inlets, waterways,
and drainage channels.
~ 6. Protect Slopes
U
a. Design and construct cut and fill slopes in a manner that will minimize erosion.
`~ Applicable practices include, but are not limited to, reducing continuous length of
~.J slope with terracing and diversions, reducing slope steepness, and roughening slope
surfaces (e.g., track walking).
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b. Off-site stormwater (run-on) or groundwater shall be diverted away from slopes and
i__1 disturbed areas with interceptor dikes, pipes, and/or swales. Off-site stormwater
~ should be managed separately from stormwater generated on the site.
v c. At the top of slopes, collect drainage in pipe slope drains or protected channels to
prevent erosion.
~ i. West of the Cascade Mountains Crest: Temporary pipe slope drains shall
v handle the peak 10-minute velocity of flow from a Type lA, 10-year, 24-hour
frequency storm for the developed condition. Alternatively, the 10-year, 1-
~ hour flow rate predicted by an approved continuous runoff model, increased
~ by a factor of 1.6, may be used. The hydrologic analysis shall use the existing
land cover condition for predicting flow rates from tributary areas outside the
'~ project limits. For tributary areas on the project site, the analysis shall use the
u temporary or permanent project land cover condition, whichever will produce
the highest flow rates. If using the WWHM to predict flows, bare soil areas
'~ should be modeled as "landscaped area."
ii. East of the Cascade Mountains Crest: Temporary pipe slope drains shall
~ handle the expected peak flow velocity from a 6-month, 3-hour storm for the
developed condition, referred to as the short duration storm.
n d. Excavated material shall be placed on the uphill side of trenches, consistent with
' safety and space considerations.
U
e. Check dams shall be placed at regular intervals within constructed channels that
,--~ are cut down a slope.
~ a. All storm drain inlets made operable during construction shall be protected so that
Lj stormwater runoff does not enter the conveyance system without first being filtered
or treated to remove sediment.
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u b. Inlet protection devices shall be cleaned or removed and replaced when sediment
has filled one-third of the available storage (unless a different standard is specified
`~ by the product manufacturer).
,~ 8. Stabilize Channels and Outlets
a. All temporary on-site conveyance channels shall be designed, constructed, and
stabilized to prevent erosion from the following expected peak flows:
~ i. West of the Cascade Mountains Crest: Channels shall handle the peak 10
~ minute velocity of flow from a Type lA, 10-year, 24-hour frequency storm for
the developed condition. Alternatively, the 10-year, 1-hour flow rate indicated
~ by an approved continuous runoff model, increased by a factor of 1.6, may be
used. The hydrologic analysis shall use the existing land cover condition for
predicting flow rates from tributary areas outside the project limits. For
I--, tributary areas on the project site, the analysis shall use the temporary or
~ permanent project land cover condition, whichever will produce the highest
flow rates. If using the WWHM to predict flows, bare soil areas should be
,-, modeled as "landscaped area."
~ ii. East of the Cascade Mountains Crest: Channels shall handle the expected peak
r flow velocity from a 6-month, 3-hour storm for the developed condition
! ,
referred to as the short duration storm.
v
b. Stabilization, including armoring material, adequate to prevent erosion of outlets
,
adjacent stream banks, slopes, and downstream reaches shall be provided at the
~ outlets of all conveyance systems.
9. Control Pollutants
~ a. 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.
'--~ b. Cover, containment, and protection from vandalism shall be provided for all
~ chemicals, liquid products, petroleum products, and other materials that have the
potential to pose a threat to human health or the environment. On-site fueling tanks
shall include secondary containment.
~ c. Maintenance, fueling, and repair of heavy equipment and vehicles shall be
conducted using spill prevention and control measures. Contaminated surfaces shall
be cleaned immediately following any spill incident.
`~ d. Wheel wash or tire bath wastewater shall be discharged to a separate on-site
e. Application of fertilizers and pesticides, shall be conducted in a manner and at
~ application rates that will not result in loss of chemical to stormwater runoff.
~ Manufacturers' label requirements for application rates and procedures shall be
followed.
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~ - -
~ f. BMPs shall be used to prevent or treat contamination of stormwater runoff by pH
~ modifying sources. These sources include, but are not limited to: bulk cement,
~ cement kiln dust, fly ash, new concrete washing and curing waters, waste streams
generated from concrete grinding and sawing, exposed aggregate processes,
dewatering concrete vaults, concrete pumping and mixer washout waters.
U Permittees shall adjust the pH of stormwater if necessary to prevent violations of
water quality standards.
'-I g. Permittees shall obtain written approval from Ecology prior to using chemical
treatment, other than COZ or dry ice to adjust pH.
10. Control De-Watering
~
v a. Foundation, vault, and trench de-watering water, which have similar characteristics
to stormwater runoff at the site, shall be discharged into a controlled conveyance
`-' system prior to discharge to a sediment trap or sediment pond.
u
b. Clean, non-turbid de-watering water, such as well-point ground water, can be
, discharged to systems tributary to, or directly into surface waters of the state, as
~ specified in S9.D.8, provided the de-watering flow does not cause erosion or
~ flooding of receiving waters. Clean de-watering water should not be routed through
~ stormwater sediment ponds.
v c. Other de-watering disposal options may include:
i. infiltration
n
,~
ii. transport offsite in a vehicle, such as a vacuum flush truck, for legal disposal in
a manner that does not pollute state waters,
~ iii. Ecology-approved on-site chemical treatment or other suitable treatment
technologies,
~ iv. sanitary sewer discharge with local sewer district approval, if there is no other
~I option, or
~ v. use of a sedimentation bag with outfall to a ditch or Swale for small volumes of
localized de-watering.
d. Highly turbid or contaminated dewatering water shall be handled separately from
stormwater.
v
11. Maintain BMPs
n
~
a. All temporary and permanent erosion and sediment control BMPs shall be
~J
maintained-and-repaired-as-needed to-assure-cont~~Ued-performance-of-their
intended function in accordance with BMP specifications.
n
~ b. All temporary erosion and sediment control BMPs shall be removed within 30 days
after final site stabilization is achieved or after the temporary BMPs are no longer
~ needed.
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12. Manage the Project
a. Development projects shall be phased to the maximum degree practicable and shall
take into account seasonal work limitations.
b. Inspection and Monitoring
All BMPs shall be inspected, maintained, and repaired as needed to assure
continued performance of their intended function. Site inspections and monitoring
shall be conducted in accordance with S4.
c. Maintaining an Updated Construction SWPPP
The SWPPP shall be maintained, updated, and implemented in accordance with
Conditions S3, S4 and S9.
E. SWPPP - Mai Contents and Requirements
The SWPPP shall also include a vicinity map or general location map (e.g. USGS
Quadrangle map, a portion of a county or city map, or other appropriate map) with
enough detail to identify the location of the construction site and receiving waters within
one mile of the site.
