HomeMy WebLinkAbout1502 Bldg E E Lauridsen Blvd - Maier Hall Stormwater Pollution Prevention Plan - BuildingTECHNICAL
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Stormwater Pollution Prevention Plan
Owner
Peninsula College
For
Peninsula College, Maier Hall
Prepared For
Northwest Regional Office
3190 160th Avenue SE
Bellevue, WA 98008 -5452
425- 649 -7000
Operator /Contractor.
David Wegener
Project Site Location
1502 E Lauridsen Blvd, Port Angeles WA 98362
Certified Erosion and Sediment Control Lead
SWPPP Prepared By
KPFF Consulting Engineers
1601 Fifth Avenue, Suite 1600
Seattle, WA 98101
(206) 622 -5822
Rebekah Weston, Civil Engineer
SWPPP Preparation Date
5/13/2009
Approximate Project Construction Dates
July 1 2009
March 2011
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5 1 Roles and Responsibilities
5.2 Team Members
6 0 Site Inspections and Momtormg
Contents
1 0 Introduction. 1
2.0 Site Description 3
2.1 Existing Conditions .3
2.2 Proposed Construction Activities .3
3 0 Construction Stormwater BMPs .5
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15
16
6 1 Site Inspection 16
6 1 1 Site Inspection Frequency 16
6 1.2 Site Inspection Documentation 17
6.2 Stormwater Quality Monitoring 17
6.2.1 Turbidity 17
6.2.2 pH. 18
7 0 Reportmg and Recordkeeping 19
7 1 Recordkeeping 19
7 1 1 Site Log Book 19
7 1.2 Records Retention 19
7 1 3 Access to Plans and Records 19
7 1 4 Updating the SWPPP 19
7.2 Reporting .20
ii
1
1
3 1 The 12 BMP Elements 5
3 1 1 Element #1 Mark Clearing Limits .5
3 1.2 Element #2 Establish Construction Access .5
3 1 3 Element #3 Control Flow Rates 6
3 1 4 Element #4 Install Sediment Controls 6
3 1.5 Element #5 Stabilize Soils 6
3 1 6 Element #6 Protect Slopes 7
3 1 7 Element #7 Protect Drain Inlets 7
3 1 8 Element #8 Stabilize Channels and Outlets 7
3 1 9 Element #9 Control Pollutants 7
3 1 10 Element #10 Control Dewatering 8
3 1 11 Element #11 Maintain BMPs 8
3 1 12 Element #12 Manage the Project 8
4 0 Construction Phasing and BMP Implementation. 12
5 0 Pollution Prevention Team 14
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1
1
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7.2 1
7.2.2
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Discharge Monitoring Reports
Notification of Noncompliance
Site Plans
Construction BMPs
Alternative BMPs
General Permit
Site Inspection Forms (and Site Log)
Engineering Calculations
Appendix A Site plans
Site plan with TESC measures
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Construction BMPs
Alternative Construction BMP list
General Permit
Site Log and Inspection Forms
Engineering Calculations (if necessary)
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1.0 Introduction
This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the NPDES
stormwater permit requirements for the construction of Maier Hall at Peninsula College in Port
Angeles, Washington. The site is located within the limits of currently developed campus The
existing site consists of four existing buildings (Buildings F G H, and I) The site has a rolling
topography The soils at the site are Clallam gravelly sandy loam based on the Soil Conservation
Survey (SCS) for Clallam County Glacial till is expected to be at a depth of 20 to 40 inches.
This is consistent with the soils report that generally shows mottling (i.e. presence of
groundwater) for soils at shallow depths.
Construction activities will include demolition, excavation, grading, relocation of onsite
services /utilities, and construction of the Maier Hall building. The purpose of this SWPPP is to
describe the proposed construction activities and all temporary and permanent erosion and
sediment control (TESC) measures pollution prevention measures, inspection/monitoring
activities, and recordkeeping that will be implemented during the proposed construction project.
The objectives of the SWPPP are to
1 Implement Best Management Practices (BMPs) to prevent erosion and
sedimentation, and to identify reduce, eliminate or prevent stormwater
contamination and water pollution from construction activity
2. Prevent violations of surface water quality ground water quality or
sediment management standards
3 Prevent, during the construction phase, adverse water quality impacts
including impacts on beneficial uses of the receiving water by controlling
peak flow rates and volumes of stormwater runoff at the Permittee s
outfalls and downstream of the outfalls.
This SWPPP was prepared using the Ecology SWPPP Template downloaded from the Ecology
website on May 13 2009 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 several
appendices that include stormwater related reference materials The topics presented in the each
of the main sections are.
Section 1— INTRODUCTION This section provides a summary
description of the project, and the organization of the SWPPP document.
Section 2 SITE DESCRIPTION This section provides a detailed
description of the existing site conditions, proposed construction activities,
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Storm water Pollution Prevention Plan
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Storm water Pollution Prevention Plan
and calculated stormwater flow rates for existing conditions and post
construction conditions.
Section 3 CONSTRUCTION BMPs. This section provides a detailed
description of the BMPs to be implemented based on the 12 required
elements of the SWPPP
Section 4 CONSTRUCTION PHASING AND BMP
IMPLEMENTATION This section provides a description of the timing
of the BMP implementation in relation to the project schedule.
Section 5 POLLUTION PREVENTION TEAM. This section identifies
the appropriate contact names (emergency and non emergency),
monitoring personnel, and the onsite temporary erosion and sedimentation
control inspector
Section 6 INSPECTION AND MONITORING This section provides a
description of the inspection and monitoring requirements such as the
parameters of concern to be monitored, sample locations, sample
frequencies, and sampling methods for all stormwater discharge locations
from the site
Section 7 RECORDKEEPING This section describes the requirements
for documentation of the BMP implementation, site inspections,
monitoring results, and changes to the implementation of certain BMPs
due to site factors experienced during construction.
Supporting documentation and standard forms are provided in the following Appendices
Site plans
Construction BMPs
Alternative Construction BMP list
General Permit
Site Log and Inspection Forms
Engineering Calculations
2
2.1 Existing Conditions
2.0 Site Description
The site is located within the limits of currently developed campus in Port Angeles, Washington.
Campus is located south of East Lauridsen Blvd and east of Porter Street. A site vicinity map is
provided in Appendix A. The site is 3.36 acres in size The soils at the site are Clallam gravelly
sandy loam based on the Soil Conservation Survey (SCS) for Clallam County Glacial till is
expected to be at a depth of 20 to 40 inches This is consistent with the soils report that generally
shows mottling (i.e. presence of groundwater) for soils at shallow depths.
The existing stormwater system conveys runoff to an outfall east of Building G
2.2 Proposed Construction Activities
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Storm water Pollution Prevention Plan
The proposed development includes the construction of the Maier Hall building at Peninsula
College in Port Angeles Washington. Stormwater detention will be required for this project.
Stormwater detention calculations for the new building and associated impervious surfaces were
completed using the Western Washington Hydrology Method (WWHM) Using the pre
developed and developed mitigated flow frequencies, the detention volume was obtained from
WWHM. The detention volume was then compared with the storage volume available in the
wetlands to the south. The depressed area will exceed the volume required for detention. New
sanitary electrical, gas, and storm drain utilities will also be constructed.
Water quality treatment will be provided for runoff from a portion of the east access road and the
parking area (8,063 SF) The runoff from the east access drive and parking area will sheet flow
to a filter strip to a lined trench with a perforated pipe. The trench will have free draining
material that will additionally filter the runoff prior to being conveyed to the wetland. The sizing
for the water quality control is based on the narrow area filter strip from the SWMMWW
Construction activities will include site preparation, TESC installation, demolition, excavation
for the building foundations, site -wide grading, and paving. The schedule and phasing of BMPs
during construction is provided in Section 4 0
Stormwater runoff volumes were calculated using the Western Washington Hydrology Model
(WWHM) The temporary sedimentation trap that will be used during construction was designed
using the 2 year storm event since construction will not occur over a long time -frame
(approximately one year)
Storm water Pollution Prevention Plan
After the building is constructed and all new utilities are installed, the site will be graded and
paved.
The following summarizes details regarding site areas
Total site area. 3.36 acres
Percent impervious area before construction. 33 0
Percent impervious area after construction. 35 4
Disturbed area during construction. 3 36 acres
2 year stormwater runoff peak flow prior to construction
(existing) 1 09 cfs
10 -year stormwater runoff peak flow prior to construction
(existing) 1 88 cfs
2 -year stormwater runoff peak flow during construction. 0 64 cfs
10 -year stormwater runoff peak flow during construction. 1 38 cfs
2 -year stormwater runoff peak flow after construction
(reduced by wetland detention) 0 15 cfs
10 -year stormwater runoff peak flow after construction.
(reduced by wetland detention) 0.27 cfs
All stormwater flow calculations are provided in Appendix F
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3.0 Construction Stormwater BMPs
3.1 The 12 BMP Elements
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 durmg 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 existmg BMPs are
ineffective or failing.
Construction Fence
Stormwater Pollution Prevention Plan
3.1.1 Element #1 Mark Clearing Limits
To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of
construction will be clearly marked before land disturbing activities begin. Trees that are to be
preserved, as well as all sensitive areas and their buffers, shall be clearly delineated, both m the
field and on the plans. In general, natural vegetation and native topsoil shall be retained in an
undisturbed state to the maximum extent possible. The BMPs relevant to marking the clearing
limits that will be applied for this project include
See Temporary Erosion Control and Sedimentation (TESC) Plan on Appendix A for
location of construction fence
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 sweepmg, and street cleaning shall be employed to prevent
sediment from entering state waters. All wash wastewater shall be controlled on site. The
specific BMPs related to establishing construction access that will be used on this project
include
Stabilized Construction Entrance (BMP C105)
See Temporary Erosion Control and Sedimentation (TESC) Plan on Appendix A for
location of stabilized construction entrance.
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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.
Baker Tank or approved equivalent
Sediment Trap (BMP 240)
In general, discharge rates of stormwater from the site will be controlled where increases in
impervious area or soil compaction during construction could lead to downstream erosion, or
where necessary to meet local agency stormwater discharge requirements.
3.1.4 Element #4 Install Sediment Controls
All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal
BMP before leaving the construction site or prior to being discharged to an infiltration facility
The specific BMPs to be used for controlling sediment on this project include
Silt Fence (BMP C233)
Sediment Trap (BMP C240)
Storm Drain Inlet Protection (BMP C220)
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
3.1.5 Element #5 Stabilize Soils
Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent
erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be
used on this project include.
BMP 121 Mulching
Plastic Covering (BMP C123)
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Storm water Pollution Prevention Plan
Mulching (BMP C121)
Interceptor Dike and Swale (BMP C200)
In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be
temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized from erosion,
protected with sediment trapping measures, and where possible, be located away from storm
drain inlets, waterways, and drainage channels
3.1.6 Element #6 Protect Slopes
All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes
erosion. The following specific BMPs will be used to protect slopes for this project:
3.1.7 Element #7 Protect Drain Inlets
Storm water Pollution Prevention Plan
All storm drain inlets and culverts made operable during construction shall be protected to
prevent unfiltered or untreated water from entering the drainage conveyance system. However
the first priority is to keep all access roads clean of sediment and keep street wash water separate
from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP
C220) will be implemented for all drainage inlets and culverts that could potentially be impacted
by sediment -laden runoff on and near the project site The following inlet protection measures
will be applied on this project:
Storm Drain Inlet Protection (BMP C220)
3.1.8 Element #8 Stabilize Channels and Outlets
Where site runoff is to be conveyed in channels, or discharged to a stream or some other natural
drainage point, efforts will be taken to prevent downstream erosion. The specific BMPs for
channel and outlet stabilization that shall be used on this project include.
