RPT - CSWPPP - 2023.09.05Construction Stormwater General Permit
Stormwater Pollution Prevention Plan
(SWPPP)
for
SoundBuilt Homes
Prepared for:
The Washington State Department of Ecology
Southwest Regional Office
Permittee / Owner Developer Operator / Contractor
SoundBuilt Homes TBD TBD
9955 Tahoma Blvd, Yelm, WA 98597
Certified Erosion and Sediment Control Lead (CESCL)
Name Organization Contact Phone Number
TBD TBD TBD
SWPPP Prepared By
Name Organization Contact Phone Number
Augustus Brinckmeyer Hatton Godat Pantier, Inc. (360) 943-1599
SWPPP Preparation Date
September 5, 2023
Project Construction Dates
Activity / Phase Start Date End Date
Site Development & Grading April 2024 April 2026
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Table of Contents
1 Project Information .............................................................................................................. 4
1.1 Existing Conditions ...................................................................................................... 4
1.2 Proposed Construction Activities .................................................................................. 4
2 Construction Stormwater Best Management Practices (BMPs) ........................................... 6
2.1 The 13 Elements .......................................................................................................... 6
2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits ........................................ 6
2.1.2 Element 2: Establish Construction Access ............................................................ 6
2.1.3 Element 3: Control Flow Rates ............................................................................. 6
2.1.4 Element 4: Install Sediment Controls .................................................................... 7
2.1.5 Element 5: Stabilize Soils ..................................................................................... 7
2.1.6 Element 6: Protect Slopes..................................................................................... 8
2.1.7 Element 7: Protect Drain Inlets ............................................................................. 8
2.1.8 Element 8: Stabilize Channels and Outlets ........................................................... 8
2.1.9 Element 9: Control Pollutants ................................................................................ 9
2.1.10 Element 10: Control Dewatering ..........................................................................10
2.1.11 Element 11: Maintain BMPs .................................................................................11
2.1.12 Element 12: Manage the Project ..........................................................................11
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs .................................13
3 Pollution Prevention Team .................................................................................................13
4 Monitoring and Sampling Requirements ............................................................................14
4.1 Site Inspection ............................................................................................................14
4.2 Stormwater Quality Sampling ......................................................................................14
4.2.1 Turbidity Sampling ...............................................................................................14
4.2.2 pH Sampling ........................................................................................................15
5 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies .........................16
5.1 303(d) Listed Waterbodies ..........................................................................................16
5.2 TMDL Waterbodies .....................................................................................................16
6 Reporting and Record Keeping ..........................................................................................16
6.1 Record Keeping ..........................................................................................................16
6.1.1 Site Log Book ......................................................................................................16
6.1.2 Records Retention ...............................................................................................16
6.1.3 Updating the SWPPP ...........................................................................................17
6.2 Reporting ....................................................................................................................17
6.2.1 Discharge Monitoring Reports ..............................................................................17
6.2.2 Notification of Noncompliance ..............................................................................17
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List of Tables
Table 1 – pH-Modifying Sources ................................................................................................ 9
Table 2 – Team Information ......................................................................................................13
Table 3 – Turbidity Sampling Method ........................................................................................14
Table 4 – pH Sampling Method .................................................................................................16
List of Appendices
Appendix/Glossary
A. Site Map
B. BMP Detail
C. Correspondence
D. Site Inspection Form
E. Construction Stormwater General Permit (CSWGP)
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List of Acronyms and Abbreviations
Acronym / Abbreviation Explanation
303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies
BFO Bellingham Field Office of the Department of Ecology
BMP(s) Best Management Practice(s)
CESCL Certified Erosion and Sediment Control Lead
CO2 Carbon Dioxide
CRO Central Regional Office of the Department of Ecology
CSWGP Construction Stormwater General Permit
CWA Clean Water Act
DMR Discharge Monitoring Report
DO Dissolved Oxygen
Ecology Washington State Department of Ecology
EPA United States Environmental Protection Agency
ERO Eastern Regional Office of the Department of Ecology
ERTS Environmental Report Tracking System
ESC Erosion and Sediment Control
GULD General Use Level Designation
NPDES National Pollutant Discharge Elimination System
NTU Nephelometric Turbidity Units
NWRO Northwest Regional Office of the Department of Ecology
pH Power of Hydrogen
RCW Revised Code of Washington
SPCC Spill Prevention, Control, and Countermeasure
su Standard Units
SWMMEW Stormwater Management Manual for Eastern Washington
SWMMWW Stormwater Management Manual for Western Washington
SWPPP Stormwater Pollution Prevention Plan
TESC Temporary Erosion and Sediment Control
SWRO Southwest Regional Office of the Department of Ecology
TMDL Total Maximum Daily Load
VFO Vancouver Field Office of the Department of Ecology
WAC Washington Administrative Code
WSDOT Washington Department of Transportation
WWHM Western Washington Hydrology Model
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1 Project Information
Project/Site Name: Tahoma Terra Commercial
Street/Location: 9955 Tahoma Blvd SE
City: Yelm State: WA Zip code: 98597
Subdivision: Tahoma Terra
Receiving waterbody: Groundwater/Thompson Creek
1.1 Existing Conditions
Total acreage (including support activities such as off-site equipment staging yards, material storage
areas, borrow areas).
Total acreage: 13.62
Disturbed acreage: 11.07
Existing structures: N/A
Landscape topography: The existing site slopes from east to west. Slopes vary from 0.5 to
20 percent. The site is relatively flat, with steeper slopes leading
down to the Thompson Creek area.
Drainage patterns: Stormwater sheet flows across the site following the existing slopes
from east to west. Thompson Creek and a wetland are directly west
of the site. Runoff most likely sheets flow across adjacent property
to these features with limited infiltration.
Existing Vegetation: The site is sparsely forested. Low shrubs, vegetation, and weeds
make up most of the cover.
Critical Areas (wetlands,
streams, high erosion
risk, steep or difficult to
stabilize slopes):
The site is within a Category I Critical Aquifer Recharge Area,
Wetland on site, Thompson creek, and steep slopes are present on
the site.
List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving
waterbody: N/A
1.2 Proposed Construction Activities
Description of site development (example: subdivision):
Commercial subdivision. The project proposes to construct nine multifamily apartment buildings, storage
units and mixed use commercial across 15 buildings. The Retail portion of the site includes two retail
buildings. The project also proposes required drainage, landscaping, sewer, and water service
improvements.
Description of construction activities (example: site preparation, demolition, excavation):
Site development and grading, utility installation, concrete and asphalt paving, building construction,
landscaping.
Description of site drainage including flow from and onto adjacent properties. Must be consistent
with Site Map in Appendix A:
Stormwater runoff will be generated by runoff from the new roof areas, concrete , and landscaping. Roof
drains will collect runoff from the new buildings and convey them via PVC pipe to the permeable
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pavement basin. Catch basins will collect runoff from the paved surfaces for large storm events. All
precipitation tributary to permeable pavement will infiltrate in place.
Description of final stabilization (example: extent of revegetation, paving, landscaping):
Final stabilization will consist of paved areas, new multi-family-homes, storage buildings, retail buildings,
and lawn/landscaped areas.
Proposed activities regarding contaminated soils or groundwater (example: on-site treatment
system, authorized sanitary sewer discharge):
N/A
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2 Construction Stormwater Best Management Practices (BMPs)
The SWPPP is a living document reflecting current conditions and changes throughout the life of the
project. These changes may be informal (i.e., hand-written notes and deletions). Update the SWPPP
when the CESCL has noted a deficiency in BMPs or deviation from original design.
2.1 The 13 Elements
2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits
To protect adjacent properties and to reduce the area of soil exposed during construction, the limits of
construction will be clearly marked before land-disturbing activities begin. The BMPs relevant to marking
the clearing limits that will be applied for this project include:
• High-Visibility Fence (BMP C103)
Install High-Visibility Fencing at locations shown and per the details and notes on the approved
Temporary Erosion and Sediment Control Plans.
2.1.2 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 street
sweeping and street cleaning shall be employed to prevent sediment from entering state waters. The
project may plan to use the existing asphalt as a construction entrance, although demolition of the
entrance asphalt apron may require the implementation of a construction access BMP. The specific BMP
related to establishing construction access that will be used on this project include:
• Stabilized Construction Entrance (BMP C105)
The contractor shall install stabilized construction entrances at the locations and per the details shown on
the approved Temporary Erosion and Sediment Control Plans.
2.1.3 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. Construction during the wet season is expected so adequate protection
will be needed. The site proposes to utilize BMP C209, outlet projection for ditches, to control and prevent
sediment from leaving the construction site.
The project site is located west of the Cascade Mountain Crest. As such, the project must comply with
Minimum Requirement 7 (Ecology 2014). In general, discharge rates of stormwater from the site will be
controlled where increases in impervious area or soil compaction during construction could lead to
downstream erosion, or where necessary to meet local agency stormwater discharge requirements (e.g.
discharge to combined sewer systems).
Will you construct stormwater retention and/or detention facilities?
Yes No
Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-
retention, porous pavement) to control flow during construction?
Yes No
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2.1.4 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 the receiving waterbody. The project
does anticipate construction during the wet season, which w ill produce high flow rates therefore the
project will employ:
• Silt Fence (BMP C233)
• Temporary Sediment Pond (BMP C241)
Install Filter Fabric Fencing/Silt Fencing at High-Visibility Fencing locations shown and per the details and
notes on the approved Temporary Erosion and Sediment Control Plans.
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 wash off of sediments from adjacent streets in runoff.
2.1.5 Element 5: Stabilize Soils
Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion
throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project
include:
• Temporary and Permanent Seeding (BMP C120)
• Mulching (BMP C121)
• Surface Roughening (BMP C130)
The project site is located west of the Cascade Mountain Crest. From October 1 through April 30, no soils
shall remain exposed and unworked for more than 2 days. From May 1 to September 30, no soils shall
remain exposed and unworked for more than 7 days. Soils shall be stabilized at the end of the shift before
a holiday or weekend if needed based on the weather forecast. These stabilization requirements apply to
all soils onsite, whether at final grade or not. The local permitting authority may adjust these time limits if it
can be shown that a development site’s erosion and runoff potential justifies a different standard.
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 the transportation of sediment
from the construction site to receiving waters will be prevented.
In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be temporarily
covered with plastic sheeting or seeded and mulched. 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.
West of the Cascade Mountains Crest
Season Dates Number of Days Soils Can be
Left Exposed
During the Dry Season May 1 – September 30 7 days
During the Wet Season October 1 – April 30 2 days
Anticipated project dates: Start date: April 2024 End date: April 2026
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Will you construct during the wet season?
Yes No
2.1.6 Element 6: Protect Slopes
All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes erosion.
The following specific BMPs will be used to protect slopes for this project:
• Temporary and Permanent Seeding (BMP C120)
• Mulching (BMP C121)
• Surface Roughening (BMP C130)
All slopes where grading occurs or where vegetation has been removed shall be seeded per the notes
and details in the approved Temporary Erosion and Sediment Control Plans and in BMP C120. In no
case shall soils remain unworked and unstabilized for more than 7 days during the dry season (May 1 to
September 30) or more than 2 days during the wet season (October 1 to April 30).
Will steep slopes be present at the site during construction?
Yes No
2.1.7 Element 7: Protect Drain Inlets
All storm drain inlets and culverts made operable during construction shall be protected to prevent
unfiltered or untreated water from entering the drainage conveyance system. However, the first priority is
to keep all access roads clean of sediment and keep street wash water separate from entering storm
drains until treatment can be provided. The following inlet protection measures will be applied on this
project:
o Storm Drain Inlet Protection (BMP C220)
Inlet protection is the last component of a treatment train and protection of drain inlets include s additional
sediment and erosion control measures. Inlet protection devices will be cleaned (or removed and
replaced) when sediment has filled the device by one third (1/3) or as specified by the manufacturer.
Inlets will be inspected weekly at a minimum and daily during storm events.
2.1.8 Element 8: Stabilize Channels and Outlets
Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream
banks, slopes, and downstream reaches, will be installed at the outlets of all conveyance systems.
Where site runoff is to be conveyed in channels or discharged to a stream or some other natural
discharge point, efforts will be taken to prevent downstream erosion. Conveyance channels will be utilized
during construction to control stormwater runoff. Channels will be protected per BMP C202, Riprap
Channel Lining, to prevent additional sediment migration and per BMP C 209, Outlet Protection, to
prevent sediment from leaving the site.
The project site is located west of the Cascade Mountain Crest. In the event channels become necessary
to construction, all temporary on-site conveyance channels shall be designed, constructed, and stabilized
to prevent erosion from the expected 10-minute velocity of flow from a Type 1A, 10-year, 24-hour
recurrence interval storm for the developed condition. Alternatively, the 10-year, 1-hour peak flow rate
indicated by an approved continuous runoff simulation model, increased by a factor of 1.6, shall be u sed.
Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent streambanks,
slopes, and downstream reaches shall be provided at the outlets of all conveyance systems.
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2.1.9 Element 9: Control Pollutants
All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and
disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and
preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of
debris. BMPs to be implemented to control specific sources of pollutants are discussed below.
Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on -site?
Yes No
Maintenance, fueling, and/or repair of heavy equipment and vehicles required to occur on-site shall follow
the requirements listed below. If the contractor chooses to store fueling tanks or petroleum product
storage containers onsite, they will amend this SWPPP to provide total volume of fuel stored onsite, the
capacity of the second containment for each tank, and provide a Spill Prevention, C ontrol, and
Countermeasures (SPCC) Plan which complies with Federal regulations of the Clean Water Act (CWA).
Vehicles, construction equipment, and/or petroleum product storage/dispensing:
• All vehicles, equipment, and petroleum product storage/dispensing areas will be inspected
regularly to detect any leaks or spills, and to identify maintenance needs to prevent leaks or spills.
• On-site fueling tanks and petroleum product storage containers shall include secondary
containment.
• Spill prevention measures, such as drip pans, will be used when conducting maintenance and
repair of vehicles or equipment.
• In order to perform emergency repairs on-site, temporary plastic will be placed beneath and, if
raining, over the vehicle.
• Contaminated surfaces shall be cleaned immediately following any discharge or spill incident.
Will wheel wash or tire bath system BMPs be used during construction?
Yes No
Will pH-modifying sources be present on-site?
Yes No
Table 1 – pH-Modifying Sources
None
Bulk cement
Cement kiln dust
Fly ash
Other cementitious materials
New concrete washing or curing waters
Waste streams generated from concrete grinding and sawing
Exposed aggregate processes
Dewatering concrete vaults
Concrete pumping and mixer washout waters
Recycled concrete
Recycled concrete stockpiles
Other (i.e., calcium lignosulfate) [please describe: ]
Demolition:
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• Dust released from demolished sidewalks will be controlled using Dust Control measures (BMP
C140)
• Process water and slurry resulting from sawcutting and surfacing operations will be prevented
from entering the waters of the State by implementing Sawcutting and Surfacing Pollution
Prevention measures (BMP C152)
Concrete and grout:
• Process water and slurry resulting from concrete work will be prevented from entering the waters
of the State by implementing Concrete Handling measures (BMP C151)
Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches, streets, or
streams. Excess concrete must not be dumped on-site, except in designated concrete washout areas
with appropriate BMPs installed.
Will uncontaminated water from water-only based shaft drilling for construction of building, road, and
bridge foundations be infiltrated provided the wastewater is managed in a way that prohibits discharge to
surface waters?
Yes No
Sanitary wastewater:
• Portable sanitation facilities will be firmly secured, regularly maintained, and emptied when
necessary.
Solid Waste:
• Solid waste will be stored in secure, clearly marked containers.
Other:
• Other BMPs will be administered as necessary to address any additional pollutant sources onsite.
2.1.10 Element 10: Control Dewatering
Dewatering will most likely be necessary due to the high groundwater conditions at this site.
All dewatering water from open cut excavation, tunneling, foundation work, trench, or underground vaults
shall be discharged into a controlled conveyance system. Channels will be stabilized per Element #8.
Highly turbid dewatering water from soils known or suspected to be contaminated, or from use of
construction equipment, will require additional monitoring and treatment as required for the specific
pollutants based on the receiving waters into which the discharge is occurring. Such monitoring is the
responsibility of the contractor.
The dewatering of soils known to be free of contamination will trigger BMPs to trap sediment and reduce
turbidity. At a minimum, geotextile fabric socks/bags/cells will be used to filter this material. Other BMPs
to be used for sediment trapping and turbidity reduction include the following:
• Concrete Handling (BMP C151)
• Infiltration
• Use of a sedimentation bag, with outfall to a ditch or swale for small volumes of localized
dewatering
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2.1.11 Element 11: Maintain BMPs
All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained and
repaired as needed to ensure continued performance of their intended function.
Maintenance and repair shall be conducted in accordance with each particular BMP specification (see
Volume II of the SWMMWW or Chapter 7 of the SWMMEW).
Visual monitoring of all BMPs installed at the site 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 may be reduced to once every calendar
month.
All temporary ESC BMPs shall be removed within 30 days after final site stabilization is achieved or after
the temporary BMPs are no longer needed.
Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal of either
BMPs or vegetation shall be permanently stabilized.
Additionally, protection must be provided for all BMPs installed for the permanent control of stormwater
from sediment and compaction. BMPs that are to remain in place following completion of construction
shall be examined and restored to full operating condition. If sediment enters these BMPs during
construction, the sediment shall be removed and the facility shall be returned to conditions specified in
the construction documents.
2.1.12 Element 12: Manage the Project
The project will be managed based on the following principles:
• Projects will be phased to the maximum extent practicable and seasonal work limitations will be
taken into account.
• Inspection and monitoring:
o Inspection, maintenance and repair of all BMPs will occur as needed to ensure
performance of their intended function.
o Site inspections and monitoring will be conducted in accordance with Special Condition
S4 of the CSWGP. Sampling locations are indicated on the Site Map. Sampling station(s)
are located in accordance with applicable requirements of the CSWGP.
• Maintain an updated SWPPP.
o The SWPPP will be updated, maintained, and implemented in accordance with Special
Conditions S3, S4, and S9 of the CSWGP.
As site work progresses the SWPPP will be modified routinely to reflect changing site conditions. The
SWPPP will be reviewed monthly to ensure the content is current.
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.
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• Retain sediment on site.
• 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 (C162).
• Seasonal Work Limitations
• From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only
be permitted if shown to the satisfaction of the local permitting authority that silt -laden runoff will
be prevented from leaving the site through a combination of the following:
o Site conditions including existing vegetative coverage, slope, soil type, and proximity to
receiving waters; and
o Limitations on activities and the extent of disturbed areas; and
o Proposed erosion and sediment control measures.
• Based on the information provided and/or local weather conditions, the local permitting authority
may expand or restrict the seasonal limitation on site disturbance.
• The following activities are exempt from the seasonal clearing and grading limitations:
o Routine maintenance and necessary repair of erosion and sediment control BMPs;
o Routine maintenance of public facilities or existing utility structures that do not expose the
soil or result in the removal of the vegetative cover to soil; and
o Activities where there is 100 percent infiltration of surface water runoff within the site in
approved and installed erosion and sediment control facilities.
Coordination with Utilities and Other Jurisdictions
• Care has been taken to coordinate with utilities, other construction projects, and the local
jurisdiction in preparing this SWPPP and scheduling the construction work.
Inspection and Monitoring
• All BMPs shall be inspected, maintained, and repaired as needed to assure continued
performance of their intended function. Site inspections shall be conducted by a person who is
knowledgeable in the principles and practices of erosion and sediment control. This person has
the necessary skills to:
o Assess the site conditions and construction activities that could impact the quality of
stormwater, and
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o Assess the effectiveness of erosion and sediment control measures used to control the
quality of stormwater discharges.
• A Certified Erosion and Sediment Control Lead shall be on-site or on-call at all times (BMP
C160).
• Whenever inspection and/or monitoring reveals that the BMPs identified in this SWPPP are
inadequate, due to the actual discharge of or potential to discharge a significant amount of any
pollutant, appropriate BMPs or design changes shall be implemented as soon as possible.
Maintaining an Updated Construction SWPPP
• This SWPPP shall be retained on-site or within reasonable access to the site.
• The SWPPP shall be modified whenever there is a change in the design, construction, operation,
or maintenance at the construction site that has, or could have, a significant effect on the
discharge of pollutants to waters of the state.
• The SWPPP shall be modified if, during inspections or investigations conducted by the
owner/operator, or the applicable local or state regulatory authority, it is determined that the
SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges
from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs
designed to correct problems identified. Revisions to the SWPPP shall be completed within seven
(7) days following the inspection.
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs
Permeable pavements are proposed as part of this project and will require protection during construction
to reduce compaction and sedimentation. Permeable pavement areas will be marked and vehicle traffic
limited during construction. Construction runoff will be directed towards existing onsite swales to be used
as Temporary Sediment Ponds during construction prior to release to Thompson Creek. At time of
permeable pavement construction, native soils and any accumulated sediment will be over -excavated
and tested by a geotechnical engineer to ensure the long-term infiltration rate meets the design infiltration
rate.
3 Pollution Prevention Team
Table 2 – Team Information
Title Name(s) Phone Number
Certified Erosion and
Sediment Control Lead
(CESCL)
TBD TBD
Resident Engineer Hatton Godat Pantier – Chloe McIntyre (360) 943-1599
Emergency Ecology Contact Report-a-Spill Hotline (360) 407-6300
Emergency Permittee/ Owner
Contact
Evan Mann (253) 820-7835
Non-Emergency Owner
Contact
Evan Mann (253) 820-7835
Monitoring Personnel TBD TBD
Ecology Regional Office Southwest Regional Office (360) 407-6300
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4 Monitoring and Sampling Requirements
Monitoring includes visual inspection, sampling for water quality parameters of concern, and
documentation of the inspection and sampling 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
• Stormwater sampling data
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 must be maintained on-site or within reasonable access to the site and be made available upon
request to Ecology or the local jurisdiction.
Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See CSWGP
Special Condition S8 and Section 5 of this template.
4.1 Site Inspection
Site inspections will be conducted at least once every calendar week and within 24 hours following any
discharge from the site. For sites that are temporarily stabilized and inactive, the required frequency is
reduced to once per calendar month.
The discharge point(s) are indicated on the Site Map (see Appendix A) and in accordance with the
applicable requirements of the CSWGP.
4.2 Stormwater Quality Sampling
4.2.1 Turbidity Sampling
Requirements include calibrated turbidity meter or transparency tube to sample site discharges for
compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per
calendar week.
Method for sampling turbidity:
Table 3 – Turbidity Sampling Method
Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size)
Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size)
The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency less than
33 centimeters.
If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to or greater
than 6 cm, the following steps will be conducted:
1. Review the SWPPP for compliance with Special Condition S9. Make appropriate revisions within
7 days of the date the discharge exceeded the benchmark.
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2. Immediately begin the process to fully implement and maintain appropriate source control and/or
treatment BMPs as soon as possible. Address the problems within 10 days of the date the
discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible
within 10 days, Ecology may approve additional time when the Permittee requests an extension
within the initial 10-day response period.
3. Document BMP implementation and maintenance in the site log book.
If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following steps will
be conducted:
1. Telephone or submit an electronic report to the applicable Ecology Region’s Environmental
Report Tracking System (ERTS) within 24 hours.
• Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason,
Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300 or
http://www.ecy.wa.gov/programs/spills/forms/nerts_online/SWRO_nerts_online.html
2. Immediately begin the process to fully implement and maintain appropriate source control and/or
treatment BMPs as soon as possible. Address the problems within 10 days of the date the
discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible
within 10 days, Ecology may approve additional time when the Permittee requests an extension
within the initial 10-day response period
3. Document BMP implementation and maintenance in the site log book.
4. Continue to sample discharges daily until one of the following is true:
• Turbidity is 25 NTU (or lower).
• Transparency is 33 cm (or greater).
• Compliance with the water quality limit for turbidity is achieved.
o 1 - 5 NTU over background turbidity, if background is less than 50 NTU
o 1% - 10% over background turbidity, if background is 50 NTU or greater
• The discharge stops or is eliminated.
4.2.2 pH Sampling
pH monitoring is required for “Significant concrete work” (i.e., greater than 1000 cubic yards poured
concrete over the life of the project). The use of recycled concrete or engineered soils (soil amendments
including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD] or fly ash) also
requires pH monitoring.
For significant concrete work, pH sampling will start the first day concrete is poured and continue until it is
cured, typically three (3) weeks after the last pour.
For engineered soils and recycled concrete, pH sampling begins when engineered soils or recycled
concrete are first exposed to precipitation and continue s until the area is fully stabilized.
If the measured pH is 8.5 or greater, the following measures will be taken:
1. Prevent high pH water from entering storm sewer systems or surface water.
2. Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriate technology
such as carbon dioxide (CO2) sparging (liquid or dry ice).
3. Written approval will be obtained from Ecology prior to the use of chemical treatment other than
CO2 sparging or dry ice.
P a g e | 16
Method for sampling pH:
Table 4 – pH Sampling Method
pH meter
pH test kit
Wide range pH indicator paper
5 Discharges to 303(d) or Total Maximum Daily Load (TMD L)
Waterbodies
5.1 303(d) Listed Waterbodies
Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH?
Yes No
5.2 TMDL Waterbodies
Waste Load Allocation for CWSGP discharges: N/A
Discharges to TMDL receiving waterbodies will meet in -stream water quality criteria at the point of
discharge.