The SWPPP shall also include a legible site map (or maps) showing the entire
construction site. The following features shall be identified, unless not applicable due to
site conditions:
1. The direction of north, property lines, and existing structures and roads;
2. Cut and fill slopes indicating the top and bottom of slope catch lines;
3. Approximate slopes, contours, and direction of stormwater flow before and after
major grading activities;
4. Areas of soil disturbance and areas that will not be disturbed;
5. Locations of structural and nonstructural controls (BMPs) identified in the SWPPP
6. Locations of off-site material, stockpiles, waste storage, borrow areas, and
vehicle/equipment storage areas;
7. Locations of all surface water bodies, including wetlands;
8. Locations where stormwater or non-stormwater discharges off-site and/or to a surface
water body, including wetlands;
9. Location of water quality sampling station(s), if sampling is required by state or local
permitting authority; and
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10. Areas where final stabilization has been accomplished and no further construction-
phase permit requirements apply.
510. NOTICE OF TERMINATION
~ A. The site is eligible for termination when either of the following conditions have been met:
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1. The site has undergone final stabilization, all temporary BMPs have been removed,
and all stormwater discharges associated with construction activity have been
eliminated; or
~ 2. All portions of the site which have not undergone final stabilization per S 10.A.1 have
~ been sold and/or transferred (per Condition G9), and the Permittee no longer has
operational control of the construction activity.
s--i
~ B. When the site is eligible for termination, the Permittee shall submit a complete and
accurate Notice of Termination (NOT) form, signed in accordance with General
r`t Condition G2, to:
u
Department of Ecology
r--~ Water Quality Program -Construction Stormwater
~ PO Box 47696
Olympia, Washington 98504-7696
n C. The termination is effective on the date the NOT form was received by Ecology, unless
~ the Permittee is notified by Ecology within 30 days that termination request is denied
because the eligibility requirements in Condition S 10.A have not been met.
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Page 30 of 46
GENERAL CONDITIONS
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G1. DISCHARGE VIOLATIONS
All discharges and activities authorized by this general permit shall be consistent with the
terms and conditions of this general permit. Any discharge of any pollutant more frequent
than or at a level in excess of that identified and authorized by the general permit shall
constitute a violation of the terms and conditions of this permit.
G2. SIGNATORY REQUIREMENTS
A. All permit applications shall bear a certification of correctness to be signed:
1. In the case of corporations, by a responsible corporate officer of at least the level of
vice president of a corporation;
2. In the case of a partnership, by a general partner of a partnership;
3. In the case of sole proprietorship, by the proprietor; or
4. In the case of a municipal, state, or other public facility, by either a principal
executive officer or ranking elected official.
B. All reports required by this permit and other information requested by Ecology shall be
signed by a person described above or by a duly authorized representative of that person.
A person is a duly authorized representative only if:
1. The authorization is made in writing by a person described above and submitted to
the Ecology.
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~ j 2. The authorization specifies either an individual or a position having responsibility for
the overall operation of the regulated facility, such as the position of plant manager,
n superintendent, position of equivalent responsibility, or an individual or position
~j having overall responsibility for environmental matters.
C. Changes to authorization. If an authorization under paragraph G2.B.2 above is no longer
accurate because a different individual or position has responsibility for the overall
operation of the facility, a new authorization satisfying the requirements of paragraph
n G2.B.2 above shall be submitted to Ecology prior to or together with any reports,
J information, or applications to be signed by an authorized representative.
~ D. Certification. Any person signing a document under this section shall make the following
~1 certification:
~ "I certify under penalty of law, that this document and all attachments were
~ prepared under my direction or supervision in accordance with a system
designed to assure that qualified personnel properly gathered and evaluated
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Page 31 of 46
the information submitted. Based on my inquiry of the person or persons who
manage the system, or those persons directly responsible for gathering
information, the information submitted is, to the best of my knowledge and
belief, true, accurate, and complete. I am aware that there are significant
penalties for submitting false information, including the possibility of fine and
imprisonment for knowing violations."
G3. RIGHT OF INSPECTION AND ENTRY
The Permittee shall allow an authorized representative of Ecology, upon the presentation of
credentials and such other documents as may be required by law:
A. To enter upon the premises where a discharge is located or where any records shall be
kept under the terms and conditions of this permit.
B. To have access to and copy - at reasonable times and at reasonable cost -any records
required to be kept under the terms and conditions of this permit.
C. To inspect - at reasonable times -any facilities, equipment (including monitoring and
control equipment), practices, methods, or operations regulated or required under this
permit.
D. To sample or monitor - at reasonable times -any substances or parameters at any location
for purposes of assuring permit compliance or as otherwise authorized by the Clean
Water Act.
G4. GENERAL PERMIT MODIFICATION AND REVOCATION
This permit may be modified, revoked and reissued, or terminated in accordance with the
provisions of Chapter 173-226 WAC. Grounds for modification, revocation and reissuance,
or termination include, but are not limited to, the following:
A. When a change which occurs in the technology or practices for control or abatement of
pollutants applicable to the category of dischargers covered under this permit;
B. When effluent limitation guidelines or standards are promulgated pursuant to the CWA or
Chapter 90.48 RCW, for the category of dischargers covered under this permit;
C. When a water quality management plan containing requirements applicable to the
category of dischargers covered under this permit is approved; or
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l~ D. When information is obtained which indicates that cumulative_effects-an-th~en~ir-onment
from dischargers covered under this permit are unacceptable.
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~ G5. REVOCATION OF COVERAGE UNDER THE PERMIT
Pursuant with Chapter 43.21B RCW and Chapter 173-226 WAC, the Director may terminate
coverage for any discharger under this permit for cause. Cases where coverage may be
terminated include, but are not limited to, the following:
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A. Violation of any term or condition of this permit;
J B. Obtaining coverage under this permit by misrepresentation or failure to disclose fully all
relevant facts;
C. A change in any condition that requires either a temporary or permanent reduction or
elimination of the permitted discharge;
D. Failure or refusal of the Permittee to allow entry as required in RCW 90.48.090;
E
A d
.
etermination that the permitted activity endangers human health or the environment
or contributes to water quality standards violations;
F. Nonpayment of permit fees or penalties assessed pursuant to RCW 90.48.465 and
Chapter 173-224 WAC;
~
0 G. Failure of the Permittee to satisfy the public notice requirements of WAC 173-226-
130(5), when applicable.
n The Director may require any discharger under this permit to apply for and obtain coverage
u under an individual permit or another more specific general permit. Permittees who have
their coverage revoked for cause according to WAC 173-226-240 may request temporary
coverage under this permit during the time an individual permit is being developed, provided
the request is made within ninety (90) days from the time of revocation and is submitted
along with a complete individual permit application form.
G6. REPORTING A CAUSE FOR MODIFICATION
The Permittee shall submit a new application, or a supplement to the previous application,
n whenever a material change to the construction activity or in the quantity or type of discharge
U is anticipated which is not specifically authorized by this permit. This application shall be
submitted at least sixty (60) days prior to any proposed changes. The filing of a request by
the Permittee for a permit modification, revocation and reissuance, or termination, or a
i
not
fication of planned changes or anticipated noncompliance does not relieve the Permittee
of the duty to comply with the existing permit until it is modified or reissued
.
~ G7. COMPLIANCE WITH OTHER LAWS AND STATUTES
n Nothing in this permit shall be construed as excusing the Permittee from compliance with
any applicable federal, state, or local statutes, ordinances, or regulations.
,--, G8. DUTY TO REAPPLY
~ ~ T-he-Permittee-shall-applyfar permi renewa at east r80 ays prior to the specified
expiration date of this permit.