No BMPs to be implemented.
3.1.9 Element #9 Control Pollutants
All pollutants, including waste materials and demolition debris, that occur onsite shall be
handled and disposed of in a manner that does not cause contamination of stormwater Good
housekeeping and preventative measures will be taken to ensure that the site will be kept clean,
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Stormwater Pollution Prevention Plan
well organized, and free of debris. If required, BMPs to be implemented to control specific
sources of pollutants are discussed below
3.1.10 Element #10 Control Dewatering
Removal of foundation, vault, and trench seepage, which have similar characteristics to
stormwater runoff at the site shall be discharged into a controlled conveyance system prior to
discharge to sediment trap or sediment pond. Channels must be stabilized, as specified in
Element #8
If construction dewatering is necessary the city of Port Angeles should be contacted for the
disposal of the dewatermg water
3.1.11 Element #11— Maintain BMPs
All temporary and permanent erosion and sediment control BMPs shall be maintained and
repaired as needed to assure continued performance of their intended function. Maintenance and
repair shall be conducted in accordance with each particular BMPs specifications (attached)
Visual monitoring of the BMPs will be conducted at least once every calendar week and within
24 hours of any stormwater or non stormwater discharge from the site. If the site becomes
inactive, and is temporarily stabilized, the inspection frequency will be reduced to once every
month.
All temporary erosion and sediment control BMPs shall be removed within 30 days after the
final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped
sediment shall be removed or stabilized on site. Disturbed soil resulting from removal of BMPs
or vegetation shall be permanently stabilized.
3.1.12 Element #12 Manage the Project
Erosion and sediment control BMPs for this project have been designed based on the following
principles
Design the project to fit the existing topography soils, and drainage
patterns
Emphasize erosion control rather than sediment control.
Minimize the extent and duration of the area exposed.
Keep runoff velocities low
Retain sediment on site.
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Storm water Pollution Prevention Plan
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.
As this project site is located west of the Cascade Mountain Crest, the project will be managed
according to the following key project components
Phasing of Construction
The construction project is being phased to the extent practicable in order
to prevent soil erosion, and, to the maximum extent possible, the transport
of sediment from the site during construction.
Revegetation of exposed areas and maintenance of that vegetation shall be
an integral part of the clearing activities during each phase of construction,
per the Scheduling BMP (C 162).
Seasonal Work Limitations
From October 1 through April 30 clearing, grading, and other soil
disturbing activities shall only be permitted if shown to the satisfaction of
the local permitting authority that silt laden runoff will be prevented from
leaving the site through a combination of the following:
Site conditions including existing vegetative coverage, slope, soil
type, and proximity to receiving waters and
Limitations on activities and the extent of disturbed areas and
Proposed erosion and sediment control measures.
Based on the information provided and/or local weather conditions, the
local permittmg authority may expand or restrict the seasonal limitation on
site disturbance.
The following activities are exempt from the seasonal clearing and grading
limitations
Routine maintenance and necessary repair of erosion and sediment
control BMPs
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Stormwater Pollution Prevention Plan
Routine maintenance of public facilities or existing utility
structures that do not expose the soil or result m the removal of the
vegetative cover to soil, and
Activities where there is 100 percent infiltration of surface water
runoff within the site in approved and installed erosion and
sediment control facilities.
Coordination with Utilities and Other Jurisdictions
Care has been taken to coordinate with utilities, other construction
projects, and the local jurisdiction in preparing this SWPPP and
scheduling the construction work.
Inspection and Monitoring
All BMPs shall be inspected, maintained, and repaired as needed to assure
continued performance of their intended function. Site inspections shall
be conducted by a person who is knowledgeable in the principles and
practices of erosion and sediment control. This person has the necessary
skills to
Assess the site conditions and construction activities that could
impact the quality of stormwater and
Assess the effectiveness of erosion and sediment control measures
used to control the quality of stormwater discharges
A Certified Erosion and Sediment Control Lead shall be on -site or on -call
at all times.
Whenever inspection and /or monitoring reveals that the BMPs identified
in this SWPPP are inadequate, due to the actual discharge of or potential
to discharge a significant amount of any pollutant, appropriate BMPs or
design changes shall be implemented as soon as possible.
Mamtammg an Updated Construction SWPPP
This SWPPP shall be retained on -site or within reasonable access to the
site.
The SWPPP shall be modified whenever there is a change in the design,
construction, operation, or maintenance at the construction site that has, or
could have, a significant effect on the discharge of pollutants to waters of
the state
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Storm water Pollution Prevention Plan
The SWPPP shall be modified if during inspections or investigations
conducted by the owner /operator or the applicable local or state
regulatory authority it is determined that the SWPPP is ineffective in
eliminating or significantly minimizing pollutants in stormwater
discharges from the site The SWPPP shall be modified as necessary to
include additional or modified BMPs designed to correct problems
identified. Revisions to the SWPPP shall be completed within seven (7)
days following the inspection.
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4.0 Construction Phasing and BMP
Implementation
The BMP implementation schedule will be driven by the construction schedule. The following
provides a sequential list of the proposed construction schedule milestones and the corresponding
BMP implementation schedule. The list contains key milestones such as wet season
construction.
The BMP implementation schedule listed below is keyed to proposed phases of the construction
project, and reflects differences in BMP installations and inspections that relate to wet season
construction. The project site is located west of the Cascade Mountain Crest. As such, the dry
season is considered to be. from May 1 to September 30 and the wet season is considered to be
from October 1 to April 30
Estimate of Construction start date 07/01/2009
Estimate of Construction finish date. 03/2011
Mobilize equipment on site. 07/06/2009
Mobilize and store all ESC and soil stabilization products
(store materials on hand BMP C150) 07/09/2009
Install ESC measures 07/10/2009
Install stabilized construction entrance 07/13/2009
Begin clearing and grubbing: 07/15/2009
Demolish existing building structure 07/17/2009
Site grading begins 08/2009
Site grading ends 09/2009
Excavation for building foundations 07/21/2009
Temporary erosion control measures (hydroseeding) 08/2009
Excavate and install new utilities and services 08/2009
Begin implementing soil stabilization and sediment
control BMPs throughout the site in preparation for wet
season. 09/24/2009
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Storm water Pollution Prevention Plan
Wet Season starts:
Site inspections and monitoring conducted weekly and
for applicable rain events as detailed in Section 6 of this
SWPPP•
Implement Element #12 BMPs and manage site to
minimize soil disturbance during the wet season
No site work such as grading or excavation planned.
Begin building construction
Begin concrete pour
Dry Season starts:
Prepare for wet season
Wet Season starts.
Dry Season starts.
Building construction complete
Final landscaping and planting begins
Permanent erosion control measures
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Storm water Pollution Prevention Plan
10/01/2009
10/01/2009
10/01/2009
11/2009
11/2009
05/01/2010
09/24/2010
10/01/2010
05/01/2011
03/2011
02/2011
03/2011
5 1 Roles and Responsibilities
5.0 Pollution Prevention Team
The pollution prevention team consists of personnel responsible for implementation of the
SWPPP including the following:
Certified Erosion and Sediment Control Lead (CESCL) primary
contractor contact, responsible for site inspections (BMPs, visual
monitoring, sampling, etc.) to be called upon in case of failure of any
ESC measures.
Resident Engineer For projects with engineered structures only
(sediment ponds /traps, sand filters, etc.) site representative for the owner
that is the project's supervising engineer responsible for inspections and
issuing instructions and drawings to the contractor's site supervisor or
representative
Emergency Ecology Contact individual to be contacted at Ecology in
case of emergency Go to the following website to get the name and
number for the Ecology contact information.
http. /www.ecv.wa. gov /ora.html.
Emergency Owner Contact individual that is the site owner or
representative of the site owner to be contacted in the case of an
emergency
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Storm water Pollution Prevention Plan
Non Emergency Ecology Contact individual that is the site owner or
representative of the site owner than can be contacted if required.
Monitoring Personnel personnel responsible for conducting water
quality monitoring; for most sites this person is also the Certified Erosion
and Sediment Control Lead.
5.2 Team Members
Names and contact information for those identified as members of the pollution prevention team
are provided in the following table.
Title
Certified Erosion and Sediment Control Lead (CESCL)
Resident Engineer
Emergency Ecology Contact
Emergency Owner Contact
Non Emergency Ecology Contact
Monitoring Personnel
Kevin Fitzpatrick
David Wegner
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Name(s)
Storm water Pollution Prevention Plan
Phone Number
425 649 -7033
360 460 9481
6.0 Site Inspections and Monitoring
Stormwater Pollution Prevention Plan
Monitoring includes visual inspection, monitoring for water quality parameters of concern, and
documentation of the mspection and monitoring findings in a site log book. A site log book will
be maintained for all on -site construction activities and will include
A record of the implementation of the SWPPP and other permit
requirements
Site inspections and,
Stormwater quality monitoring.
For convenience, the inspection form and water quality monitoring forms included in this
SWPPP include the required information for the site log book. This SWPPP may function as the
site log book if desired, or the forms may be separated and included in a separate site log book.
However, if separated, the site log book but must be maintained on -site or within reasonable
access to the site and be made available upon request to Ecology or the local jurisdiction.
6.1 Site Inspection
All BMPs will be inspected, maintained, and repaired as needed to assure continued performance
of their intended function. The inspector will be a Certified Erosion and Sediment Control Lead
(CESCL) per BMP C160 The name and contact information for the CESCL is provided in
Section 5 of this SWPPP
Site inspection will occur in all areas disturbed by construction activities and at all stormwater
discharge points Stormwater will be examined for the presence of suspended sediment,
turbidity discoloration, and oily sheen. The site inspector will evaluate and document the
effectiveness of the installed BMPs and determine if it is necessary to repair or replace any of the
BMPs to improve the quality of stormwater discharges All mamtenance and repairs will be
documented in the site log book or forms provided in this document. All new BMPs or design
changes will be documented in the SWPPP as soon as possible
6.1.1 Site Inspection Frequency
Site inspections will be conducted at least once a week and within 24 hours following any
discharge from the site. For sites with temporary stabilization measures, the site inspection
frequency can be reduced to once every month.
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6.1.2 Site Inspection Documentation
The site inspector will record each site inspection using the site log inspection forms provided in
Appendix E. The site inspection log forms may be separated from this SWPPP document, but
will be maintained on -site or within reasonable access to the site and be made available upon
request to Ecology or the local jurisdiction.
6.2 Stormwater Quality Monitoring
Storm water Pollution Prevention Plan
6.2.1 Turbidity
Turbidity sampling and monitoring will be conducted during the entire construction phase of the
project. Samples will be collected daily at the catch basin east of the site (Ex. SDMH) If there
is no flow in this catch basin, the attempt to sample will be recorded in the site log book and
reported to Ecology in the monthly Discharge Monitoring Report (DMR) as `No Discharge
Samples will be analyzed for turbidity using the EPA 180 1 analytical method.
The key benchmark turbidity value. is 25 nephelometric turbidity units (NTU) for the
downstream receiving water body If the 25 NTU benchmark is exceeded in any sample
collected from Ex SDMH, the following steps will be conducted.
1 Ensure all BMPs specified in this SWPPP are installed and functioning as
intended.
2. Assess whether additional BMPs should be implemented, and document
modified BMPs in the SWPPP as necessary
3 Sample discharge daily until the discharge is 25 NTU or lower
If the turbidity exceeds 250 NTU at any time, the following steps will be conducted.