6 Reporting and Record Keeping
6.1 Record Keeping
6.1.1 Site Log Book
A site log book will be maintained for all on-site construction activities and will include:
• A record of the implementation of the SWPPP and other permit requirements
• Site inspections
• Sample logs
6.1.2 Records Retention
Records will be retained during the life of the project and for a minimum of three (3) years following the
termination of permit coverage in accordance with Special Condition S5.C of the CSWGP.
Permit documentation to be retained on-site:
• CSWGP
• Permit Coverage Letter
• SWPPP
• Site Log Book
Permit documentation will be provided within 14 days of receipt of a written request from Ecology. A copy
of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in
accordance with Special Condition S5.G.2.b of the CSWGP.
P a g e | 17
6.1.3 Updating the SWPPP
The SWPPP will be modified if:
• Found ineffective in eliminating or significantly minimizing pollutants in stormwater discharges
from the site.
• There is a change in design, construction, operation, or maintenance at the construction site that
has, or could have, a significant effect on the discharge of pollutants to waters of the State.
The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine additional
or modified BMPs are necessary for compliance. An updated timeline for BMP implementation will be
prepared.
6.2 Reporting
6.2.1 Discharge Monitoring Reports
Cumulative soil disturbance is one (1) acre or larger; therefore, Discharge Monitoring Reports
(DMRs) will be submitted to Ecology monthly. If there was no discharge during a given monitoring period
the DMR will be submitted as required, reporting “No Discharge”. The DMR due date is fifteen (15) days
following the end of each calendar month.
DMRs will be reported online through Ecology’s WQWebDMR System.
6.2.2 Notification of Noncompliance
If any of the terms and conditions of the permit is not met, and the resulting noncompliance may cause a
threat to human health or the environment, the following actions will be taken:
1. Ecology will be notified within 24-hours of the failure to comply by calling the applicable Regional
office ERTS phone number (Regional office numbers listed below).
2. Immediate action will be taken to prevent the discharge/pollution or otherwise stop or correct the
noncompliance. 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.
Anytime turbidity sampling indicates turbidity is 250 NTUs or greater, or water transparency is 6 cm or
less, the Ecology Regional office will be notified by phone within 24 hours of analysis as required by
Special Condition S5.A of the CSWGP.
• Southwest Region at (360) 407-6300 for Clallam, Clark, Cowlitz, Grays Harbor, Jefferson,
Lewis, Mason, Pacific, Pierce, Skamania, Thurston, or Wahkiakum
P a g e | 18
Include the following information:
1. Your name and / Phone number
2. Permit number
3. City / County of project
4. Sample results
5. Date / Time of call
6. Date / Time of sample
7. Project name
In accordance with Special Condition S4.D.5.b of the CSWGP, the Ecology Regional office will be notified
if chemical treatment other than CO2 sparging is planned for adjustment of high pH water.
P a g e | 19
Appendix/Glossary
A. Site Map
C
PERMEABLE
PAVEMENT
(TYP)
TYPE 1 CATCH
BASIN (TYP)
ROOF DRAIN (TYP)
N
HATTON
GODAT
PANTIERN.T.S.
6" PERFORATED
PIPE DISTRIBUTION
TO PERMEABLE
PAVEMENT (TYP)
SITE PLAN
ROOF DRAIN
CLEANOUT (TYP)
ROOF DRAINS TO PERMEABLE
PAVEMENT (TYP)TAHOMA BLVD SETA+20A TE55A &200E5&IAL
BERRY
VALLEY
RD SET5A&T
A
L2T
L2T
L2T
L2T
L2T
T+20A %L9' SE <EL0 :A
%E55< 9ALLE< 5' SE <EL0 :A
PERMEABLE
PAVEMENT
(TYP)
6" PERFORATED
PIPE DISTRIBUTION
TO PERMEABLE
PAVEMENT (TYP)
P a g e | 20
B. BMP Details
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-9
BMP C103: High Visibility Fence
Purpose
Fencing is intended to:
1. Restrict clearing to approved limits
2. Prevent disturbance of sensitive areas, their buffers, and other areas
required to be left undisturbed.
3. Limit construction traffic to designated construction entrances, exits or
internal roads.
4. Protect areas where survey tape markers may not provide adequate
protection.
Conditions of Use
To establish clearing limits plastic, fabric, or metal fence may be used:
x At the boundary of sensitive areas, their buffers, and other areas required
to be left uncleared.
x As necessary to control vehicle access to and on the site.
Design and Installation Specifications
High visibility plastic fence shall be composed of a high-density polyethylene material
and shall be at least 4 feet in height. Posts for the fencing shall be steel or wood and
placed every 6 feet on center (maximum) or as needed to ensure rigidity. The fencing
shall be fastened to the post every 6 inches with a polyethylene tie. The fence color
shall be high visibility orange. The fence tensile strength shall be 360 lbs./ft. using the
ASTM D4595 testing method.
If appropriate install fabric silt fence in accordance with BMP C233 to act as high
visibility fence. Silt fence shall be at least 3 feet high and must be highly visible to meet
the requirements of this BMP.
Metal fences shall be designed and installed according to the manufacturer’s
specifications. Metal fences shall be at least 3 feet high and must be highly visible.
Fences shall not be wired or stapled to trees.
Maintenance Standards
If the fence has been damaged or visibility reduced, it shall be repaired or replaced
immediately, and visibility restored.
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-10
BMP C105: Stabilized Construction Entrance/Exit
Purpose
To reduce the amount of sediment transported onto paved roads by vehicles or
equipment by constructing a stabilized pad of quarry spalls at entrances and exits for
construction sites.
Conditions of Use
Construction entrances shall be stabilized wherever traffic will enter or leave a
construction site if paved roads or other paved areas are within 1,000 feet of the site.
For residential construction, such as within a subdivision, provide stabilized construction
entrances for each residence, rather than only at the main subdivision entrance.
Stabilized surfaces shall be of sufficient length/width to provide vehicle access/parking,
based on lot size/configuration.
On large commercial, highway, and road projects, the designer should include enough
extra materials in the contract to allow for additional stabilized entrances not shown in
the initial Construction SWPPP. It is difficult to determine exactly where access to these
projects will take place; additional materials will enable the contractor to install them
where needed.
Design and Installation Specifications
See Figure II - 3.2 for details. Note: the 100 foot minimum length of the entrance shall
be reduced to the maximum practicable size when the size or configuration of the site
does not allow the full length (100 feet).
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-11
Figure II - 3.2 Stabilized Construction Entrance.
(Drawing courtesy of WSDOT Standard Plans)
Construct stabilized construction entrances with a 12-inch thick pad of 4-inch to 8-inch
quarry spalls, a 4-inch course of asphalt treated base (ATB), or use existing pavement.
Do not use crushed concrete, recycled concrete, cement, or calcium chloride for
construction entrance stabilization because these products raise pH levels in
stormwater and concrete discharge to surface waters of the State is prohibited.
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:
o Grab Tensile Strength (ASTM D4751): 200 psi min.
o Grab Tensile Elongation (ASTM D4632): 30% max.
o Mullen Burst Strength (ASTM D3786-80a): 400 psi min.
o AOS (ASTM D4751): 20-45 (U.S. standard sieve size).
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-12
x Fencing (see BMP C103) shall be installed as necessary to restrict traffic
to the construction entrance.
x 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.
x Consider early installation of the first lift of asphalt in areas that will be
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.
x Construction entrances should avoid crossing existing sidewalks and back
of walk drains. If a construction entrance must cross a sidewalk or back of
walk drain, the full length of the sidewalk and back of walk drain must be
covered and protected from sediment leaving the site.
Products Approved as Equivalent
Products approved by Ecology as equivalent to meet the requirements of BMP C105
are acceptable for use in Thurston County. The products that Ecology has approved as
functionally equivalent are available for review on Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-
permittee-guidance-resources/Emerging-stormwater-treatment-technologies
Maintenance Standards
Quarry spalls shall be added if the pad is no longer in accordance with the
specifications.
x A volume of quarry spalls equal to 5% of the surface area X the depth
must be kept on site for maintenance purposes.
x 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 replacement/cleaning of the existing
quarry spalls, street sweeping, an increase in the dimensions of the
entrance or the installation of a wheel wash.
x 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, construct a
small sump to contain the wash water if possible. Wash the sediment into
the sump where it can be controlled.
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-13
x Perform street sweeping by hand or with a high efficiency sweeper. Do not
use a non-high efficiency mechanical sweeper because this creates dust
and throws soils into storm systems or conveyance ditches.
x Any quarry spalls loosened from the pad, that end up on the roadway shall
be removed immediately.
x If vehicles are entering or exiting the site at points other than the
construction entrance(s), fencing (see BMP C103) shall be installed to
control traffic.
x Upon project completion and site stabilization, all construction accesses
intended as permanent access for maintenance shall be permanently
stabilized.
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-19
BMP C120: Temporary and Permanent Seeding
Purpose
Seeding reduces erosion by stabilizing exposed soils. A well-established vegetative
cover is one of the most effective methods of reducing erosion.
Conditions of Use
x Seeding shall be used throughout the project on disturbed areas that have
reached final grade or that will remain unworked for more than 30 days.
x The optimum seeding windows for western Washington are April 1
through June 30 and September 1 through October 1.
x Between July 1 and August 30 seeding requires irrigation until 75 percent
grass cover is established.
x Between October 1 and March 30 seeding requires a cover of mulch or an
erosion control blanket until 75 percent grass cover is established.
x Mulch is required at all times for seeding because it protects seeds from
heat, moisture loss, and transport due to runoff. Mulch can be applied on
top of the seed or simultaneously by hydroseeding. See BMP C121:
Mulching for specifications.
x All disturbed areas shall be reviewed in late August to early September
and all seeding should be completed by the end of September.
Otherwise, vegetation will not establish itself enough to provide more than
average protection.
x At final site stabilization, all disturbed areas not otherwise vegetated or
stabilized shall be seeded and mulched. Final stabilization means the
completion of all soil disturbing activities at the site and the establishment
of a permanent vegetative cover, or equivalent permanent stabilization
measures (such as pavement, riprap, gabions or geotextiles) which will
prevent erosion. See BMP LID.02: Post-Construction Soil Quality and
Depth
Design and Installation Specifications
General
x Install channels intended for vegetation before starting major earthwork and
hydroseed with a Bonded Fiber Matrix. For vegetated channels that will have
high flows, install erosion control blankets over hydroseed. Before allowing
water to flow in vegetated channels, establish 75 percent vegetation cover. If
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-20
vegetated channels cannot be established by seed before water flow; install
sod in the channel bottom – over hydromulch and erosion control blankets.
x To prevent seed from being washed away, confirm that all required surface
water control measures have been installed.
x Hydroseed applications shall include a minimum of 1,500 pounds per acre of
mulch with 2 percent tackifier. See BMP C121: Mulching for specifications.
x Areas that will have seeding only and not landscaping may need compost or
meal-based mulch included in the hydroseed in order to establish vegetation.
Re-install native topsoil or use BMP LID.02 - Post-Construction Soil Quality
and Depth on the disturbed soil surface before application.
x When installing seed via hydroseeding operations, only about 1/3 of the seed
actually ends up in contact with the soil surface. This reduces the ability to
establish a good stand of grass quickly. To overcome this, consider
increasing see quantities by up to 50 percent.
Roughening and Rototilling
x The seedbed should be firm and rough. All soil shall be roughened
regardless of slope. If compaction is required for engineering purposes,
slopes must be track walked before seeding. Backblading or smoothing of
slopes greater than 4:1 is not allowed if they are to be seeded.
x New and more effective restoration-based landscape practices rely on
deeper incorporation than that provided by a simple single-pass rototilling
treatment. Wherever practical, initially rip the subgrade to improve long-
term permeability, infiltration, and water inflow qualities. At a minimum,
permanent areas shall use BMP LID.02 - Post-Construction Soil Quality
and Depth to achieve organic matter and permeability performance
defined in engineered soil/landscape systems. For systems that are
deeper than 8 inches, perform the rototilling process in multiple lifts, or the
prepared soil system shall be prepared properly and then placed to
achieve the specified depth.
Fertilizers
x Organic matter is the most appropriate form of “fertilizer” because it
provides nutrients (including nitrogen, phosphorus, and potassium) in the
least water-soluble form. A natural system typically releases 2 to
10 percent of its nutrients annually. Chemical fertilizers have since been
formulated to simulate what organic matter does naturally.
x In general, 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer can be
used at a rate of 90 pounds per acre. Slow-release fertilizers should
always be used because they are more efficient and have fewer
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-21
environmental impacts. It is recommended that areas being seeded for
final landscaping conduct soil tests to determine the exact type and
quantity of fertilizer needed. This will prevent the over-application of
fertilizer. Fertilizer should not be added to the hydromulch machine or
agitated more than 20 minutes before it is to be used. If agitated too
much, the slow-release coating is destroyed. Do not use fertilizers in areas
that have been amended with compost or used BMP LID.02 - Post-
Construction Soil Quality and Depth.
x There are numerous products available on the market that take the place
of chemical fertilizers. These include several with seaweed extracts that
are beneficial to soil microbes and organisms. If 100 percent cottonseed
meal is used as the mulch in hydroseed, chemical fertilizer may not be
necessary. Cottonseed meal is a good source of long-term, slow-release,
available nitrogen.
Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix
x On steep slopes, use bonded fiber matrix (BFM) or mechanically bonded fiber
matrix (MBFM) products. BFM/MBFM products are applied at a minimum rate of
3,000 pounds per acre of mulch with approximately 10 percent tackifier.
Application is made so that a minimum of 95 percent soil coverage is achieved.
Numerous products are available commercially and should be installed per
manufacturer’s instructions. Most products require 24 to 36 hours to cure before
a rainfall and cannot be installed on wet or saturated soils. Generally, these
products come in 40 to 50 pound bags and include all necessary ingredients
except for seed and fertilizer.
x Install products per manufacturer’s instructions.
x BFMs and MBFMs have some advantages over blankets, including:
o No surface preparation required
o Can be installed via helicopter in remote areas
o On slopes steeper than 2.5:1, blanket installers may need to be
roped and harnessed for safety
o BFMs and MBFMs are at least $1,000 per acre cheaper to install.
x In most cases, the shear strength of blankets is not a factor when used on
slopes, only when used in channels. BFMs and MBFMs are good alternatives to
blankets in most situations where vegetation establishment is the goal.
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-22
Seeding and Seed Mixtures
x When installing seed via hydroseeding operations, only about 1/3 of the seed
actually ends up in contact with the soil surface. This reduces the ability to
establish a good stand of grass quickly. One way to overcome this is to increase
seed quantities by up to 50 percent.
x Vegetation establishment can also be enhanced by dividing the hydromulch
operation into two phases:
o Phase 1 – Install all seed and fertilizer with 25 to 30 percent mulch and
tackifier onto soil in the first lift;
o Phase 2 – Install the rest of the mulch and tackifier over the first lift.
Or, enhance vegetation by:
o Installing the mulch, seed, fertilizer, and tackifier in one lift.
o Spread or blow straw over the top of the hydromulch at a rate of about
800 to 1,000 pounds per acre.
o Hold straw in place with a standard tackifier.
Both of these approaches will increase cost moderately but will greatly improve
and enhance vegetative establishment. The increased cost may be offset by the
reduced need for:
o Irrigation
o Reapplication of mulch
o Repair of failed slope surfaces.
This technique works with standard hydromulch (1,500 pounds per acre
minimum) and Bonded Fiber Matrix/Mechanically Bonded Fiber Matrix
BFM/MBFMs (3,000 pounds per acre minimum).
x Seed installed as a temporary measure may be installed by hand if it will be
covered by straw, mulch, or topsoil. Seed installed as a permanent measure
may be installed by hand on small areas (usually less than 1 acre) that will be
covered with mulch, topsoil, or erosion blankets.
x The seed mixes listed below include recommended mixes for both temporary and
permanent seeding. These mixes, with the exception of the wet area seed mix,
shall be applied at a rate of 120 pounds per acre. This rate can be reduced if soil
amendments or slow-release fertilizers are used. Apply the wet area seed mix at
a rate of 60 pounds per acre.
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-23
x Consult local suppliers or the Thurston County Conservation District for
recommendations because the appropriate mix depends on a variety of factors,
including location, exposure, soil type, slope, and expected foot traffic.
Alternative seed mixes approved by the County may be used.
x Table II - 3.2 represents the standard mix for those areas where just a temporary
vegetative cover is required.
Table II - 3.2 Temporary Erosion Control Seed Mix
%
Weight
%
Purity
%
Germination
Chewings or annual blue grass
Festuca rubra var. commutata or Poa anna
40 98 90
Perennial rye
Lolium perenne
50 98 90
Redtop or colonial bentgrass
Agrostis alba or Agrostis tenuis
5 92 85
White dutch clover
Trifolium repens
5 98 90
x Table II - 3.3 Provides just one recommended possibility for landscaping seed.
Table II - 3.3 Landscaping Seed Mix
%
Weight
%
Purity
%
Germination
Perennial rye blend
Lolium perenne
70 98 90
Chewings and red fescue blend
Festuca rubra var. commutata or Festuca rubra
30 98 90
x This turf seed mix in Table II - 3.4 is for dry situations where there is no
need for much water. The advantage is that this mix requires very little
maintenance.
Table II - 3.4 Low-Growing Turf Seed Mix
%
Weight
%
Purity
%
Germination
Dwarf tall fescue (several varieties)
Festuca arundinacea var.
45 98 90
Dwarf perennial rye (Barclay)
Lolium perenne var. barclay
30 98 90
Red fescue
Festuca rubra
20 98 90
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-24
Colonial bentgrass
Agrostis tenuis
5 98 90
x Table II - 3.5 presents a mix recommended for bioswales and other
intermittently wet areas.
Table II - 3.5 Bioswale Seed Mixa
%
Weight
%
Purity
%
Germination
Tall or meadow fescue
Festuca arundinacea or Festuca elatior
75-80 98 90
Seaside/Creeping bentgrass
Agrostis palustris
10-15 92 85
Redtop bentgrass
Agrostis alba or Agrostis gigantea
5-10 90 80
a Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix
x The seed mix shown in Table II - 3.6 is a recommended low-growing,
relatively non-invasive seed mix appropriate for very wet areas that are
not regulated wetlands. Other mixes may be appropriate, depending on
the soil type and hydrology of the area. Recent research suggests that
bentgrass (agrostis sp.) should be emphasized in wet-area seed mixes.
Apply this mixture at a rate of 60 pounds per acre.
Table II - 3.6 Wet Area Seed Mix
%
Weight
%
Purity
%
Germination
Tall or meadow fescue
Festuca arundinacea or Festuca elatior
60-70 98 90
Seaside/Creeping bentgrass
Agrostis palustris
10-15 98 85
Meadow foxtail
Alepocurus pratensis
10-15 90 80
Alsike clover
Trifolium hybridum
1-6 98 90
Redtop bentgrass
Agrostis alba
1-6 92 85
a Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix
x The meadow seed mix in Table II - 3.7 is recommended for areas that will
be maintained infrequently or not at all and where native plant colonization
is desired. Likely applications include rural road and utility right-of-way.
Seeding should take place in September or very early October in order to
obtain adequate establishment prior to the winter months. The
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-25
appropriateness of clover in the mix may need to be considered, as this
can be a fairly invasive species. If the soil is amended, the addition of
clover may not be necessary.
Table II - 3.7 Meadow Seed Mix
%
Weight
%
Purity
%
Germination
Redtop or Oregon bentgrass
Agrostis alba or Agrostis oregonensis
20 92 85
Red fescue
Festuca rubra
70 98 90
White dutch clover
Trifolium repens
10 98 90
Maintenance Standards
x Reseed any seeded areas that fail to establish at least 80 percent cover
(100 percent cover for areas that receive sheet or concentrated flows).
x If reseeding is ineffective, an alternate method, such as sodding,
mulching, or nets/blankets shall be used.
x If winter weather prevents adequate grass growth, time limits may be
relaxed at the discretion of the County when sensitive areas would
otherwise be protected.
x After adequate cover is achieved, any areas that experience erosion shall
be reseeded and protected by mulch. If the erosion problem is drainage
related, the problem shall be fixed, and the eroded area reseeded and
protected by mulch.
x Supply seeded areas with adequate moisture, but do not water to the
extent that it causes runoff.
Products Approved as Equivalent
Products approved by Ecology as equivalent to meet the requirements of BMP C120
are acceptable for use in Thurston County. The approved products are available for
review on Ecology’s website at:
https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-
permittee-guidance-resources/Emerging-stormwater-treatment-technologies
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-26
BMP C121: Mulching
Purpose
To provide immediate temporary protection from erosion. Mulch also enhances plant
establishment by conserving moisture and holding fertilizer, seed, and topsoil in place,
and moderating soil temperatures. There is an enormous variety of mulches, but only
the most common types are discussed in this section.
Conditions of Use
As a temporary cover measure, use mulch:
x On disturbed areas that require cover measures for less than 30 days.
x At all times for seeded areas, especially during the wet season and hot
summer months.
x During the wet season on slopes steeper than 3H:1V with more than 10
feet of vertical relief.
Mulch may be applied at any time of the year and must be refreshed periodically.
For seeded areas mulch may be made up of 100 percent:
x cottonseed meal;
x fibers made from wood, recycled cellulose, hemp, kenaf;
x compost;
x or blends of these.
Tackifier shall be plant-based, such a guar or alpha plantago, or chemical-based such
as polyacrylamide or polymers.
Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of
application.
Recycled cellulose may contain polychlorinated biphenyl (PCBs). Ecology recommends
that products should be evaluated for PCBs prior to use.
Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of
use. PAM shall not be directly applied to water or allowed to enter a water body.
Any mulch or tackifier product used shall be installed per manufacturer’s instructions.
THURSTON COUNTY DRAINAGE DESIGN AND EROSION CONTROL MANUAL
June 2022 Volume II – Construction Stormwater Pollution Prevention 3-27
Design and Installation Specifications
For mulch materials, application rates, and specifications, see Table II - 3.8. Consult
with the local supplier or the local conservation district for their recommendations.
Increase the application rate until the ground is 95% covered (i.e. not visible under the
mulch layer). Note: Thicknesses may be increased for disturbed areas in or near
sensitive areas or other areas highly susceptible to erosion.
Mulch used within the ordinary high-water mark of surface waters should be selected to
minimize potential flotation of organic matter. Composted organic materials have higher
specific gravities (densities) than straw, wood, or chipped material. Consult with WDFW
as part of the Hydraulic Project Approval for mulch mixes allowed, if applicable.
Where the option of “Compost” is selected, it should be a coarse compost that meets
the following size gradations when tested in accordance with the U.S. Composting
Council “Test Methods for the Examination of Compost and Composting” (TMECC) Test
Method 02.02-B.
Coarse Compost
x Minimum Percent passing 3” sieve openings 100%
x Minimum Percent passing 1” sieve openings 90%
x Minimum Percent passing ¾” sieve openings 70%
x Minimum Percent passing ¼” sieve openings 40%
Maintenance Standards
x The thickness of the cover must be maintained.
x Any areas that experience erosion shall be re-mulched 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 re-mulched.
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Table II - 3.8 Mulch Standards and Guidelines
Mulch
Material Quality Standards
Application
Rates Remarks
Straw Air-dried; free from
undesirable seed and
coarse material.
2 to 3 inches
thick; 5 bales
per 1,000 sf or
2 to 3 tons per
acre
Cost-effective when applied with adequate
thickness. Hand-application requires
greater thickness than blown straw. Straw
thickness 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 since light winds will
blow it away. Straw, however, has several
deficiencies to consider when selecting
mulch materials. It often introduces and/or
encourages the propagation of weed
species and has no significant long-term
benefits. Use straw only if mulches with
long-term benefits are unavailable. It also
shall not be used within the ordinary high-
water elevation of surface waters (due to
flotation).
Hydromulch No growth inhibiting
factors.
Approx. 25-30
lbs per 1,000 sf
or 1,500-2,000
lbs per acre
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 3/4 to 1
inch clog hydromulch equipment. Keep
fibers to less than 3/4 inch.
Composted
Mulch and
Compost
No visible water or dust
during handling. Must be
purchased from supplier
with Solid Waste
Handling Permit (unless
exempt) and produced in
accordance with WAC
173-350.
2-in thick min.;
approx. 100
tons per acre
(approx. 800 lbs
per yard)
Increase thickness to 3 inches to improve
effectiveness. 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. Do not use composted mulch
near wetlands or near phosphorous
impaired water bodies.
Chipped Site
Vegetation
Average size shall be
several inches.
Gradations from fines to
6 inches in length for
texture, variation, and
interlocking properties.
2-in thick min. A cost-effective way to dispose of debris
from clearing and grubbing, and eliminates
problems associated with burning. Should
not be used on slopes above about 10
percent because of its tendency to be
transported by runoff. 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.
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Mulch
Material Quality Standards
Application
Rates Remarks
Wood-based
Mulch or
Wood Straw
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.
2-in. thick min.;
approx. 100
tons per acre
(approx. 800
lbs. per cubic
yard)
Often called “hog or hogged fuel.” 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).
Wood Strand
Mulch
A blend of loose, long,
thin wood pieces derived
from native conifer or
deciduous trees with high
length-to-width ratio.