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~-1 G9. TRANSFER OF GENERAL PERMIT COVERAGE
~1 Coverage under this general permit is automatically transferred to a new discharger,
including operators of lots/parcels within a common plan of development or sale, if:
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A. A written, signed agreement (Transfer of Coverage Form) between the current dischar er
g
(Pennittee) and new discharger containing a specific date for transfer of permit
responsibility, coverage, and liability is submitted to the Director; and
B. The Director does not notify the current discharger and new discharger of the Director's
~1 intent to revoke coverage under the general permit. If this notice is not given, the transfer
,J is effective on the date specified in the written agreement.
r-1 When a current discharger (Permittee) transfers a portion of a permitted site, the current
discharger shall also submit an updated application form (NOI) to the Director indicating the
remaining permitted acreage after the transfer. When a current discharger (Permittee)
r-~ transfers all portions of a permitted site to one or more new dischargers, the current
~ discharger shall also submit a notice of termination (NOT) form to the Director.
~.J
,.~ G10. REMOVED SUBSTANCES
~ Collected screenings, grit, solids, sludges, filter backwash, or other pollutants removed in the
r~ course of treatment or control of stormwater shall not be resuspended or reintroduced to the
final effluent stream for discharge to state waters.
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G11. DUTY TO PROVIDE INFORMATION
The Pennittee shall submit to Ecology, within a reasonable time, all information which
Ecology may request to determine whether cause exists for modifying, revoking and
reissuing, or terminating this permit or to determine compliance with this permit. The
U Permittee shall also submit to Ecology upon request, copies of records required to be kept by
this permit [40 CFR 122.41(h)].
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u G12.OTHER REQUIREMENTS OF 40 CFR
~ All other requirements of 40 CFR 122.41 and 122.42 are incorporated in this permit by
reference.
~ G13. ADDITIONAL MONITORING
~ Ecology may establish specific monitoring requirements in addition to those contained in this
permit by administrative order or permit modification.
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~..~ G14. PENALTIES FOR VIOLATING PERMIT CONDITIONS
f~ Any person who is found guilty of willfully violating the terms and conditions of this permit
~~ shall be deemed guilty of a crime, and upon conviction thea~e9f shallbe~unished_b-y-a fne-of
up to ten thousand dollars ($10,000) and costs of prosecution, or by imprisonment in the
n discretion of the court. Each day upon which a willful violation occurs may be deemed a
~j separate and additional violation.
n Any person who violates the terms and conditions of a waste discharge permit shall incur, in
~ addition to any other penalty as provided by law, a civil penalty in the amount of up to ten
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~i thousand dollars ($10,000) for every such violation. Each and every such violation shall be a
separate and distinct offense, and in case of a continuing violation, every day's continuance
shall be deemed to be a separate and distinct violation.
G15. UPSET
~~--a
Definition - "Upset" means an exceptional incident in which there is unintentional and
temporary noncompliance with technology-based permit effluent limitations because of
n factors beyond the reasonable control of the Permittee. An upset does not include
~ noncompliance to the extent caused by operational error, improperly designed treatment
facilities, inadequate treatment facilities, lack of preventive maintenance, or careless or
r-~ improper operation.
U An upset constitutes an affirmative defense to an action brought for noncompliance with such
~ technology-based permit effluent limitations if the requirements of the following paragraph
u are met.
`~ A Permittee who wishes to establish the affirmative defense of upset shall demonstrate,
~ through properly signed, contemporaneous operating logs or other relevant evidence that: 1)
an upset occurred and that the Permittee can identify the cause(s) of the upset; 2) the
permitted facility was being properly operated at the time of the upset; 3) the Permittee
submitted
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no
ce o
e upset as requ
red in condition SS.F; and 4) the Permittee complied
with any remedial measures required under this permit.
n In any enforcement proceeding, the Permittee seeking to establish the occurrence of an upset
U has the burden of proof.
~ G16. PROPERTY RIGHTS
u
This permit does not convey any property rights of any sort, or any exclusive privilege.
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G17. DUTY TO COMPLY
U
~ The Permittee shall comply with all conditions of this permit. Any permit noncompliance
constitutes a violation of the Clean Water Act and is grounds for enforcement action; for
u permit termination, revocation and reissuance, or modification; or denial of a permit renewal
application.
v G18. TOXIC POLLUTANTS
n The Permittee shall comply with effluent standards or prohibitions established under Section
~ ~ 307(a) of the Clean Water Act~o~toxic_p~llutants v~ithin the-time pr-ovided-in-the-regulation
that establish those standards or prohibitions, even if this permit has not yet been modified to
n incorporate the requirement.
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G19. PENALTIES FOR TAMPERING
~ The Clean Water Act provides that any person who falsifies, tampers with, or knowingly
~--1 renders inaccurate any monitoring device or method required to be maintained under this
permit shall, upon conviction, be punished by a fine of not more than $10,000 per violation,
~ or by imprisonment for not more than two years per violation, or by both. If a conviction of
~ a person is for a violation committed after a first conviction of such person under this
Condition, punishment shall be a fine of not more than $20,000 per day of violation, or
~ imprisonment of not more than four (4) years, or both.
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G20. REPORTING PLANNED CHANGES
n
~ The Permittee shall, as soon as possible, give notice to Ecology of planned physical
alterations, modifications or additions to the permitted construction activity, which will result
n in:
u
A. The permitted facility being determined to be a new source pursuant to 40 CFR
u B. A significant change in the nature or an increase in quantity of pollutants discharged,
,~ including but not limited to: for sites 5 acres or larger, a 20% or greater increase in
~ acreage disturbed by construction activity;
C. A change in or addition of surface water(s) receiving stormwater or non-stormwater from
~ the construction activity; or
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D. A change in the construction plans and/or activity that affects the Permittee's monitoring
'~ requirements in Special Condition S4.
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Following such notice, permit coverage may be modified, or revoked and reissued pursuant
'-1 to 40 CFR 122.62(a) to specify and limit any pollutants not previously limited. Until such
Lj modification is effective, any new or increased discharge in excess of permit limits or not
specifically authorized by this permit constitutes a violation.
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~ G21. REPORTING OTHER INFORMATION
,~ Where the Permittee becomes aware that it failed to submit any relevant facts in a permit
application, or submitted incorrect information in a permit application or in any report to
~ Ecology, it shall promptly submit such facts or information.
~ G22. REPORTING ANTICIPATED NON-COMPLIANCE
~i
The Permittee shall give advance notice to Ecology by submission of a new application or
'~ supplement thereto at least forty-five (45) days prior to commencement of such discharges,
~,l of any facility expansions, production increases, or other planned changes, such as process
modifications, in the permitted facility or activity which may result in noncompliance with
~ permit limits or conditions. Any maintenance of facilities, which might necessitate
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unavoidable interruption of operation and degradation of effluent quality, shall be scheduled
during non-critical water quality periods and carried out in a manner approved by Ecology.