1 Notify Ecology by phone within 24 hours of analysis (see Section 5 0 of
this SWPPP for contact information)
2. Continue sampling daily until the discharge is 25 NTU or lower Initiate
additional treatment BMPs such as off -site treatment, infiltration, filtration
and chemical treatment within 24 hours, and implement those additional
treatment BMPs as soon as possible, but within a minimum of 7 days
3 Describe inspection results and remedial actions taken in the site log book
and in monthly discharge monitoring reports as described in Section 7 0 of
this SWPPP
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Stormwater Pollution Prevention Plan
6.2.2 pH
Sampling and monitoring for pH will occur during the phase of construction when concrete
pouring will be conducted until fully cured (3 weeks from last pour) and discharges are
documented to be below pH 8 5 Samples will be collected weekly at the sedimentation pond
prior to discharge to surface water Samples will be analyzed for pH using a calibrated pH meter
and recorded in the site log book.
The key benchmark pH value for stormwater is a maximum of 8.5 If a pH greater than 8 5 is
measured in the sedimentation trap /pond(s) that has the potential to discharge to surface water,
the following steps will be conducted.
1 Prevent (detain) all discharges from leaving the site and entering surface
waters or storm drains if the pH is greater than 8 5
2 Implement CO spargmg or dry ice treatment in accordance with Ecology
BMP C252
3 Describe inspection results and remedial actions that are taken in the site
log book and in monthly discharge monitoring reports as described in
Section 7 0 of this SWPPP
71 Recordkeeping
7.1.1 Site Log Book
A site log book will be maintained for all on -site construction activities and will include
Site inspections and,
Stormwater quality monitoring.
For convenience, the inspection form and water quality monitoring forms included in this
SWPPP include the required information for the site log book.
7.1.2 Records Retention
A record of the implementation of the SWPPP and other permit
requirements,
Records of all monitoring information (site log book, inspection reports /checklists, etc.), this
Stormwater Pollution Prevention Plan, and any other documentation of compliance with permit
requirements will be retained during the life of the construction project and for a minimum of
three years following the termination of permit coverage m accordance with permit condition
S5 C
7.1.3 Access to Plans and Records
7.0 Reporting and Recordkeeping
The SWPPP General Permit, Notice of Authorization letter and Site Log Book will be retained
on site or within reasonable access to the site and will be made immediately available upon
request to Ecology or the local jurisdiction. A copy of this SWPPP will be provided to Ecology
within 14 days of receipt of a written request for the SWPPP from Ecology Any other
information requested by Ecology will be submitted within a reasonable time A copy of the
SWPPP or access to the SWPPP will be provided to the public when requested in writing in
accordance with permit condition S5 G
7.1.4 Updating the SWPPP
In accordance with Conditions S3 S4.B and S9.B.3 of the General Permit, this SWPPP will be
modified if the SWPPP is ineffective in eliminating or significantly minimizing pollutants in
stormwater discharges from the site or there has been a change in design, construction, operation,
or maintenance at the site that has a significant effect on the discharge, or potential for discharge,
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Stormwater Pollution Prevention Plan
Storm water Pollution Prevention Plan
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 Reports (DMRs) will be submitted to Ecology monthly 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 the place of monitoring results The DMR due date is 15
days following the end of each month.
7.2.2 Notification of Noncompliance
If any of the terms and conditions of the permit are not met, and it causes a threat to human
health or the environment, the following steps will be taken in accordance with permit section
S5.F
1 Ecology will be immediately notified of the failure to comply
2 Immediate action will be taken to control the noncompliance issue and to
correct the problem. If applicable, sampling and analysis of any
noncompliance will be repeated immediately and the results submitted to
Ecology within five (5) days of becoming aware of the violation.
3 A detailed written report describing the noncompliance will be submitted
to Ecology within five (5) days, unless requested earlier by Ecology
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.
20
21
Storm water Pollution Prevention Plan
Appendix A Site Plans
Temporary Erosion and Sedimentation Control (TESC) Plan
TESC Details
22
Storm water Pollution Prevention Plan
23
Storm water Pollution Prevention Plan
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MAP STEEL MI ON FLIER FMK 11&611AL
1111)71105 OR EMI OVERLAP FLIER MARC
NM 5' NO MIEN MIH STAPLES OR NE 1165
NTs
20' to 40 ION
TEMPORARY EROSION
SEDIMENTATION CONTROL TRAP DETAIL
AS REQUIRED too (YIN.)
20' MIN.
R0/10E FILL WIDTH OF
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RAP LEN CAPAt21Y
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FILTER FABRIC MATERIAL,
MIRAFI 106 at EQUAL
USE STAPLES OR WIRE RIM
If TO ATTACH FABRIC TO WIRE
IX GROUND
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I STEEL FINE A
POSTS S 4'O.C.(TYP
FLIER FAUNS MATERIAL
CRATE YRAR 1400 CR EQUAL
MD UNDER GATE TO 115D
DR -PLACE
,2'x2'x14 GA. WELDED
WIRE FABRIC OR EQUAL
IX INLET I, I I
FILTER FABRIC FENCE DETAIL
NA
INLET PROTECTION 0
NIS CL 1
ME:
UPON DOPLETIOI OF 11E PROJECT OR MEN DIRECTED BY TIE OVER. 11E FILTER
FABRIC FENCE 9MLL BE MOVED IN ITS ENTIRETY APO DISPOSED OF BY THE CONTRACTOR.
IX GRAZE
SECTION A-A
CL1
MISTIMED
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BIRD FILTER FABRIC
IN TRENCH FILLED
WITH GRAVEL 5001
FILL FOR DRAINS
EROStONAIONIENT CONTROL (ESC) NOTES
1. THE 101.169611011. CONSTRUCTION, YANIEMAMCE, Rs OS:EMIT AND IMMIX OF TIDE
6C NOUNS 5 THE IESPO®)TY OF TIE APR)CAIR/ONTRACIBR INTL ALL
CONSTRUCTION 5 APPROVED.
2. THE ESC FAMES 91001 OR 1109 FUN MUST BE CONS1609) N CO LEmCRO! VIM AIL
OEAREC AND BANG ACIMIES, AND IN SUCH A MAKER AS 10 INSU E 7NAT SDIIDIT
LADEN RATER DOS MDT LEAVE TIE STE. ENTER THE NADINE 5)5101 OR VIOLATE
APPUGTBIE WATER SMNDARDS
1 THE ESC FACE)IES 9106 SI INS PUN ARE THE 11)10405 REOO7m45 FOR ANRfPA1ED
SITE CO5IRO5 065 THE CSSIR)CION PETBDD, THESE ESC FAMES SHALL BE
UPGRADED 0(a A0TIDNAL SUES, REIDGTQ1 OF DINES MID SILT ME M El) BY TIE
CONTRACTOR AS NEEDED FOR OLDPECTED STOOL EVENTS
4. 1HE ESC FACERES SHALL BE RESPECTED DAILY BY THE C (11105RIR AID NARAN O AS
NECESSARY CR AS ORECIE BY 16 MY OF POT MOLES TO ENSURE TIER CONTINUED
PUNCOOOIG
9 STREWED CO57961101I ENIRANOS SKILL EE INSTALLED AT 11E BDWNONC OF
0151511041 AND NA TADWD FOR ME DIRATDN OF 115 PROECT. AD011OM1 MEASURE
MAY EE FENDED 10 DBE IMAT PAYED AREAS ME KEPT DEAN FOR THE DURATION OF DE
PROECT.
B. WATER FAO) DSflI AMEN 9UUL BE DEEMED TO THE TRAP OR BAKER TAN SOP MA
9EET ROW 6 1DPORARY OtAIMGE SIDES COISIRECIED AS 11(005 CR AS NEON BY
THE DEFECTOR.
7. SEOIOIT TRAP 91A11 BE FED LOCATED TO ACCOBIOJATE ONSTRUC15J SEQUENCE E
CONSTRUCTION ACIMIY REVD115 LOCATING NE 9DILEHT TRAP 91001 THE DTAVATION OR E
WATER EMERY 591E 105105 AMINE IEAIYDD, 11E (11RACBR MAY USE A
STOUN6 TANK SWISS, 9X21 AS A BAIDR 6 RANH4 -RFNI.
8. THE SHAPE Cr LIE SDNE111 TRAP MAY VARY AS 6576, TO FAW)UIE ORS1RUCIDN
EOIDYENT MOMENT ABET THE SITE. BUT NE TRAP STALL PRONE A WRUNG VILI E ND
LESS 111AN 18000 COBC FEET.
B. CONTRAQ10B SNAIL PRONE BA0OP RODS WTH OJEBO NT IERSYOMH TO DENVER
TREATED WATER INTO 51.E SINN 5)5100 AT THE TIE. LOCATION TO BE APPROVED BY OTT
DEFECTOR.
ID. DISCHA EE TO LIE 6-51E STORY DRAM SHALL BE EOM= BY THE CORlRACIOL
II. CONTRACTOR SHALL PHD4mE CONSTRUCTER FENCING AS 550.110 FOR SYETY A110 AS
DIELIED BY THE On 1119£555.
12. 5)101 BASINS 9uLL BE 010IED DALY BY SEE COLINAS= WATER IFANIO THE STE
MIRING COSTRUCITN, NOUNS WATER CARIDD BY THE TRUCE INS. TALL BE OEM. NNE
CONTRACTOR SHALL OEM 5)101 BASINS AND MOOR EMU 9DIYEIRAIDN CO O.
NE0HDDS IF IEOSSMY MD AS MIECIFD BY THE 019'EC1OL
11 SCAVATNN SE OIATEWNG NAT NCIUDES MONDE TO 011-915. CAIOI BASINS. OR
5EIM 9101 BE IIPIHDIIIED ONLY AFilR APPROVAL BY LIE 519'ECER.
14. CONSTRUCTION 60901 CONTROL MORES MIST 1E IN RACE AND ARROWS PRIOR TO ANY
EARTH DISTURBANCE
15. NO 5101108 SHALL BE TRACKED O11D PAVED AREAS MERE OF THE 051510(151151
B ONNY CO ONTO (=PAVED SIREN OR ROADWAYS 9DODET SEMI BE =MEN FRS
TRUCKS AND EQIAVDIT RON 10 LEAVING THE COSNUCDOI 91E. N THE EVENT OR FAI)IE
OF TIE ESC 6361 REELING IN SEDIMENT 1600110 ONTO PAVED AREAS OUTS= OF LEE
CORS101)CDO1 BOUNDARY, NNE CONTRACTOR 514411 &REMIT MEAMES IY)I004TLLY TO
CORRECT THE 9TUAINN
18. THE CONTRACTOR TALL EYRDY EIERGEDY MEASURES 10 REMOVE SEDIMENT FRCP PAVED
SURFACES, AS NFEM.. STREET METRE 94411. BE CORSDERD AN DER5IICY MEA9RE AND
NOT A NM CONCERT CT TIE ESC SWIRL SEDIMENT TRACED 610 PAVED SURFACE
SHALL NOT E WASHED STD STEM ORRIS 6 CDDR U11111 N EIS
17. AREAS SNIPPED CF VEIETAIIOI SHALL BE STASh ED WIN N 7 DAIS BENIN NAY 10( Alm
SEPTUM 361. AND MIN 2 DAYS MI6 OCI5R Ti) MD PPM 700 STABILIZE NH
/PROM ESC 1E1106 (E6 SEEDING. 1005844 FETDI5 EROSION 1ARIEI5, ETC)
18. THE ESC FACB)115 OR NACRE SITES 91)11. BE NSPECIED MD YNNWIED ONCE EMI MERE
DUR0)0 C06615116 AREA EACH RAIN OF 0.5 DINES OR NOR (OVER A 24 HOUR PER E),
MD I(MEIMIELY YALE MY NEEDED REPAOS
19. UPON FINAL COIPIETIOI OF 115 PROJECT, AIL EC MEASURES SHALL BE REINED BY NE
CS1RAC1St GM 91LL BE TAKEN TO AYOD SEDI0.7IT D41ERNG THE DAMAGE SYSTEM
DURING THE ROOM PROCESS.
