HomeMy WebLinkAboutRS_CSWPP_20220414_v1Construction Stormwater General Permit (CSWGP)
Stormwater Pollution Prevention Plan
(SWPPP)
for
Cyprus Lane
Prepared for:
Department of Ecology
Northwest Regional Office
Permittee / Owner Developer Operator / Contractor
Tuscany Construction
PO Box 2170
Renton, WA 98056
Tuscany Construction
PO Box 2170
Renton, WA 98056
TBD
5816 NE 4th Place, Renton WA 98059
Certified Erosion and Sediment Control Lead (CESCL)
Name Organization Contact Phone Number
TBD TBD TBD
SWPPP Prepared By
Name Organization Contact Phone Number
Andrew Oh Core Design Inc. 425-885-7877
SWPPP Preparation Date
08/11/22
Project Construction Dates
Activity / Phase Start Date End Date
Construction 4/01/2023 9/30/2024
GENERAL INSTRUCTIONS AND CAVEATS
This template presents the recommended structure and content for preparation of a
Construction Stormwater General Permit (CSWGP) Stormwater Pollution Prevention Plan
(SWPPP).
The Department of Ecology’s (Ecology) CSWGP requirements inform the structure and content
of this SWPPP template; however, you must customize this template to reflect the
conditions of your site.
A Construction Stormwater Site Inspection Form can be found on Ecology’s website.
https://www.ecology.wa.gov/Regulations-Permits/Permits-certifications/Stormwater-general-
permits/Construction-stormwater-permit
Using the SWPPP Template
Each section will include instructions and space for information specific to your project. Please
read the instructions for each section and provide the necessary information when prompted.
This Word template can be modified electronically. You may add/delete text, copy and paste,
edit tables, etc. Some sections may be completed with brief answers while others may require
several pages of explanation.
Follow this link to a copy of the Construction Stormwater General Permit:
https://www.ecology.wa.gov/Regulations-Permits/Permits-certifications/Stormwater-general-
permits/Construction-stormwater-permit
Cyprus Lane i
Table of Contents
Contents
1.0 Project Information ........................................................................................................................... 1
1.1 Existing Conditions ........................................................................................................................ 1
1.2 Proposed Construction Activities .................................................................................................. 2
2.0 Construction Stormwater Best Management Practices (BMPs) ....................................................... 3
2.1 The 13 Elements (2.1) ................................................................................................................... 3
2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits ....................................................... 3
2.1.2 Element 2: Establish Construction Access ............................................................................ 3
2.1.3 Element 3: Control Flow Rates .............................................................................................. 4
2.1.4 Element 4: Install Sediment Controls .................................................................................... 5
2.1.5 Element 5: Stabilize Soils ...................................................................................................... 5
2.1.6 Element 6: Protect Slopes ..................................................................................................... 6
2.1.7 Element 7: Protect Drain Inlets ............................................................................................. 6
2.1.8 Element 8: Stabilize Channels and Outlets ........................................................................... 7
2.1.9 Element 9: Control Pollutants ............................................................................................... 7
2.1.10 Element 10: Control Dewatering ........................................................................................ 10
2.1.11 Element 11: Maintain BMPs................................................................................................ 10
2.1.12 Element 12: Manage the Project ........................................................................................ 11
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs ............................................... 11
3.0 Pollution Prevention Team ............................................................................................................. 12
4.0 Monitoring and Sampling Requirements ........................................................................................ 13
4.1 Site Inspection ............................................................................................................................. 13
4.2 Stormwater Quality Sampling ..................................................................................................... 13
4.2.1 Turbidity Sampling .............................................................................................................. 13
4.2.2 pH Sampling ........................................................................................................................ 15
5.0 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies .................................... 16
5.1 303(d) Listed Waterbodies .......................................................................................................... 16
5.2 TMDL Waterbodies ..................................................................................................................... 16
6.0 Reporting and Record Keeping ....................................................................................................... 17
Cyprus Lane ii
6.1 Record Keeping ........................................................................................................................... 17
6.1.1 Site Log Book ....................................................................................................................... 17
6.1.2 Records Retention ............................................................................................................... 17