2-in. thick min. Cost-effective protection when applied with
adequate thickness. A minimum of 95-
percent of the wood strand shall have
lengths between 2 and 10 inches, with a
width and thickness between 1/16 and 3/8-
inches. The mulch shall not contain resin,
tannin, or other compounds in quantities
that would be detrimental to plant life.
Sawdust or wood shavings shall not be
used as mulch. (WSDOT specification 9-
14.4(4))
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BMP C130: Surface Roughening
Purpose
To aid in the establishment of vegetative cover, reduce runoff velocity, increase
infiltration, and provide for sediment trapping through the provision of a rough soil
surface. Horizontal depressions are created by operating a tiller or other suitable
equipment on the contour or by leaving slopes in a roughened condition by not fine
grading them.
Use this BMP in conjunction with other BMPs such as seeding, mulching, or sodding.
Conditions for Use
x All slopes steeper than 3:1 and greater than 5 vertical feet require surface
roughening to a depth of 2 to 4 inches prior to seeding.
x Areas that will not be stabilized immediately may be roughened to reduce
runoff velocity until seeding takes place.
x Slopes with a stable rock face do not require roughening.
x Slopes where mowing is planned should not be excessively roughened.
Design and Installation Specifications
There are different methods for achieving a roughened soil surface on a slope, and the
selection of an appropriate method depends upon the type of slope. Roughening
methods include stair-step grading, grooving, contour furrows, and tracking. See Figure
II - 3.2 for tracking and contour furrows. Factors to be considered in choosing a method
are slope steepness, mowing requirements, and whether the slope is formed by cutting
or filling.
x Disturbed areas that will not require mowing may be stair-step graded,
grooved, or left rough after filling.
x Stair-step grading is particularly appropriate in soils containing large
amounts of soft rock. Each “step” catches material that sloughs from
above and provides a level site where vegetation can become established.
Stairs should be wide enough to work with standard earth moving
equipment. Stair steps must be on contour or gullies will form on the
slope.
x Areas that will be mowed (these areas should have slopes less steep than
3:1) may have small furrows left by disking, harrowing, raking, or seed-
planting machinery operated on the contour.
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Figure II - 3.2 Surface Roughening by Tracking and Contour Furrows
x Graded areas with slopes greater than 3:1 but less than 2:1 shall be
roughened before seeding. This can be accomplished in a variety of
ways, including "track walking," or driving a crawler tractor up and down
the slope, leaving a pattern of cleat imprints parallel to slope contours.
x Tracking is done by operating equipment up and down the slope to leave
horizontal depressions in the soil.
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Maintenance Standards
x Areas that are surfaced roughened should be seeded as quickly as
possible.
x Regular inspections should be made of the area. If rills appear, re-
roughen and re-seed immediately.
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BMP C140: Dust Control
Purpose
To prevent wind transport of dust from disturbed soil surfaces onto roadways, drainage
ways, and surface waters.
Conditions of Use
Dust control must be used in areas (including roadways) subject to surface and air
movement of dust, where on-site and off-site impacts to roadways, drainage ways or
surface waters are likely.
Design and Installation Specifications
x Vegetate or mulch areas that will not receive vehicle traffic. In areas
where planting, mulching, or paving is impractical, apply gravel or
landscaping rock.
x Limit dust generation by clearing only those areas where immediate
activity will take place, leaving the remaining area(s) in the original
condition, if stable. Maintain the original ground cover as long as
practical.
x Construct natural or artificial windbreaks or windscreens. These may be
designed as enclosures for small dust sources.
x Sprinkle the site with water until surface is wet. Repeat as needed. To
prevent carryout of mud onto street, see Stabilized Construction Entrance
(BMP C105).
x Irrigation water can be used for dust control. Install irrigation systems as a
first step on sites where dust control is a concern.
x Spray exposed soil areas with a dust palliative, following the
manufacturer’s instructions and cautions regarding handling and
application. Oil based products are prohibited from use as a dust
suppressant. The County may approve other dust palliatives such as
calcium chloride or PAM.
x PAM (BMP C126) added to water at a rate of 0.5 lbs. per 1,000 gallons of
water per acre and applied from a water truck is more effective than water
alone. This is due to the increased infiltration of water into the soil and
reduced evaporation. In addition, small soil particles are bonded together
and are not as easily transported by wind. Adding PAM may actually
reduce the quantity of water needed for dust control. PAM has also
shown to be relatively affordable and thus an extremely cost-effective dust
control method.
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x Techniques that can be used for unpaved roads and lots include:
o Lower speed limits. High vehicle speed increases the amount of
dust stirred up from unpaved roads and lots.
o Upgrade the road surface strength by improving particle size,
shape, and mineral types that make up the surface and base
materials.
o Add surface gravel to reduce the source of dust emission. Limit the
amount of fine particles (those smaller than .075 mm) to 10 to
20 percent.
o Use geotextile fabrics to increase the strength of new roads or
roads undergoing reconstruction.
o Encourage the use of alternate, paved routes, if available.
o Restrict roadway use by tracked vehicles and heavy trucks to
prevent damage to road surface and base.
o Apply chemical dust suppressants using the admix method,
blending the product with the top few inches of surface material.
Suppressants may also be applied as surface treatments.
o Pave unpaved permanent roads and other trafficked areas.
o Use vacuum street sweepers.
o Remove mud and other dirt promptly so it does not dry and then
turn into dust.
o Limit dust-causing work on windy days.
x Contact the Olympic Region Clean Air Agency (ORCAA) for guidance and
training on other dust control measures. Compliance with the ORCAA
constitutes compliance with this BMP.
Maintenance Standards
Respray area as necessary to keep dust to a minimum.
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BMP C151: Concrete Handling
Purpose
Concrete work can generate process water and slurry that contain fine particles and
high pH, both of which can violate water quality standards in the receiving water.
Concrete spillage or concrete discharge to surface waters of the State is prohibited.
Use this BMP to minimize and eliminate concrete, concrete process water, and concrete
slurry from entering waters of the State.
Conditions of Use
Any time concrete is used; these management practices shall be utilized, since concrete
work can generate process water and slurry that contain fine particles and high pH, both
of which can violate water quality standards in the receiving water.
Concrete construction projects include, but are not limited to, the following:
x Curbs
x Sidewalks
x Roads
x Bridges
x Foundations
x Floors
x Runways
Disposal options for concrete, in order of preference are:
1. Off-site disposal locations
2. Concrete wash-out areas (see BMP C154: Concrete Washout Area)
3. De minimis washout to formed areas awaiting concrete
Design and Installation Specifications
x Washout concrete truck drums at an approved off-site location or in
designated concrete washout areas only. Do not wash out concrete trucks
onto the ground (including formed areas awaiting concrete), or into storm
drains, open ditches, streets, or streams. Refer to BMP C154 for
information on concrete washout areas.
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o Unused concrete remaining in the truck and pump shall be
returned to the originating batch plant for recycling, as feasible.
Do not dump excess concrete on site, except in designated
concrete washout areas as allowed in BMP C154.
x Small concrete handling equipment (e.g., hand tools screeds, shovels,
rakes, floats, trowels, and wheelbarrows) shall be washed into designated
concrete washout areas or into formed areas awaiting concrete pour.
x At no time shall concrete be washed off into the footprint of an area where
an infiltration feature will be installed.
x Equipment that cannot be easily moved, such as concrete paving
machines, shall only be washed in areas that do not directly drain to
natural or constructed stormwater conveyances or potential infiltration
areas.
x Do not allow washwater from areas, such as concrete aggregate
driveways, to drain directly (without detention or treatment) to natural or
constructed stormwater conveyances.
x When no designated concrete washout areas (or formed areas, allowed
as described above) are available, contain washwater and leftover product
in a lined container. Lining shall be a minimum of 10-mil polyethylene
sheeting and shall be free of holes, tears, or other defects that
compromise the impermeability of the material. Dispose of contained
concrete and concrete washwater (process water) in a manner that does
not violate groundwater or surface water quality standards.
x Always use forms or solid barriers for concrete pours, such as pilings,
within 15-feet of surface waters.
x Refer to BMPs C252: Treating and Disposing of High pH Water for pH
adjustment requirements.
x Refer to the Construction Stormwater General Permit (CSWGP) for pH
monitoring requirements if the project involves one of the following
activities:
o Significant concrete work (as defined in the CSWGP).
o The use of soils amended with (but not limited to) Portland cement-
treated base, cement kiln dust or fly ash.
o Discharging stormwater to segments of water bodies on the 303(d)
list (Category 5) for high pH.
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Maintenance Standards
Check containers for holes in the liner daily during concrete pours and repaired the
same day.
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BMP C152: Sawcutting and Surfacing Pollution Prevention
Purpose
Sawcutting or surfacing operations generate slurry and process water that contains fine
particles and high pH (concrete cutting), both of which can violate the water quality
standards in the receiving water. Concrete spillage or concrete discharge to surface
waters of the State is prohibited. Use this BMP to minimize and eliminate process water
and slurry from entering waters of the State.
Conditions of Use
Utilize these management practices anytime sawcutting and surfacing operations take
place. Sawcutting and surfacing operations include, but are not limited to, the following:
x Sawing
x Coring
x Grinding
x Roughening
x Hydro-demolition
x Bridge and road surfacing
Design and Installation Specifications
x Vacuum slurry and cuttings during cutting and surfacing operations.
x Slurry and cuttings shall not remain on permanent concrete or asphalt
pavement overnight.
x Slurry and cuttings shall not drain to any natural or constructed drainage
conveyance including stormwater systems. This may require temporarily
blocking catch basins.
x Dispose collected slurry and cuttings in a manner that does not violate
groundwater or surface water quality standards.
x Do not allow process water that is generated during hydro-demolition,
surface roughening or similar operations to drain to any natural or
constructed drainage conveyance including stormwater systems and
dispose it in a manner that does not violate groundwater or surface water
quality standards.
x Handle and dispose cleaning waste material and demolition debris in a
manner that does not cause contamination of water. If the area is swept
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with a pick-up sweeper, haul the material out of the area to an appropriate
disposal site.
Maintenance Standards
Continually monitor operations to determine whether slurry, cuttings, or process water
could enter waters of the state. If inspections show that a violation of water quality
standards could occur, stop operations and immediately implement preventive
measures such as berms, barriers, secondary containment, and/or vacuum trucks.
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BMP C154: Concrete Washout Area
Purpose
To prevent or reduce the discharge of pollutants to stormwater from concrete waste by
conducting washout off-site or performing on-site washout in a designated area to
prevent pollutants from entering surface waters or groundwater.
Conditions of Use
Concrete washout area best management practices are implemented on construction
projects where:
x Concrete is used as a construction material
x It is not possible to dispose of all concrete wastewater and washout off-
site (ready mix plant, etc.).
x Concrete truck drums are washed on-site.
Note that auxiliary concrete truck components (e.g. chutes and hoses) and small
concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels,
and wheelbarrows) may be washed into formed areas awaiting concrete pour. At no
time shall concrete be washed off into the footprint of an area where an infiltration
feature will be installed.
Design and Installation Specifications
Implementation
The following steps will help reduce stormwater pollution from concrete wastes:
x Perform washout of concrete truck drums at an approved off-site location
or in designated concrete washout areas only.
x Do not wash out concrete onto non-formed areas, or into storm drains,
open ditches, streets, or streams.
x Wash equipment difficult to move, such as concrete paving machines, in
areas that do not directly drain to natural or constructed stormwater
conveyance or potential infiltration areas.
x Do not allow excess concrete to be dumped on-site, except in designated
concrete washout areas as allowed above.
x Concrete washout areas may be prefabricated concrete washout
containers, or self-installed structures (above-grade or below-grade).
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x Prefabricated containers are most resistant to damage and protect against
spills and leaks. Companies may offer delivery service and provide
regular maintenance and disposal of solid and liquid waste.
x If self-installed concrete washout areas are used, below-grade structures
are preferred over above-grade structures because they are less prone to
spills and leaks.
x Self-installed above-grade structures should only be used if excavation is
not practical.
x Construct and maintain concrete washout areas in sufficient quantity and
size to contain all liquid and concrete waste generated by washout
operations.
Education
x Discuss the concrete management techniques described in this BMP with
the ready-mix concrete supplier before any deliveries are made.
x Educate employees and subcontractors on the concrete waste
management techniques described in this BMP.
x Arrange for contractor’s superintendent or Certified Erosion and Sediment
Control Lead (CESCL) to oversee and enforce concrete waste
management procedures.
x A sign shall be installed adjacent to each temporary concrete washout
facility to inform concrete equipment operators to utilize the proper
facilities.
Contracts
Incorporate requirements for concrete waste management into concrete supplier and
subcontractor agreements.
Location and Placement
x Locate concrete washout areas at least 50 feet from sensitive areas such
as storm drains, open ditches, water bodies, or wetlands.
x Allow convenient access to the concrete washout area for concrete trucks,
preferably near the area where the concrete is being poured.
x If trucks need to leave a paved area to access the concrete washout area,
prevent track-out with a pad of rock or quarry). These areas should be far
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enough away from other construction traffic to reduce the likelihood of
accidental damage and spills.
x The number of concrete washout areas you install should depend on the
expected demand for storage capacity.
x On large sites with extensive concrete work, concrete washout areas
should be placed in multiple locations for ease of use by concrete truck
drivers.
Concrete Truck Washout Procedures
x Perform washout of concrete truck drums in designated concrete washout
areas only.
x Concrete washout from concrete pumper bins can be washed into
concrete pumper trucks and discharged into designated concrete washout
areas or properly disposed of off-site.
Concrete Washout Area Installation
x Concrete washout areas should be constructed as shown on the details
below, with a recommended minimum length and width of 10 feet, but with
sufficient quantity and volume to contain all liquid and concrete waste
generated by washout operations.
x Plastic lining material shall be a minimum of 10 mil polyethylene sheeting and
should be free of holes, tears, or other defects that compromise the
impermeability of the material.
x Lath and flagging should be commercial type.
x Liner seams shall be installed in accordance with manufacturers’
recommendations.
x Soil base shall be prepared free of rocks or other debris that may cause tears
or holes in the plastic lining material.
Maintenance Standards
Inspection and Maintenance
x Inspect and verify that concrete washout areas are in place prior to the
commencement of concrete work. Once concrete wastes are washed into
the designated washout area and allowed to harden, the concrete should
be broken up, removed, and disposed of per applicable solid waste
regulations. Dispose of hardened concrete on a regular basis.
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x During periods of concrete work, inspect daily to verify continued
performance.
x Check overall condition and performance.
x Check remaining capacity (% full).
x If using self-installed washout facilities, verify plastic liners are
intact and sidewalls are not damaged.
x If using prefabricated containers, check for leaks.
x Concrete washout areas shall be maintained to provide adequate holding
capacity with a minimum freeboard of 12 inches.
x Concrete washout areas must be cleaned, or new facilities must be
constructed and ready for use once the washout is 75% full.
x If the concrete washout area is nearing capacity, vacuum and dispose of
the waste material in an approved manner.
x Do not discharge liquid or slurry to waterways, storm drains, or
directly onto the ground.
x Do not use sanitary sewer without local sewer service provider
approval.
x Place a secure, non-collapsing, non-water collecting cover over the
concrete washout facility prior to predicted wet weather to prevent
accumulation and overflow of precipitation.
x Remove and dispose of hardened concrete and return the structure
to a functional condition. Concrete may be reused on-site or
hauled away for disposal or recycling.
x When you remove materials from a self-installed concrete washout area,
build a new structure; or, if the previous structure is still intact, inspect for
signs of weakening or damage, and make any necessary repairs. Re-line
the structure with new plastic after each cleaning.
Removal of Concrete Washout Areas
x When concrete washout areas are no longer required for the work, the
hardened concrete, slurries and liquids shall be removed and properly
disposed of.
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x Materials used to construct temporary concrete washout areas shall be
removed from the site of the work and disposed of or recycled.
x Holes, depressions or other ground disturbance caused by the removal of
the concrete washout areas shall be backfilled, repaired, and stabilized to
prevent erosion.
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Figure II - 3.4 Concrete Washout Area with Wood Planks
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Figure II - 3.5 Concrete Washout Area with Straw Bales
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Figure II - 3.6 Prefabricated Concrete Washout Container w/Ramp
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BMP C160: Certified Erosion and Sediment Control Lead
Purpose
To ensure compliance with all local, state, and federal erosion and sediment control and
water quality requirements by designating at least one person as the responsible
representative in charge of erosion and sediment control (ESC), and water quality
protection. The designated person shall be the Certified Erosion and Sediment Control
Lead (CESCL).
Conditions of Use
A CESCL shall be made available on projects disturbing ground 1 acre or larger and
that discharge stormwater to surface waters of the state. Sites less than one acre may
have a person without CESCL certification conduct inspections; sampling is not required
on sites that disturb less than an acre.
The CESCL shall:
x Have a current certificate proving attendance in an erosion and sediment
control training course that meets the minimum ESC training and
certification requirements established by Ecology (see Ecology’s 2012
Stormwater Management Manual for Western Washington for details).
Ecology will maintain a list of ESC training and certification providers at:
https://ecology.wa.gov/Regulations-Permits/Permits-
certifications/Certified-erosion-sediment-control
OR
x Be a Certified Professional in Erosion and Sediment Control (CPESC); for
additional information go to: http://www.envirocertintl.org/cpesc/
Specifications
x CESCL certification shall remain valid for 3 years.
x The CESCL shall have authority to act on behalf of the contractor or
project proponent and shall be available, or on call, 24 hours per day
throughout the period of construction.
x The Construction SWPPP shall include the name, telephone number, fax
number, and address of the designated CESCL.
x A CESCL may provide inspection and compliance services for multiple
construction projects in the same geographic region but must be on site
whenever earthwork activities are occurring that could generate release of
turbid water.
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x Duties and responsibilities of the CESCL shall include, but are not limited to
the following:
x Maintaining permit file on site at all times which includes the
Construction SWPPP and any associated permits and plans.
x Directing BMP installation, inspection, maintenance, modification, and
removal.
x Updating all project drawings and the Construction SWPPP with
changes made.
x Completing any sampling requirements including reporting results
using electronic Discharge Monitoring Reports (WebDMR). Keeping
daily logs, and inspection reports. Inspection reports shall include:
o Inspection date/time.
o Weather information; general conditions during inspection and
approximate amount of precipitation since the last inspection.
o A summary or list of all BMPs implemented, including
observations of all erosion/sediment control structures or
practices. The following shall be noted:
1. Locations of BMPs inspected
2. Locations of BMPs that need maintenance
3. Locations of BMPs that failed to operate as designed or
intended
4. Locations of where additional or different BMPs are
required.
x Visual monitoring results, including a description of discharged
stormwater. The presence of suspended sediment, turbid water,
discoloration, and oil sheen shall be noted, as applicable.
x Any water quality monitoring performed during inspection.
x General comments and notes, including a brief description of any
BMP repairs, maintenance or installations made as a result of the
inspection.
x Facilitate, participate in, and take corrective actions resulting from
inspections performed by outside agencies or the owner.
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BMP C162: Scheduling
Purpose
To reduce the amount and duration of soil exposed to erosion by wind, rain, runoff, and
vehicle tracking by sequencing a construction project.
Conditions of Use
The construction sequence schedule is an orderly listing of all major land-disturbing
activities together with the necessary erosion and sedimentation control measures
planned for the project. This type of schedule guides the contractor on work to be done
before other work is started so that serious erosion and sedimentation problems can be
avoided.
Following a specified work schedule that coordinates the timing of land-disturbing
activities and the installation of control measures is perhaps the most cost-effective way
of controlling erosion during construction. The removal of surface ground cover leaves
a site vulnerable to accelerated erosion. Construction procedures that limit land
clearing, provide timely installation of erosion and sedimentation controls, and restore
protective cover quickly can significantly reduce the erosion potential of a site.
Design Considerations
x Avoid construction during rainy periods.
x Schedule projects to disturb only small portions of the site at any one time.
x Complete grading as soon as possible.
x Immediately stabilize the disturbed portion before grading the next portion.
x Practice staged seeding in order to revegetate cut and fill slopes as the
work progresses.
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BMP C207: Check Dams
Purpose
Construction of check dams across a swale or ditch are used to reduce the velocity of
concentrated flow and dissipate energy at the check dam.
Conditions of Use
x Use check dams where temporary channels or permanent channels are
not yet vegetated, channel lining is infeasible, and velocity checks are
required.
x 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 Thurston County and/or another
applicable permitting agency.
x Do not place check dams below the expected backwater from any
salmonid bearing water between October 1 and May 31 to ensure that
there is no loss of high flow refuge habitat for overwintering juvenile
salmonids and emergent salmonid fry.
Design and Installation Specifications
x Whatever material is used, the dam should form a triangle when viewed
from the side. This prevents undercutting as water flows over the face of
the dam rather than falling directly onto the ditch bottom.
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x Before installing check dams impound and bypass upstream water flow
away from the work area. Options for bypassing include pumps, siphons,
or temporary channels.
x Check dams in association with sumps work more effectively at slowing
flow and retaining sediment than just a check dam alone. Provide a deep
sump immediately upstream of the check dam.
x In some cases, if carefully located and designed, check dams can remain
as permanent installations with very minor regrading. They may be left as
either spillways, in which case accumulated sediment would be graded
and seeded, or as check dams to prevent further sediment from leaving
the site.
x Construct rock check dams with appropriately sized rock. Place the rock
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.
x Check dams may also 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.
x Place check dams perpendicular to the flow of water.
x 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.
x Keep the maximum height at 2 feet at the center of the dam.
x Keep the center of the check dam at least 12 inches lower than the outer
edges at natural ground elevation.
x Keep the side slopes of the check dam at 2:1 or flatter.
x 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.
x Use filter fabric foundation under a rock or sandbag 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.
x 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
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greater than 4 percent. The area beneath the check dams shall be
seeded and mulched immediately after dam removal.
x Ensure that channel appurtenances, such as culvert entrances below
check dams, are not subject to damage or blockage from displaced
stones. Figure II - 3.13 depicts a typical rock check dam.
Maintenance Standards
x Check dams shall be monitored for performance and sediment
accumulation during and after each runoff producing rainfall. Sediment
shall be removed when it reaches one half the sump depth.
x Anticipate submergence and deposition above the check dam and erosion
from high flows around the edges of the dam.
x If significant erosion occurs between dams, install a protective riprap liner
in that portion of the channel.
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Figure II - 3.13 Check Dams
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BMP C220: Storm Drain Inlet Protection
Purpose
Inlet protection prevents coarse sediment from entering drainage systems prior to
permanent stabilization of a disturbed area.
Conditions of Use
Use this BMP where storm drain inlets are to be made operational before permanent
stabilization of the disturbed drainage area. Provide protection for all storm drain inlets
downslope and within 500 feet of a disturbed or construction area, unless the runoff that
enters the catch basin will be conveyed to a sediment trapping BMP. Inlet protection
may be used anywhere to protect the drainage system. It is likely that the drainage
system will still require cleaning.
Also consider inlet protection for lawn and yard drains on new home construction.
These small and numerous drains coupled with lack of gutters in new home
construction can add significant amounts of sediment into the roof drain system. If
possible delay installing lawn and yard drains until just before landscaping or cap these
drains to prevent sediment from entering the system until completion of landscaping.
Provide 18-inches of sod around each finished lawn and yard drain.
Table II - 3.14 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.
Limit contributing drainage areas for an individual inlet to 1 acre or less. If possible,
provide emergency overflows with additional end-of-pipe treatment where stormwater
ponding would cause a hazard.
For projects where the final lift of asphalt or concrete will not be completed for a period
of time, an asphalt taper shall be constructed around the storm drain inlet frame. Where
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weepholes are required, the pipe shall be placed in the center of the catch basin filter
and extended beyond the taper.
Table II - 3.14 Storm Drain Inlet Protection
Type of Inlet Protection
Emergency
Overflow
Applicable for
Paved/Earthen
Surfaces Conditions of Use
Drop Inlet Protection
Excavated drop inlet
protection
Yes, temporary
flooding will
occur
Earthen Applicable for heavy flows. Easy to
maintain. Large Area Requirement:
30’ X 30’/acre.
Block and gravel drop
inlet protection
Yes Paved or
Earthen
Applicable for heavy concentrated
flows. Will not pond.
Gravel and wire drop
inlet protection
No Applicable for heavy concentrated
flows. Will pond. Can withstand
traffic.
Catch basin filters Yes Paved or
Earthen
Frequent maintenance required.
Curb Inlet Protection
Curb inlet protection
with a wooden weir
Small capacity
overflow
Paved Used for sturdy, more compact
installation.
Block and gravel curb
inlet protection
Yes Paved Sturdy, but limited filtration.
Culvert Inlet Protection
Culvert inlet sediment
trap
18 month expected life.
Design and Installation Specifications
Excavated Drop Inlet Protection – An excavated impoundment around the storm drain
inlet. Sediment settles out of the stormwater prior to entering the storm drain. Design
and installation specifications for excavated drop inlet protection include:
x Provide a depth 1 to 2 feet as measured from the crest of the inlet
structure.
x Slope sides of excavation no steeper than 2H:1V.
x Minimum volume of excavation 35 cubic yards.
x Shape the excavation to fit site, with longest dimension oriented toward
the longest inflow area.
x Install provisions for draining to prevent standing water problems.
x Clear the area of all debris.
x Grade the approach to the inlet uniformly.