20. GRADNO SHALL BE STRIVED BY OCTOBER 311, MD ND EXCAVATION OR FLL RAIMENT
TALL BE PERFORM 801054 OCTOBER 31st Alm AR✓d 1st MINOUT *PRDVS1. FRS TEE
CRY OF PORT ANGELES
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[Slo Project A2008 -125 B 12II
Construclion Documents
7 May 2009
Constructability
Review -95% CD
TESC
DETAILS
C1 1
Appendix B Construction BMPs
Stabilized Construction Entrance (BMP C105)
Baker Tank or Approved Equivalent
Sediment Trap (BMP 240)
Silt Fence (BMP C233)
Sediment Trap (BMP C240)
Storm Dram Inlet Protection (BMP C220)
Plastic Covering (BMP C123)
Mulching (BMP C121)
Interceptor Dike and Swale (BMP C200)
24
Storm water Pollution Prevention Plan
25
Stormwater Pollution Prevention Plan
BMP C105. Stabilized Construction Entrance
Purpose
Conditions of Use
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.
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 m 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) J 200 psi min
Grab Tensile Elongation (ASTM D4632) I 30% max.
Mullen Burst Strength (ASTM D3786 -80a) j 400 psi min.
AOS (ASTM D4751) I 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 m 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
preventing sediment from being tracked onto pavement or if the hog
fuel is being earned onto pavement. Hog fuel is prohibited in
permanent roadbeds because organics m the subgrade soils cause
degradation of the subgrade support over time
Fencing (see BMPs C103 and C104) shall be installed as necessary to
restrict traffic to the construction entrance.
4 -8 Volume 11— Construction Stormwater Pollution Prevention February 2005
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 o Quarry spalls (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 spalls 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 BMPs 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.
Insta ll driveway culvert
if there is a roadside
ditch present
4' -8' quarry spills
Geotextile
12' min. thickness
Driveway shall meet the
requirements of the
permitting agency
It is recommended that
the entrance be
crowned so that runoff
drains off the pad
Provide full width of
Ingress/egress area
Figure 4.2 Stabilized Construction Entrance
February 2005 Volume ll Construction Stonnwater Pollution Prevention
4 -9
BMP C240• Sediment Trap
Purpose
Conditions of Use
A sediment trap is a small temporary pondmg area with a gravel outlet
used to collect and store sediment from sites cleared and/or graded dunng
construction. Sediment traps, along with other perimeter controls, shall be
installed before any land disturbance takes place in the drainage area.
Pnor 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
structures.
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,
relatively level, vegetated areas (see BMP C234 Vegetated Strip). This
is the only way to effectively remove fine particles from runoff unless
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
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
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
for traps and ponds. This includes combined facilities and infiltration
facilities. When permanent facilities are used as temporary sedimentation
facilities, the surface area requirement of a sediment trap or pond must be
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
4 -102 Volume II Construction Stormwater Pollution Prevention February 2005
Design and See Figures 4.22 and 4.23 for details.
Installation If permanent runoff control facilities are part of the project, they
Specifications
should be used for sediment retention.
February 2005
Either a permanent 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.
A skimmer may be used for the sediment trap outlet if approved by the
Local Permitting Authority
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(Q2 /V
where
Q2 Design inflow based on the peak discharge from the
developed 2 -year runoff event from the contributing
drainage area as computed in the hydrologic analysis. The
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.
V
FS
The settling velocity of the soil particle of interest. The
0 02 mm (medium silt) particle with an assumed density of
2.65 g /cm has been selected as the particle of interest and
has a settling velocity (V of 0 00096 ft/sec
A safety factor of 2 to account for non -ideal settling.
Therefore, the equation for computing surface area becomes
SA 2 x Q2 /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 II Construction Storm water Pollution Prevention 4 -103
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.
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.
T
(.9 3.5' -5'
Note: Trap may be formed by berm or by
partial or complete excavation
I I III 1 11 =1 11=111=1
III I I i 1 11 1 I I 111 1 I
i=111=111=111=11 1=111=1
111-
Native soil or I
compacted backfill 1 11
Geotextile
Flat Bottom
Surface area determined
at top of weir
I 1.5' Min.
1' Min
T
s/" 15"
Washed gravel
Figure 4.22 Cross Section of Sediment Trap
6' Min.
1 Min. depth overflow spillway
Figure 4.23 Sediment Trap Outlet
I 4' Min.
1
1 Min. Overflow
1 Min.
1
1
2 "-4" Rock RipRap
Geotextile
H
Discharge to stabilized
conveyance, outlet, or
level spreader
11=111=W-111_
1 I I -111 T 111 1 I 1 I 11
Il I I I =1=ITI=T__I I=
_I =_I Min. 1 depth
1 I I 2'-4 rock
111 -111 111 1 I I1 =111- 111 111 Min.1 depth 3/4 1.5'
1 111 I I 1 111 1 washed gravel
4 -104 Volume II Construction Stormwater Pollution Prevention February 2005
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
Joints in fitter fabric shall be spliced at
posts. Use staples, wire rings or
equivalent to attach fabric to posts
`iP11 11
:11` -I
6' ma:.
Post spacing may be increased
to 8' if wire backing Is used
I T"— Minimum 4"x4 trench
2 "x2" by 14 Ga. wire or
equivalent, if standard
strength fabric used
Filter fabric
Backfill trench with native soil
or 3/4" 1.5" washed gravel
2 "x2' wood posts, steel fence
posts, or equivalent
Figure 4.19 Silt Fence
C
E
f.V
I C
E
N
Design and Drainage area of 1 acre or less or in combination with sediment basin
Installation in a larger site
Specifications
Maximum slope steepness (normal (perpendicular) to fence line) 1 1
Maximum sheet or overland flow path length to the fence of 100 feet.
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)•
4 -94 Volume Il Construction Stormwater Pollution Prevention February 2005
February 2005
Polymeric Mesh AOS
(ASTM D4751)
Water Permittivity
(ASTM D4491)
Grab Tensile Strength
(ASTM D4632)
Grab Tensile Strength
(ASTM D4632)
'Ultraviolet Resistance 70% minimum
(ASTM D4355)
Table 4.10
Geotextile Standards
0 60 mm maximum for slit film wovens #30 sieve). 0.30
mm maximum for all other geotextile types #50 sieve).
0.15 mm minimum for all fabric types #100 sieve).
0 02 sec minimum
180 lbs. Minimum for extra strength fabric.
100 lbs minimum for standard strength fabric.
30% maximum
Standard strength fabncs shall be supported with wire mesh, chicken
wire, 2 -inch x 2 -mch wire safety fence, or jute mesh to increase the
strength of the fabnc. 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
lasting, and can be left in place after the project is completed, if
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 mamtam temporary silt fences at the
locations shown in the Plans. The silt fences shall be constructed in
the areas of clearing, grading, or drainage pnor to starting those
activities. A silt fence shall not be considered temporary if the silt
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 approved location as determined by the Engineer, to form geotextile
lengths as required. All sewn seams shall be located at a support post.
Alternatively, two sections of silt 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
through the fence at the overlap
Volume ll Construction Stormwater Pollution Prevention 4 -95
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
the 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
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 buned 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
scounng can not occur When wire or polymenc back -up support
mesh is used, the wire or polymenc 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
the ends of the fence, where the fence shall be turned uphill such that
the silt fence captures the runoff water and prevents water from
flowing around the end of the fence.
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
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
every 10 feet along the fence where the fence must cross contours.
The slope of the fence line where contours must be crossed shall not
be steeper than 3 1
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 ll Construction Stormwater Pollution Prevention February 2005
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
having 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 spacmg of 2 inches, or a prefabncated 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.
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,
and as close as possible to the fabric, enabling posts to support the
fabric from upstream water pressure
Install posts with the nipples facing away from the silt fence fabnc
Attach the fabric to each post with three ties, all spaced within the top
8 inches of the fabnc 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.
Wrap approximately 6 inches of fabric around the end posts and secure
with 3 ties.
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.
The installation should be checked and corrected for any deviation
before compaction. Use a flat bladed shovel to tuck fabric deeper into
the ground if necessary
Compaction is vitally important for effective results Compact the soil
immediately next to the silt fence fabnc with the front wheel of the
tractor skid steer, or roller exerting at least 60 pounds per square mch.
Compact the upstream side first and then each side twice for a total of
four trips.
February 2005 Volume II Construction Stormwater Pollution Prevention
4 -97
Maintenance
Standards
Any damage shall be repaired immediately
If concentrated flows are evident uphill of the fence, they must be
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 actmg 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
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
breakdown, it shall be replaced.
Pending height
max. 24
Attach fabric to
upstream aide et post
FLOW
01. ever web side et
Wit fence 2 to 4Owes
arid, deltic exerting
PO paJ, or greater
100% cam
y%
No more than 24" of a 36" fabric
is allowed above ground.
Oppradon
1 l f r. r// I
/l ;1/ l� /r
f Est Q9i��/4a v.rni,>.:. y i
Hadar:Mid third point
(76 mm aldi,)
POET SPACING:
T max. on open runs
4' max. en peeling areas
POST DEPTH:
As much below ground
as fabric above ground
Sliding [lade
(1 B mm vridtN)
Rol of sit fence
Fabic
above
I
Top of Fatxic
Belt
Sit Fence
Vibratory plow is not acceptable because of hofitontat compaction
Figure 4.20 Silt Fence Installation by Slicing Method
4 -98 Volume II Construction Stormwater Pollution Prevention
ATTACHMENT DEGAS:
Getter labile et posts. 'needed.
Mitre tree des per post, all within rep ref fabric.
Poatton each de diagonally. puncturing holes vertically
a minimum of A aped
Hang each tie on a pmt nipple and tighten securely.
Use cable des (50114 or sot are.
Post
installed
after
compaction
Completed irataladon
February 2005
BMP C220 Storm Drain Inlet Protection
Purpose To prevent coarse sediment from entering drainage systems pnor to
permanent stabilization of the disturbed area.
Conditions of Use
Type of Inlet
Protection
Drop Inlet Protection
Excavated drop inlet
protection
Block and gravel drop
inlet protection
1 Gravel and wire drop
inlet protection
Catch basin filters
Curb Inlet Protection
Curb inlet protection
with a wooden weir
Block and gravel curb
inlet protection
Culvert Inlet Protection
Culvert inlet sediment
trap
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 basm 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 dramage
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 pondmg
would cause a hazard. If an emergency overflow is provided, additional
end -of -pipe treatment may be required.
Yes,
temporary
flooding will
occur
Yes
No
Yes
Storm
Emergency
Overflow
Small capacity
overflow
Yes
Table 4.9
Drain Inlet Protetion
Applicable for
Paved/ Earthen
Surfaces
Earthen
Paved or Earthen
Paved or Earthen
Paved
Paved
4 -82 Volume 11 Construction Stormwater Pollution Prevention
Conditions of Use
Applicable for heavy flows. Easy
to maintain. Large area
Requirement: 30' X 30' /acre
Applicable for heavy concentrated
flows. Will not pond.
Applicable for heavy concentrated
flows. Will pond. Can withstand
traffic.
Frequent maintenance required.
Used for sturdy more compact
installation.
Sturdy but limited filtration.
18 month expected life.