G23. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT
~! Any discharger authorized by this permit may request to be excluded from coverage under
U the general permit by applying for an individual permit. The discharger shall submit to the
Director an application as described in WAC 173-220-040 or WAC 173-216-070, whichever
n is applicable, with reasons supporting the request. These reasons shall fully document how an
Lj individual permit will apply to the applicant in a way that the general permit cannot. Ecology
may make specific requests for information to support the request. The Director shall either
issue an individual permit or deny the request with a statement explaining the reason for the
denial. When an individual permit is issued to a discharger otherwise subject to the
construction stormwater general permit, the applicability of the construction stormwater
r~ general permit to that Permittee is automatically terminated on the effective date of the
~ individual permit.
G24. APPEALS
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u A. The terms and conditions of this general permit, as they apply to the appropriate class of
dischargers, are subject to appeal by any person within 30 days of issuance of this general
~} permit, in accordance with Chapter 43.21B RCW, and Chapter 173-226 WAC.
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B. The terms and conditions of this general permit, as they apply to an individual discharger,
~1 are appealable in accordance with Chapter 43.21B RCW within 30 days of the effective
~I date of coverage of that discharger. Consideration of an appeal of general permit
coverage of an individual discharger is limited to the general permit's applicability or
'~ nonapplicability to that individual discharger.
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C. The appeal of general permit coverage of an individual discharger does not affect any
~? other dischargers covered under this general permit. If the terms and conditions of this
U general permit are found to be inapplicable to any individual discharger(s), the matter
shall be remanded to Ecology for consideration of issuance of an individual permit or
n permits.
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G25. SEVERABILITY
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L.__i The provisions of this permit are severable, and if any provision of this permit, or application
of any provision of this permit to any circumstance, is held invalid, the application of such
r , provision to other circumstances, and the remainder of this permit shall not be affected
thereby.
,~ G26. BYPASS PROHIBITED
~ A. Bypass Procedures
~ Bypass, which is the intentional diversion of waste streams from any portion of a
treatment facility, is prohibited for stormwater events below the design criteria for
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- -- - -- -
~--~ stormwater management. Ecology may take enforcement action against a Permittee for
bypass unless one of the following circumstances (l, 2, 3 or 4) is applicable.
~l
~ 1. Bypass of stormwater is consistent with the design criteria and part of an approved
management practice in the applicable stormwater management manual.
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2. Bypass for essential maintenance without the potential to cause violation of permit
limits or conditions.
'~,
~ Bypass is authorized if it is for essential maintenance and does not have the potential
to cause violations of limitations or other conditions of this permit, or adversely
impact public health.
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3. Bypass of stormwater is unavoidable, unanticipated, and results in noncompliance of
this permit.
`~ This bypass is permitted only if:
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a. Bypass is unavoidable to prevent loss of life, personal injury, or severe property
n damage. "Severe property damage" means substantial physical damage to
property, damage to the treatment facilities which would cause them to become
inoperable, or substantial and permanent loss of natural resources which can
n reasonably be expected to occur in the absence of a bypass;
U b. There are no feasible alternatives to the bypass, such as the use of auxiliary
treatment facilities, retention of untreated wastes, maintenance during normal
U periods of equipment downtime (but not if adequate backup equipment should
have been installed in the exercise of reasonable engineering judgment to prevent
n a bypass which occurred during normal periods of equipment downtime or
preventative maintenance), or transport of untreated wastes to another treatment
facility; and
c. Ecology is properly notified of the bypass as required in Special Condition SS
F
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of this permit.
~ 4. A planned action that would cause bypass of stormwater and has the potential to
result in noncompliance of this permit during a storm event.
The Permittee shall notify Ecology at least thirty (30) days before the planned date of
b
Th
ypass.
e notice shall contain:
a. a description of the bypass and its cause;
n b. an analysis of all known alternatives which would eliminate, reduce, or mitigate
u the-need-for-bypass ,
n c. acost-effectiveness analysis of alternatives including comparative resource
Ll damage assessment;
,--~ d. the minimum and maximum duration of bypass under each alternative;
~ e. a recommendation as to the preferred alternative for conducting the bypass;
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f. the projected date of bypass initiation;
g. a statement of compliance with SEPA;
h. a request for modification of water quality standards as provided for in WAC 173-
201A-110, if an exceedance of any water quality standard is anticipated; and
i. steps taken or planned to reduce, eliminate, and prevent reoccurrence of the
bypass.
5. For probable construction bypasses, the need to bypass is to be identified as early in
the planning process as possible. The analysis required above shall be considered
during preparation of the Stonnwater Pollution Prevention Plan (SWPPP) and shall
be included to the extent practical. In cases where the probable need to bypass is
determined early, continued analysis is necessary up to and including the construction
period in an effort to minimize or eliminate the bypass.
Ecology will consider the following prior to issuing an administrative order for this
type bypass:
a. If the bypass is necessary to perform construction or maintenance-related
activities essential to meet the requirements of this permit.
b. If there are feasible alternatives to bypass, such as the use of auxiliary treatment
facilities, retention of untreated wastes, stopping production, maintenance during
normal periods of equipment down time, or transport of untreated wastes to
another treatment facility.
c. If the bypass is planned and scheduled to minimize adverse effects on the public
and the environment.
After consideration of the above and the adverse effects of the proposed bypass and
any other relevant factors, Ecology will approve, conditionally approve, or deny the
request. The public shall be notified and given an opportunity to comment on bypass
incidents of significant duration, to the extent feasible. Approval of a request to
bypass will be by administrative order issued by Ecology under RCW 90.48.120.
B. Du to Miti ate
The Permittee is required to take all reasonable steps to minimize or prevent any
discharge or sludge use or disposal in violation of this permit that has a reasonable
likelihood of adversely affecting human health or the environment.
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---- - ---------- - - - - -----
APPENDIX A -DEFINITIONS
AKART is an acronym for "all known, available, and reasonable methods of prevention, control,
'~ and treatment." AKART represents the most current methodology that can be reasonably
~j required for preventing, controlling, or abating the pollutants and controlling pollution associated
with a discharge.
~f
U Applicable TMDL means a TMDL for turbidity, fine sediment, high pH, or phosphorus, which
has been completed and approved by EPA prior to November 16, 2005, or prior to the date the
n operator's complete permit application is received by Ecology, whichever is later.
v
Applicant means an operator seeking coverage under this permit.
~j Best Management Practices (BMPs) means schedules of activities, prohibitions of practices,
maintenance procedures, and other physical, structural and/or managerial practices to prevent or
n reduce the pollution of waters of the state. BMPs include treatment systems, operating
procedures, and practices to control: stormwater associated with construction activity, spillage
or leaks, sludge or waste disposal, or drainage from raw material storage.
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Bu er means an area designated by a local jurisdiction that is contiguous to and intended to
protect a sensitive area
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B ass means the intentional diversion of waste streams from any portion of a treatment facility.
n Calendar Week (same as Week) means a period of seven consecutive days starting on Sunday.
Certified Erosion and Sediment Control Lead (CESCL) means a erson who has Curren
p t
~ certification through an approved erosion and sediment control training program that meets the
minimum training standards established by Ecology (see BMP C160 in the SWMM).
Clean Water Act (CWA) means the Federal Water Pollution Control Act enacted by Public Law
~ 92-500, as amended by Public Laws 95-217, 95-576, 96-483, and 97-117; USC 1251 et seq.