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x Drill weep holes into the side of the inlet.
x Protect weep holes with screen wire and washed aggregate.
x Seal weep holes when removing structure and stabilizing area.
x 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 II - 3.14. Design and installation specifications
for block gravel filters include:
x Provide a height of 1 to 2 feet above inlet.
x Recess the first row of blocks 2-inches into the ground for stability.
x Support subsequent courses by placing a 2x4 through the block opening.
x Do not use mortar
x Lay some blocks in the bottom row on their side for dewatering the pool.
x Place hardware cloth or comparable wire mesh with ½-inch openings over
all block openings.
x Place gravel just below the top of blocks on slopes of 2H:1V or flatter.
x An alternative design is a gravel berm surrounding the inlet, as follows:
Provide a slope of 3H:1V on the upstream side of the berm.
Provide a slope of 2H:1V on the downstream side of the berm.
Provide a 1-foot wide level stone area between the gravel berm and
the inlet.
Use stones 3 inches in diameter or larger on the upstream slope of the
berm.
Use gravel ½ - to ¾-inch at a minimum thickness of 1-foot on the
downstream slope of the berm.
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Figure II - 3.14 Block and Gravel Filter
Gravel and Wire Mesh Filter- A gravel barrier placed over the top of the inlet. This
method does not provide an overflow. Design and installation specifications for gravel
and wire mesh filters include:
x Use a hardware cloth or comparable wire mesh with ½-inch openings.
Place wire mesh over the drop inlet so that the wire extends a
minimum of 1-foot beyond each side of the inlet structure.
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Overlap the strips if more than one strip of mesh is necessary.
x Place coarse aggregate over the wire mesh.
Provide at least a 12-inch depth of coarse aggregate over the entire
inlet opening and extend at least 18-inches on all sides.
Catch Basin Filters – Use inserts designed by manufacturers for construction sites.
The limited sediment storage capacity increases the amount of inspection and
maintenance required, which may be daily for heavy sediment loads. To reduce
maintenance requirements, combine a catch basin 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 rights-of-way. Design
and installation specifications for catch basin filters include:
x Provides 5 cubic feet of storage.
x Requires dewatering provisions.
x Provides a high-flow bypass that will not clog under normal use at a
construction site.
x Insert the catch basin filter in the catch basin just below the grating.
Curb Inlet Protection with Wooden Weir – Barrier formed around a curb inlet with a
wooden frame and gravel. Design and installation specifications for curb inlet protection
with wooden weirs include:
x Use wire mesh with 1/2-inch openings.
x Use extra strength filter cloth.
x Construct a frame.
x Attach the wire and filter fabric to the frame.
x Pile coarse washed aggregate against wire/fabric.
x Place weight on frame anchors.
x See Figure II - 3.15
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Figure II - 3.15 Curb Inlet with Wooden Weir
(Figure courtesy of Maryland Standards and Specifications for Soil Erosion and Sediment Control)
Block and Gravel Curb Inlet Protection – Barrier formed around a curb inlet with
concrete blocks and gravel. See Figure II - 3.16. Design and installation specifications
for block and gravel curb inlet protection include:
x Use wire mesh with ½-inch openings.
x Place two concrete blocks on their sides abutting the curb at either side of
the inlet opening. These are spacer blocks.
x Place a 2x4 stud through the outer holes of each spacer block to align the
front blocks.
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x Place blocks on their sides across the front of the inlet and abutting the
spacer blocks.
x Place wire mesh over the outside vertical face.
x Pile coarse aggregate against the wire to the top of the barrier.
Curb and Gutter Sediment Barrier – Sandbag or rock berm (riprap and aggregate)
3 feet high and 3 feet wide in a horseshoe shape. See Figure II - 3.17. Design and
installation specifications for curb and gutter sediment barrier include:
x Construct a horseshoe shaped berm, faced with coarse aggregate if using
riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet.
x Construct a horseshoe shaped sedimentation trap on the upstream side of
the berm. Size the sediment trap to sediment trap standards for protecting
a culvert inlet.
Maintenance Standards
x Inspect all forms of inlet protection frequently, especially after storm
events. If the insert becomes clogged, it should be cleaned or replaced.
x 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.
x Do not wash sediment into storm drains while cleaning. Spread all
excavated material evenly over the surrounding land area or stockpile and
stabilize as appropriate.
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Figure II - 3.16 Block and Gravel Curb Inlet Protection
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Figure II - 3.17 Curb and Gutter Barrier
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BMP C233: Silt Fence
Purpose
To reduce 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 II - 3.19 for details on silt fence construction.
Conditions of Use
x Silt fence may be used downslope of all disturbed areas.
x 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.
x Silt fence is not intended to treat concentrated flows, nor is it intended to
treat substantial amounts of overland flow. Convey any concentrated flows
through the drainage system to a sediment pond.
x Silt fences should not be constructed in streams or use in V-shaped
ditches. They are not an adequate method of silt control for anything
deeper than sheet or overland flow.
Design and Installation Specifications
x Use in combination with other construction stormwater BMPs.
Figure II - 3.19 Silt Fence
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x Maximum slope steepness (perpendicular to the silt fence line) 1H:1V.
x Maximum sheet or overland flow path length to the silt fence of 100 feet.
x Do not allow flows greater than 0.5 cfs.
x The geotextile used for filter fabric 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 II - 3.15):
Table II - 3.15 Geotextile Standards
Polymeric Mesh AOS (ASTM
D4751)
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).
Water Permittivity (ASTM D4491) 0.02 sec-1 minimum
Grab Tensile Strength (ASTM
D4632)
180 lbs. Minimum for extra strength fabric.
100 lbs minimum for standard strength fabric.
Grab Tensile Strength (ASTM
D4632)
30% maximum
Ultraviolet Resistance (ASTM
D4355)
70% minimum
x Support standard strength fabrics with wire mesh, chicken wire, 2-inch x
2-inch wire, safety fence, or jute mesh to increase the strength of the
fabric. Silt fence materials are available that have synthetic mesh backing
attached.
x Silt fence 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.
x 100 percent biodegradable silt fence is available that is strong, long
lasting, and can be left in place after the project is completed.
x Include the following Standard Notes for silt fence on construction plans
and specifications. Refer to Figure II - 3.19 for standard silt fence details.
1. The contractor shall install and maintain temporary silt fences at the
locations shown in the Plans.
2. Silt fences shall be constructed in the areas of clearing, grading, or
drainage prior to starting those activities.
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3. 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.
4. The minimum height of the top of silt fence shall be 2 feet and the
maximum height shall be 2-1/2 feet above the original ground
surface.
5. 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.
6. 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.
7. 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 side of the posts with the
geotextile being up-slope of the mesh back-up support.
8. Mesh support, if used, shall consist of steel wire with a maximum
mesh spacing of 2-inches, or a prefabricated polymeric mesh. The
strength of the wire or polymeric mesh shall be equivalent to or
greater than 180 lbs. grab tensile strength. The polymeric mesh
must be as resistant to the same level of ultraviolet radiation as the
filter fabric it supports.
9. The geotextile at the bottom of the fence shall be buried in a trench
to a minimum depth of 4 inches below the ground surface. The
trench shall be backfilled, and the soil tamped in place over the
buried portion of the geotextile, such that no flow can pass beneath
the fence and scouring cannot occur. When wire or polymeric
back-up support mesh is used, the wire or polymeric mesh shall
extend into the trench a minimum of 3 inches.
10. Drive or place the fence posts a minimum of 18 inches into the
ground. A minimum depth of 12 inches is allowed if topsoil or other
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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 3H:1V 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.
11. 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.
12. If the fence must cross contours, with the exception of the ends of
the fence, 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 slope of the fence line where
contours must be crossed shall not be steeper than 3:1.
o The 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.
o The l 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.
13. Wood, steel or equivalent posts shall be used. The spacing of the
support posts shall be a maximum of 6-feet. Posts shall consist of
either:
o Wood posts with minimum dimensions of 2 inches by
2 inches and 3 feet minimum length. Wood posts shall be
free of defects such as knots, splits, or gouges.
o No. 6 rebar or larger.
o ASTM A 120 steel pipe with a minimum diameter of
1 inch.
o U, T, L, or C shape steel posts with a minimum weight of
1.35 lbs./ft.
o Other steel posts having equivalent strength and
bending resistance to the post sizes listed above.
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x Silt fence installation using the slicing method specification details follow.
Refer to Figure II – 3.20 for slicing method details.
1. 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.
2. Install posts 3 to 4 feet apart in critical retention areas and 6 to 7
feet apart in standard applications.
3. 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.
4. Install posts with the nipples facing away from the silt fence fabric.
5. Attach the filter fabric to each post with three ties, all spaced within
the top 8 inches of the fabric. Attach each tie diagonally
45 degrees through the fabric, with each puncture at least 1 inch
vertically apart. In addition, position each tie to hang on a post
nipple when tightening to prevent sagging.
6. Wrap approximately 6 inches of fabric around the end posts and
secure with three ties.
7. No more than 24 inches of a 36-inch fabric is allowed above ground
level.
8. Compact the soil immediately next to the silt fence fabric with the
front wheel of the tractor, skid steer, or roller exerting at least 60
pounds per square inch. Compact the upstream side first and then
each side twice for a total of four trips. 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.
Maintenance Standards
x Any damage shall be repaired immediately.
x If concentrated flows are evident uphill of the fence, they must be
intercepted and conveyed to a sediment trapping BMP.
x It is important to check the uphill side of the fence for signs of the fence
clogging and acting as a barrier to flow and then causing channelization of
flows parallel to the fence. If this occurs, replace the fence and remove
the trapped sediment.
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x 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.
x If the filter fabric (geotextile) has deteriorated due to ultraviolet breakdown,
it shall be replaced.
Figure II – 3.20 Silt Fence Installation by Slicing Method
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BMP C235: Wattles
Purpose
To reduce the velocity and spread the flow of rill and sheet runoff, and to capture and
retain sediment.
Wattles are temporary erosion and sediment control barriers consisting of straw,
compost, or other material that is wrapped in netting made of natural plant fiber or
similar encasing material.
Conditions of Use
x Wattles shall consist of cylinders of plant material such as weed-free
straw, coir, wood chips, excelsior, or wood fiber or shavings encased with
netting made of natural plant fibers unaltered by synthetic materials.
x Use Wattles:
1. In disturbed areas that require immediate erosion protection.
2. On exposed soils during the period of short construction delays, or
over winter months.
3. On slopes requiring stabilization until permanent vegetation can be
established.
x The material used dictates the effectiveness period of the wattle. Wattles
are typically effective for one to two wet seasons.
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x If conditions are appropriate, wattles can be staked to the ground using
willow cuttings for added revegetation.
x Prevent rilling beneath wattles by properly entrenching and abutting
wattles together to prevent water from passing between them.
Figure II - 3.21 Straw Wattles
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Design Criteria
x See Figure II - 3.23 for typical construction details. WSDOT Standard Plan
I-30.30-00 also provides information on Wattles
(http://www.wsdot.wa.gov/Design/Standards/Plans.htm#SectionI)
x Wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length.
x Install wattles perpendicular to the flow direction and parallel to the slope
contour.
x Place wattles in narrow trenches, staked along the contour of disturbed or
newly constructed slopes (on contour) to a depth of 3 to 5 inches on clay
soils and soils with gradual slopes. On loose soils, steep slopes, and
areas with high rainfall, the trenches should be dug to a depth of 5 to
7 inches, or 1/2 to 2/3 of the thickness of the wattle.
x Start building trenches and installing wattles from the base of the slope
and work up. Spread excavated material evenly along the uphill slope and
compact using hand tamping or other methods.
x Construct trenches at intervals of 10 to 25-feet depending on the
steepness of the slope, soil type, and rainfall. The steeper the slope the
closer together the trenches need to be. See Table II – 3.17 for spacing
information.
x Install the wattles snugly into the trenches and abut tightly end to end. Do
not overlap the ends.
x Install stakes at each end of the wattle, and at 4-foot centers along entire
length of wattle.
x If required, install pilot holes for the stakes using a straight bar to drive
holes through the wattle and into the soil.
x Wooden stakes shall be approximately 3/4 x 3/4 x 24 inches. Willow
cuttings or 3/8-inch rebar can also be used for stakes.
x Stakes should be driven through the middle of the wattle, leaving 2 to 3-
inches of the stake protruding above the wattle.
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Table II – 3.17 Wattle Spacing Table
8” Diameter Wattle Spacing Table
Slope Maximum Spacing
1H:1V 10’-0”
2H:1V 20’-0”
3H:1V 30’-0”
4H:1V 40’-0”
Maintenance Standards
x Wattles may require maintenance to ensure they are in contact with soil
and thoroughly entrenched, especially after significant rainfall on steep
sandy soils.
x Inspect the slope after significant storms and repair any areas where
wattles are not tightly abutted, or water has scoured beneath the wattles.
P a g e | 21
C. Correspondence
P a g e | 22
D. Site Inspection Form
Construction Stormwater Site Inspection Form
Page 1
Project Name Permit # Inspection Date Time
Name of Certified Erosion Sediment Control Lead (CESCL) or qualified inspector if less than one acre
Print Name:
Approximate rainfall amount since the last inspection (in inches):
Approximate rainfall amount in the last 24 hours (in inches):
Current Weather Clear Cloudy Mist Rain Wind Fog
A. Type of inspection: Weekly Post Storm Event Other
B. Phase of Active Construction (check all that apply):
Pre Construction/installation of erosion/sediment
controls
Clearing/Demo/Grading Infrastructure/storm/roads
Concrete pours Vertical
Construction/buildings
Utilities
Offsite improvements Site temporary stabilized Final stabilization
C. Questions:
1. Were all areas of construction and discharge points inspected? Yes No
2. Did you observe the presence of suspended sediment, turbidity, discoloration, or oil sheen Yes No
3. Was a water quality sample taken during inspection? (refer to permit conditions S4 & S5) Yes No
4. Was there a turbid discharge 250 NTU or greater, or Transparency 6 cm or less?* Yes No
5. If yes to #4 was it reported to Ecology? Yes No
6. Is pH sampling required? pH range required is 6.5 to 8.5. Yes No
If answering yes to a discharge, describe the event. Include when, where, and why it happened; what action was taken,
and when.
*If answering yes to # 4 record NTU/Transparency with continual sampling daily until turbidity is 25 NTU or less/ transparency is 33
cm or greater.
Sampling Results: Date:
Parameter Method (circle one) Result Other/Note
NTU cm pH
Turbidity tube, meter, laboratory
pH Paper, kit, meter
Construction Stormwater Site Inspection Form
Page 2
D. Check the observed status of all items. Provide “Action Required “details and dates.
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
1
Clearing
Limits
Before beginning land disturbing
activities are all clearing limits,
natural resource areas (streams,
wetlands, buffers, trees) protected
with barriers or similar BMPs? (high
visibility recommended)
2
Construction
Access
Construction access is stabilized
with quarry spalls or equivalent
BMP to prevent sediment from
being tracked onto roads?
Sediment tracked onto the road
way was cleaned thoroughly at the
end of the day or more frequent as
necessary.
3
Control Flow
Rates
Are flow control measures installed
to control stormwater volumes and
velocity during construction and do
they protect downstream
properties and waterways from
erosion?
If permanent infiltration ponds are
used for flow control during
construction, are they protected
from siltation?
4
Sediment
Controls
All perimeter sediment controls
(e.g. silt fence, wattles, compost
socks, berms, etc.) installed, and
maintained in accordance with the
Stormwater Pollution Prevention
Plan (SWPPP).
Sediment control BMPs (sediment
ponds, traps, filters etc.) have been
constructed and functional as the
first step of grading.
Stormwater runoff from disturbed
areas is directed to sediment
removal BMP.
5
Stabilize
Soils
Have exposed un-worked soils
been stabilized with effective BMP
to prevent erosion and sediment
deposition?
Construction Stormwater Site Inspection Form
Page 3
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
5
Stabilize Soils
Cont.
Are stockpiles stabilized from erosion,
protected with sediment trapping
measures and located away from drain
inlet, waterways, and drainage
channels?
Have soils been stabilized at the end of
the shift, before a holiday or weekend
if needed based on the weather
forecast?
6
Protect
Slopes
Has stormwater and ground water
been diverted away from slopes and
disturbed areas with interceptor dikes,
pipes and or swales?
Is off-site storm water managed
separately from stormwater generated
on the site?
Is excavated material placed on uphill
side of trenches consistent with safety
and space considerations?
Have check dams been placed at
regular intervals within constructed
channels that are cut down a slope?
7
Drain Inlets
Storm drain inlets made operable
during construction are protected.
Are existing storm drains within the
influence of the project protected?
8
Stabilize
Channel and
Outlets
Have all on-site conveyance channels
been designed, constructed and
stabilized to prevent erosion from
expected peak flows?
Is stabilization, including armoring
material, adequate to prevent erosion
of outlets, adjacent stream banks,
slopes and downstream conveyance
systems?
9
Control
Pollutants
Are waste materials and demolition
debris handled and disposed of to
prevent contamination of stormwater?
Has cover been provided for all
chemicals, liquid products, petroleum
products, and other material?
Has secondary containment been
provided capable of containing 110%
of the volume?
Were contaminated surfaces cleaned
immediately after a spill incident?
Were BMPs used to prevent
contamination of stormwater by a pH
modifying sources?
Construction Stormwater Site Inspection Form
Page 4
Element # Inspection BMPs
Inspected
BMP needs
maintenance
BMP
failed
Action
required
(describe in
section F)
yes no n/a
9
Cont.
Wheel wash wastewater is handled
and disposed of properly.
10
Control
Dewatering
Concrete washout in designated areas.
No washout or excess concrete on the
ground.
Dewatering has been done to an
approved source and in compliance
with the SWPPP.
Were there any clean non turbid
dewatering discharges?
11
Maintain
BMP
Are all temporary and permanent
erosion and sediment control BMPs
maintained to perform as intended?
12
Manage the
Project
Has the project been phased to the
maximum degree practicable?
Has regular inspection, monitoring and
maintenance been performed as
required by the permit?
Has the SWPPP been updated,
implemented and records maintained?
13
Protect LID
Is all Bioretention and Rain Garden
Facilities protected from
sedimentation with appropriate BMPs?
Is the Bioretention and Rain Garden
protected against over compaction of
construction equipment and foot
traffic to retain its infiltration
capabilities?
Permeable pavements are clean and
free of sediment and sediment laden-
water runoff. Muddy construction
equipment has not been on the base
material or pavement.
Have soiled permeable pavements
been cleaned of sediments and pass
infiltration test as required by
stormwater manual methodology?
Heavy equipment has been kept off
existing soils under LID facilities to
retain infiltration rate.
E. Check all areas that have been inspected.
All in place BMPs All disturbed soils All concrete wash out area All material storage areas
All discharge locations All equipment storage areas All construction entrances/exits
Construction Stormwater Site Inspection Form
Page 5
F. Elements checked “Action Required” (section D) describe corrective action to be taken. List the element number;
be specific on location and work needed. Document, initial, and date when the corrective action has been completed
and inspected.
Element
#
Description and Location Action Required Completion
Date
Initials
Attach additional page if needed
Sign the following certification:
“I certify that this report is true, accurate, and complete, to the best of my knowledge and belief”
Inspected by: (print) (Signature) Date:
Title/Qualification of Inspector:
P a g e | 23
E. Construction Stormwater General Permit (CSWGP)
Issuance Date: November 18, 2020
Effective Date: January 1, 2021
Expiration Date: December 31, 2025
CONSTRUCTION STORMWATER
GENERAL PERMIT
National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge
General Permit for Stormwater Discharges Associated with Construction Activity
State of Washington
Department of Ecology
Olympia, Washington 98504
In compliance with the provisions of Chapter 90.48 Revised Code of Washington (State of Washington Water Pollution Control Act) and Title 33 United States Code, Section 1251 et seq. The Federal Water Pollution Control Act (The Clean Water Act)
Until this permit expires, is modified, or revoked, Permittees that have properly obtained coverage under this general permit are authorized to discharge in accordance with the special and general conditions that follow.
__________________________________ Vincent McGowan, P.E. Water Quality Program Manager Washington State Department of Ecology
Construction Stormwater General Permit Page i
TABLE OF CONTENTS
LIST OF TABLES .................................................................................................................................. ii
SUMMARY OF PERMIT REPORT SUBMITTALS ...................................................................................... 1
SPECIAL CONDITIONS ......................................................................................................................... 3
S1. Permit Coverage .............................................................................................................................. 3
S2. Application Requirements ............................................................................................................... 7
S3. Compliance with Standards ............................................................................................................. 9
S4. Monitoring Requirements, Benchmarks, and Reporting Triggers ................................................. 10
S5. Reporting and Recordkeeping Requirements ................................................................................ 17
S6. Permit Fees .................................................................................................................................... 20
S7. Solid and Liquid Waste Disposal .................................................................................................... 20
S8. Discharges to 303(D) or TMDL Waterbodies ................................................................................. 20
S9. Stormwater Pollution Prevention Plan .......................................................................................... 23
S10. Notice Of Termination ................................................................................................................... 32
GENERAL CONDITIONS ..................................................................................................................... 34
G1. Discharge Violations....................................................................................................................... 34
G2. Signatory Requirements ................................................................................................................ 34
G3. Right of Inspection and Entry ......................................................................................................... 35
G4. General Permit Modification and Revocation ............................................................................... 35
G5. Revocation of Coverage Under tPermit ......................................................................................... 35
G6. Reporting a Cause for Modification ............................................................................................... 36
G7. Compliance with Other Laws and Statutes .................................................................................... 36
G8. Duty to Reapply.............................................................................................................................. 36
G9. Removed Substance ....................................................................................................................... 36
G10. Duty to Provide Information .......................................................................................................... 36
G11. Other Requirements of 40 CFR ...................................................................................................... 37
G12. Additional Monitoring .................................................................................................................... 37
G13. Penalties for Violating Permit Conditions ...................................................................................... 37
G14. Upset .............................................................................................................................................. 37
G15. Property Rights .............................................................................................................................. 37
G16. Duty to Comply .............................................................................................................................. 37
G17. Toxic Pollutants .............................................................................................................................. 38
G18. Penalties for Tampering ................................................................................................................. 38
G19. Reporting Planned Changes ........................................................................................................... 38
G20. Reporting Other Information ......................................................................................................... 38
G21. Reporting Anticipated Non-Compliance ........................................................................................ 38
Construction Stormwater General Permit Page ii
G22. Requests to Be Excluded From Coverage Under the Permit ......................................................... 39
G23. Appeals........................................................................................................................................... 39
G24. Severability..................................................................................................................................... 39
G25. Bypass Prohibited .......................................................................................................................... 39
APPENDIX A – DEFINITIONS .............................................................................................................. 42
APPENDIX B – ACRONYMS ................................................................................................................ 50
LIST OF TABLES
Table 1 Summary of Required Submittals ................................................................................................ 1
Table 2 Summary of Required On-site Documentation ........................................................................... 2
Table 3 Summary of Primary Monitoring Requirements ....................................................................... 12
Table 4 Monitoring and Reporting Requirements ................................................................................. 14
Table 5 Turbidity, Fine Sediment & Phosphorus Sampling and Limits for
303(d)-Listed Waters ................................................................................................................ 22
Table 6 pH Sampling and Limits for 303(d)-Listed Waters ..................................................................... 22
Construction Stormwater General Permit Page 1
SUMMARY OF PERMIT REPORT SUBMITTALS
Refer to the Special and General Conditions within this permit for additional submittal requirements.
Appendix A provides a list of definitions. Appendix B provides a list of acronyms.
Table 1 Summary of Required Submittals
Permit
Section
Submittal Frequency First Submittal Date
S5.A and
S8
High Turbidity/Transparency Phone
Reporting
As Necessary Within 24 hours
S5.B Discharge Monitoring Report Monthly* Within 15 days following the
end of each month
S5.F and
S8
Noncompliance Notification –
Telephone Notification
As necessary Within 24 hours
S5.F Noncompliance Notification – Written
Report
As necessary Within 5 Days of
non-compliance
S9.D Request for Chemical Treatment Form As necessary Written approval from
Ecology is required prior to
using chemical treatment
(with the exception of dry ice,
CO2 or food grade vinegar to
adjust pH)
G2 Notice of Change in Authorization As necessary
G6 Permit Application for Substantive
Changes to the Discharge
As necessary
G8 Application for Permit Renewal 1/permit cycle No later than 180 days
before expiration
S2.A Notice of Permit Transfer As necessary
G19 Notice of Planned Changes As necessary
G21 Reporting Anticipated Non-compliance As necessary
NOTE: *Permittees must submit electronic Discharge Monitoring Reports (DMRs) to the Washington State
Department of Ecology monthly, regardless of site discharge, for the full duration of permit coverage. Refer
to Section S5.B of this General Permit for more specific information regarding DMRs.
Construction Stormwater General Permit Page 2
Table 2 Summary of Required On-site Documentation
Document Title
Permit Conditions
Permit Coverage Letter See Conditions S2, S5
Construction Stormwater General Permit (CSWGP) See Conditions S2, S5
Site Log Book See Conditions S4, S5
Stormwater Pollution Prevention Plan (SWPPP) See Conditions S5, S9
Site Map See Conditions S5, S9
Construction Stormwater General Permit Page 3
SPECIAL CONDITIONS
S1. PERMIT COVERAGE
A. Permit Area
This Construction Stormwater General Permit (CSWGP) covers all areas of Washington State,
except for federal operators and Indian Country as specified in Special Condition S1.E.3 and 4.