February 2005
Design and Excavated Drop Inlet Protection An excavated impoundment around the
Installation storm drain. Sediment settles out of the stormwater prior to entenng the
Specifications storm drain.
Depth 1 -2 ft as measured from the crest of the inlet structure.
Side Slopes of excavation no steeper than 2.1
Minimum volume of excavation 35 cubic yards.
Shape basin to fit site with longest dimension onented toward the
longest inflow aiea.
Install provisions for draining to prevent standmg water problems.
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
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
Lay some blocks in the bottom row on their side for dewatering the
pool.
Place hardware cloth or comparable wire mesh with '/2 -inch openings
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.
Inlet slope of 3 1
Outlet slope of 2 1
1 -foot wide level stone area between the structure and the inlet.
Inlet slope stones 3 inches in diameter or larger
Outlet slope use gravel V2- to 1/4-inch at a minimum thickness of 1 -foot.
February 2005 Volume II Construction Stormwater Pollution Prevention
4 -83
1
1
1
1
1
1
1
Plan View
Drain
Grate
5
0
°V
1°0o �g4
0 00 o O Do oc., 00 �o 0
op
ob°o II o
d 0 o e d•o.Q o,
O
S.
Section A A
o
JD
Y
°b0 �a OO
0 .d gJOOp
F A
11
-A
Concrete Block
Gravel Backfill Overflow
Water
PAIMSZSZS
„0 ,,t28 0 o c4 Water
•6
O 'OoOao� o O
O� 0 00
Drop Inlet
ti
O
o• oaVO
o.O Q -O
1 mo o
a oo
4009 c�° Gravel
I 1‘ 9 �,d
O o Backfill
o.! o
Do
Wire Screen or
Filter Fabric
Ponding Height
Concrete
Block
Notes:
1 Drop inlet sediment barriers are to be used for small, nearly level drainage areas. (less than 5
2. Excavate a basin of sufficient size adjacent to the drop inlet.
3. The top of the structure (ponding height) must be well below the ground elevation downslope to prevent
runoff from bypassing the inlet. A temporary dike may be necessary on the dowslope side of the structure.
Figure 414 Block and Gravel Filter
Gravel and Wire Mesh Filter A gravel bamer placed over the top of the
inlet. This structure does not provide an overflow
Hardware cloth or comparable wire mesh with'h -mch openings.
Coarse aggregate.
Height 1 -foot or more, 18 inches wider than inlet on all sides.
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 strip of mesh is necessary, overlap the strips.
Place coarse aggregate over the wire mesh.
The depth of the gravel should be at least 12 inches over the entire
inlet opening and extend at least 18 inches on all sides.
4 -84 Volume ll Construction Stormwater Pollution Prevention February 2005
February 2005
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
therefore may be a better method for inlets located along active nghts -of-
way
5 cubic feet of storage
Dewatenng provisions.
High -flow bypass that will not clog under normal use at a construction
site
The catchbasin filter is inserted in the catchbasin just below the
grating.
Curb Inlet Protection with Wooden Weir Bamer 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.
Pile coarse washed aggregate against wire /fabnc.
Place weight on frame anchors.
Block and Gravel Curb Inlet. Protection Bamer formed around an inlet
with concrete blocks and gravel. See Figure 4 14
Wire mesh with' cinch 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
the front blocks.
Place blocks on their sides across the front of the inlet and abutting the
spacer blocks.
Place wire mesh over the outside vertical face.
Pile coarse aggregate against the wire to the top of the barrier
Curb and Gutter Sediment Barrier Sandbag or rock berm (nprap and
aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure
4 1.6
Construct a horseshoe shaped berm, faced with coarse aggregate if
using nprap, 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 mlet.
Volume ll Construction Stormwater Pollution Prevention 4 -85
I
I
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 surroundmg land area or stockpile
and stabilize as appropnate.
4 -86 Volume II Construction Stormwater Pollution Prevention February 2005
Plan View
r Back of Sidewalk
Back of Curb
arc .o p
o p
b a
ov a
?1Z: $gyp y� q
'V� O�V i� o
A Q oJ O o; p p.0°� Sjo
.a,
Wire Screen
Filter Fabric
Section A A 3 Drain Gravel
(20mm)
3/4' Drain Gravel
(20mm)
Wire Screen or
Filter Fabric
Ove sil
4 Wood Stud
(100x50 Timber Stud)
A Catch Basin
2x4 Wood Stud
Concrete Block
Curb Inlet
Ponding Height
ON
Oo C.3
Concrete Block
1 Curb Inlet
Concrete Block
Catch Basin
NOTES:
1 Use block and gravel type sediment barrier when curb inlet is located in gently sloping 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 II Construction Stormwater Pollution Prevention
4 -87
Plan View
RUNOFF
Back of Sidewalk
V
RUNOFF rILLWAI
w
Gravel Filled Sandbags
Stacked Tightly
Burlap Sacks to
Overlap onto Curb
N
Figure 4.16 Curb and Gutter Barrier
Catch Basin
Curb Inlet
Back of Curb,
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 geotextile' fabric, are filled with gravel, layered and packed tightly
3 Leave a one sandbag gap in the top row to provide a spillway for overflow
4 Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from
the traveled way immediately
4 88 Volume ll Construction Stormwater Pollution Prevention February 2005
BMP C123 Plastic Covering
Purpose Plastic covenng provides immediate, short term erosion protection to
slopes and disturbed areas.
Conditions of Plastic covenng 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)
applications.
Clear plastic sheeting can be used over newly- seeded areas to create a
greenhouse effect and encourage grass growth if the hydroseed was
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.
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 and/or unstable slopes.
While plastic is inexpensive to purchase, the added cost of installation,
maintenance, removal, and disposal make this an expensive matenal,
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
1 Temporary ditch liner.
2. Pond liner in temporary sediment pond,
3 Liner for bermed temporary fuel storage area if plastic is not
reactive to the type of fuel being stored,
4 Emergency slope protection dunng heavy rains, and,
5 Temporary drainpipe elephant trunk used to direct water
4 -26 Volume II Construction Stormwater Pollution Prevention February 2005
Design and
Installation
Specifications
Maintenance
Standards
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, nprap, or other
suitable protection shall be installed at the toe of the slope in order to
reduce the velocity of runoff.
Torn sheets must be replaced and open seams repaired.
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
February 2005 Volume ll Construction Stormwater Pollution Prevention
4 -27
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.
Dunng 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 matenals, 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 matenals have higher specific gravities (densities) than straw,
wood, or chipped matenal.
Maintenance The thickness of the cover must be maintained.
Standards
Any 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 -20 Volume lI Construction Stormwater Pollution Prevention February 2005
Mulch
Material
Straw
Hydromulch No growth
inhibiting factors.
Composted
Mulch and
Compost
Chipped Site
I Vegetation
Wood -based
Mulch
February 2005
Quality Standards
Air -dried; free from
undesirable seed and
coarse material.
No visible water or
dust during
handling. Must be
purchased frorn
supplier with Solid
Waste Handling,
Permit (unless
exempt).
Average size shall
be several inches.
Gradations from
fines to 6 inches in
length for texture,
variation, and
interlocking
properties.
No visible water or
dust during
handling. Must be
purchased from a
supplier with a Solid
Waste Handling
Permit or one
exempt from solid
waste regulations.
Table 4.7
Mulch Standards and Guidelines
Application
Rates
2' 3 thick; 5
bales per 1000 sf
or 2 3 tons per
acre
Approx. 25 -30
lbs per 1000 sf
or 1500 2000
lbs per acre
2' thick min.
approx. 100 tons
per acre (approx.
800 lbs per yard)
2' minimum
thickness
2' thick; approx.
100 tons per acre
(approx. 800 lbs.
per cubic yard)
Remarks
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 be held 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 -term benefits are
unavailable locally It should also not be used within the
ordinary high -water elevation of surface waters (due to
flotation).
Shall be applied with hydromulcher Shall not be used
without seed and tackifier unless the application rate is at
least doubled. Fibers longer than about 1/4-1 inch clog
hydromulch equipment. Fibers should be kept to less than'
inch.
More effective control can be obtained by increasing
thickness to 3 Excellent mulch for protecting final grades
until landscaping because it can be directly seeded or tilled
into soil as an amendment. Composted mulch has a coarser
size gradation than compost. It is more stable and practical
to use in wet areas and during rainy weather conditions.
This is a cost effective way to dispose of debris from
clearing and grubbing, and it eliminates the problems
associated with burning. Generally it should not be used on
slopes above approx. 10% because of its tendency to be
transported by runoff. It is not recommended within 200
feet of surface waters. If seeding is expected shortly after
mulch, the decomposition of the chipped vegetation may tie
up nutrients important to grass establishment.
This material is often called `hog or hogged fuel. It is
usable as a material for Stabilized Construction Entrances
(BMP C105) and as a mulch. The use of mulch ultimately
improves the organic matter in the soil. Special caution is
advised regarding the source and composition of wood
based mulches. Its preparation typically does not provide
any weed seed control, so evidence of residual vegetation in
its composition or known inclusion of weed plants or seeds
should be monitored and prevented (or minimized).
Volume 11 Construction Stormwater Pollution Prevention 4 -21
Element #2 Establish Construction Access
BMP C106 Wheel Wash
Element #5 Stabilize Soils
BMP 124 Sodding
Element #6 Protect Slopes
BMP 122 Nets and Blankets
BMP 207 Check Dams
BMP 201 Grass Lined Channel
Appendix C Alternative BMPs
Element #1 Mark Clearing Limits
BMP C104 Stake and Wire Fence
Element #3 Control Flow Rates
BMP C241 Temporary Sediment Pond
Element #4 Install Sediment Controls
BMP 241 Temporary Sediment Pond (See above Element #3)
26
Storm water Pollution Prevention Plan
The following includes a list of possible alternative BMPs for each of the 12 elements 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.
27
Stormwater Pollution Prevention Plan
BMP C104. Stake and Wire Fence
Purpose
Conditions of Use
Design and
Installation
Specifications
Maintenance
Standards
February 2005
3' MIN.
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.
To establish cleanng limits, stake or wire fence may be used.
At the boundary of sensitive areas, their buffers, and other areas
required to be left uncleared.
As necessary, to control vehicle access to and on the site
See Figure 4 1 for details.
More substantial fencing shall be used if the fence does not prevent
encroachment mto those areas that are not to be disturbed.
If the fence has been damaged or visibility reduced, it shall be
repaired or replaced immediately and visibility restored.
Do Not Nail or Staple
Survey Flagging Wire Wire to Trees
fl/\
1O'-20'
Metal
Fence Post
11-1_11-111-111-111-111 I I III 11 111 II III T
12 MIN.
Figure 4.1 Stake and Wire Fence
Volume II Construction Stormwater Pollution Prevention 4 -7
BMP C106. Wheel Wash
Purpose
Conditions of Use
Wheel washes reduce the amount of sediment transported onto paved
roads by motor vehicles.
When a stabilized construction entrance (see BMP C105) is not preventing
sediment from being tracked onto pavement.
Wheel washing is generally an effective BMP when installed with
careful attention to topography For example, a wheel wash can be
detnmental if installed at the top of a slope abutting a nght -of way
where the water from the dripping truck can run unimpeded into the
street.
Pressure washing combined with an adequately sized and surfaced pad
with direct drainage to a large 10 -foot x 10 -foot sump can be very
effective.
Design and Suggested details are shown in Figure 4.3 The Local Permitting
Installation Authonty may allow other designs. A minimum of 6 inches of asphalt
Specifications treated base (ATB) over crushed base material or 8 inches over a good
subgrade is recommended to pave the wheel wash.