Combined Sewer means a sewer which has been designed to serve as a sanitary sewer and a
r~ storm sewer, and into which inflow is allowed by local ordinance.
v
Common plan ofdevelopment or sale means a site where multiple separate and distinct
,~ construction activities may be taking place at different times on different schedules, but still
under a single plan. Examples include: 1) phased projects and proje~ts~vith~n„lt_s iple fl~ng~r
~o s, even i`~ t e separate phases or filings/lots will be constructed under separate contract or by
r~ separate owners (e.g., a development where lots are sold to separate builders); 2) a development
~ plan that may be phased over multiple years, but is still under a consistent plan for long-term
development; and 3) projects in a contiguous area that may be unrelated but still under the same
~ contract, such as construction of a building extension and a new parking lot at the same facility.
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~ If the project is part of a common plan of development or sale, the disturbed area of the entire
plan shall be used in determining permit requirements.
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Composite Sample A mixture of grab samples collected at the same sampling point at different
times, formed either by continuous sampling or by mixing discrete samples. May be "time-
composite" (collected at constant time intervals) or "flow-proportional" (collected either as a
constant sample volume at time intervals proportional to stream flow, or collected by increasing
the volume of each aliquot as the flow increases while maintaining a constant time interval
~ between the aliquots.
~!
Construction Activity means land disturbing operations including clearing, grading or excavation
~ which disturbs the surface of the land. Such activities may include road construction,
~ construction of residential houses, office buildings, or industrial buildings, and demolition
`~ activity.
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Demonstrably Equivalent means that the technical basis for the selection of all stormwater BMPs
U is documented within a SWPPP, including:
~ 1. The method and reasons for choosing the stormwater BMPs selected;
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1 2. The pollutant removal performance expected from the BMPs selected;
- 3. The technical basis supporting the performance claims for the BMPs selected,
~ including any available data concerning field performance of the BMPs selected;
4. An assessment of how the selected BMPs will comply with state water quality
standards; and
5. An assessment of how the selected BMPs will satisfy both applicable federal
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ogy-
ased treatment requirements and state requirements to use all known
,
available, and reasonable methods of prevention, control, and treatment (AKART).
~
J Department means the Washington State Department of Ecology.
Detention means the temporary storage of stormwater to improve quality and/or to reduce the
~ mass flow rate of discharge.
De-watering means the act of pumping ground water or stormwater away from an active
~ construction site.
~J
Director means the Director of the Washington Department of Ecology or his/her authorized
`~
~I representative.
Discharger means an owner or operator of any facility or activity subject to regulation under
~I Chapter 90.48 RCW or the Federal Clean Water Act.
Domestic Wastewater means water carrying human wastes, including kitchen, bath, and laundry
wastes from residences, buildings, industrial establishments, or other places, together with such
~ ground water infiltration or surface waters as may be present.
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Engineered soils The use of soil amendments including, but not limited, to Portland cement
treated base (CTB), cement kiln dust (CKD), or fly ash to achieve certain desirable soil
characteristics.
v
Ec7uivalent BMPs means operational, source control, treatment, or innovative BMPs which result
~ in equal or better quality of stormwater discharge to surface water or to ground water than BMPs
~-1 selected from the SWMM.
~ Erosion means the wearing away of the land surface by running water, wind, ice, or other
~l geological agents, including such processes as gravitational creep.
'~ Erosion and Sediment Control BMPs means BMPs that are intended to prevent erosion and
~l ~ sedimentation, such as preserving natural vegetation, seeding, mulching and matting, plastic
covering, filter fences, sediment traps, and ponds. Erosion and sediment control BMPs are
'~ synonymous with stabilization and structural BMPs.
v
Final Stabilization (same as ully stabilized or full stabilization) means the establishment of a
r? permanent vegetative cover, or equivalent permanent stabilization measures (such as riprap,
gabions or geotextiles) which prevents erosion.
Ground Water means water in a saturated zone or stratum beneath the land surface or a surface
U water body.
~ Injection well means a "well" that is used for the subsurface emplacement of fluids. (see Well)
tJ
Jurisdiction means a political unit such as a city, town or county; incorporated for local self-
n government.
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National Pollutant Discharge Elimination System (NPDES) means the national program for
n issuing, modifying, revoking and reissuing, terminating, monitoring, and enforcing permits, and
imposing and enforcing pretreatment requirements, under sections 307, 402, 318, and 405 of the
Federal Clean Water Act, for the discharge of pollutants to surface waters of the state from point
n sources. These permits are referred to as NPDES permits and, in Washington State, are
administered by the Washington Department of Ecology.
Notice oflntent (NOI) means the application for, or a request for coverage under this general
permit pursuant to WAC 173-226-200.
~ Notice of Termination (NOT) means a request for termination of coverage under this general
permit as specified by Special Condition S 10 of this permit.
L~
n Operator means any party associated with a construction project that meets either of the
following two criteria:
U 1. The party has operational control over construction plans and specifications, including the
ability to make modifications to those plans and specifications; or
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Page 42 of 46
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v 2. The party has day-to-day operational control of those activities at a project which are
necessary to ensure compliance with a SWPPP for the site or other permit conditions (e.g., they
~ are authorized to direct workers at a site to carry out activities required by the SWPPP or comply
v with other permit conditions).
~ Out all means the location where stormwater leaves the site. It also includes the location where
v stormwater is discharged to a surface waterbody within a site, but does not include discharges to
on-site stormwater treatment/infiltration devices or storm sewer systems.
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Permittee means individual or entity that receives notice of coverage under this general permit.
-~ ~ means a liquid's acidity or alkalinity. A pH of 7 is defined as neutral. Large variations above
or below this value are considered harmful to most aquatic life.
~)
~ pHMonitoring Period means the time period in which the pH of stormwater runoff from a site
shall be tested a minimum of once every seven days to determine if stormwater is above pH 8.5.
Point Source means any discernible, confined, and discrete conveyance, including but not
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limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, and container from
'--} which pollutants are or may be discharged to surface waters of the state. This term does not
include return flows from irrigated agriculture. (See Fact Sheet for further explanation.)
~--~ Pollutant means dredged spoil, solid waste, incinerator residue, filter backwash, sewage,
garbage, domestic sewage sludge (biosolids), munitions, chemical wastes, biological materials,
~ radioactive materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt, and
~ industrial, municipal, and agricultural waste. This term does not include sewage from vessels
within the meaning of section 312 of the CWA, nor does it include dredged or fill material
`~ discharged in accordance with a permit issued under section 404 of the CWA.
Ll
Pollution means contamination or other alteration of the physical, chemical, or biological
~! properties of waters of the state; including change in temperature, taste, color, turbidity, or odor
~J of the waters; or such discharge of any liquid, gaseous, solid, radioactive or other substance into
any waters of the state as will or is likely to create a nuisance or render such waters harmful,
detrimental or injurious to the public health, safety or welfare; or to domestic, commercial,
~1 industrial, agricultural, recreational, or other legitimate beneficial uses; or to livestock, wild
animals, birds, fish or other aquatic life.
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~j Receiving Water means the waterbody at the point of discharge. If the discharge is to a storm
sewer system, either surface or subsurface, the receiving water is the waterbody that the storm
'~ sewer system discharges to. Systems designed primarily for other purposes such as for ground
~j water drainage, redirecting stream natural flows, nr fnr c~~e_y_ance_o.~ir-rigatien v~ater~r~
flows that coincidentally convey stormwater are considered the receiving water.