B. Operators Required to Seek Coverage Under this General Permit
1. Operators of the following construction activities are required to seek coverage under
this CSWGP:
a. Clearing, grading and/or excavation that results in the disturbance of one or more
acres (including off-site disturbance acreage related to construction-support activity
as authorized in S1.C.2) and discharges stormwater to surface waters of the State;
and clearing, grading and/or excavation on sites smaller than one acre that are part
of a larger common plan of development or sale, if the common plan of
development or sale will ultimately disturb one acre or more and discharge
stormwater to surface waters of the State.
i. This category includes forest practices (including, but not limited to, class IV
conversions) that are part of a construction activity that will result in the
disturbance of one or more acres, and discharge to surface waters of the State
(that is, forest practices that prepare a site for construction activities); and
b. Any size construction activity discharging stormwater to waters of the State that the
Washington State Department of Ecology (Ecology):
i. Determines to be a significant contributor of pollutants to waters of the State
of Washington.
ii. Reasonably expects to cause a violation of any water quality standard.
2. Operators of the following activities are not required to seek coverage under this CSWGP
(unless specifically required under Special Condition S1.B.1.b, above):
a. Construction activities that discharge all stormwater and non-stormwater to
groundwater, sanitary sewer, or combined sewer, and have no point source
discharge to either surface water or a storm sewer system that drains to surface
waters of the State.
b. Construction activities covered under an Erosivity Waiver (Special Condition S1.F).
c. Routine maintenance that is performed to maintain the original line and grade,
hydraulic capacity, or original purpose of a facility.
C. Authorized Discharges
1. Stormwater Associated with Construction Activity. Subject to compliance with the terms
and conditions of this permit, Permittees are authorized to discharge stormwater
associated with construction activity to surface waters of the State or to a storm sewer
system that drains to surface waters of the State. (Note that “surface waters of the
Construction Stormwater General Permit Page 4
State” may exist on a construction site as well as off site; for example, a creek running
through a site.)
2. Stormwater Associated with Construction Support Activity. This permit also authorizes
stormwater discharge from support activities related to the permitted construction site
(for example, an on-site portable rock crusher, off-site equipment staging yards, material
storage areas, borrow areas, etc.) provided:
a. The support activity relates directly to the permitted construction site that is
required to have an NPDES permit; and
b. The support activity is not a commercial operation serving multiple unrelated
construction projects, and does not operate beyond the completion of the
construction activity; and
c. Appropriate controls and measures are identified in the Stormwater Pollution
Prevention Plan (SWPPP) for the discharges from the support activity areas.
3. Non-Stormwater Discharges. The categories and sources of non-stormwater discharges
identified below are authorized conditionally, provided the discharge is consistent with
the terms and conditions of this permit:
a. Discharges from fire-fighting activities.
b. Fire hydrant system flushing.
c. Potable water, including uncontaminated water line flushing.
d. Hydrostatic test water.
e. Uncontaminated air conditioning or compressor condensate.
f. Uncontaminated groundwater or spring water.
g. Uncontaminated excavation dewatering water (in accordance with S9.D.10).
h. Uncontaminated discharges from foundation or footing drains.
i. Uncontaminated or potable water used to control dust. Permittees must minimize
the amount of dust control water used.
j. Routine external building wash down that does not use detergents.
k. Landscape irrigation water.
The SWPPP must adequately address all authorized non-stormwater discharges, except for
discharges from fire-fighting activities, and must comply with Special Condition S3. At a
minimum, discharges from potable water (including water line flushing), fire hydrant system
flushing, and pipeline hydrostatic test water must undergo the following: dechlorination to a
concentration of 0.1 parts per million (ppm) or less, and pH adjustment to within 6.5 – 8.5
standard units (su), if necessary.
D. Prohibited Discharges
The following discharges to waters of the State, including groundwater, are prohibited:
Construction Stormwater General Permit Page 5
1. Concrete wastewater
2. Wastewater from washout and clean-up of stucco, paint, form release oils, curing
compounds and other construction materials.
3. Process wastewater as defined by 40 Code of Federal Regulations (CFR) 122.2 (See
Appendix A of this permit).
4. Slurry materials and waste from shaft drilling, including process wastewater from shaft
drilling for construction of building, road, and bridge foundations unless managed
according to Special Condition S9.D.9.j.
5. Fuels, oils, or other pollutants used in vehicle and equipment operation and
maintenance.
6. Soaps or solvents used in vehicle and equipment washing.
7. Wheel wash wastewater, unless managed according to Special Condition S9.D.9.
8. Discharges from dewatering activities, including discharges from dewatering of trenches
and excavations, unless managed according to Special Condition S9.D.10.
E. Limits on Coverage
Ecology may require any discharger to apply for and obtain coverage under an individual permit
or another more specific general permit. Such alternative coverage will be required when
Ecology determines that this CSWGP does not provide adequate assurance that water quality
will be protected, or there is a reasonable potential for the project to cause or contribute to a
violation of water quality standards.
The following stormwater discharges are not covered by this permit:
1. Post-construction stormwater discharges that originate from the site after completion of
construction activities and the site has undergone final stabilization.
2. Non-point source silvicultural activities such as nursery operations, site preparation,
reforestation and subsequent cultural treatment, thinning, prescribed burning, pest and
fire control, harvesting operations, surface drainage, or road construction and
maintenance, from which there is natural runoff as excluded in 40 CFR Subpart 122.
3. Stormwater from any federal operator.
4. Stormwater from facilities located on Indian Country as defined in 18 U.S.C.§1151,
except portions of the Puyallup Reservation as noted below.
Indian Country includes:
a. All land within any Indian Reservation notwithstanding the issuance of any patent,
and, including rights-of-way running through the reservation. This includes all
federal, tribal, and Indian and non-Indian privately owned land within the
reservation.
b. All off-reservation Indian allotments, the Indian titles to which have not been
extinguished, including rights-of-way running through the same.
c. All off-reservation federal trust lands held for Native American Tribes.
Construction Stormwater General Permit Page 6
Puyallup Exception: Following the Puyallup Tribes of Indians Land Settlement Act of
1989, 25 U.S.C. §1773; the permit does apply to land within the Puyallup
Reservation except for discharges to surface water on land held in trust by the
federal government.
5. Stormwater from any site covered under an existing NPDES individual permit in which
stormwater management and/or treatment requirements are included for all stormwater
discharges associated with construction activity.
6. Stormwater from a site where an applicable Total Maximum Daily Load (TMDL)
requirement specifically precludes or prohibits discharges from construction activity.
F. Erosivity Waiver
Construction site operators may qualify for an Erosivity Waiver from the CSWGP if the following
conditions are met:
1. The site will result in the disturbance of fewer than five (5) acres and the site is not a
portion of a common plan of development or sale that will disturb five (5) acres or
greater.
2. Calculation of Erosivity “R” Factor and Regional Timeframe:
a. The project’s calculated rainfall erosivity factor (“R” Factor) must be less than five
(5) during the period of construction activity, (See the CSWGP homepage
http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html for a
link to the EPA’s calculator and step by step instructions on computing the “R”
Factor in the EPA Erosivity Waiver Fact Sheet). The period of construction activity
starts when the land is first disturbed and ends with final stabilization. In addition:
b. The entire period of construction activity must fall within the following timeframes:
i. For sites west of the Cascades Crest: June 15 – September 15.
ii. For sites east of the Cascades Crest, excluding the Central Basin:
June 15 – October 15.
iii. For sites east of the Cascades Crest, within the Central Basin: no timeframe
restrictions apply. The Central Basin is defined as the portions of Eastern
Washington with mean annual precipitation of less than 12 inches. For a map of
the Central Basin (Average Annual Precipitation Region 2), refer to:
http://www.ecy.wa.gov/programs/wq/stormwater/construction/resourcesguida
nce.html.
3. Construction site operators must submit a complete Erosivity Waiver certification form at
least one week before disturbing the land. Certification must include statements that the
operator will:
a. Comply with applicable local stormwater requirements; and
b. Implement appropriate erosion and sediment control BMPs to prevent violations of
water quality standards.
4. This waiver is not available for facilities declared significant contributors of pollutants as
defined in Special Condition S1.B.1.b or for any size construction activity that could
Construction Stormwater General Permit Page 7
reasonably expect to cause a violation of any water quality standard as defined in Special
Condition S1.B.1.b.ii.
5. This waiver does not apply to construction activities which include non-stormwater
discharges listed in Special Condition S1.C.3.
6. If construction activity extends beyond the certified waiver period for any reason, the
operator must either:
a. Recalculate the rainfall erosivity “R” factor using the original start date and a new
projected ending date and, if the “R” factor is still under 5 and the entire project
falls within the applicable regional timeframe in Special Condition S1.F.2.b,
complete and submit an amended waiver certification form before the original
waiver expires; or
b. Submit a complete permit application to Ecology in accordance with Special
Condition S2.A and B before the end of the certified waiver period.
S2. APPLICATION REQUIREMENTS
A. Permit Application Forms
1. Notice of Intent Form
a. Operators of new or previously unpermitted construction activities must submit a
complete and accurate permit application (Notice of Intent, or NOI) to Ecology.
b. Operators must apply using the electronic application form (NOI) available on Ecology’s
website (http://ecy.wa.gov/programs/wq/stormwater/construction/index.html).
Permittees unable to submit electronically (for example, those who do not have an
internet connection) must contact Ecology to request a waiver and obtain instructions
on how to obtain a paper NOI.
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, Washington 98504-7696
c. The operator must submit the NOI at least 60 days before discharging stormwater
from construction activities and must submit it prior to the date of the first public
notice (See Special Condition S2.B, below, for details). The 30-day public comment
period begins on the publication date of the second public notice. Unless Ecology
responds to the complete application in writing, coverage under the general permit
will automatically commence on the 31st day following receipt by Ecology of a
completed NOI, or the issuance date of this permit, whichever is later; unless Ecology
specifies a later date in writing as required by WAC173-226-200(2). See S8.B for
Limits on Coverage for New Discharges to TMDL or 303(d)-Listed Waters.
d. If an applicant intends to use a Best Management Practice (BMP) selected on the
basis of Special Condition S9.C.4 (“demonstrably equivalent” BMPs), the applicant
must notify Ecology of its selection as part of the NOI. In the event the applicant
selects BMPs after submission of the NOI, the applicant must provide notice of the
Construction Stormwater General Permit Page 8
selection of an equivalent BMP to Ecology at least 60 days before intended use of
the equivalent BMP.
e. Applicants must notify Ecology if they are aware of contaminated soils and/or
groundwater associated with the construction activity. Provide detailed information
with the NOI (as known and readily available) on the nature and extent of the
contamination (concentrations, locations, and depth), as well as pollution
prevention and/or treatment BMPs proposed to control the discharge of soil and/or
groundwater contaminants in stormwater. Examples of such detail may include, but
are not limited to:
i. List or table of all known contaminants with laboratory test results showing
concentration and depth,
ii. Map with sample locations,
iii. Related portions of the Stormwater Pollution Prevention Plan (SWPPP) that
address the management of contaminated and potentially contaminated
construction stormwater and dewatering water,
iv. Dewatering plan and/or dewatering contingency plan.
2. Transfer of Coverage Form
The Permittee can transfer current coverage under this permit to one or more new
operators, including operators of sites within a Common Plan of Development, provided:
i. The Permittee submits a complete Transfer of Coverage Form to Ecology,
signed by the current and new discharger and containing a specific date for
transfer of permit responsibility, coverage and liability (including any
Administrative Orders associated with the permit); and
ii. Ecology does not notify the current discharger and new discharger of intent to
revoke coverage under the general permit. If this notice is not given, the
transfer is effective on the date specified in the written agreement.
When a current discharger (Permittee) transfers a portion of a permitted site, the current
discharger must also indicate the remaining permitted acreage after the transfer.
Transfers do not require public notice.
3. Modification of Coverage Form
Permittees must notify Ecology regarding any changes to the information provided on
the NOI by submitting an Update/Modification of Permit Coverage form in accordance
with General Conditions G6 and G19. Examples of such changes include, but are not
limited to:
i. Changes to the Permittee’s mailing address,
ii. Changes to the on-site contact person information, and
iii. Changes to the area/acreage affected by construction activity.
Construction Stormwater General Permit Page 9
B. Public Notice
For new or previously unpermitted construction activities, the applicant must publish a public
notice at least one time each week for two consecutive weeks, at least 7 days apart, in a
newspaper with general circulation in the county where the construction is to take place. The
notice must be run after the NOI has been submitted and must contain:
1. A statement that “The applicant is seeking coverage under the Washington State
Department of Ecology’s Construction Stormwater NPDES and State Waste Discharge
General Permit.”
2. The name, address, and location of the construction site.
3. The name and address of the applicant.
4. The type of construction activity that will result in a discharge (for example, residential
construction, commercial construction, etc.), and the total number of acres to be
disturbed over the lifetime of the project.
5. The name of the receiving water(s) (that is, the surface water(s) to which the site will
discharge), or, if the discharge is through a storm sewer system, the name of the
operator of the system and the receiving water(s) the system discharges to.
6. The statement: Any persons desiring to present their views to the Washington State
Department of Ecology regarding this application, or interested in Ecology’s action on this
application, may notify Ecology in writing no later than 30 days of the last date of
publication of this notice. Ecology reviews public comments and considers whether
discharges from this project would cause a measurable change in receiving water quality,
and, if so, whether the project is necessary and in the overriding public interest according
to Tier II antidegradation requirements under WAC 173-201A-320. Comments can be
submitted to: Department of Ecology, PO Box 47696, Olympia, Washington 98504-7696
Attn: Water Quality Program, Construction Stormwater.
S3. COMPLIANCE WITH STANDARDS
A. Discharges must not cause or contribute to a violation of surface water quality standards
(Chapter 173-201A WAC), groundwater quality standards (Chapter 173-200 WAC),
sediment management standards (Chapter 173-204 WAC), and human health-based
criteria in the Federal water quality criteria applicable to Washington. (40 CFR Part 131.45)
Discharges that are not in compliance with these standards are prohibited.
B. Prior to the discharge of stormwater and non-stormwater to waters of the State, the
Permittee must apply All Known, Available, and Reasonable methods of prevention,
control, and Treatment (AKART). This includes the preparation and implementation of an
adequate SWPPP, with all appropriate BMPs installed and maintained in accordance with
the SWPPP and the terms and conditions of this permit.
C. Ecology presumes that a Permittee complies with water quality standards unless discharge
monitoring data or other site-specific information demonstrates that a discharge causes or
contributes to a violation of water quality standards, when the Permittee complies with the
following conditions. The Permittee must fully:
Construction Stormwater General Permit Page 10
1. Comply with all permit conditions, including; planning, sampling, monitoring,
reporting, and recordkeeping conditions.
2. Implement stormwater BMPs contained in stormwater management manuals
published or approved by Ecology, or BMPs that are demonstrably equivalent to BMPs
contained in stormwater management manuals published or approved by Ecology,
including the proper selection, implementation, and maintenance of all applicable and
appropriate BMPs for on-site pollution control. (For purposes of this section, the
stormwater manuals listed in Appendix 10 of the Phase I Municipal Stormwater Permit
are approved by Ecology.)
D. Where construction sites also discharge to groundwater, the groundwater discharges must
also meet the terms and conditions of this CSWGP. Permittees who discharge to
groundwater through an injection well must also comply with any applicable requirements
of the Underground Injection Control (UIC) regulations, Chapter 173-218 WAC.
S4. MONITORING REQUIREMENTS, BENCHMARKS, AND
REPORTING TRIGGERS
A. Site Log Book
The Permittee must maintain a site log book that contains a record of the implementation of
the SWPPP and other permit requirements, including the installation and maintenance of
BMPs, site inspections, and stormwater monitoring.
B. Site Inspections
Construction sites one (1) acre or larger that discharge stormwater to surface waters of the
State must have site inspections conducted by a Certified Erosion and Sediment Control Lead
(CESCL). Sites less than one (1) acre may have a person without CESCL certification conduct
inspections. (See Special Conditions S4.B.3 and B.4, below, for detailed requirements of the
Permittee’s CESCL.)
Site inspections must include all areas disturbed by construction activities, all BMPs, and all
stormwater discharge points under the Permittee’s operational control.
1. The Permittee must have staff knowledgeable in the principles and practices of erosion
and sediment control. The CESCL (sites one acre or more) or inspector (sites less than one
acre) must have the skills to assess the:
a. Site conditions and construction activities that could impact the quality of
stormwater; and
b. Effectiveness of erosion and sediment control measures used to control the quality
of stormwater discharges. The SWPPP must identify the CESCL or inspector, who
must be present on site or on-call at all times. The CESCL (sites one (1) acre or more)
must obtain this certification through an approved erosion and sediment control
training program that meets the minimum training standards established by Ecology.
(See BMP C160 in the manual, referred to in Special Condition S9.C.1 and 2.)
2. The CESCL or inspector must examine stormwater visually for the presence of suspended
sediment, turbidity, discoloration, and oil sheen. BMP effectiveness must be evaluated to
Construction Stormwater General Permit Page 11
determine if it is necessary to install, maintain, or repair BMPs to improve the quality of
stormwater discharges.
Based on the results of the inspection, the Permittee must correct the problems
identified, by:
a. Reviewing the SWPPP for compliance with Special Condition S9 and making
appropriate revisions within 7 days of the inspection.
b. Immediately beginning the process of fully implementing and maintaining
appropriate source control and/or treatment BMPs, within 10 days of the
inspection. If installation of necessary treatment BMPs is not feasible within 10
days, Ecology may approve additional time when an extension is requested by a
Permittee within the initial 10-day response period.
c. Documenting BMP implementation and maintenance in the site log book.
3. The CESCL or inspector must inspect all areas disturbed by construction activities, all
BMPs, and all stormwater discharge points at least once every calendar week and within
24 hours of any discharge from the site. (For purposes of this condition, individual
discharge events that last more than one (1) day do not require daily inspections. For
example, if a stormwater pond discharges continuously over the course of a week, only
one (1) inspection is required that week.) Inspection frequency may be reduced to once
every calendar month for inactive sites that are temporarily stabilized.
4. The Permittee must summarize the results of each inspection in an inspection report or
checklist and enter the report/checklist into, or attach it to, the site log book. At a
minimum, each inspection report or checklist must include:
a. Inspection date and time.
b. Weather information.
c. The general conditions during inspection.
d. The approximate amount of precipitation since the last inspection.
e. The approximate amount of precipitation within the last 24 hours.
f. A summary or list of all implemented BMPs, including observations of all
erosion/sediment control structures or practices.
g. A description of:
i. BMPs inspected (including location).
ii. BMPs that need maintenance and why.
iii. BMPs that failed to operate as designed or intended, and
iv. Where additional or different BMPs are needed, and why.
h. A description of stormwater discharged from the site. The Permittee must note the
presence of suspended sediment, turbidity, discoloration, and oil sheen, as
applicable.
Construction Stormwater General Permit Page 12
i. Any water quality monitoring performed during inspection.
j. General comments and notes, including a brief description of any BMP repairs,
maintenance, or installations made following the inspection.
k. An implementation schedule for the remedial actions that the Permittee plans to
take if the site inspection indicates that the site is out of compliance. The remedial
actions taken must meet the requirements of the SWPPP and the permit.
l. A summary report of the inspection.
m. The name, title, and signature of the person conducting the site inspection, a phone
number or other reliable method to reach this person, and the following statement:
I certify that this report is true, accurate, and complete to the best of my knowledge
and belief.
Table 3 Summary of Primary Monitoring Requirements
Size of Soil
Disturbance 1
Weekly Site
Inspections
Weekly
Sampling w/
Turbidity Meter
Weekly
Sampling w/
Transparency
Tube
Weekly pH
Sampling 2
CESCL
Required for
Inspections?
Sites that disturb less
than 1 acre, but are
part of a larger
Common Plan of
Development
Required Not Required Not Required Not Required No
Sites that disturb 1
acre or more, but
fewer than 5 acres
Required Sampling Required –
either method 3
Required Yes
Sites that disturb 5
acres or more
Required Required Not Required 4 Required Yes
1 Soil disturbance is calculated by adding together all areas that will be affected by construction activity.
Construction activity means clearing, grading, excavation, and any other activity that disturbs the surface of the
land, including ingress/egress from the site.
2 If construction activity results in the disturbance of 1 acre or more, and involves significant concrete work (1,000
cubic yards of concrete or recycled concrete placed or poured over the life of a project) or the use of engineered
soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD], or
fly ash), and stormwater from the affected area drains to surface waters of the State or to a storm sewer
stormwater collection system that drains to other surface waters of the State, the Permittee must conduct pH
sampling in accordance with Special Condition S4.D.
3 Sites with one or more acres, but fewer than 5 acres of soil disturbance, must conduct turbidity or transparency
sampling in accordance with Special Condition S4.C.4.a or b.
4 Sites equal to or greater than 5 acres of soil disturbance must conduct turbidity sampling using a turbidity meter
in accordance with Special Condition S4.C.4.a.
Construction Stormwater General Permit Page 13
C. Turbidity/Transparency Sampling Requirements
1. Sampling Methods
a. If construction activity involves the disturbance of five (5) acres or more, the
Permittee must conduct turbidity sampling per Special Condition S4.C.4.a, below.
b. If construction activity involves one (1) acre or more but fewer than five (5) acres of
soil disturbance, the Permittee must conduct either transparency sampling or
turbidity sampling per Special Condition S4.C.4.a or b, below.
2. Sampling Frequency
a. The Permittee must sample all discharge points at least once every calendar week
when stormwater (or authorized non-stormwater) discharges from the site or
enters any on-site surface waters of the state (for example, a creek running through
a site); sampling is not required on sites that disturb less than an acre.
b. Samples must be representative of the flow and characteristics of the discharge.
c. Sampling is not required when there is no discharge during a calendar week.
d. Sampling is not required outside of normal working hours or during unsafe
conditions.
e. If the Permittee is unable to sample during a monitoring period, the Permittee must
include a brief explanation in the monthly Discharge Monitoring Report (DMR).
f. Sampling is not required before construction activity begins.
g. The Permittee may reduce the sampling frequency for temporarily stabilized,
inactive sites to once every calendar month.
3. Sampling Locations
a. Sampling is required at all points where stormwater associated with construction
activity (or authorized non-stormwater) is discharged off site, including where it
enters any on-site surface waters of the state (for example, a creek running through
a site).
b. The Permittee may discontinue sampling at discharge points that drain areas of the
project that are fully stabilized to prevent erosion.
c. The Permittee must identify all sampling point(s) in the SWPPP and on the site map
and clearly mark these points in the field with a flag, tape, stake or other visible
marker.
d. Sampling is not required for discharge that is sent directly to sanitary or combined
sewer systems.
e. The Permittee may discontinue sampling at discharge points in areas of the project
where the Permittee no longer has operational control of the construction activity.
Construction Stormwater General Permit Page 14
4. Sampling and Analysis Methods
a. The Permittee performs turbidity analysis with a calibrated turbidity meter
(turbidimeter) either on site or at an accredited lab. The Permittee must record the
results in the site log book in nephelometric turbidity units (NTUs).
b. The Permittee performs transparency analysis on site with a 1¾ inch diameter, 60
centimeter (cm)-long transparency tube. The Permittee will record the results in the
site log book in centimeters (cm).
Table 4 Monitoring and Reporting Requirements
Parameter Unit Analytical Method Sampling
Frequency
Benchmark
Value
Turbidity NTU SM2130 Weekly, if
discharging 25 NTUs
Transparency Cm
Manufacturer
instructions, or
Ecology guidance
Weekly, if
discharging 33 cm
5. Turbidity/Transparency Benchmark Values and Reporting Triggers
The benchmark value for turbidity is 25 NTUs. The benchmark value for transparency is
33 centimeters (cm). Note: Benchmark values do not apply to discharges to segments of
water bodies on Washington State’s 303(d) list (Category 5) for turbidity, fine sediment,
or phosphorus; these discharges are subject to a numeric effluent limit for turbidity.
Refer to Special Condition S8 for more information and follow S5.F – Noncompliance
Notification for reporting requirements applicable to discharges which exceed the
numeric effluent limit for turbidity.
a. Turbidity 26 – 249 NTUs, or Transparency 32 – 7 cm:
If the discharge turbidity is 26 to 249 NTUs; or if discharge transparency is 32 to 7
cm, the Permittee must:
i. Immediately begin the process to fully implement and maintain appropriate
source control and/or treatment BMPs, and no later than 10 days of the date
the discharge exceeded the benchmark. If installation of necessary treatment
BMPs is not feasible within 10 days, Ecology may approve additional time when
the Permittee requests an extension within the initial 10-day response period.
ii. Review the SWPPP for compliance with Special Condition S9 and make
appropriate revisions within 7 days of the date the discharge exceeded the
benchmark.
iii. Document BMP implementation and maintenance in the site log book.
b. Turbidity 250 NTUs or greater, or Transparency 6 cm or less:
If a discharge point’s turbidity is 250 NTUs or greater, or if discharge transparency is
less than or equal to 6 cm, the Permittee must complete the reporting and adaptive
Construction Stormwater General Permit Page 15
management process described below. For discharges which are subject to a
numeric effluent limit for turbidity, see S5.F – Noncompliance Notification.
i. Within 24 hours, telephone or submit an electronic report to the applicable
Ecology Region’s Environmental Report Tracking System (ERTS) number (or
through Ecology’s Water Quality Permitting Portal [WQWebPortal] – Permit
Submittals when the form is available), in accordance with Special Condition S5.A.