Use a low clearance truck to test the wheel wash before paving. Either a
belly dump or lowboy will work well to test clearance.
Keep the water level from 12 to 14 inches deep to avoid damage to truck
hubs and filling the truck tongues with water
Midpoint spray nozzles are only needed in extremely muddy conditions.
Wheel wash systems should be designed with a small grade change, 6 to
12 inches for a 10 -foot wide pond, to allow sediment to flow to the low
side of pond to help prevent re- suspension of sediment. A drainpipe with
a 2- to 3 -foot riser should be installed on the low side of the pond to allow
for easy cleaning and refilling. Polymers may be used to promote
coagulation and flocculation in a closed -loop system. Polyacrylamide
(PAM) added to the wheel wash water at a rate of 0.25 0.5 pounds per
1,000 gallons of water mcreases effectiveness and reduces cleanup time.
If PAM is already being used for dust or erosion control and is being
applied by a water truck, the same truck can be used to change the wash
water
Maintenance The wheel wash should start out the day with fresh water
Standards The wash water should be changed a minimum of once per day On
large earthwork jobs where more than 10 -20 trucks per hour are
expected, the wash water will need to be changed more often.
Wheel wash or tire bath wastewater shall be discharged to a separate on-
site treatment system, such as closed -loop recirculation or land
application, or to the sanitary sewer with proper local sewer district
approval.
4 -10 Volume II Construction Stormwater Pollution Prevention February 2005
2% 5 1 5:1
Slope" Slope Slope
1 1
L Slope\
Wheel Wash Plan
15' --15' 20' 15-- 50'
F
Elevation View
Section A -A
N.T S.
Figure 4.3 Wheel Wash
Schedule 40
1 W schedule 40 for sprayers
II
I I
I
t l
II
I
Water level
1f 1
1 1 Slope
1^
Notes.
1 Asphalt construction entrance 6 in. asphalt treated base (ATB).
2. 3 -inch trash pump with floats on the suction hose.
3 Midpoint spray nozzles, if needed.
4 6 -inch sewer pipe with butterfly valves. Bottom one is a drain. Locate top pipes invert 1 foot
above bottom of wheel wash.
5 8 foot x 8 foot sump with 5 feet of catch. Build so can be cleaned with trackhoe.
6 Asphalt curb on the low road side to direct water back to pond
7 6 -inch sleeve under road.
8 Ball valves.
9 15 foot. ATB apron.to protect ground from splashing water
February 2005 Volume ll Construction Stormwater Pollution Prevention
2%
Slope
4 -11
BMP C241 Temporary Sediment Pond
Purpose Sediment ponds remove sediment from runoff origmating 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 Pnor to leaving a construction site, stormwater runoff must pass through a
sediment pond or other appropnate sediment removal best management
practice
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 mstalled 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
and safety must be addressed. If fencmg of the pond is required, the
type of fence and its location shall be shown on the ESC plan.
Structures having a maximum storage capacity at the top of the dam of
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
restrict the lower onfice with gravel to increase residence time while
still allowing dewatering of the basin.
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
above final grade. Final grading of the infiltration facility shall occur
only when all contributing drainage areas are fully stabilized. The
infiltration pretreatment facility should be fully constructed and used
with the sedimentation basin to help prevent clogging.
Determining Pond Geometry
Obtain the discharge from the hydrologic calculations of the peak flow
for the 2 -year runoff event (Q The 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.
February 2005
Volume ll Construction Stormwater Pollution Prevention 4 -105
Determine the required surface area at the top of the riser pipe with the
equation.
SA 2 x Q /0 00096 or
2080 square feet per cfs of inflow
See BMP C240 for more information on the denvation of the surface
area calculation.
The basic geometry of the pond can now be determmed using the
following design criteria.
Required surface area SA (from Step 2 above) at top of riser
Minimum 3 5 -foot depth from top of riser to bottom of pond.
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 fencmg 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.
Minimum 1 -foot deep spillway
Length -to -width ratio between 3 1 and 6 1
Sizing of Discharge Mechanisms
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 for a 100 -year storm. If, due to site
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
through the dewatenng orifice cannot be utilized when calculating the
100 -year storm elevation because of its potential to become clogged,
therefore, available spillway storage must begin at the pnncipal spillway
riser crest.
The principal spillway designed by the procedures contained in this
standard will result in some reduction in the peak rate of runoff.
However, the nser outlet design will not adequately control the basin
discharge to the predevelopment discharge limitations as stated m
Minimum Requirement #7 Flow Control. However, if the basin for a
permanent stormwater detention pond is used for a temporary
sedimentation basin, the control structure for the permanent pond can be
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.
4 -106 Volume ll Construction Stormwater Pollution Prevention February 2005
February 2005
Key divider into slope
to prevent flow
arourplityor 4.
The pond length shall be 3 to 6
times the maximum pond width
Inflow
Pon. length
Note: Pond may be formed by berm or
by partial or complete excavation
Dewatering device
(see riser detail)
1'_ I
Wire- backed silt fence
staked haybales wrapped
with filter fabric, or
equivalent divider
Polyethylene cap
Perforated polyethylene
drainage tubing, diameter
min. 2" larger than
dewatering orifice.
Tubing shall comply
with ASTM F667 and
AASHTO M294
Silt fence or
equivalent divider
Riser pipe
(principal spillway)
open at top with
trash rack
18' min.
Sediment
b
Watertight
coupling Tack weld
Figure 4.24 Sediment Pond Plan View
1=4.. li n
Provide adequate
strapping
Crest of
emergency spillway jmin. Width
Corrugated
metal riser
I 6' min. r
Concrete ba
II1L
l X161
Discharge to stabilized
Dewatering Concrete base conveyance outlet or
orifice (see riser detail) level spreader
Figure 4.25 Sediment Pond Cross Section
1
2X riser dia. Min. ----I
Figure 4.26 Sediment Pond Riser Detail
Volume II Construction Stormwater Pollution Prevention
Emergency overflow
spillwa
Discharge to stabilized
conveyance, outlet, or
level spreader
Embankment compacted 95%
ervious materials such as
gravel or clean sand shall
not be used
3.5' min.
Dewatering orifice, schedule,
_.x. steel stub min.
Dia meter as per calculations
Alternatively, metal stakes
and wire may be used to
prevent flotation
4 -107
100
10
mmurAir
ICI
Ag
A4 7°1-
Airzwaiz
4V /Y /FAU
AWE/ AVM
/11 AMPAIIV
IN /1n'
FLY /MV
Ii 7 /A r
III 72 54 48
X
Figure 4.27 Riser Inflow Curves
42
36
33
30
27
24
o
HEAD IN FEET (m easu from crest of riser)
Q r =9 739 DH
Q. ifice =3 782 D 2 H 112
0 in cfs D and It in feet
Slope change occurs at weir- orifice transition
4 -108 Volume II Construction Stormwater Pollution Prevention
10
a
February 2005
February 2005
Principal Spillway- Determine the required diameter for the pnncipal
spillway (riser pipe). The diameter shall be the minimum necessary to
pass the pre developed 10 -year peak flow (Q10) Use Figure 4.28 to
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 dewatenng onfice(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
orifice. Determine the required area of the orifice with the following
equation.
A (2h)
A° 0 6x3600Tg os
where A orifice area (square feet)
A pond surface area (square feet)
h head of water above orifice (height of riser in feet)
T
dewatenng time (24 hours)
g acceleration of gravity (32.2 feet/second
Convert the required surface area to the required diameter D of the orifice.
D 24x A 13.54x A
7r
The vertical, perforated tubing connected to the dewatenng onfice must be
at least 2 inches larger in diameter than the orifice to improve flow
characteristics. The size and number of perforations in the tubing should
be large enough so that the tubmg does not restrict flow The orifice
should control the flow rate
Additional Design Specifications
The pond shall be divided into two roughly equal volume cells by a
permeable divider that will reduce turbulence while allowing
movement of water between cells. The divider shall be at least one
half the height of the nser and a minimum of one foot below the top of
the riser Wire- backed, 2- to 3 -foot high, extra strength filter fabric
supported by treated 4 "x4 "s can be used as a divider Alternatively,
staked straw bales wrapped with filter fabric (geotextile) may be used.
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
Volume ll Construction Storm water Pollution Prevention 4 -109
this provision are allowed as long as the divider is permeable,
structurally sound, and designed to prevent erosion under or around
the barrier
To aid in determinmg sediment depth, one -foot intervals shall be
prommently marked on the riser
If an embankment of more than 6 feet is proposed, the pond must
comply with the cntena contained in Volume III regarding dam safety
for detention BMPs.
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 nser and barrel and other pipe
connections.
2. Adequate anchoring of riser
3 Proper soil compaction of the embankment and nser footmg.
4 Proper construction of anti -seep devices.
Maintenance Sediment shall be removed from the pond when it reaches 1 —foot in
Standards depth.
Any damage to the pond embankments or slopes shall be repaired.
4 -110 Volume II Construction Stormwater Pollution Prevention February 2005
c
1
1
1
1
1
1
1
1
r
BMP C232 Gravel Filter Berm
Purpose
A gravel filter berm is constructed on rights -of -way or traffic areas within
a construction site to retam sediment by using a filter berm of gravel or
crushed rock.
Conditions of Use Where a temporary measure is needed to retain sediment from rights -of-
way or in traffic areas on construction sites.
Design and Berm material shall be 3 to 3 inches in size, washed well -grade gravel
Installation or crushed rock with less than 5 percent fines.
Specifications
Spacing of berms.
Every 300 feet on slopes less than 5 percent
Every 200 feet on slopes between 5 percent and 10 percent
Every 100 feet on slopes greater than 10 percent
Berm dimensions:
1 foot high with 3 1 side slopes
8 linear feet per 1 cfs runoff based on the 10 -year, 24 -hour design
storm
Maintenance Regular inspection is required. Sediment shall be removed and filter
Standards material replaced as needed.
February 2005
Volume ll Construction Stormwater Pollution Prevention 4 -93
BMP C124. Sodding
Purpose
Conditions of Use
Design and
Installation
Specifications
The purpose of sodding is to establish permanent turf for immediate
erosion protection and to stabilize drainage ways where concentrated
overland flow will occur
Sodding may be used in the following areas.
Disturbed areas that require short-term or long -term cover
Disturbed areas that require immediate vegetative cover
All waterways that require vegetative lining. Waterways may also be
seeded rather than sodded, and protected with a net or blanket.
Sod shall be free of weeds, of uniform thickness (approximately 1 -inch
thick), and shall have a dense root mat for mechanical strength.
The following steps are recommended for sod installation.
Shape and smooth the surface to final grade in accordance with the
approved gradmg plan. The swale needs to be overexcavated 4 to 6
inches below design elevation to allow room for placing soil
amendment and sod.
Amend 4 inches (minimum) of compost into the top 8 inches of the
soil if the organic content of the soil is less than ten percent or the
permeability is less than 0 6 inches per hour Compost used should
meet Ecology publication 94 -038 specifications for Grade A quality
compost.
Fertilize according to the supplier's recommendations
Work lime and fertilizer 1 to 2 inches into the soil, and smooth the
surface.
Lay strips of sod beginning at the lowest area to be sodded and
perpendicular to the direction of water flow Wedge stnps securely
into place. Square the ends of each strip to provide for a close, tight
fit. Stagger joints at least 12 inches. Staple on slopes steeper than
3H 1V Staple the upstream edge of each sod stnp
Roll the sodded area and irrigate.
When sodding is carried out in alternating strips or other patterns, seed
the areas between the sod immediately after sodding.