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~j Representative means a stormwater or wastewater sample which represents the flow and
characteristics of the discharge. Representative samples may be a grab sample, a time-
s proportionate composite sample, or a flow proportionate sample. Ecology's Construction
~j Stormwater Monitoring Manual provides guidance on representative sampling.
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Sanitary Sewer means a sewer which is designed to convey domestic wastewater.
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~ Sediment means the fragmented material that originates from the weathering and erosion of rocks
or unconsolidated deposits, and is transported by, suspended in, or deposited by water.
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v Sedimentation means the depositing or formation of sediment.
`~ Sensitive area means a waterbody, wetland, stream, aquifer recharge area, or channel migration
~J zone.
'-1 SEPA (State Environmental Policy Act) means the Washington State Law, RCW 43.21C.020,
,J intended to prevent or eliminate damage to the environment.
Sign~cantAmount means an amount of a pollutant in a discharge that is amenable to available
and reasonable methods of prevention or treatment; or an amount of a pollutant that has a
reasonable potential to cause a violation of surface or ground water quality or sediment
management standards.
~..~
SiQ-riif cant Concrete Work means greater than 1000 cubic yards poured concrete or recycled
~ concrete.
~ Significant Contributor o Pollutants means a facility determined by Ecology to be a contributor
n of a signifrcant amount(s) of a pollutant(s) to waters of the state of Washington.
u
Site means the land or water area where any "facility or activity" is physically located or
conducted.
Source Control BMPs means h sic
p y al, structural or mechanical devices or facilities that are
intended to prevent pollutants from entering stormwater. A few examples of source control
~ BMPs are erosion control practices, maintenance of stormwater facilities, constructing roofs over
~--~ storage and working areas, and directing wash water and similar discharges to the sanitary sewer
or a dead end sump.
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~ Stabilization means the application of appropriate BMPs to prevent the erosion of soils, such as,
temporary and permanent seeding, vegetative covers, mulching and matting, plastic covering and
sodding. See also the definition of Erosion and Sediment Control BMPs.
~J
Storm Drain means any drain which drains directly into a storm sewer svstem, usually found
'~ along roadways or in parking lots.
Storm Sewer Svstem means a means a conveyance, or system of conveyances (including roads
`-1 with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade
~1 channels, or storm drains designed or used for collecting or conveying stormwater. This does
not include systems which are part of a combined sewer or Publicly Owned Treatment Works
~ (POTW) as defined at 40 CFR 122.2.
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Page 44 of 46
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u Stormwater means that portion of precipitation that does not naturally percolate into the ground
or evaporate, but flows via overland flow, interflow, pipes, and other features of a sormwater
~ drainage system into a defined surface water body, or a constructed infiltration facility.
~J
Stormwater Management Manual (SWMM) or Manual means the technical manual published by
~ Ecology for use by local governments that contain descriptions of and design criteria for BMPs
v to prevent, control, or treat pollutants in Stormwater.
'~ Stormwater Pollution Prevention Plan (SWPPP) means a documented plan to implement
~i measures to identify, prevent, and control the contamination of point source discharges of
Stormwater.
~ Surface Waters ofthe State includes lakes, rivers, ponds, streams, inland waters, salt waters, and
all other surface waters and water courses within the jurisdiction of the state of Washington.
n
u Total Maximum Daily Load (TMDLZ means a calculation of the maximum amount of a pollutant
that a waterbody can receive and still meet state water quality standards. Percentages of the total
~ maximum daily load are allocated to the various pollutant sources. A TMDL is the sum of the
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~ allowable loads of a single pollutant from all contributing point and nonpoint sources. The
TMDL calculations shall include a "margin of safety" to ensure that the waterbody can be
~ protected in case there are unforeseen events or unknown sources of the pollutant. The
~ calculation shall also account for seasonable variation in water quality.
r-~ Treatment BMPs means BMPs that are intended to remove pollutants from sormwater. A few
examples of treatment BMPs are detention ponds, oil/water separators, biofiltration, and
constructed wetlands.
~ Transparency means a measurement of water clarity in centimeters (cm), using a 60 cm.
transparency tube. The transparency tube is used to estimate the relative clarity or transparency
r~ of water by noting the depth at which a black and white Secchi disc becomes visible when water
~ is released from a value in the bottom of the tube. A transparency tube is sometimes referred to
as a "turbidity tube".
n
u Turbidi The clarity of water expressed as nephelometric turbidity units (NTU) and measured
with a calibrated turbidimeter.
n
~ Waste Load Allocation ,
- WLA) means the portion of a receiving water s loading capacity that is
n allocated to one of its existing or future point sources of pollution. WLAs constitute a type of
water quality based effluent limitation (40 CFR 130.2(h)).
.I
~ Water Quality means the chemical, physical, and biological characteristics of water, usually with
~ respect to its suitability for a particular purpose.
n Waters o the State includes those waters as defined as "waters of the United States" in 40 CFR
~ Subpart 122.2 within the geographic boundaries of Washington State and "waters of the state" as
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v defined in Chapter 90.48 RCW which include lakes, rivers, ponds, streams, inland waters,
underground waters, salt waters, and all other surface waters and water courses within the
~ jurisdiction of the state of Washington.
Well means a bored, drilled or driven shaft, or dug hole whose depth is greater than the
`-' largest surface dimension. (see Injection Well)
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Page 46 of 46
APPENDIX B -ACRONYMS
AKART' All Known, Available, and Reasonable Methods of Prevention, Control, and
Treatment
BMP Best Management Practice
CESCL Certified Erosion and Sediment Control Lead
CFR Code of Federal Regulations
CKD Cement Kiln Dust
cm Centimeters
CTB Cement Treated Base
CWA Clean Water Act
DMR Discharge Monitoring Report
EPA Environmental Protection Agency
ESC Erosion and Sediment Control
NOI Notice of Intent
NOT Notice of Termination
NPDES National Pollutant Discharge Elimination System
NTU Nephelometric Turbidity Unit
RCW Revised Code of Washington
SEPA State Environmental Policy Act
S WMM Stormwater Management Manual
SWPPP Stormwater Pollution Prevention Plan
TMDL Total Maximum Daily Load
UIC Underground Injection Control
USC United States Code
USEPA United States Environmental Protection Agency
WAC Washington Administrative Code
WQ Water Quality
WWHM Western Washington Hydrology Model
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Appendix E -Site Inspection Forms (and Site Log)
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The re:;ults 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
SWPP>'' and the site inspection forms be kept onsite at all times during construction, 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 inspection,
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, s
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
,J inspection, and the results of that monitoring
,~ g. General comments and notes, including a brief description of any
~ BMP r repairs, maintenance or installations made as a result of the
inspection.
~ h. A statement that, in the 'ud
~ ~ gment 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
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~ permit. If the site inspection indicates that the site is out of
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compliance, the inspection report shall include a summary of the
~ _- - - remedial actions required to_bring-t_he_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'.