• Central Region (Okanogan, Chelan, Douglas, Kittitas, Yakima, Klickitat,
Benton): (509) 575-2490
• Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield,
Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman):
(509) 329-3400
• Northwest Region (Kitsap, Snohomish, Island, King, San Juan, Skagit,
Whatcom): (425) 649-7000
• Southwest Region (Grays Harbor, Lewis, Mason, Thurston, Pierce, Clark,
Cowlitz, Skamania, Wahkiakum, Clallam, Jefferson, Pacific): (360) 407-6300
These numbers and a link to the ERTS reporting page are also listed at the following
website: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html.
ii. Immediately begin the process to fully implement and maintain appropriate
source control and/or treatment BMPs as soon as possible, addressing the
problems within 10 days of the date the discharge exceeded the benchmark. If
installation of necessary treatment BMPs is not feasible within 10 days, Ecology
may approve additional time when the Permittee requests an extension within
the initial 10-day response period.
iii. Sample discharges daily until:
a) Turbidity is 25 NTUs (or lower); or
b) Transparency is 33 cm (or greater); or
c) The Permittee has demonstrated compliance with the water quality
standard for turbidity:
1) No more than 5 NTUs over background turbidity, if background is less
than 50 NTUs, or
2) No more than 10% over background turbidity, if background is 50
NTUs or greater; or
*Note: background turbidity in the receiving water must be
measured immediately upstream (upgradient) or outside of the area
of influence of the discharge.
d) The discharge stops or is eliminated.
iv. Review the SWPPP for compliance with Special Condition S9 and make
appropriate revisions within seven (7) days of the date the discharge exceeded
the benchmark.
Construction Stormwater General Permit Page 16
v. Document BMP implementation and maintenance in the site log book.
Compliance with these requirements does not relieve the Permittee from responsibility to
maintain continuous compliance with permit benchmarks.
D. pH Sampling Requirements – Significant Concrete Work or Engineered Soils
If construction activity results in the disturbance of 1 acre or more, and involves significant
concrete work (significant concrete work means greater than 1000 cubic yards placed or
poured concrete or recycled concrete used over the life of a project) or the use of engineered
soils (soil amendments including but not limited to Portland cement-treated base [CTB],
cement kiln dust [CKD], or fly ash), and stormwater from the affected area drains to surface
waters of the State or to a storm sewer system that drains to surface waters of the State, the
Permittee must conduct pH sampling as set forth below. Note: In addition, discharges to
segments of water bodies on Washington State’s 303(d) list (Category 5) for high pH are subject
to a numeric effluent limit for pH; refer to Special Condition S8.
1. The Permittee must perform pH analysis on site with a calibrated pH meter, pH test kit,
or wide range pH indicator paper. The Permittee must record pH sampling results in the
site log book.
2. During the applicable pH monitoring period defined below, the Permittee must obtain a
representative sample of stormwater and conduct pH analysis at least once per week.
a. For sites with significant concrete work, the Permittee must begin the pH sampling
period when the concrete is first placed or poured and exposed to precipitation, and
continue weekly throughout and after the concrete placement, pour and curing
period, until stormwater pH is in the range of 6.5 to 8.5 (su).
b. For sites with recycled concrete where monitoring is required, the Permittee must
begin the weekly pH sampling period when the recycled concrete is first exposed to
precipitation and must continue until the recycled concrete is fully stabilized with
the stormwater pH in the range of 6.5 to 8.5 (su).
c. For sites with engineered soils, the Permittee must begin the pH sampling period
when the soil amendments are first exposed to precipitation and must continue
until the area of engineered soils is fully stabilized.
3. The Permittee must sample pH in the sediment trap/pond(s) or other locations that
receive stormwater runoff from the area of significant concrete work or engineered soils
before the stormwater discharges to surface waters.
4. The benchmark value for pH is 8.5 standard units. Anytime sampling indicates that pH is
8.5 or greater, the Permittee must either:
a. Prevent the high pH water (8.5 or above) from entering storm sewer systems or
surface waters of the state; or
b. If necessary, adjust or neutralize the high pH water until it is in the range of pH 6.5 to
8.5 (su) using an appropriate treatment BMP such as carbon dioxide (CO2) sparging, dry
ice or food grade vinegar. The Permittee must obtain written approval from Ecology
before using any form of chemical treatment other than CO2 sparging, dry ice or food
grade vinegar.
Construction Stormwater General Permit Page 17
S5. REPORTING AND RECORDKEEPING REQUIREMENTS
A. High Turbidity Reporting
Anytime sampling performed in accordance with Special Condition S4.C indicates turbidity has
reached the 250 NTUs or more (or transparency less than or equal to 6 cm), high turbidity
reporting level, the Permittee must notify Ecology within 24 hours of analysis either by calling
the applicable Ecology Region’s Environmental Report Tracking System (ERTS) number by
phone or by submitting an electronic ERTS report (through Ecology’s Water Quality Permitting
Portal (WQWebPortal) – Permit Submittals when the form is available). See the CSWGP website
for links to ERTS and the WQWebPortal. (http://www.ecy.wa.gov/programs/wq/stormwater/
construction/index.html) Also, see phone numbers in Special Condition S4.C.5.b.i.
B. Discharge Monitoring Reports (DMRs)
Permittees required to conduct water quality sampling in accordance with Special Conditions
S4.C (Turbidity/Transparency), S4.D (pH), S8 (303[d]/TMDL sampling), and/or G12 (Additional
Sampling) must submit the results to Ecology.
Permittees must submit monitoring data using Ecology's WQWebDMR web application
accessed through Ecology’s Water Quality Permitting Portal.
Permittees unable to submit electronically (for example, those who do not have an internet
connection) must contact Ecology to request a waiver and obtain instructions on how to obtain
a paper copy DMR at:
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, WA 98504-7696
Permittees who obtain a waiver not to use WQWebDMR must use the forms provided to them
by Ecology; submittals must be mailed to the address above. Permittees must submit DMR
forms to be received by Ecology within 15 days following the end of each month.
If there was no discharge during a given monitoring period, all Permittees must submit a DMR
as required with “no discharge” entered in place of the monitoring results. DMRs are required
for the full duration of permit coverage (from the first full month following the effective date of
permit coverage up until Ecology has approved termination of the coverage). For more
information, contact Ecology staff using information provided at the following website:
www.ecy.wa.gov/programs/wq/permits/paris/contacts.html.
C. Records Retention
The Permittee must retain records of all monitoring information (site log book, sampling
results, inspection reports/checklists, etc.), Stormwater Pollution Prevention Plan, copy of the
permit coverage letter (including Transfer of Coverage documentation) and any other
documentation of compliance with permit requirements for the entire life of the construction
project and for a minimum of five (5) years following the termination of permit coverage. Such
information must include all calibration and maintenance records, and records of all data used
to complete the application for this permit. This period of retention must be extended during
Construction Stormwater General Permit Page 18
the course of any unresolved litigation regarding the discharge of pollutants by the Permittee
or when requested by Ecology.
D. Recording Results
For each measurement or sample taken, the Permittee must record the following information:
1. Date, place, method, and time of sampling or measurement.
2. The first and last name of the individual who performed the sampling or measurement.
3. The date(s) the analyses were performed.
4. The first and last name of the individual who performed the analyses.
5. The analytical techniques or methods used.
6. The results of all analyses.
E. Additional Monitoring by the Permittee
If the Permittee samples or monitors any pollutant more frequently than required by this
permit using test procedures specified by Special Condition S4 of this permit, the sampling
results for this monitoring must be included in the calculation and reporting of the data
submitted in the Permittee’s DMR.
F. Noncompliance Notification
In the event the Permittee is unable to comply with any part of the terms and conditions of this
permit, and the resulting noncompliance may cause a threat to human health or the
environment (such as but not limited to spills or fuels or other materials, catastrophic pond or
slope failure, and discharges that violate water quality standards), or exceed numeric effluent
limitations (see S8 – Discharges to 303(d) or TMDL Waterbodies), the Permittee must, upon
becoming aware of the circumstance:
1. Notify Ecology within 24 hours of the failure to comply by calling the applicable Regional
office ERTS phone number (refer to Special Condition S4.C.5.b.i, or go to
https://ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue to find
contact information for the regional offices.)
2. Immediately take action to prevent the discharge/pollution, or otherwise stop or correct
the noncompliance, and, if applicable, repeat sampling and analysis of any noncompliance
immediately and submit the results to Ecology within five (5) days of becoming aware of
the violation (See S5.F.3, below, for details on submitting results in a report).
3. Submit a detailed written report to Ecology within five (5) days of the time the Permittee
becomes aware of the circumstances, unless requested earlier by Ecology. The report must
be submitted using Ecology’s Water Quality Permitting Portal (WQWebPortal) – Permit
Submittals, unless a waiver from electronic reporting has been granted according to S5.B.
The report must contain a description of the noncompliance, including exact dates and
times, and if the noncompliance has not been corrected, the anticipated time it is expected
to continue; and the steps taken or planned to reduce, eliminate, and prevent
reoccurrence of the noncompliance.
Construction Stormwater General Permit Page 19
The Permittee must report any unanticipated bypass and/or upset that exceeds any
effluent limit in the permit in accordance with the 24-hour reporting requirement
contained in 40 C.F.R. 122.41(l)(6).
Compliance with these requirements does not relieve the Permittee from responsibility
to maintain continuous compliance with the terms and conditions of this permit or the
resulting liability for failure to comply. Upon request of the Permittee, Ecology may waive
the requirement for a written report on a case-by-case basis, if the immediate
notification is received by Ecology within 24 hours.
G. Access to Plans and Records
1. The Permittee must retain the following permit documentation (plans and records) on
site, or within reasonable access to the site, for use by the operator or for on-site review
by Ecology or the local jurisdiction:
a. General Permit
b. Permit Coverage Letter
c. Stormwater Pollution Prevention Plan (SWPPP)
d. Site Log Book
e. Erosivity Waiver (if applicable)
2. The Permittee must address written requests for plans and records listed above (Special
Condition S5.G.1) as follows:
a. The Permittee must provide a copy of plans and records to Ecology within 14 days of
receipt of a written request from Ecology.
b. The Permittee must provide a copy of plans and records to the public when
requested in writing. Upon receiving a written request from the public for the
Permittee’s plans and records, the Permittee must either:
i. Provide a copy of the plans and records to the requester within 14 days of a
receipt of the written request; or
ii. Notify the requester within 10 days of receipt of the written request of the
location and times within normal business hours when the plans and records
may be viewed; and provide access to the plans and records within 14 days of
receipt of the written request; or
Within 14 days of receipt of the written request, the Permittee may submit a
copy of the plans and records to Ecology for viewing and/or copying by the
requester at an Ecology office, or a mutually agreed location. If plans and
records are viewed and/or copied at a location other than at an Ecology office,
the Permittee will provide reasonable access to copying services for which a
reasonable fee may be charged. The Permittee must notify the requester
within 10 days of receipt of the request where the plans and records may be
viewed and/or copied.
Construction Stormwater General Permit Page 20
S6. PERMIT FEES
The Permittee must pay permit fees assessed by Ecology. Fees for stormwater discharges covered
under this permit are established by Chapter 173-224 WAC. Ecology continues to assess permit
fees until the permit is terminated in accordance with Special Condition S10 or revoked in
accordance with General Condition G5.
S7. SOLID AND LIQUID WASTE DISPOSAL
The Permittee must handle and dispose of solid and liquid wastes generated by construction
activity, such as demolition debris, construction materials, contaminated materials, and waste
materials from maintenance activities, including liquids and solids from cleaning catch basins and
other stormwater facilities, in accordance with:
A. Special Condition S3, Compliance with Standards.
B. WAC 173-216-110.
C. Other applicable regulations.
S8. DISCHARGES TO 303(d) OR TMDL WATERBODIES
A. Sampling and Numeric Effluent Limits For Certain Discharges to 303(d)-Listed
Water Bodies
1. Permittees who discharge to segments of water bodies listed as impaired by the State of
Washington under Section 303(d) of the Clean Water Act for turbidity, fine sediment,
high pH, or phosphorus, must conduct water quality sampling according to the
requirements of this section, and Special Conditions S4.C.2.b-f and S4.C.3.b-d, and must
comply with the applicable numeric effluent limitations in S8.C and S8.D.
2. All references and requirements associated with Section 303(d) of the Clean Water Act
mean the most current listing by Ecology of impaired waters (Category 5) that exists on
January 1, 2021, or the date when the operator’s complete permit application is received
by Ecology, whichever is later.
B. Limits on Coverage for New Discharges to TMDL or 303(d)-Listed Waters
Construction sites that discharge to a TMDL or 303(d)-listed waterbody are not eligible for
coverage under this permit unless the operator:
Construction Stormwater General Permit Page 21
1. Prevents exposing stormwater to pollutants for which the waterbody is impaired, and
retains documentation in the SWPPP that details procedures taken to prevent exposure
on site; or
2. Documents that the pollutants for which the waterbody is impaired are not present at
the site, and retains documentation of this finding within the SWPPP; or
3. Provides Ecology with data indicating the discharge is not expected to cause or
contribute to an exceedance of a water quality standard, and retains such data on site
with the SWPPP. The operator must provide data and other technical information to
Ecology that sufficiently demonstrate:
a. For discharges to waters without an EPA-approved or -established TMDL, that the
discharge of the pollutant for which the water is impaired will meet in-stream water
quality criteria at the point of discharge to the waterbody; or
b. For discharges to waters with an EPA-approved or -established TMDL, that there is
sufficient remaining wasteload allocation in the TMDL to allow construction
stormwater discharge and that existing dischargers to the waterbody are subject to
compliance schedules designed to bring the waterbody into attainment with water
quality standards.
Operators of construction sites are eligible for coverage under this permit only after
Ecology makes an affirmative determination that the discharge will not cause or
contribute to the existing impairment or exceed the TMDL.
C. Sampling and Numeric Effluent Limits for Discharges to Water Bodies on the 303(d) List
for Turbidity, Fine Sediment, or Phosphorus
1. Permittees who discharge to segments of water bodies on the 303(d) list (Category 5) for
turbidity, fine sediment, or phosphorus must conduct turbidity sampling in accordance
with Special Condition S4.C.2 and comply with either of the numeric effluent limits noted
in Table 5 below.
2. As an alternative to the 25 NTUs effluent limit noted in Table 5 below (applied at the
point where stormwater [or authorized non-stormwater] is discharged off-site),
Permittees may choose to comply with the surface water quality standard for turbidity.
The standard is: no more than 5 NTUs over background turbidity when the background
turbidity is 50 NTUs or less, or no more than a 10% increase in turbidity when the
background turbidity is more than 50 NTUs. In order to use the water quality standard
requirement, the sampling must take place at the following locations:
a. Background turbidity in the 303(d)-listed receiving water immediately upstream
(upgradient) or outside the area of influence of the discharge.
b. Turbidity at the point of discharge into the 303(d)-listed receiving water, inside the
area of influence of the discharge.
3. Discharges that exceed the numeric effluent limit for turbidity constitute a violation of
this permit.
4. Permittees whose discharges exceed the numeric effluent limit must sample discharges
daily until the violation is corrected and comply with the non-compliance notification
requirements in Special Condition S5.F.
Construction Stormwater General Permit Page 22
Table 5 Turbidity, Fine Sediment & Phosphorus Sampling and Limits for 303(d)-Listed Waters
Parameter identified in
303(d) listing
Parameter
Sampled Unit Analytical
Method
Sampling
Frequency
Numeric Effluent
Limit1
• Turbidity
• Fine Sediment
• Phosphorus
Turbidity NTU SM2130 Weekly, if
discharging
25 NTUs, at the point
where stormwater is
discharged from the
site; OR
In compliance with
the surface water
quality standard for
turbidity (S8.C.2.a)
1 Permittees subject to a numeric effluent limit for turbidity may, at their discretion, choose either
numeric effluent limitation based on site-specific considerations including, but not limited to,
safety, access and convenience.
D. Discharges to Water Bodies on the 303(d) List for High pH
1. Permittees who discharge to segments of water bodies on the 303(d) list (Category 5) for
high pH must conduct pH sampling in accordance with the table below, and comply with
the numeric effluent limit of pH 6.5 to 8.5 su (Table 6).
Table 6 pH Sampling and Limits for 303(d)-Listed Waters
Parameter identified in 303(d)
listing
Parameter
Sampled/Units
Analytical
Method
Sampling
Frequency
Numeric Effluent
Limit
High pH pH /Standard
Units pH meter Weekly, if
discharging
In the range of
6.5 – 8.5 su
2. At the Permittee’s discretion, compliance with the limit shall be assessed at one of the
following locations:
a. Directly in the 303(d)-listed waterbody segment, inside the immediate area of
influence of the discharge; or
b. Alternatively, the Permittee may measure pH at the point where the discharge
leaves the construction site, rather than in the receiving water.
3. Discharges that exceed the numeric effluent limit for pH (outside the range of 6.5 – 8.5 su)
constitute a violation of this permit.
4. Permittees whose discharges exceed the numeric effluent limit must sample discharges
daily until the violation is corrected and comply with the non-compliance notification
requirements in Special Condition S5.F.
E. Sampling and Limits for Sites Discharging to Waters Covered by a TMDL or another
Pollution Control Plan
Construction Stormwater General Permit Page 23
1. Discharges to a waterbody that is subject to a Total Maximum Daily Load (TMDL) for
turbidity, fine sediment, high pH, or phosphorus must be consistent with the TMDL. Refer
to http://www.ecy.wa.gov/programs/wq/tmdl/TMDLsbyWria/TMDLbyWria.html for
more information on TMDLs.
a. Where an applicable TMDL sets specific waste load allocations or requirements for
discharges covered by this permit, discharges must be consistent with any specific
waste load allocations or requirements established by the applicable TMDL.
i. The Permittee must sample discharges weekly, unless otherwise specified by
the TMDL, to evaluate compliance with the specific waste load allocations or
requirements.
ii. Analytical methods used to meet the monitoring requirements must conform
to the latest revision of the Guidelines Establishing Test Procedures for the
Analysis of Pollutants contained in 40 CFR Part 136.
iii. Turbidity and pH methods need not be accredited or registered unless
conducted at a laboratory which must otherwise be accredited or registered.
b. Where an applicable TMDL has established a general waste load allocation for
construction stormwater discharges, but has not identified specific requirements,
compliance with Special Conditions S4 (Monitoring) and S9 (SWPPPs) will constitute
compliance with the approved TMDL.
c. Where an applicable TMDL has not specified a waste load allocation for construction
stormwater discharges, but has not excluded these discharges, compliance with
Special Conditions S4 (Monitoring) and S9 (SWPPPs) will constitute compliance with
the approved TMDL.
d. Where an applicable TMDL specifically precludes or prohibits discharges from
construction activity, the operator is not eligible for coverage under this permit.
S9. STORMWATER POLLUTION PREVENTION PLAN
The Permittee must prepare and properly implement an adequate Stormwater Pollution
Prevention Plan (SWPPP) for construction activity in accordance with the requirements of this
permit beginning with initial soil disturbance and until final stabilization.
A. The Permittee’s SWPPP must meet the following objectives:
1. To identify best management practices (BMPs) which prevent erosion and sedimentation,
and to reduce, eliminate or prevent stormwater contamination and water pollution from
construction activity.
2. To prevent violations of surface water quality, groundwater quality, or sediment
management standards.
3. To control peak volumetric flow rates and velocities of stormwater discharges.
Construction Stormwater General Permit Page 24
B. General Requirements
1. The SWPPP must include a narrative and drawings. All BMPs must be clearly referenced in
the narrative and marked on the drawings. The SWPPP narrative must include
documentation to explain and justify the pollution prevention decisions made for the
project. Documentation must include:
a. Information about existing site conditions (topography, drainage, soils, vegetation, etc.).
b. Potential erosion problem areas.
c. The 13 elements of a SWPPP in Special Condition S9.D.1-13, including BMPs
used to address each element.
d. Construction phasing/sequence and general BMP implementation schedule.
e. The actions to be taken if BMP performance goals are not achieved—for example,
a contingency plan for additional treatment and/or storage of stormwater that
would violate the water quality standards if discharged.
f. Engineering calculations for ponds, treatment systems, and any other designed
structures. When a treatment system requires engineering calculations, these
calculations must be included in the SWPPP. Engineering calculations do not need to
be included in the SWPPP for treatment systems that do not require such calculations.
2. The Permittee must modify the SWPPP 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, or would be, ineffective in eliminating or significantly
minimizing pollutants in stormwater discharges from the site. The Permittee must then:
a. Review the SWPPP for compliance with Special Condition S9 and make appropriate
revisions within 7 days of the inspection or investigation.
b. Immediately begin the process to fully implement and maintain appropriate source
control and/or treatment BMPs as soon as possible, addressing the problems no later
than 10 days from the inspection or investigation. If installation of necessary treatment
BMPs is not feasible within 10 days, Ecology may approve additional time when an
extension is requested by a Permittee within the initial 10-day response period.
c. Document BMP implementation and maintenance in the site log book.
The Permittee must modify the SWPPP whenever there is a change in design,
construction, operation, or maintenance at the construction site that has, or could have,
a significant effect on the discharge of pollutants to waters of the State.
C. Stormwater Best Management Practices (BMPs)
BMPs must be consistent with:
1. Stormwater Management Manual for Western Washington (most current approved
edition at the time this permit was issued), for sites west of the crest of the Cascade
Mountains; or
Construction Stormwater General Permit Page 25
2. Stormwater Management Manual for Eastern Washington (most current approved
edition at the time this permit was issued), for sites east of the crest of the Cascade
Mountains; or
3. Revisions to the manuals listed in Special Condition S9.C.1 & 2, or other stormwater
management guidance documents or manuals which provide an equivalent level of
pollution prevention, that are approved by Ecology and incorporated into this permit in
accordance with the permit modification requirements of WAC 173-226-230; or
4. Documentation in the SWPPP that the BMPs selected provide an equivalent level of
pollution prevention, compared to the applicable stormwater management manuals,
including:
a. The technical basis for the selection of all stormwater BMPs (scientific, technical studies,
and/or modeling) that support the performance claims for the BMPs being selected.
b. An assessment of how the selected BMP will satisfy AKART requirements and the
applicable federal technology-based treatment requirements under 40 CFR part 125.3.
D. SWPPP – Narrative Contents and Requirements
The Permittee must include each of the 13 elements below in Special Condition S9.D.1-13 in
the narrative of the SWPPP and implement them unless site conditions render the element
unnecessary and the exemption from that element is clearly justified in the SWPPP.
1. Preserve Vegetation/Mark Clearing Limits
a. Before beginning land-disturbing activities, including clearing and grading, clearly
mark all clearing limits, sensitive areas and their buffers, and trees that are to be
preserved within the construction area.
b. Retain the duff layer, native topsoil, and natural vegetation in an undisturbed state
to the maximum degree practicable.
2. Establish Construction Access
a. Limit construction vehicle access and exit to one route, if possible.
b. Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent
BMPs, to minimize tracking sediment onto roads.
c. Locate wheel wash or tire baths on site, if the stabilized construction entrance is not
effective in preventing tracking sediment onto roads.
d. If sediment is tracked off site, clean the affected roadway thoroughly at the end of
each day, or more frequently as necessary (for example, during wet weather).
Remove sediment from roads by shoveling, sweeping, or pickup and transport of the
sediment to a controlled sediment disposal area.
e. Conduct street washing only after sediment removal in accordance with Special
Condition S9.D.2.d.
f. Control street wash wastewater by pumping back on site or otherwise preventing it
from discharging into systems tributary to waters of the State.
Construction Stormwater General Permit Page 26
3. Control Flow Rates
a. Protect properties and waterways downstream of construction sites from erosion
and the associated discharge of turbid waters due to increases in the velocity and
peak volumetric flow rate of stormwater runoff from the project site, as required by
local plan approval authority.
b. Where necessary to comply with Special Condition S9.D.3.a, construct stormwater
infiltration or detention BMPs as one of the first steps in grading. Assure that
detention BMPs function properly before constructing site improvements (for
example, impervious surfaces).
c. If permanent infiltration ponds are used for flow control during construction,
protect these facilities from sedimentation during the construction phase.
4. Install Sediment Controls
The Permittee must design, install and maintain effective erosion controls and sediment
controls to minimize the discharge of pollutants. At a minimum, the Permittee must:
a. Construct sediment control BMPs (sediment ponds, traps, filters, infiltration
facilities, etc.) as one of the first steps in grading. These BMPs must be functional
before other land disturbing activities take place.
b. Minimize sediment discharges from the site. The design, installation and
maintenance of erosion and sediment controls must address factors such as the
amount, frequency, intensity and duration of precipitation, the nature of resulting
stormwater runoff, and soil characteristics, including the range of soil particle sizes
expected to be present on the site.
c. Direct stormwater runoff from disturbed areas through a sediment pond or other
appropriate sediment removal BMP, before the runoff leaves a construction site or
before discharge to an infiltration facility. Runoff from fully stabilized areas may be
discharged without a sediment removal BMP, but must meet the flow control
performance standard of Special Condition S9.D.3.a.
d. Locate BMPs intended to trap sediment on site in a manner to avoid interference
with the movement of juvenile salmonids attempting to enter off-channel areas or
drainages.
e. Provide and maintain natural buffers around surface waters, direct stormwater to
vegetated areas to increase sediment removal and maximize stormwater
infiltration, unless infeasible.
f. Where feasible, design outlet structures that withdraw impounded stormwater
from the surface to avoid discharging sediment that is still suspended lower in the
water column.