Maintenance If the grass is unhealthy the cause shall be determined and appropriate
Standards action taken to reestablish a healthy groundcover If it is impossible to
establish a healthy groundcover due to frequent saturation, instability, or
some other cause, the sod shall be removed, the area seeded with an
appropriate mix, and protected with a net or blanket
4 -28 Volume 11 Construction Stormwater Pollution Prevention February 2005
BMP C201 Grass -Lined Channels
Purpose
Conditions of Use
Channels that will be vegetated should be installed before major
earthwork and hydroseeded with a bonded fiber matrix (BFM) 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
hydroseed. If vegetation cannot be established from seed before water
is allowed in the ditch, sod should be installed in the bottom of the
ditch in lieu of hydromulch and blankets.
Design and Locate the channel where it can conform to the topography and other
Installation features such as roads.
Specifications Locate them to use natural drainage systems to the greatest extent
possible
Avoid sharp changes in alignment or bends and changes in grade.
Do not reshape the landscape to fit the drainage channel.
The maximum design velocity shall be based on soil conditions, type
of vegetation, and method of revegetation, but at no times shall
velocity exceed 5 feet/second. The channel shall not be overtopped by
the peak runoff from a 10 -year, 24 -hour storm, assuming a Type IA
ramfall distribution." Alternatively use 1 6 times the 10 -year, 1 -hour
flow indicated by an approved continuous runoff model to determme a
flow rate which the channel must contain.
Where the grass -lined channel will also function as a permanent
stormwater conveyance facility, consultant the drainage conveyance
requirements of the local government with jurisdiction.
An established grass or vegetated lining is required before the channel
can be used to convey stormwater, unless stabilized with nets or
blankets.
February 2005
To provide a channel with a vegetative lining for conveyance of runoff.
See Figure 4 7 for typical grass -lined channels
This practice applies to construction sites where concentrated runoff need:
to be contained to prevent erosion or flooding.
When a vegetative lining can provide sufficient stability for the
channel cross section and at lower velocities of water (normally
dependent on grade) This means that the channel slopes are generally
less than 5 percent and space is available for a relatively large cross
section.
Typical uses include roadside ditches, channels at property boundaries,
outlets for diversions, and other channels and drainage ditches in low
areas.
Volume 11 Construction Stormwater Pollution Prevention 4 -59
If design velocity of a channel to be vegetated by seeding exceeds 2
ft/sec, a temporary channel liner is required. Geotextile or special
mulch protection such as fiberglass rovmg or straw and netting provide
stability until the vegetation is fully established. See Figure 4 9
Check dams shall be removed when the grass has matured 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.
If vegetation is established by sodding, the permissible velocity for
established vegetation may be used and no temporary liner is needed.
Do not subject grass -lined channel to sedimentation from disturbed
areas Use sediment trapping BMPs upstream of the channel.
V- shaped grass channels generally apply where the quantity of water
is small, such as in short reaches along roadsides. The V- shaped cross
section is least desirable because it is difficult to stabilize the bottom
where velocities may be high.
Trapezoidal grass channels are used where runoff volumes are large
and slope is low so that velocities are nonerosive to vegetated linings.
(Note it is difficult to construct small parabolic shaped channels.)
Subsurface drainage, or riprap channel bottoms, may be necessary on
sites that are subject to prolonged wet conditions due to long duration
flows or a high water table.
Provide outlet protection at culvert ends and at channel intersections.
Grass channels, at a minimum, should carry peak runoff for temporary
construction drainage facilities from the 10 -year, 24 -hour storm
without eroding. Where flood hazard exists, increase the capacity
according to the potential damage.
Grassed channel side slopes generally are constructed 3 1 or flatter to
aid in the establishment of vegetation and for maintenance.
Construct channels a minimum of 0.2 foot larger around the periphery
to allow for soil bulking durmg seedbed preparations and sod buildup
Maintenance During the establishment period, check grass -lined channels after every
Standards rainfall.
After grass is established, periodically check the channel, check it after
every heavy rainfall event. Immediately make repairs.
It is particularly important to check the channel outlet and all road
crossings for bank stability and evidence of piping or scour holes.
Remove all significant sediment accumulations to maintain the
designed carrying capacity Keep the grass in a healthy, vigorous
condition at all times, since it is the primary erosion protection for the
channel.
4 -60 Volume I! Construction Stormwater Pollution Prevention February 2005
1
I
1
Typical V- Shaped Channel Cross section
44,
'VOA
rllLl
Grass -Lined
Overcut channel 2' (50mm)
to allow bulking during
seedbed preparation
and growth of vegetation.
Typical Parabolic Channel Cross Section
1 \V
With Channel Liner
Typical Trapezoidal Channel Cross Section
,,uh, •,il
Design Depth
NiVl,\„iih
Filter
Fabric
v \lr
Filter
Fabric
Figure 4.8 Typical Grass -Lined Channels
With Rock Center
iferloP
(150 225mm)
Key in Fabric
6' -9
(150 225mm)
Key In Fabric
`With Rock Center
for Base Flow
-J WI/l V-I,' L\INV\i/
February 2005 Volume ll Construction Stormwater Pollution Prevention
Filter
Fabric
\‘1\ \vN`Ji
With Rock Center For Base Flow
4 -61
OVERCUT CHANNEL
2 °(50mm) TO ALLOW
MILKING DURING SEEDBED
PREPARATION
6' (150mm)
(150mm) /j /j�
Intermittent Check Slot
Overlap 6' (150mm) minimum
Excavate Channel to Design
Grade and Cross Section
Shingle -lap spliced ends or begin new
roll in an intermittent check slot
7/
it
Prepare soil and apply seed before
installing blankets, mats or other
temporary channel liner system
i4\,i, .I \I Ni 'iiI
TYPICAL INSTALLATION
WITH EROSION CONTROL
BLANKETS OR TURF
REINFORCEMENT MATS
j vim
e
4P'
y 41P
Design Depth
9
j
Longitudinal Anchor Trench
Figure 4.9 Temporary Channel Liners
4 -62 Volume ll Construction Stormwater Pollution Prevention
NOTES.
1 Design velocities exceeding 2 ft/sec (0.5m/sec) require temporary blankets, mats or similar
liners to protect seed and soil until vegetation becomes established.
2. Grass -lined channels with design velocities exceeding 6 ft/sec (2m/sec) should include
turf reinforcement mats.
Longitudinal
anchor trench
4
February 2005
BMP C207 Check Dams
Purpose Construction of small dams across a swale or ditch reduces the velocity of
concentrated flow and dissipates energy at the check dam.
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
wetlands without approval from a permitting agency
Check dams shall not be placed below the expected backwater from
any salmomd beanng water between October 1 and May 31 to ensure
that there is no loss of high flow refuge habitat for overwintering
juvenile salmomds and emergent salmonid fry
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
Specifications the dam rather than falling directly onto the ditch bottom.
Check dams in association with sumps work more effectively at slowmg
flow and retaining sediment than dust 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, m which case accumulated sediment
would be graded and seeded, or as check dams to prevent further
sediment from leaving the site.
Check dams can be constructed of either rock or pea 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.
Check dams should be placed perpendicular to the flow of water
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.
Conditions of Use
February 2005
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.
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
a minimum of 18 inches to avoid washouts from overflow around the
dam.
Volume II Construction Stormwater Pollution Prevention 4 -75
Use filter fabric foundation under a rock or sand bag check dam. If a
blanket ditch liner is used, this is not necessary A piece 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
dumping of rock 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
the expected design flow through the channel.
In the case of grass -lined ditches and swales, all check dams and
accumulated sediment shall be removed when the grass has matured
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.
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.
Maintenance Check dams shall be monitored for performance and sediment
Standards accumulation dunng and after each runoff producing rainfall. Sediment
shall be removed when it reaches one half the sump depth.
Anticipate submergence and deposition above the check dam and
erosion from high flows around the edges of the dam.
If significant erosion occurs between dams, install a protective nprap
liner in that portion of the channel.
4 -76 Volume 11 Construction Stormwater Pollution Prevention February 2005
View Looking Upstream
III1iI
Section A A
FLOW
NOTE.
Key stone into channel banks and
extend it beyond the abutments a
minimum of 18' (0.5m) to prevent
flow around dam.
24 0.6m) ,o�
Oo o po
X000
sy, r gQ° Q opO�o°
°dno 0 0 000.
i j am j\ ice j j j j�
Spacing Between Check Dams
L the distance such that points A and
B' are of equal elevation.
POINT A
jam /j 1 7 -7 7 f
r 12' (150mm)
0 1_
D o o O �dQO 0 p /k /A
-0 oo p o 24 (06m)
000 g.' po00 lc>
8' (2.4m)
'L
Figure 4.13 Check Dams
18" (0.5m)
z POINT B'
February 2005 Volume ll Construction Stormwater Pollution Prevention
NOT TO SCALE
4 -77
BMP C208 Triangular Silt Dike (Geotextile- Encased Check Dam)
Purpose
Conditions of use
Made of urethane foam sewn into a woven geosynthetic fabric.
It is triangular, 10 inches to 14 inches high in the center, with a 20 -inch to
28 -inch base A 2 —foot apron extends beyond both sides of the triangle
along its standard section of 7 feet. A sleeve at one end allows attachment
of additional sections as needed.
Install with ends curved up to prevent water from flowing around the
ends.
The fabric flaps and check dam units are attached to the ground with
wire staples. Wire staples should be No 11 gauge wire and should be
200 mm to 300 mm m length.
When multiple units are installed, the sleeve of fabric at the end of the
unit shall overlap the abutting unit and be stapled.
Check dams should be located and installed as soon as construction
will allow
Check dams should be placed perpendicular to the flow of water
When used as check dams, the leading edge must be secured with
rocks, sandbags, or a small key slot and staples.
In the case of grass -lined ditches and swales, check dams and
accumulated sediment shall be removed when the grass has matured
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.
Maintenance Tnangular silt dams shall be monitored for performance and sediment
Standards accumulation during and after each runoff producing rainfall.
Design and
Installation
Specifications
Triangular silt dikes may be used as check dams, for perimeter protection,
for temporary soil stockpile protection, for drop inlet protection, or as a
temporary interceptor dike.
May be used in place of straw bales for temporary check dams in ditches
of any dimension.
May be used on soil or pavement with adhesive or staples.
TSDs have been used to build temporary
1 sediment ponds,
2 diversion ditches,
3 concrete wash out facilities,
4 curbing;
5 water bars,
6 level spreaders, and,
7 berms.
4 -78 Volume ll Construction Stormwater Pollution Prevention February 2005
Sediment shall be removed when it reaches one half the height of the
dam.
Anticipate submergence and deposition above the triangular silt dam
and erosion from high flows around the edges of the dam.
Immediately repair any damage or any undercutting of the dam.
February 2005 Volume 11 Construction Stormwater Pollution Prevention
4 -79
Appendix D General Permit
28
Storm water Pollution Prevention Plan
29
Storm water Pollution Prevention Plan
Storm water Pollution Prevention Plan
Appendix E Site Inspection Forms (and Site Log)
The results of each inspection shall be summarized in an inspection report or checklist
that is entered into or attached to the site log book. It is suggested that the inspection
report or checklist be included in this appendix to keep monitoring and inspection
information in one document, but this is optional. However it is mandatory that this
SWPPP and the site inspection forms be kept onsite at all times during 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,
ii. locations of BMPs that need maintenance,
in. the reason maintenance is needed,
iv locations of BMPs that failed to operate as designed or
intended, and
v locations where additional or different BMPs are needed, and
the reason(s) why
e. A description of stormwater discharged from the site. The presence
of suspended sediment, turbid water discoloration, and/or oil
sheen shall be noted, as applicable
f A description of any water quality monitoring performed during
inspection, and the results of that monitoring.
g. General comments and notes, including a brief description of any
BMP repairs, maintenance or installations made as a result of the
inspection.
h. A statement that, in the judgment of the person conducting the site
inspection, the site is either in compliance or out of compliance
with the terms and conditions of the SWPPP and the NPDES
30
1.