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~ When the site inspection indicates that the site is not in compliance with any terms and
,J 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),
Li and/or conduct maintenance of existing BMPs; and achieve compliance with all
applicable standards and permit conditions. In addition, if the noncompliance causes a
r! threat to human health or the environment, the Permittee shall comply with the
~I Noncompliance Notification requirements in Special Condition SS.F of the permit.
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Site Inspection Form
General Information
Project ivame:
Inspector Name: Title:
CESCL#:
Date: Time:
Inspection Type: ^ After a rain event
^ Weekly
^ Turbidity/transparency benchmark exceedance
^ Other
Weather
Precipitation Since last inspection In last 24 hours
Descriptiion of General Site Conditions:
Inspection of BMPs
Element d: Mark Clearing Limits
BMP:
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Location Inspected-
Y N
- -Functioning - -
Y N NIP
---------- _-
Problem/Corrective Action
~ BMP:
'~ Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
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Element 2: Establish Construction Access
~ BMP:
~ Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
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BMP:
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Location
Y N Functioning
Y N NIP
Problem/Corrective Action
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Element 3: Control Flow Rates
`-' BMP:
u Inspected
Location Y N Functioning
y N NIP Problem/Corrective Action
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~ Location Inspected
Y N Functioning
Problem/Corrective Action
Y N NIP
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BMP:
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Location Y N Functioning
y N NIP Problem/Corrective Action
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BMP-:-- ------- -- - --- -- -
Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
BMP:
Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
BMP:
Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
BMP:
Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
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~ Element S: Stabilize Soils
BMP:
LJ Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
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`--~ Location Inspected
Y N Functioning
Y N NIP problem/Corrective Action
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Location Inspected
Y N Functioning
y N NIP
Problem/Corrective Action
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Y N Functioning
Y N NIP
Problem/Corrective Action
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BMP:
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`~ Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
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Y N Functioning
Y N NIP
Problem/Corrective Action
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Problem/Corrective Action
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~ Element 7: Protect Drain Inlets
BMP:
~
Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
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`~ Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
r--,
'-' BMP:
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' Location Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
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Element 8: Stabilize Channels and Outlets
~ BMP:
`~ Location Inspected
Y N Functioning
Y N NIP problem/Corrective Action
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Y N Functioning
y N NIP
Problem/Corrective Action
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`~ Locration Inspected
Y N Functioning
Y N NIP
Problem/Corrective Action
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BMP:
Location Inspected
Y N
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Y N NIP
Problem/Corrective Action
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Element 9: Control Pollutants
BMP:
Location Inspected
Y N
BMP:
Location Inspected
Y N
Element 10: Control Dewatering
BMP:
Location Inspected
Y N
BMP:
Location Inspected
Y N
BMP:
Location Inspected
Y N
Functioning
Y N NIP
Functioning
Y N NIP
Functioning
Y N NIP
Functioning
Y N NIP
Functioning
Y N NIP
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Problem/Corrective Action
Problem/Corrective Action
Problem/Corrective Action
Problem/Corrective Action
Problem/Corrective Action
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Turbidity
Discoloration
She:en
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~
---- ---------- ----Water Quality-Monitoring
-- Was arty water quality monitoring conducted? ^ Yes ^ N
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If water quality monitoring was conducted, record results here:
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If water quality monitoring indicated turbidity 250 NTU or greater; or transparency 6
n cm or less, was Ecology notified by phone within 24 hrs?
~ ^ Yes ^ No
If Ecology was notified, indicate the date, time, contact name and phone number
'~ below:
u Date:
Time:
'-' Contact Name:
L-~ P'hone #:
~ General Comments and Notes
~ Include BMP re airs, maintenance, or installations made as a result of the ins ection
.
Were Photos Taken? ^ Yes ^ No
,~ If hoto:> taken, describe hotos below:
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Appendix F -Engineering Calculations
49
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- - ---
~- - - -swpp precons -vent-Summary -- - --_- --------
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j E ev nt Peak Q (cfs) !Peak T (hrs) Hyd Vol (acft) Area (ac) Method ~Raintype
6 month; 0.0000 ~ 0.00 _ 0.0000` _ 0.0000 J SCS !TYPElA
2 year 6.4955 E 8.00 3.0681 71.3300 SCS ~TYPEIA
10 ye~~r j 19.0234 8.00 6.9190 71.3300 SCS jTYPElA
100 year I 33.8778 8.00 11.5029 71.3300 SCS ~TYPElA
,-, Recoird Id: swpp preconst
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Design Method SCS _ Rainfall type TYPElA
Hyd Into 10.00 min Peaking Factor ~ 484.00
Abstraction Coeff 0.20
Perviouus Area (AMC 2) 71.33 ac DCIA ~ 0.00 ac ',
Perviouus CN 79.00 DC CN ~ ~0.00
~P rvie ous TC 2.08 min DC TC ~ 0.00 min
Pervious CN Calc
~-
- Description SubArea Sub cn
~
Pasture or range (poor) ~ 71.33 ac ~ 79.00
~
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erv
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ompos
ted CN (AMC 2) ~ 79.00
-=
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Type _~-Description ~ !Length Slope Coeff I Misc TT
Sheet Dense grasses :0.24 115.00 ft 10.00% 0.2400 j2.0~0 in - 2.08 min
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~ Pervious TC 2.08 min
~ swpp const Event Summary
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Event Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac Method ~Rainty
6 month i 4.4498 8.01 2.0827 71.3300 SCS TYPElA
2 year ~ 13.7466 8.01 4.9817 71.3300 SCS ;TYPElA
10 year I 29.2938 ~ 8.01 9.8242 71.3300 SCS jTYPEIA
100 year ~ 46.1232 8.00 15.0988 71.3300 SCS ITYPElA
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Design Method _-
SCS Rainfall type
TYPEIA
~Hyd rIrI itv 10.00 min Peaking Factor ~ I 484.00
Abstraction Coeff ; 0.20
Pervious Area (AMC 2) ~ 71.33 ac DCIA `~ I 0.00 ac
Pervious CN 86.00 i DC CN ~j 0.00
Pervious TC 4.24 min DC TC j 0.00 min
~- Pervious CN Calc
~- Description SubArea I Sub cn
~.-- Newly graded area ~ 71.33 ac ~ 86.00
- Pervious Composited CN (AMC 2) ~
! 86.00
~-- Pervious TC Calc
',~ Type ~ Description Length Slope Coeff Misc TT
Cultivated Soil w1 residue cover 20.00 2 00
Sheet
1
50% 0
1700 4.24
(s>20%).. .
.