6.1.3 Updating the SWPPP ........................................................................................................... 17
6.2 Reporting ..................................................................................................................................... 18
6.2.1 Discharge Monitoring Reports ............................................................................................ 18
6.2.2 Notification of Noncompliance ........................................................................................... 18
List of Tables
Table 1 – Summary of Site Pollutant Constituents ....................................................................................... 1
Table 2 – Pollutants ....................................................................................................................................... 7
Table 3 – pH-Modifying Sources ................................................................................................................... 9
Table 4 – Dewatering BMPs ........................................................................................................................ 10
Table 5 – Management ............................................................................................................................... 11
Table 7 – Team Information ........................................................................................................................ 12
Table 8 – Turbidity Sampling Method ......................................................................................................... 13
Table 8 – pH Sampling Method ................................................................................................................... 15
List of Appendices
A. Site Map
B. BMP Detail
C. Correspondence
D. Site Inspection Form
E. Construction Stormwater General Permit (CSWGP)
F. 303(d) List Waterbodies / TMDL Waterbodies Information
G. Contaminated Site Information
H. Engineering Calculations
Cyprus Lane iii
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
Cyprus Lane 1
1.0 Project Information
Project/Site Name: Cyprus Lane
Street/Location: 5816 NE 4th Place
City: Renton State: WA Zip code: 98059
Subdivision: Cyprus Lane
Receiving waterbody: Lake Washington
1.1 Existing Conditions
Total acreage (including support activities such as off-site equipment staging yards, material
storage areas, borrow areas).
Total acreage: 4.83 Acres
Disturbed acreage: 4.83 Acres
Existing structures: Two existing single family homes with three detached garages.
Landscape topography: The northeast corner of the site is the high point. The site slopes
south and west.
Drainage patterns: Runoff on the west side flows onto Nile Avenue NE while runoff on
the south side flows into NE 4th Place.
Existing Vegetation: Some existing vegetation with mostly forested areas.
Critical Areas (wetlands, streams, high erosion risk, steep or difficult to stabilize slopes):
No critical areas on site.
List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the
receiving waterbody:
Table 1 includes a list of suspected and/or known contaminants associated with the construction
activity.
Table 1 – Summary of Site Pollutant Constituents
Constituent
(Pollutant) Location Depth Concentration
No pollutants
Cyprus Lane 2
1.2 Proposed Construction Activities
Description of site development (example: subdivision):
Single-Family subdivision creating 14 lots with associated roadways, utilities, and stormwater
facilities.
Description of construction activities (example: site preparation, demolition, excavation):
Erosion control measures will be installed. Existing structures and hardscape will be
demolished. Site will be cleared and graded. Utilities will be installed. Hardscape will be
installed. Homes will be built.
Description of site drainage including flow from and onto adjacent properties. Must be consistent
with Site Map in Appendix A:
Runoff on the west side flows onto Nile Avenue NE while runoff on the east side flows into NE
4th Place.
Description of final stabilization (example: extent of revegetation, paving, landscaping):
All disturbed areas will be stabilized with landscaping or hardscaping.
Contaminated Site Information:
Proposed activities regarding contaminated soils or groundwater (example: on-site treatment
system, authorized sanitary sewer discharge):
Not Applicable.
Cyprus Lane 3
2.0 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)
2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits
All projects will clearly mark any clearing limits, sensitive areas, buffers, and trees that will be
preserved prior to beginning any land disturbing activities. Clearly mark limits both in the field
and on the plans
List and describe BMPs: BMP C103: High Visibility Fence
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B
Responsible Staff: Project CESL
2.1.2 Element 2: Establish Construction Access
All construction projects subject to vehicular traffic shall provide a means of preventing soil from
the construction site to enter the city streets. At minimum, there shall be a rock pad construction
entrance at every vehicle access point. If the rock pad itself is insufficient, a wheel wash may
be necessary. Note: The applicant should consider placing the entrance in the area for future
driveway(s), as the rock can be used for driveway base material. The entrance(s) shall be
inspected weekly and if excessive sediment is found, more rock shall be added to ensure proper
functioning.
List and describe BMPs: BMP C105: Stabilized Construction Entrance
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B
Responsible Staff: Project CESL
Cyprus Lane 4
2.1.3 Element 3: Control Flow Rates
Flow Control BMPs must be used to protect properties and waterways downstream of the
construction site from the effects of the associated discharge of turbid waters. Stormwater
retention or detention facilities will be constructed as one of the first steps in grading.
The permanent detention vault will be constructed early in the construction process and be used
as temporary sediment facilities.