5. Stabilize Soils
a. The Permittee must stabilize exposed and unworked soils by application of effective
BMPs that prevent erosion. Applicable BMPs include, but are not limited to:
temporary and permanent seeding, sodding, mulching, plastic covering, erosion
Construction Stormwater General Permit Page 27
control fabrics and matting, soil application of polyacrylamide (PAM), the early
application of gravel base on areas to be paved, and dust control.
b. The Permittee must control stormwater volume and velocity within the site to
minimize soil erosion.
c. The Permittee must control stormwater discharges, including both peak flow rates
and total stormwater volume, to minimize erosion at outlets and to minimize
downstream channel and stream bank erosion.
d. Depending on the geographic location of the project, the Permittee must not allow
soils to remain exposed and unworked for more than the time periods set forth
below to prevent erosion.
West of the Cascade Mountains Crest
During the dry season (May 1 - September 30): 7 days
During the wet season (October 1 - April 30): 2 days
East of the Cascade Mountains Crest, except for Central Basin*
During the dry season (July 1 - September 30): 10 days
During the wet season (October 1 - June 30): 5 days
The Central Basin*, East of the Cascade Mountains Crest
During the dry Season (July 1 - September 30): 30 days
During the wet season (October 1 - June 30): 15 days
*Note: The Central Basin is defined as the portions of Eastern Washington
with mean annual precipitation of less than 12 inches.
e. The Permittee must stabilize soils at the end of the shift before a holiday or
weekend if needed based on the weather forecast.
f. The Permittee must stabilize soil stockpiles from erosion, protected with sediment
trapping measures, and where possible, be located away from storm drain inlets,
waterways, and drainage channels.
g. The Permittee must minimize the amount of soil exposed during construction activity.
h. The Permittee must minimize the disturbance of steep slopes.
i. The Permittee must minimize soil compaction and, unless infeasible, preserve topsoil.
6. Protect Slopes
a. The Permittee must design and construct cut-and-fill slopes in a manner to minimize
erosion. Applicable practices include, but are not limited to, reducing continuous
length of slope with terracing and diversions, reducing slope steepness, and
roughening slope surfaces (for example, track walking).
b. The Permittee must divert off-site stormwater (run-on) or groundwater away from
slopes and disturbed areas with interceptor dikes, pipes, and/or swales. Off-site
stormwater should be managed separately from stormwater generated on the site.
c. At the top of slopes, collect drainage in pipe slope drains or protected channels to
prevent erosion.
Construction Stormwater General Permit Page 28
i. West of the Cascade Mountains Crest: Temporary pipe slope drains must handle
the peak 10-minute flow rate from a Type 1A, 10-year, 24-hour frequency storm
for the developed condition. Alternatively, the 10-year, 1-hour flow rate
predicted by an approved continuous runoff model, increased by a factor of 1.6,
may be used. The hydrologic analysis must use the existing land cover condition
for predicting flow rates from tributary areas outside the project limits. For
tributary areas on the project site, the analysis must use the temporary or
permanent project land cover condition, whichever will produce the highest flow
rates. If using the Western Washington Hydrology Model (WWHM) to predict
flows, bare soil areas should be modeled as "landscaped area.”
ii. East of the Cascade Mountains Crest: Temporary pipe slope drains must handle
the expected peak flow rate from a 6-month, 3-hour storm for the developed
condition, referred to as the short duration storm.
d. Place excavated material on the uphill side of trenches, consistent with safety and
space considerations.
e. Place check dams at regular intervals within constructed channels that are cut down
a slope.
7. Protect Drain Inlets
a. Protect all storm drain inlets made operable during construction so that stormwater
runoff does not enter the conveyance system without first being filtered or treated
to remove sediment.
b. Clean or remove and replace inlet protection devices when sediment has filled one-
third of the available storage (unless a different standard is specified by the product
manufacturer).
8. Stabilize Channels and Outlets
a. Design, construct and stabilize all on-site conveyance channels to prevent erosion
from the following expected peak flows:
i. West of the Cascade Mountains Crest: Channels must handle the peak 10-
minute flow rate from a Type 1A, 10-year, 24-hour frequency storm for the
developed condition. Alternatively, the 10-year, 1-hour flow rate indicated by
an approved continuous runoff model, increased by a factor of 1.6, may be
used. The hydrologic analysis must use the existing land cover condition for
predicting flow rates from tributary areas outside the project limits. For
tributary areas on the project site, the analysis must use the temporary or
permanent project land cover condition, whichever will produce the highest
flow rates. If using the WWHM to predict flows, bare soil areas should be
modeled as "landscaped area.”
ii. East of the Cascade Mountains Crest: Channels must handle the expected peak
flow rate from a 6-month, 3-hour storm for the developed condition, referred
to as the short duration storm.
b. Provide stabilization, including armoring material, adequate to prevent erosion of
outlets, adjacent stream banks, slopes, and downstream reaches at the outlets of all
conveyance systems.
Construction Stormwater General Permit Page 29
9. Control Pollutants
Design, install, implement and maintain effective pollution prevention measures to
minimize the discharge of pollutants. The Permittee must:
a. Handle and dispose of all pollutants, including waste materials and demolition
debris that occur on site in a manner that does not cause contamination of
stormwater.
b. Provide cover, containment, and protection from vandalism for all chemicals, liquid
products, petroleum products, and other materials that have the potential to pose a
threat to human health or the environment. Minimize storage of hazardous
materials on-site. Safety Data Sheets (SDS) should be supplied for all materials
stored. Chemicals should be kept in their original labeled containers. On-site fueling
tanks must include secondary containment. Secondary containment means placing
tanks or containers within an impervious structure capable of containing 110% of
the volume of the largest tank within the containment structure. Double-walled
tanks do not require additional secondary containment.
c. Conduct maintenance, fueling, and repair of heavy equipment and vehicles using
spill prevention and control measures. Clean contaminated surfaces immediately
following any spill incident.
d. Discharge wheel wash or tire bath wastewater to a separate on-site treatment
system that prevents discharge to surface water, such as closed-loop recirculation
or upland land application, or to the sanitary sewer with local sewer district
approval.
e. Apply fertilizers and pesticides in a manner and at application rates that will not
result in loss of chemical to stormwater runoff. Follow manufacturers’ label
requirements for application rates and procedures.
f. Use BMPs to prevent contamination of stormwater runoff by pH-modifying sources.
The sources for this contamination include, but are not limited to: bulk cement,
cement kiln dust, fly ash, new concrete washing and curing waters, recycled
concrete stockpiles, waste streams generated from concrete grinding and sawing,
exposed aggregate processes, dewatering concrete vaults, concrete pumping and
mixer washout waters. (Also refer to the definition for "concrete wastewater" in
Appendix A – Definitions.)
g. Adjust the pH of stormwater or authorized non-stormwater if necessary to prevent
an exceedance of groundwater and/or surface water quality standards.
h. Assure that washout of concrete trucks is performed off-site or in designated
concrete washout areas only. Do not wash out concrete truck drums onto the
ground, or into storm drains, open ditches, streets, or streams. Washout of small
concrete handling equipment may be disposed of in a formed area awaiting
concrete where it will not contaminate surface or groundwater. Do not dump excess
concrete on site, except in designated concrete washout areas. Concrete spillage or
concrete discharge directly to groundwater or surface waters of the State is
Construction Stormwater General Permit Page 30
prohibited. At no time shall concrete be washed off into the footprint of an area
where an infiltration BMP will be installed.
i. Obtain written approval from Ecology before using any chemical treatment, with
the exception of CO2, dry ice or food grade vinegar, to adjust pH.
j. Uncontaminated water from water-only based shaft drilling for construction of
building, road, and bridge foundations may be infiltrated provided the wastewater is
managed in a way that prohibits discharge to surface waters. Prior to infiltration,
water from water-only based shaft drilling that comes into contact with curing
concrete must be neutralized until pH is in the range of 6.5 to 8.5 (su).
10. Control Dewatering
a. Permittees must discharge foundation, vault, and trench dewatering water, which
have characteristics similar to stormwater runoff at the site, in conjunction with BMPs
to reduce sedimentation before discharge to a sediment trap or sediment pond.
b. Permittees may discharge clean, non-turbid dewatering water, such as well-point
groundwater, to systems tributary to, or directly into surface waters of the State, as
specified in Special Condition S9.D.8, provided the dewatering flow does not cause
erosion or flooding of receiving waters. Do not route clean dewatering water through
stormwater sediment ponds. Note that “surface waters of the State” may exist on a
construction site as well as off site; for example, a creek running through a site.
c. Other dewatering treatment or disposal options may include:
i. Infiltration
ii. Transport off site in a vehicle, such as a vacuum flush truck, for legal disposal in
a manner that does not pollute state waters.
iii. Ecology-approved on-site chemical treatment or other suitable treatment
technologies (See S9.D.9.i, regarding chemical treatment written approval).
iv. Sanitary or combined sewer discharge with local sewer district approval, if
there is no other option.
v. Use of a sedimentation bag with discharge to a ditch or swale for small
volumes of localized dewatering.
d. Permittees must handle highly turbid or contaminated dewatering water separately
from stormwater.
11. Maintain BMPs
a. Permittees must maintain and repair all temporary and permanent erosion and
sediment control BMPs as needed to assure continued performance of their
intended function in accordance with BMP specifications.
b. Permittees must remove all temporary erosion and sediment control BMPs within
30 days after achieving final site stabilization or after the temporary BMPs are no
longer needed.
Construction Stormwater General Permit Page 31
12. Manage the Project
a. Phase development projects to the maximum degree practicable and take into
account seasonal work limitations.
b. Inspect, maintain and repair all BMPs as needed to assure continued performance
of their intended function. Conduct site inspections and monitoring in accordance
with Special Condition S4.
c. Maintain, update, and implement the SWPPP in accordance with Special Conditions
S3, S4, and S9.
13. Protect Low Impact Development (LID) BMPs
The primary purpose of on-site LID Stormwater Management is to reduce the disruption of
the natural site hydrology through infiltration. LID BMPs are permanent facilities.
a. Permittees must protect all LID BMPs (including, but not limited to, Bioretention and
Rain Garden facilities) from sedimentation through installation and maintenance of
erosion and sediment control BMPs on portions of the site that drain into the
Bioretention and/or Rain Garden facilities. Restore the BMPs to their fully
functioning condition if they accumulate sediment during construction. Restoring
the facility must include removal of sediment and any sediment-laden bioretention/
rain garden soils, and replacing the removed soils with soils meeting the design
specification.
b. Permittees must maintain the infiltration capabilities of LID BMPs by protecting
against compaction by construction equipment and foot traffic. Protect completed
lawn and landscaped areas from compaction due to construction equipment.
c. Permittees must control erosion and avoid introducing sediment from surrounding
land uses onto permeable pavements. Do not allow muddy construction equipment
on the base material or pavement. Do not allow sediment-laden runoff onto
permeable pavements or base materials.
d. Permittees must clean permeable pavements fouled with sediments or no longer
passing an initial infiltration test using local stormwater manual methodology or the
manufacturer’s procedures.
e. Permittees must keep all heavy equipment off existing soils under LID BMPs that
have been excavated to final grade to retain the infiltration rate of the soils.
E. SWPPP – Map Contents and Requirements
The Permittee’s SWPPP must also include a vicinity map or general location map (for example,
a USGS quadrangle map, a portion of a county or city map, or other appropriate map) with
enough detail to identify the location of the construction site and receiving waters within one
mile of the site.
The SWPPP must also include a legible site map (or maps) showing the entire construction site.
The following features must be identified, unless not applicable due to site conditions.
1. The direction of north, property lines, and existing structures and roads.
2. Cut and fill slopes indicating the top and bottom of slope catch lines.
Construction Stormwater General Permit Page 32
3. Approximate slopes, contours, and direction of stormwater flow before and after major
grading activities.
4. Areas of soil disturbance and areas that will not be disturbed.
5. Locations of structural and nonstructural controls (BMPs) identified in the SWPPP.
6. Locations of off-site material, stockpiles, waste storage, borrow areas, and
vehicle/equipment storage areas.
7. Locations of all surface water bodies, including wetlands.
8. Locations where stormwater or non-stormwater discharges off-site and/or to a surface
waterbody, including wetlands.
9. Location of water quality sampling station(s), if sampling is required by state or local
permitting authority.
10. Areas where final stabilization has been accomplished and no further construction-phase
permit requirements apply.
11. Location or proposed location of LID facilities.
S10. NOTICE OF TERMINATION
Partial terminations of permit coverage are not authorized.
A. The site is eligible for termination of coverage when it has met any of the following
conditions:
1. The site has undergone final stabilization, the Permittee has removed all temporary
BMPs (except biodegradable BMPs clearly manufactured with the intention for the
material to be left in place and not interfere with maintenance or land use), and all
stormwater discharges associated with construction activity have been eliminated; or
2. All portions of the site that have not undergone final stabilization per Special Condition
S10.A.1 have been sold and/or transferred (per Special Condition S2.A), and the
Permittee no longer has operational control of the construction activity; or
3. For residential construction only, the Permittee has completed temporary stabilization
and the homeowners have taken possession of the residences.
B. When the site is eligible for termination, the Permittee must submit a complete and
accurate Notice of Termination (NOT) form, signed in accordance with General
Condition G2, to:
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, WA 98504-7696
Construction Stormwater General Permit Page 33
When an electronic termination form is available, the Permittee may choose to submit a
complete and accurate Notice of Termination (NOT) form through the Water Quality Permitting
Portal rather than mailing a hardcopy as noted above.
The termination is effective on the 31st calendar day following the date Ecology receives a
complete NOT form, unless Ecology notifies the Permittee that termination request is denied
because the Permittee has not met the eligibility requirements in Special Condition S10.A.
Permittees are required to comply with all conditions and effluent limitations in the permit
until the permit has been terminated.
Permittees transferring the property to a new property owner or operator/Permittee are
required to complete and submit the Notice of Transfer form to Ecology, but are not required
to submit a Notice of Termination form for this type of transaction.
Construction Stormwater General Permit Page 34
GENERAL CONDITIONS
G1. DISCHARGE VIOLATIONS
All discharges and activities authorized by this general permit must be consistent with the terms
and conditions of this general permit. Any discharge of any pollutant more frequent than or at a
level in excess of that identified and authorized by the general permit must constitute a violation of
the terms and conditions of this permit.
G2. SIGNATORY REQUIREMENTS
A. All permit applications must bear a certification of correctness to be signed:
1. In the case of corporations, by a responsible corporate officer.
2. In the case of a partnership, by a general partner of a partnership.
3. In the case of sole proprietorship, by the proprietor.
4. In the case of a municipal, state, or other public facility, by either a principal executive
officer or ranking elected official.
B. All reports required by this permit and other information requested by Ecology (including
NOIs, NOTs, and Transfer of Coverage forms) must be signed by a person described above
or by a duly authorized representative of that person. A person is a duly authorized
representative only if:
1. The authorization is made in writing by a person described above and submitted to
Ecology.
2. The authorization specifies either an individual or a position having responsibility for
the overall operation of the regulated facility, such as the position of plant manager,
superintendent, position of equivalent responsibility, or an individual or position
having overall responsibility for environmental matters.
C. Changes to authorization. If an authorization under paragraph G2.B.2 above is no longer
accurate because a different individual or position has responsibility for the overall
operation of the facility, a new authorization satisfying the requirements of paragraph
G2.B.2 above must be submitted to Ecology prior to or together with any reports,
information, or applications to be signed by an authorized representative.
D. Certification. Any person signing a document under this section must make the following
certification:
I certify under penalty of law, that this document and all attachments were
prepared under my direction or supervision in accordance with a system
designed to assure that qualified personnel properly gathered and evaluated the
information submitted. Based on my inquiry of the person or persons who
manage the system, or those persons directly responsible for gathering
information, the information submitted is, to the best of my knowledge and
belief, true, accurate, and complete. I am aware that there are significant
penalties for submitting false information, including the possibility of fine and
imprisonment for knowing violations.
Construction Stormwater General Permit Page 35
G3. RIGHT OF INSPECTION AND ENTRY
The Permittee must allow an authorized representative of Ecology, upon the presentation of
credentials and such other documents as may be required by law:
A. To enter upon the premises where a discharge is located or where any records are kept
under the terms and conditions of this permit.
B. To have access to and copy, at reasonable times and at reasonable cost, any records
required to be kept under the terms and conditions of this permit.
C. To inspect, at reasonable times, any facilities, equipment (including monitoring and control
equipment), practices, methods, or operations regulated or required under this permit.
D. To sample or monitor, at reasonable times, any substances or parameters at any location for
purposes of assuring permit compliance or as otherwise authorized by the Clean Water Act.
G4. GENERAL PERMIT MODIFICATION AND REVOCATION
This permit may be modified, revoked and reissued, or terminated in accordance with the
provisions of Chapter 173-226 WAC. Grounds for modification, revocation and reissuance, or
termination include, but are not limited to, the following:
A. When a change occurs in the technology or practices for control or abatement of pollutants
applicable to the category of dischargers covered under this permit.
B. When effluent limitation guidelines or standards are promulgated pursuant to the CWA or
Chapter 90.48 RCW, for the category of dischargers covered under this permit.
C. When a water quality management plan containing requirements applicable to the
category of dischargers covered under this permit is approved, or
D. When information is obtained that indicates cumulative effects on the environment from
dischargers covered under this permit are unacceptable.
G5. REVOCATION OF COVERAGE UNDER THE PERMIT
Pursuant to Chapter 43.21B RCW and Chapter 173-226 WAC, the Director may terminate coverage
for any discharger under this permit for cause. Cases where coverage may be terminated include,
but are not limited to, the following:
A. Violation of any term or condition of this permit.
B. Obtaining coverage under this permit by misrepresentation or failure to disclose fully all
relevant facts.
C. A change in any condition that requires either a temporary or permanent reduction or
elimination of the permitted discharge.
D. Failure or refusal of the Permittee to allow entry as required in RCW 90.48.090.
E. A determination that the permitted activity endangers human health or the environment,
or contributes to water quality standards violations.
F. Nonpayment of permit fees or penalties assessed pursuant to RCW 90.48.465 and Chapter
173-224 WAC.
Construction Stormwater General Permit Page 36
G. Failure of the Permittee to satisfy the public notice requirements of WAC 173-226-130(5),
when applicable.
The Director may require any discharger under this permit to apply for and obtain coverage
under an individual permit or another more specific general permit. Permittees who have their
coverage revoked for cause according to WAC 173-226-240 may request temporary coverage
under this permit during the time an individual permit is being developed, provided the request
is made within ninety (90) days from the time of revocation and is submitted along with a
complete individual permit application form.
G6. REPORTING A CAUSE FOR MODIFICATION
The Permittee must submit a new application, or a supplement to the previous application,
whenever a material change to the construction activity or in the quantity or type of discharge is
anticipated which is not specifically authorized by this permit. This application must be submitted
at least sixty (60) days prior to any proposed changes. Filing a request for a permit modification,
revocation and reissuance, or termination, or a notification of planned changes or anticipated
noncompliance does not relieve the Permittee of the duty to comply with the existing permit until
it is modified or reissued.
G7. COMPLIANCE WITH OTHER LAWS AND STATUTES
Nothing in this permit will be construed as excusing the Permittee from compliance with any
applicable federal, state, or local statutes, ordinances, or regulations.
G8. DUTY TO REAPPLY
The Permittee must apply for permit renewal at least 180 days prior to the specified expiration
date of this permit. The Permittee must reapply using the electronic application form (NOI)
available on Ecology’s website. Permittees unable to submit electronically (for example, those who
do not have an internet connection) must contact Ecology to request a waiver and obtain
instructions on how to obtain a paper NOI.
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, WA 98504-7696
G9. REMOVED SUBSTANCE
The Permittee must not re-suspend or reintroduce collected screenings, grit, solids, sludges, filter
backwash, or other pollutants removed in the course of treatment or control of stormwater to the
final effluent stream for discharge to state waters.
G10. DUTY TO PROVIDE INFORMATION
The Permittee must submit to Ecology, within a reasonable time, all information that Ecology may
request to determine whether cause exists for modifying, revoking and reissuing, or terminating
this permit or to determine compliance with this permit. The Permittee must also submit to
Ecology, upon request, copies of records required to be kept by this permit [40 CFR 122.41(h)].
Construction Stormwater General Permit Page 37
G11. OTHER REQUIREMENTS OF 40 CFR
All other requirements of 40 CFR 122.41 and 122.42 are incorporated in this permit by reference.
G12. ADDITIONAL MONITORING
Ecology may establish specific monitoring requirements in addition to those contained in this
permit by administrative order or permit modification.
G13. PENALTIES FOR VIOLATING PERMIT CONDITIONS
Any person who is found guilty of willfully violating the terms and conditions of this permit shall be
deemed guilty of a crime, and upon conviction thereof shall be punished by a fine of up to ten
thousand dollars ($10,000) and costs of prosecution, or by imprisonment at the discretion of the
court. Each day upon which a willful violation occurs may be deemed a separate and additional
violation.
Any person who violates the terms and conditions of a waste discharge permit shall incur, in
addition to any other penalty as provided by law, a civil penalty in the amount of up to ten
thousand dollars ($10,000) for every such violation. Each and every such violation shall be a
separate and distinct offense, and in case of a continuing violation, every day’s continuance shall be
deemed to be a separate and distinct violation.
G14. UPSET
Definition – “Upset” means an exceptional incident in which there is unintentional and temporary
noncompliance with technology-based permit effluent limitations because of factors beyond the
reasonable control of the Permittee. An upset does not include noncompliance to the extent
caused by operational error, improperly designed treatment facilities, inadequate treatment
facilities, lack of preventive maintenance, or careless or improper operation.
An upset constitutes an affirmative defense to an action brought for noncompliance with such
technology-based permit effluent limitations if the requirements of the following paragraph are met.
A Permittee who wishes to establish the affirmative defense of upset must demonstrate, through
properly signed, contemporaneous operating logs or other relevant evidence that: 1) an upset
occurred and that the Permittee can identify the cause(s) of the upset; 2) the permitted facility was
being properly operated at the time of the upset; 3) the Permittee submitted notice of the upset as
required in Special Condition S5.F, and; 4) the Permittee complied with any remedial measures
required under this permit.
In any enforcement proceeding, the Permittee seeking to establish the occurrence of an upset has
the burden of proof.
G15. PROPERTY RIGHTS
This permit does not convey any property rights of any sort, or any exclusive privilege.
G16. DUTY TO COMPLY
The Permittee must comply with all conditions of this permit. Any permit noncompliance
constitutes a violation of the Clean Water Act and is grounds for enforcement action; for permit
termination, revocation and reissuance, or modification; or denial of a permit renewal application.
Construction Stormwater General Permit Page 38
G17. TOXIC POLLUTANTS
The Permittee must comply with effluent standards or prohibitions established under Section
307(a) of the Clean Water Act for toxic pollutants within the time provided in the regulations that
establish those standards or prohibitions, even if this permit has not yet been modified to
incorporate the requirement.
G18. PENALTIES FOR TAMPERING
The Clean Water Act provides that any person who falsifies, tampers with, or knowingly renders
inaccurate any monitoring device or method required to be maintained under this permit shall, upon
conviction, be punished by a fine of not more than $10,000 per violation, or by imprisonment for not
more than two years per violation, or by both. If a conviction of a person is for a violation committed
after a first conviction of such person under this condition, punishment shall be a fine of not more
than $20,000 per day of violation, or imprisonment of not more than four (4) years, or both.
G19. REPORTING PLANNED CHANGES
The Permittee must, as soon as possible, give notice to Ecology of planned physical alterations,
modifications or additions to the permitted construction activity. The Permittee should be aware
that, depending on the nature and size of the changes to the original permit, a new public notice
and other permit process requirements may be required. Changes in activities that require
reporting to Ecology include those that will result in:
A. The permitted facility being determined to be a new source pursuant to 40 CFR 122.29(b).
B. A significant change in the nature or an increase in quantity of pollutants discharged,
including but not limited to: a 20% or greater increase in acreage disturbed by construction
activity.
C. A change in or addition of surface water(s) receiving stormwater or non-stormwater from
the construction activity.
D. A change in the construction plans and/or activity that affects the Permittee’s monitoring
requirements in Special Condition S4.
Following such notice, permit coverage may be modified, or revoked and reissued pursuant to 40
CFR 122.62(a) to specify and limit any pollutants not previously limited. Until such modification is
effective, any new or increased discharge in excess of permit limits or not specifically authorized by
this permit constitutes a violation.
G20. REPORTING OTHER INFORMATION
Where the Permittee becomes aware that it failed to submit any relevant facts in a permit
application, or submitted incorrect information in a permit application or in any report to Ecology,
it must promptly submit such facts or information.
G21. REPORTING ANTICIPATED NON-COMPLIANCE
The Permittee must give advance notice to Ecology by submission of a new application or
supplement thereto at least forty-five (45) days prior to commencement of such discharges, of any
facility expansions, production increases, or other planned changes, such as process modifications,
in the permitted facility or activity which may result in noncompliance with permit limits or
conditions. Any maintenance of facilities, which might necessitate unavoidable interruption of
Construction Stormwater General Permit Page 39
operation and degradation of effluent quality, must be scheduled during non-critical water quality
periods and carried out in a manner approved by Ecology.