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: 0.17 ft
m
min
Pervious TC 4.24
mm
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Event ;Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) Method RainRain pe
6 montYi ~ 0.0000 ~ 0.00 0.0000 0.0000 SCS ~ TYPE 1 A
2 year , 7.2488 8.01 3.3173 ~ 71.3300 SCS ITYPElA
10 year 20.1416 8.01 7.3575 71.3300 SCS ~TYPElA
100 year ~ 35.2641 8.01 12.0820 71.3300 SCS ~TYPElA
`~ Record Id: swpp post const
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Design 1VIethod SCS Rainfall type TYPElA
Hyd Into 10.00 min Peaking Factor ~~ 484.00
~~~ Abstraction Coeff 0.20
Pervious Area (AMC 2) 71.33 ac DCIA ~ 0.00 ac
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iPe iorv us TC 3.84 min ~ DC TC
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0.00
0.00 min
~- ---
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Description SubArea Sub cn
~- Open spaces, lawns,parks (>75% grass) ~ 71.33 ac 80.00
~ ~ Pervious Composited CN (AMC 2) 80.00
Pervious TC Calc
Type Description Length ~ Slope Coeff Misc TT
Sheet CShort prairie grass and lawns.: 0.15 20.00 ft 1.50% 0.1500 2.00 in 3.84 mini
Pervious TC __3.84 min
trap 1 Event Summary
Event_!Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) Method Rain pe
6 month ~ 0.1644
_ 8.04 0.0817
~ ~T' Y `~-
2.8000 SCS JTYPElA
2 year 0.5217 8.03 0.1975 2.8000 SCS jTYPElA
10 year_~ 1.1249 8.02 0.3877 2.8000 SCS TYPElA
100 year i 1.7819 ~ 8.02 0.5945 2.8000 SCS ~TYPElA
Record Id: trap 1
Design Method SCS Rainfall type
Ilyd Intv 10.00 min Peaking Factor
~~~ Abstraction Coeff
Pervious Area (AMC 2) 2.80 ac DCIA
Pervious CN 86.00 DC CN ~~
Pervious TC
r-- 8.83 min DC TC
TYPEIA
484.00
0.20
0.00 ac
0.00
0.00 min
Description ~ SubArea ~ Sub cn
Newly graded area 2.80 ac i 86.00
Pervious Composited CN (AMC 2) ~ p
pp.vs~~,~ Tr races
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------~ ype --- Description Length Slope Coeff E M si c TT
Cultivated Soil w/ residue cover 50.00 2.00 8.83
Sheet ((s>20%)..: 0.17 ~ft 1.50% 0.1700 .
in min
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Pervious TC 8.83
mm
trap 2. Event Summary
Event Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) Method Ram pe
6 month 0.1761 8.04 ~ 0.-0876 3.0000 SCS ~TYPElA
2 year j 0.5590 8.03 0.2116 3.0000 SCS TYPElA
10 year ~ 1.2052 8.02 ~ 0.4154 3.0000 SCS iTYPElA
100 ye~~r j 1.9092 8.02 ~ 0.6369 ~ 3.0000 SCS TYPElA
Record Id: trap 2
Design Method SCS Rainfall type I TYPElA
Hyd Into 10.00 min Peaking Factor j 484.00
~W-..~ Abstraction Coeff ~i 0.20
Pervious Area (AMC 2) 3.00 ac ~ DCIA `~ ~~~ 0.00 ac
Pervious CN 86.00 ~ DC CN ~~~~~~ 0.00
Pervious TC 8.83 min DC TC ~ 0.00 min
Pervious CN Calc
~- Description
-~- ~-SubArea s Sub cn
_ Newly graded area ~- 3.00 ac ~~ i
- 86.00
_- Pervious Composited CN (AMC 2) i
i 86.00
_-
~ P
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erv
ous TC Calc
Type ~ Description Length Slope Coeff Misc TT
Sheet ~~~ated-Soi w rest
(s>20%)..: 0.17 ue cover ° 2.00
ft 1.50 /0 0.1700 i 8.83
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Pervious TC min
8.83
~ min
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Event ;Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) jMethod ;Raintype
6 monlh 0.1346 8.09 0.0733 2.5000 SCS iTYPEIA
2 year ~ 0.4417 8.07 _ 0.1768 2.5000 SCS ~TYPElA
10 year ~ 0.9662 8.06 0.3467 _ 2.5000 SCS TYPElA
100 ye<~r ~ 1.5403 8.06 0.5312 2.5000 SCS ITYPElA
~ Record Id: trap 3
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Design Method SCS ~ Rainfall type ~ TYPElA~
Hyd Inty 10.00 min Peaking Factor 484.00
~~ Abstraction Coeff 0.20
Pervious Area (AMC 2) 2.50 ac DCIA ~~'!~~ 0.00 ac
Pervious CN 86.00 DC CN ~ 0.00 ~. ',
Pervious TC 15.37 min DC TC ~ 0.00 min
Pervious CN Calc
~- Description SubArea ~ Sub cn
~- Newly graded area ~ 2.50 ac ~~ 86.00
~
- Pervious Composited CN (AMC 2) ~ 86.00
--
-~ Pervious TC Calc
', Type ~ Description Length Slope Coeff Misc ~ TT
Sheet Cultivated Soil w/ residue cover 100 00 1.50% 0 2.00 ' 15.37
17 ~ .1700. ~
(s>20 /
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15.37
Pervious TC
min
trap 4 Event Summary
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Event ;Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) Method ~Raintype
6 month ! 0.1435 8.03 ~ 0.0701 2.4000 31 JL~ ~TYPElA
2 year 1 0.4519 8.02 0.1690 2.4000 SCS ,ITYPElA
10 year ~ 0.9707 8.01 0.3321 _ 2.4000 SCS iTYPElA ~
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100-year-i-1-5350- -- --8:0-1- ---- 0-5094---24000 SCS ~TYPElA
Record Id: trap 4
Design Method SCS ~ Rainfall type ~' TYPElA
Hyd Intv 10.00 min Peaking Factor 1 ~ 484.00
Abstraction Coeff ~ 0.20
Pervious Area (AMC 2) ~ 2.40 ac DCIA 0.00 ac
Pervious CN 86.00 DC CN ~ I 0.00
Pervious TC 7.38 min ~ DC TC 0.00 min
Pervious CN Calc
Description SubArea 1 Sub cn
Newly graded area ~ 2.40 ac ~ 86.00
~- Pervious Composited CN (AMC 2) 86.00
~_ Pervious TC Calc
Type ~ Description Length Slope Coeff Misc TT
'Sheet Cultivated Soil w/ residue cover 40.00 2.00 7.38
1.50% 0.1700
>20%)
: 0
I
17
..
s .
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in min
7.38
P
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erv
ous TC
min
trap 5 Event Summary
Event ?Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) Method Raintype
6 month j 0.1345 8.02 0.0637 2.1800 SCS ,TYPElA
2 year ~ 0.4175 8.01 0.1525 2.1800 SCS ~T lEYP A
10 year 0.8919 ~ ~ 8.01 0.3007 2.1800 SCS jTYPElA
100 year 1.4058 8.01 0.4619~v 2.1800 SCS ~TYPElA
Record Id: trap 5
Design Method SCS Rainfall type ~ TYPElA
Hyd Inty 10.00 min Peaking Factor 484.00 I
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~ P~ ious Area (AMC 2) 2.18 ac_ DCIA ~ '
_~ ~ 0.00 ac
~ Pervious CN 86.00 DC CN 0.00
Pervious TC 5.07 min DC TC ~I
,_-~ ~ ~ , 0.00 min
LJ ~ Pervious CN Calc
Description SubArea~ ~~ Sub cn
~ ~ Newly graded area ~ 2.18 ac ~ 86.00
Pervious Composited CN (AMC 2) 86.00
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~ ~ Pervious TC Calc
Type Description Length Slope Coeff Misc TT
~ Cultivated Soil w/ residue cover 25.00
Sheet ° 1.50% 0.1700 2.00 5.07
(s>20 /o)..: 0.17 ft in min
~ Pervious TC 5.07
~ min
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