Storm water Pollution Prevention Plan
permit. If the site inspection indicates that the site is out of
compliance, the inspection report shall include a summary of the
remedial actions required to bring the site back into compliance, as
well as a schedule of implementation.
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
When the site inspection indicates that the site is not in compliance with any terms and
conditions of the NPDES permit, the Permittee shall take immediate action(s) to stop
contain, and clean up the unauthorized discharges, or otherwise stop the noncompliance,
correct the problem(s) implement appropriate Best Management Practices (BMPs)
and /or conduct maintenance of existing BMPs and achieve compliance with all
applicable standards and permit conditions In addition, if the noncompliance causes a
threat to human health or the environment, the Permittee shall comply with the
Noncompliance Notification requirements in Special Condition S5.F of the permit.
31
Storm water Pollution Prevention Plan
Site Inspection Form
General Information
1
•Project Name:
Inspector Name:
Date:
Inspection Type:
,t,oCatiOn
„WO'
Locatioff
SW-
Location
Weather
Precipitation Smce last inspection
Description of General Site Conditions:
o After a rain event
o Weekly
o Turbidity/transparency benchmark exceedance
o Other
InSpection of BINIPs
,Element 1 Mark elearing Limits
BMF'.
Inspected .:FurieWining
PrObleiniCOrreetiVe.ACtion
r.
Inspectea
1\
Element 2. Establish Construction Access
BiyiP
Location
,InSpeCted
'Y
hispeeted
Y
Functioning
32
Title:
CESCI,
Time:
ilniLast 24 hour
Probion/corfectivc,Actiim
Prohlem/CorreCtive Action
Pr�b1th/€�rrectiv4ction
Element 3. controtOo* Rinek
BMP
Location
BMP
Location
i314,
Location
BMP
Location
.BMP'
Location
InSpeatott Functioning ProblernjeOtreotive Action
FYI _ISNIP
-Inspected
Element 4 install Sediment Conkols-
13MF'•
Location
_Fninctoning,
Ptoble,tii/COttectivp Action
Itiq*oted. Functioning
y
1
1
1 1
Inspectoct 'Ainctioning
Problernicorrecti\T Actiofi
N IA 4:11
BMIP
1 1 1
1 1 1
1 1
..108Fitteci Kincti.org. un
8 t PioblerniCorioctive,Action:
Location
1, 1
Inspected. OtiOning.
1N
33
Storm water Pollution Prevention Plan
ProlildnICiorrective, Action
PrOblern/cOttective Action
PtObleni/Corrdttiye Action
Element5 Skibiiize SOils
1 .7 3 MP
tAIcation
BMP
;114)Catiori
BMP•
tocatibn
Inspected
Element PrOtect Slopes
1.* 1 „P'
Location
13MP•
Lo'cation
BP
Location.
jitspOted
Irispe*O Ctio)07Arig:
Location Probterizil(oftde.00:ACOOn
tj
Iii§boct4t f•titictioning
Inspdcted. "Flinetionink,
Y N I: VI 1 NV:.
I I
I 1
I
Inspected Kincti oig
1 I
1 1 1
11
InSpdcted ,''ktinctiOning
I; 1■4 NW:
34
Storm water Pollution Prevention Plan
'PEOlilehi/COrt0CtiveAction
PtoWein/COrteCtive Action,
PrOblerh/C OrteCtiVq.ActiOn
Probleink:OrtdetiVe•Action i
ProbleinfEbtective Action
Proli1eni/coiTOCtiye ActiOn
Element 7 .Pro4qt Prainjitlet,s'
'13mp
13MP.
LOCatiori
BMP•
LOadiOn
Location
BMP•
Location
13ISIP•
Location
)3MPT•
LOcatieit
13MP'
LoCatoit
Insge40 .Functioning
1ipeetpd proi-*tiotpog
N NI1 NO
I I
I I
I I
jngpeetOt
I I I
Element Ay. Stnliilize (Jhannels Out lets.'
Inspected Fiinctioning
Piobteni/CottectiV& ACtiOn,
11611.;
I I
I I
I I I
Ingpoct61 „Funetioning
f81;11.1 Piotlippotcoritcti8/0 ActPC11:
li=i$peCted PtiriCtioning
8
I I
I I
I I
„In§p0CtOcl.. ,.:FUngtiOning,
I I
35
Storm water Pollution Prevention Plan
Probkin/CorrectiVe,Adtiori,
pfoblerreCtiveNotiOn
'Potiletri/Coritctive
Probleinteuttectiye Action
Ptoblen Action
Efrmerit9 Control
Omp-
4CatiOn
EMI?'
:I"tcatioo
Elenien00. Con#olpowcitering.
BMP
LoCatiOn
1314
Location
B MP
Locatith,
qutatits.
,Ifigpt.ctdd
'Y
Inspected
ithctioning
Fuictionmg
I1 IiI
I I
I I
I I
Inspected Ftitictiorilfig
NIP F1/4:01)10m/O:ItteCove, Action
I I I
I I I
I I I
Inspected unctioiiiig
Inspected Functioning
:I NtO T.TobkolicottottiveAdtoie
36
Storm water Pollution Prevention Plan
PrOblenitcotrectiVe Action
PtOlileM/CorreCtlye Aetiolx
PtOblbin/Coriectiv Action
Location-
Tiirliidiity
Discohoratioh
Sheen. ,r
:Location,
Turbidity
Discoloration_
'Sheen
Stormwatei Discharges From the Site
Observed?
Problem/Corrective Action
37
Storm water Pollution Prevention Plan
Water Quality Monitoring
Was sally watert;quality monitoring conducted Yes
If water quality monitoring: was :conducted,, record results! here:
I£ water' quality monitoring indicated turbidity 250 NTU or
cm or`:less, Was Ecology notified ";by phone within 24.hrS?
Yes
,If Ecology was notified, midicate;;the .date;, *time, ,contact
.below
Date:
Time:
Contact Name:
Phoriet
General 'Comments. and-Notes.
Include.BMPyepairs, maintenance or. installations made as a result of the:,, inspection:.
WerePhotos Taken Yes No
If_ photos, taken, describe photos below
38
Storm water Pollution Prevention Plan
No
greater; :or transparency 6
No
na ne,- and'.phgne',nuniber
Existing Event Summary
Event
1 2 year
1 other
5 year
`(10 year
1 25 year
;(100 year-
'Fixed
Peak Q (cfs ►:(Peak T (hrs)
1 0957 El 8 00
1 1739
1 4907
1 8926
3.5173
4 3281
Appendix F Engineering Calculations
8 00
8 00
8 00
8 00
8 00
Record Id. Existing
(Design Method SCS JRainfall type
(Hyd Intv 10 00 min "Peaking Factor
(Abstraction Coeff
2.25 ac (DCIA
1 90 00 (DC CN
5 00 mm (DC TC
Pervious CN Calc
(Pervious Area (AMC 2)
'(Pervious CN
;(Pervious TC
Type Description
Description SubArea
Landscaped 2.25 ac
Pervious Composited CN (AMC 2)
Pervious TC Calc
Length I Slope 1 Coeff
1
Pervious TC
Storm water Pollution Prevention Plan
Hyd Vol (acft) tArea (ac) (Method (Raintype.
0.3669 3 3600 SCS (TYPE1A
0.3928 3 3600 SCS 1TYPE1A?
0 4961 3.3600 SCS :1TYPEIA
0 6274 3.3600 SCS '(TYPE1A;
1 1698 3 3600 SCS 11TYPE1A
1 4446 3 3600 SCS '(TYPEIA:
ilirPrtly f nnnertea TC ralr
39
Misc 1 TT
(5 00 min
500 min
Directly Connected CN Calc
Description SubArea
Commercial Business 1 11 ac
DC Composited CN (AMC 2)
TYPE1A
484 00
0.20
111ac
98 00
500 min
Sub cn
90 00
90 00
Sub cn
98 00
98 00
Storm water Pollution Prevention Plan
2 year
other
5 year
'I 10 year
25 year
1100 year
Description Length Slope Coeff :I Misc I TT
1 5 00 min
I 5 00mm
Directly Connected TC
During Construction Event Summary
Event Peak Q (cfs)`IPeak T (hrs) IHyd Vol (acft) Area (ac) 'Method IRaintype
3.3600 SCS •ITYPE1A:
0 7122 8 01 0.2563 3.3600 SCS 'ITYPEIA
0 9979 8 01 0.3458 13 3600 SCS ITYPE1A
1.3751 8 01 I 0 4634 3.3600 .I SCS ,ITYPE1A'
2.9828 8 01. 0 9708 'I 3.3600 SCS ITYPE1A;
3 8070 8 01 1.2358 3.3600 I SCS :ITYPE1A,
0 6439 8 01 I 0.2351
Record Id. During Construction
;'Design Method
IHyd Intv
:'Pervious Area (AMC 2) 0 00 ac
IPervious CN .I 0 00
'Pervious TC I 0 00 mm
SCS
I 1000 mm
Directly Connected CN Calc
SubArea
336 ac
Description
Commercial Business
DC Composited CN (AMC 2)
Directly Connected TC Calc
I Type Description Length I Slope I Coeff I Misc I TT
;IFixed I I 15 00 min
Directly Connected TC I 5 00min
40
Rainfall type
Peaking Factor
Abstraction Coeff
DCIA
DC CN
DC TC
TYPE1A
484 00
0.20
3.36 ac
86 00
5 00 min
Sub cn
86 00
86 00
Pr North Event Summary
Event 1Peak Q (cfs) !Peak T (hrs) IHyd Vol (acf01Area (ac)1Method IRaintype
I 6-mon 1 0 0911 8 00 I 0 0323 1 0.5100 '1 SCS ,ITYPElAi
2 year I, 0 1506 'I, 8 00 1, 0 0520 1 0.5100 1 SCS ITYPE1A;
1110 year 1 0.2657 1 8 00 I 0 0899 I 0.5100 1 SCS ITYPE1A
100 year 0 4468 :I 8 00 I 0 1499 I 0.5100 SCS ITYPE1A:
'Design Method
1Hyd Intv
II)ervious Area (AMC 2)
'Pervious CN
1 Pervious TC
Type
!IFixed
Appended on. 08.57:01 Tuesday, May 12, 2009
Record Id. Pr North
Storm water Pollution Prevention Plan
SCS 'Rainfall type F TYPE1A
10 00 mm !1Peaking Factor 484 00
'Abstraction Coeff 0.20
0 30 ac IDCIA 0.21 ac
86 00 IDC CN 98 00
5 00 mm DC TC
5 00 mm
Pervious CN Calc
Description 1 SubArea 1 Sub cn
Open spaces, lawns,parks (>75% grass) 0.30 ac 1 86 00
;1
Pervious Composited CN (AMC 2) 86 00
Directly Connected TC 1 5 00mm
Directly Connected TC Cale
Pervious TC Calc
F. Description 1 Length I Slope 1 Coeff Misc 1 TT
'Flow to pipe system F F 5 00 mm
Pervious TC 1 5 00 min
Directly Connected CN Calc
Description 1 SubArea 1 Sub cn
Impervious surfaces (pavements, roofs, etc) I 0.21 ac 1 98 00
DC Composited CN (AMC 2) 1 98 00
Type 1 Description 1 Length I Slope 1 Coeff 1 Misc :1 TT
Fixed 1Flow to pipe system
.15 00 mm
41