G22. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT
Any discharger authorized by this permit may request to be excluded from coverage under the
general permit by applying for an individual permit. The discharger must submit to the Director an
application as described in WAC 173-220-040 or WAC 173-216-070, whichever is applicable, with
reasons supporting the request. These reasons will fully document how an individual permit will
apply to the applicant in a way that the general permit cannot. Ecology may make specific requests
for information to support the request. The Director will either issue an individual permit or deny
the request with a statement explaining the reason for the denial. When an individual permit is
issued to a discharger otherwise subject to the construction stormwater general permit, the
applicability of the construction stormwater general permit to that Permittee is automatically
terminated on the effective date of the individual permit.
G23. APPEALS
A. The terms and conditions of this general permit, as they apply to the appropriate class of
dischargers, are subject to appeal by any person within 30 days of issuance of this general
permit, in accordance with Chapter 43.21B RCW, and Chapter 173-226 WAC.
B. The terms and conditions of this general permit, as they apply to an individual discharger,
are appealable in accordance with Chapter 43.21B RCW within 30 days of the effective date
of coverage of that discharger. Consideration of an appeal of general permit coverage of an
individual discharger is limited to the general permit’s applicability or nonapplicability to
that individual discharger.
C. The appeal of general permit coverage of an individual discharger does not affect any other
dischargers covered under this general permit. If the terms and conditions of this general
permit are found to be inapplicable to any individual discharger(s), the matter shall be
remanded to Ecology for consideration of issuance of an individual permit or permits.
G24. SEVERABILITY
The provisions of this permit are severable, and if any provision of this permit, or application of any
provision of this permit to any circumstance, is held invalid, the application of such provision to
other circumstances, and the remainder of this permit shall not be affected thereby.
G25. BYPASS PROHIBITED
A. Bypass Procedures
Bypass, which is the intentional diversion of waste streams from any portion of a treatment
facility, is prohibited for stormwater events below the design criteria for stormwater
management. Ecology may take enforcement action against a Permittee for bypass unless one
of the following circumstances (1, 2, 3 or 4) is applicable.
1. Bypass of stormwater is consistent with the design criteria and part of an approved
management practice in the applicable stormwater management manual.
2. Bypass for essential maintenance without the potential to cause violation of permit limits
or conditions.
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Bypass is authorized if it is for essential maintenance and does not have the potential to
cause violations of limitations or other conditions of this permit, or adversely impact
public health.
3. Bypass of stormwater is unavoidable, unanticipated, and results in noncompliance of this
permit.
This bypass is permitted only if:
a. Bypass is unavoidable to prevent loss of life, personal injury, or severe property
damage. “Severe property damage” means substantial physical damage to property,
damage to the treatment facilities which would cause them to become inoperable,
or substantial and permanent loss of natural resources which can reasonably be
expected to occur in the absence of a bypass.
b. There are no feasible alternatives to the bypass, such as the use of auxiliary
treatment facilities, retention of untreated wastes, maintenance during normal
periods of equipment downtime (but not if adequate backup equipment should
have been installed in the exercise of reasonable engineering judgment to prevent a
bypass which occurred during normal periods of equipment downtime or
preventative maintenance), or transport of untreated wastes to another treatment
facility.
c. Ecology is properly notified of the bypass as required in Special Condition S5.F of
this permit.
4. A planned action that would cause bypass of stormwater and has the potential to result
in noncompliance of this permit during a storm event.
The Permittee must notify Ecology at least thirty (30) days before the planned date of
bypass. The notice must contain:
a. A description of the bypass and its cause
b. An analysis of all known alternatives which would eliminate, reduce, or mitigate the
need for bypassing.
c. A cost-effectiveness analysis of alternatives including comparative resource damage
assessment.
d. The minimum and maximum duration of bypass under each alternative.
e. A recommendation as to the preferred alternative for conducting the bypass.
f. The projected date of bypass initiation.
g. A statement of compliance with SEPA.
h. A request for modification of water quality standards as provided for in WAC 173-
201A-110, if an exceedance of any water quality standard is anticipated.
i. Steps taken or planned to reduce, eliminate, and prevent reoccurrence of the
bypass.
5. For probable construction bypasses, the need to bypass is to be identified as early in the
planning process as possible. The analysis required above must be considered during
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preparation of the Stormwater Pollution Prevention Plan (SWPPP) and must be included
to the extent practical. In cases where the probable need to bypass is determined early,
continued analysis is necessary up to and including the construction period in an effort to
minimize or eliminate the bypass.
Ecology will consider the following before issuing an administrative order for this type
bypass:
a. If the bypass is necessary to perform construction or maintenance-related activities
essential to meet the requirements of this permit.
b. If there are feasible alternatives to bypass, such as the use of auxiliary treatment
facilities, retention of untreated wastes, stopping production, maintenance during
normal periods of equipment down time, or transport of untreated wastes to
another treatment facility.
c. If the bypass is planned and scheduled to minimize adverse effects on the public and
the environment.
After consideration of the above and the adverse effects of the proposed bypass and any
other relevant factors, Ecology will approve, conditionally approve, or deny the request.
The public must be notified and given an opportunity to comment on bypass incidents of
significant duration, to the extent feasible. Approval of a request to bypass will be by
administrative order issued by Ecology under RCW 90.48.120.
B. Duty to Mitigate
The Permittee is required to take all reasonable steps to minimize or prevent any discharge or
sludge use or disposal in violation of this permit that has a reasonable likelihood of adversely
affecting human health or the environment.
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APPENDIX A – DEFINITIONS
AKART is an acronym for “All Known, Available, and Reasonable methods of prevention, control, and
Treatment.” AKART represents the most current methodology that can be reasonably required for
preventing, controlling, or abating the pollutants and controlling pollution associated with a discharge.
Applicable TMDL means a TMDL for turbidity, fine sediment, high pH, or phosphorus, which was
completed and approved by EPA before January 1, 2021, or before the date the operator’s complete
permit application is received by Ecology, whichever is later. TMDLs completed after a complete permit
application is received by Ecology become applicable to the Permittee only if they are imposed through
an administrative order by Ecology, or through a modification of permit coverage.
Applicant means an operator seeking coverage under this permit.
Benchmark means a pollutant concentration used as a permit threshold, below which a pollutant is
considered unlikely to cause a water quality violation, and above which it may. When pollutant
concentrations exceed benchmarks, corrective action requirements take effect. Benchmark values are
not water quality standards and are not numeric effluent limitations; they are indicator values.
Best Management Practices (BMPs) means schedules of activities, prohibitions of practices,
maintenance procedures, and other physical, structural and/or managerial practices to prevent or
reduce the pollution of waters of the State. BMPs include treatment systems, operating procedures, and
practices to control stormwater associated with construction activity, spillage or leaks, sludge or waste
disposal, or drainage from raw material storage.
Buffer means an area designated by a local jurisdiction that is contiguous to and intended to protect a
sensitive area.
Bypass means the intentional diversion of waste streams from any portion of a treatment facility.
Calendar Day A period of 24 consecutive hours starting at 12:00 midnight and ending the following
12:00 midnight.
Calendar Week (same as Week) means a period of seven consecutive days starting at 12:01 a.m. (0:01
hours) on Sunday.
Certified Erosion and Sediment Control Lead (CESCL) means a person who has current certification
through an approved erosion and sediment control training program that meets the minimum training
standards established by Ecology (See BMP C160 in the SWMM).
Chemical Treatment means the addition of chemicals to stormwater and/or authorized non-stormwater
prior to filtration and discharge to surface waters.
Clean Water Act (CWA) means the Federal Water Pollution Control Act enacted by Public Law 92-500, as
amended by Public Laws 95-217, 95-576, 96-483, and 97-117; USC 1251 et seq.
Combined Sewer means a sewer which has been designed to serve as a sanitary sewer and a storm
sewer, and into which inflow is allowed by local ordinance.
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Common Plan of Development or Sale means a site where multiple separate and distinct construction
activities may be taking place at different times on different schedules and/or by different contractors,
but still under a single plan. Examples include: 1) phased projects and projects with multiple filings or
lots, even if the separate phases or filings/lots will be constructed under separate contract or by
separate owners (e.g., a development where lots are sold to separate builders); 2) a development plan
that may be phased over multiple years, but is still under a consistent plan for long-term development;
3) projects in a contiguous area that may be unrelated but still under the same contract, such as
construction of a building extension and a new parking lot at the same facility; and 4) linear projects
such as roads, pipelines, or utilities. If the project is part of a common plan of development or sale, the
disturbed area of the entire plan must be used in determining permit requirements.
Composite Sample means a mixture of grab samples collected at the same sampling point at different
times, formed either by continuous sampling or by mixing discrete samples. May be "time-composite"
(collected at constant time intervals) or "flow-proportional" (collected either as a constant sample
volume at time intervals proportional to stream flow, or collected by increasing the volume of each
aliquot as the flow increases while maintaining a constant time interval between the aliquots.
Concrete Wastewater means any water used in the production, pouring and/or clean-up of concrete or
concrete products, and any water used to cut, grind, wash, or otherwise modify concrete or concrete
products. Examples include water used for or resulting from concrete truck/mixer/pumper/tool/chute
rinsing or washing, concrete saw cutting and surfacing (sawing, coring, grinding, roughening, hydro-
demolition, bridge and road surfacing). When stormwater comingles with concrete wastewater, the
resulting water is considered concrete wastewater and must be managed to prevent discharge to waters
of the State, including groundwater.
Construction Activity means land disturbing operations including clearing, grading or excavation which
disturbs the surface of the land (including off-site disturbance acreage related to construction-support
activity). Such activities may include road construction, construction of residential houses, office
buildings, or industrial buildings, site preparation, soil compaction, movement and stockpiling of
topsoils, and demolition activity.
Construction Support Activity means off-site acreage that will be disturbed as a direct result of the
construction project and will discharge stormwater. For example, off-site equipment staging yards,
material storage areas, borrow areas, and parking areas.
Contaminant means any hazardous substance that does not occur naturally or occurs at greater than
natural background levels. See definition of “hazardous substance” and WAC 173-340-200.
Contaminated soil means soil which contains contaminants, pollutants, or hazardous substances that do
not occur naturally or occur at levels greater than natural background.
Contaminated groundwater means groundwater which contains contaminants, pollutants, or hazardous
substances that do not occur naturally or occur at levels greater than natural background.
Demonstrably Equivalent means that the technical basis for the selection of all stormwater BMPs is
documented within a SWPPP, including:
1. The method and reasons for choosing the stormwater BMPs selected.
2. The pollutant removal performance expected from the BMPs selected.
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3. The technical basis supporting the performance claims for the BMPs selected, including any
available data concerning field performance of the BMPs selected.
4. An assessment of how the selected BMPs will comply with state water quality standards.
5. An assessment of how the selected BMPs will satisfy both applicable federal technology-based
treatment requirements and state requirements to use all known, available, and reasonable
methods of prevention, control, and treatment (AKART).
Department means the Washington State Department of Ecology.
Detention means the temporary storage of stormwater to improve quality and/or to reduce the mass
flow rate of discharge.
Dewatering means the act of pumping groundwater or stormwater away from an active construction site.
Director means the Director of the Washington State Department of Ecology or his/her authorized
representative.
Discharger means an owner or operator of any facility or activity subject to regulation under Chapter
90.48 RCW or the Federal Clean Water Act.
Domestic Wastewater means water carrying human wastes, including kitchen, bath, and laundry wastes
from residences, buildings, industrial establishments, or other places, together with such groundwater
infiltration or surface waters as may be present.
Ecology means the Washington State Department of Ecology.
Engineered Soils means the use of soil amendments including, but not limited, to Portland cement
treated base (CTB), cement kiln dust (CKD), or fly ash to achieve certain desirable soil characteristics.
Equivalent BMPs means operational, source control, treatment, or innovative BMPs which result in
equal or better quality of stormwater discharge to surface water or to groundwater than BMPs selected
from the SWMM.
Erosion means the wearing away of the land surface by running water, wind, ice, or other geological
agents, including such processes as gravitational creep.
Erosion and Sediment Control BMPs means BMPs intended to prevent erosion and sedimentation, such as
preserving natural vegetation, seeding, mulching and matting, plastic covering, filter fences, sediment traps,
and ponds. Erosion and sediment control BMPs are synonymous with stabilization and structural BMPs.
Federal Operator is an entity that meets the definition of “Operator” in this permit and is either any
department, agency or instrumentality of the executive, legislative, and judicial branches of the Federal
government of the United States, or another entity, such as a private contractor, performing
construction activity for any such department, agency, or instrumentality.
Final Stabilization (same as fully stabilized or full stabilization) means the completion of all soil
disturbing activities at the site and the establishment of permanent vegetative cover, or equivalent
permanent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent
erosion. See the applicable Stormwater Management Manual for more information on vegetative cover
expectations and equivalent permanent stabilization measures.
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Groundwater means water in a saturated zone or stratum beneath the land surface or a surface
waterbody.
Hazardous Substance means any dangerous or extremely hazardous waste as defined in RCW
70.105.010 (5) and (6), or any dangerous or extremely dangerous waste as designated by rule under
chapter 70.105 RCW; any hazardous sub-stance as defined in RCW 70.105.010(14) or any hazardous
substance as defined by rule under chapter 70.105 RCW; any substance that, on the effective date of
this section, is a hazardous substance under section 101(14) of the federal cleanup law, 42U.S.C., Sec.
9601(14); petroleum or petroleum products; and any substance or category of substances, including
solid waste decomposition products, determined by the director by rule to present a threat to human
health or the environment if released into the environment. The term hazardous substance does not
include any of the following when contained in an underground storage tank from which there is not a
release: crude oil or any fraction thereof or petroleum, if the tank is in compliance with all applicable
federal, state, and local law.
Injection Well means a well that is used for the subsurface emplacement of fluids. (See Well.)
Jurisdiction means a political unit such as a city, town or county; incorporated for local self-government.
National Pollutant Discharge Elimination System (NPDES) means the national program for issuing,
modifying, revoking and reissuing, terminating, monitoring, and enforcing permits, and imposing and
enforcing pretreatment requirements, under sections 307, 402, 318, and 405 of the Federal Clean Water
Act, for the discharge of pollutants to surface waters of the State from point sources. These permits are
referred to as NPDES permits and, in Washington State, are administered by the Washington State
Department of Ecology.
Notice of Intent (NOI) means the application for, or a request for coverage under this general permit
pursuant to WAC 173-226-200.
Notice of Termination (NOT) means a request for termination of coverage under this general permit as
specified by Special Condition S10 of this permit.
Operator means any party associated with a construction project that meets either of the following two
criteria:
• The party has operational control over construction plans and specifications, including the
ability to make modifications to those plans and specifications; or
• The party has day-to-day operational control of those activities at a project that are necessary to
ensure compliance with a SWPPP for the site or other permit conditions (e.g., they are
authorized to direct workers at a site to carry out activities required by the SWPPP or comply
with other permit conditions).
Permittee means individual or entity that receives notice of coverage under this general permit.
pH means a liquid’s measure of acidity or alkalinity. A pH of 7 is defined as neutral. Large variations
above or below this value are considered harmful to most aquatic life.
pH Monitoring Period means the time period in which the pH of stormwater runoff from a site must be
tested a minimum of once every seven days to determine if stormwater pH is between 6.5 and 8.5.
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Point Source means any discernible, confined, and discrete conveyance, including but not limited to, any
pipe, ditch, channel, tunnel, conduit, well, discrete fissure, and container from which pollutants are or
may be discharged to surface waters of the State. This term does not include return flows from irrigated
agriculture. (See the Fact Sheet for further explanation)
Pollutant means dredged spoil, solid waste, incinerator residue, filter backwash, sewage, garbage,
domestic sewage sludge (biosolids), munitions, chemical wastes, biological materials, radioactive
materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt, and industrial, municipal, and
agricultural waste. This term does not include sewage from vessels within the meaning of section 312 of
the CWA, nor does it include dredged or fill material discharged in accordance with a permit issued
under section 404 of the CWA.
Pollution means contamination or other alteration of the physical, chemical, or biological properties of
waters of the State; including change in temperature, taste, color, turbidity, or odor of the waters; or
such discharge of any liquid, gaseous, solid, radioactive or other substance into any waters of the State
as will or is likely to create a nuisance or render such waters harmful, detrimental or injurious to the
public health, safety or welfare; or to domestic, commercial, industrial, agricultural, recreational, or
other legitimate beneficial uses; or to livestock, wild animals, birds, fish or other aquatic life.
Process Wastewater means any non-stormwater which, during manufacturing or processing, comes into
direct contact with or results from the production or use of any raw material, intermediate product,
finished product, byproduct, or waste product. If stormwater commingles with process wastewater, the
commingled water is considered process wastewater.
Receiving Water means the waterbody at the point of discharge. If the discharge is to a storm sewer
system, either surface or subsurface, the receiving water is the waterbody to which the storm system
discharges. Systems designed primarily for other purposes such as for groundwater drainage, redirecting
stream natural flows, or for conveyance of irrigation water/return flows that coincidentally convey
stormwater are considered the receiving water.
Representative means a stormwater or wastewater sample which represents the flow and
characteristics of the discharge. Representative samples may be a grab sample, a time-proportionate
composite sample, or a flow proportionate sample. Ecology’s Construction Stormwater Monitoring
Manual provides guidance on representative sampling.
Responsible Corporate Officer for the purpose of signatory authority means: (i) a president, secretary,
treasurer, or vice-president of the corporation in charge of a principal business function, or any other
person who performs similar policy- or decision-making functions for the corporation, or (ii) the
manager of one or more manufacturing, production, or operating facilities, provided, the manager is
authorized to make management decisions which govern the operation of the regulated facility
including having the explicit or implicit duty of making major capital investment recommendations, and
initiating and directing other comprehensive measures to assure long term environmental compliance
with environmental laws and regulations; the manager can ensure that the necessary systems are
established or actions taken to gather complete and accurate information for permit application
requirements; and where authority to sign documents has been assigned or delegated to the manager in
accordance with corporate procedures (40 CFR 122.22).
Sanitary Sewer means a sewer which is designed to convey domestic wastewater.
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Sediment means the fragmented material that originates from the weathering and erosion of rocks or
unconsolidated deposits, and is transported by, suspended in, or deposited by water.
Sedimentation means the depositing or formation of sediment.
Sensitive Area means a waterbody, wetland, stream, aquifer recharge area, or channel migration zone.
SEPA (State Environmental Policy Act) means the Washington State Law, RCW 43.21C.020, intended to
prevent or eliminate damage to the environment.
Significant Amount means an amount of a pollutant in a discharge that is amenable to available and
reasonable methods of prevention or treatment; or an amount of a pollutant that has a reasonable
potential to cause a violation of surface or groundwater quality or sediment management standards.
Significant Concrete Work means greater than 1000 cubic yards placed or poured concrete or recycled
concrete used over the life of a project.
Significant Contributor of Pollutants means a facility determined by Ecology to be a contributor of a
significant amount(s) of a pollutant(s) to waters of the State of Washington.
Site means the land or water area where any "facility or activity" is physically located or conducted.
Source Control BMPs means physical, structural or mechanical devices or facilities that are intended to
prevent pollutants from entering stormwater. A few examples of source control BMPs are erosion
control practices, maintenance of stormwater facilities, constructing roofs over storage and working
areas, and directing wash water and similar discharges to the sanitary sewer or a dead end sump.
Stabilization means the application of appropriate BMPs to prevent the erosion of soils, such as,
temporary and permanent seeding, vegetative covers, mulching and matting, plastic covering and
sodding. See also the definition of Erosion and Sediment Control BMPs.
Storm Drain means any drain which drains directly into a storm sewer system, usually found along
roadways or in parking lots.
Storm Sewer System means a means a conveyance, or system of conveyances (including roads with
drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm
drains designed or used for collecting or conveying stormwater. This does not include systems which are
part of a combined sewer or Publicly Owned Treatment Works (POTW), as defined at 40 CFR 122.2.
Stormwater means that portion of precipitation that does not naturally percolate into the ground or
evaporate, but flows via overland flow, interflow, pipes, and other features of a stormwater drainage
system into a defined surface waterbody, or a constructed infiltration facility.
Stormwater Management Manual (SWMM) or Manual means the technical Manual published by
Ecology for use by local governments that contain descriptions of and design criteria for BMPs to
prevent, control, or treat pollutants in stormwater.
Stormwater Pollution Prevention Plan (SWPPP) means a documented plan to implement measures to
identify, prevent, and control the contamination of point source discharges of stormwater.
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Surface Waters of the State includes lakes, rivers, ponds, streams, inland waters, salt waters, and all
other surface waters and water courses within the jurisdiction of the state of Washington.
Temporary Stabilization means the exposed ground surface has been covered with appropriate
materials to provide temporary stabilization of the surface from water or wind erosion. Materials
include, but are not limited to, mulch, riprap, erosion control mats or blankets and temporary cover
crops. Seeding alone is not considered stabilization. Temporary stabilization is not a substitute for the
more permanent “final stabilization.”
Total Maximum Daily Load (TMDL) means a calculation of the maximum amount of a pollutant that a
waterbody can receive and still meet state water quality standards. Percentages of the total maximum
daily load are allocated to the various pollutant sources. A TMDL is the sum of the allowable loads of a
single pollutant from all contributing point and nonpoint sources. The TMDL calculations must include a
"margin of safety" to ensure that the waterbody can be protected in case there are unforeseen events
or unknown sources of the pollutant. The calculation must also account for seasonable variation in
water quality.
Transfer of Coverage (TOC) means a request for transfer of coverage under this general permit as
specified by Special Condition S2.A of this permit.
Treatment BMPs means BMPs that are intended to remove pollutants from stormwater. A few examples
of treatment BMPs are detention ponds, oil/water separators, biofiltration, and constructed wetlands.
Transparency means a measurement of water clarity in centimeters (cm), using a 60 cm transparency
tube. The transparency tube is used to estimate the relative clarity or transparency of water by noting
the depth at which a black and white Secchi disc becomes visible when water is released from a value in
the bottom of the tube. A transparency tube is sometimes referred to as a “turbidity tube.”
Turbidity means the clarity of water expressed as nephelometric turbidity units (NTUs) and measured
with a calibrated turbidimeter.
Uncontaminated means free from any contaminant. See definition of “contaminant” and WAC 173-340-200.
Upset means an exceptional incident in which there is unintentional and temporary noncompliance with
technology-based permit effluent limitations because of factors beyond the reasonable control of the
Permittee. An upset does not include noncompliance to the extent caused by operational error,
improperly designed treatment facilities, inadequate treatment facilities, lack of preventive
maintenance, or careless or improper operation.
Waste Load Allocation (WLA) means the portion of a receiving water’s loading capacity that is allocated
to one of its existing or future point sources of pollution. WLAs constitute a type of water quality based
effluent limitation (40 CFR 130.2[h]).
Water-Only Based Shaft Drilling is a shaft drilling process that uses water only and no additives are
involved in the drilling of shafts for construction of building, road, or bridge foundations.
Water Quality means the chemical, physical, and biological characteristics of water, usually with respect
to its suitability for a particular purpose.
Waters of the State includes those waters as defined as "waters of the United States" in 40 CFR Subpart
122.2 within the geographic boundaries of Washington State and "waters of the State" as defined in
Chapter 90.48 RCW, which include lakes, rivers, ponds, streams, inland waters, underground waters, salt
Construction Stormwater General Permit Page 49
waters, and all other surface waters and water courses within the jurisdiction of the state of
Washington.
Well means a bored, drilled or driven shaft, or dug hole whose depth is greater than the largest surface
dimension. (See Injection Well.)
Wheel Wash Wastewater means any water used in, or resulting from the operation of, a tire bath or
wheel wash (BMP C106: Wheel Wash), or other structure or practice that uses water to physically
remove mud and debris from vehicles leaving a construction site and prevent track-out onto roads.
When stormwater comingles with wheel wash wastewater, the resulting water is considered wheel
wash wastewater and must be managed according to Special Condition S9.D.9.
Construction Stormwater General Permit Page 50
APPENDIX B – ACRONYMS
AKART All Known, Available, and Reasonable Methods of Prevention,
Control, and Treatment
BMP Best Management Practice
CESCL Certified Erosion and Sediment Control Lead
CFR Code of Federal Regulations
CKD Cement Kiln Dust
cm Centimeters
CPD Common Plan of Development
CTB Cement-Treated Base
CWA Clean Water Act
DMR Discharge Monitoring Report
EPA Environmental Protection Agency
ERTS Environmental Report Tracking System
ESC Erosion and Sediment Control
FR Federal Register
LID Low Impact Development
NOI Notice of Intent
NOT Notice of Termination
NPDES National Pollutant Discharge Elimination System
NTU Nephelometric Turbidity Unit
RCW Revised Code of Washington
SEPA State Environmental Policy Act
SWMM Stormwater Management Manual
SWPPP Stormwater Pollution Prevention Plan
TMDL Total Maximum Daily Load
UIC Underground Injection Control
USC United States Code
USEPA United States Environmental Protection Agency
WAC Washington Administrative Code
WQ Water Quality
WWHM Western Washington Hydrology Model