Will you construct stormwater retention and/or detention facilities?
Yes
Will you use permanent infiltration ponds or other low impact development (example: rain
gardens, bio-retention, porous pavement) to control flow during construction?
No
List and describe BMPs: BMP C207: Check Dams
BMP C241: Temporary Sediment Pond
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B
Responsible Staff: Project CESL
Cyprus Lane 5
2.1.4 Element 4: Install Sediment Controls
Sediment barriers should be used downslope of disturbed areas. Sediment barriers are
intended to create a barrier to slow the flow of stormwater and allow the sediment to settle out
behind the barrier. Do not use sediment barriers in streams, channels, ditches or around
inlets/outlets of culverts.
List and describe BMPs: BMP C233: Silt Fence
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B.
Responsible Staff: Project CESL
2.1.5 Element 5: Stabilize Soils
Soil erosion protection is applied over the soil surface to reduce erosion from rainfall and wind. It
can also be used to aid the establishment of vegetation. Between October 1st and April 30th, no
soils shall remain exposed for more than 2 days unless they are being actively workd. From
April 1st to September 30th, no soils shall remain exposed for more than 7 days unless they are
being actively worked.
Mulching may be used individually for stabilization of periods shorter than 30 days. Seeding
should be used for soils that will remain unworked for more than 30 days. Seeding requires
mulch.
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
Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on
the weather forecast.
Anticipated project dates: Start date: April 1, 2023 End date: September 30, 2024
Will you construct during the wet season?
Yes
Cyprus Lane 6
List and describe BMPs: BMP C120: Temporary and Permanent Seeding
BMP C121: Mulching
Quicklime for Structural fill – See BMPs as outlined by project
geotechnical engineer memo in Appendix B.
Installation Schedules: Applied as needed to stabilize soils
Inspection and Maintenance plan: See BMP information provided in Appendix B.
Responsible Staff: Project CESL
2.1.6 Element 6: Protect Slopes
Design, construct and phase projects in a manner that will minimize erosion. Slopes will be
protected by diverting water at the top of the slope. Reducing slope velocities by minimizing the
continuous length of slope, which can be done through terracing. Seeding slopes will help
stabilize the slopes as well.
Will steep slopes be present at the site during construction?
No
List and describe BMPs: BMP C120: Temporary and Permanent Seeding
BMP C121: Mulching
BMP C200: Intercepter Dike and Swale
Installation Schedules: Applied as needed to stabilize soils
Inspection and Maintenance plan: See BMP information provided in Appendix B.
Responsible Staff: Project CESL
2.1.7 Element 7: Protect Drain Inlets
Catch basin protection for all nearby downstream and onsite functioning catch basins. This will
prevent sediments from entering drainage systems prior to site stabilization. Inlets will be
inspected weekly or daily during storm events.
List and describe BMPs: BMP C220: Storm Drain Inlet Protection
Installation Schedules: April 1, 2023
Cyprus Lane 7
Inspection and Maintenance plan: See BMP information provided in Appendix B
Responsible Staff: Project CESL
2.1.8 Element 8: Stabilize Channels and Outlets
All on-site conveyance channels shall be designed, constructed, and stabilized to prevent
erosion from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Provide
stabilization adequate to prevent erosion of outlets, adjacent streambanks, slopes, and
downstream reaches at the outlets of all conveyance systems.
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.
List and describe BMPs: BMP C207: Check Dams
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B.
Responsible Staff: Project CESL
2.1.9 Element 9: Control Pollutants
The following pollutants are anticipated to be present on-site:
Table 2 – Pollutants
Pollutant (and source, if applicable)
Concrete
Dust and Debris
Petroleum
Concrete
• Unused concrete remaining in the truck and pump shall be returned to the originating
batch plant to be recycled.
• Concrete truck chutes, pumps, internals, hand tools shall be washed off only into formed
areas awaiting installation of concrete or asphalt. (BMP C154)
• Equipment that cannot be easily moved shall only be washed in areas that do not
directly drain to natural or constructed stormwater conveyances.
Cyprus Lane 8
• When no formed areas are available, waste shall be discharged to a paved or lined
sump. The waste water shall be neutralizied prior to discharge.
List and describe BMPs: BMP C151: Concrete Handling
BMP C154: Concrete Washout Area
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B
Responsible Staff: Project CESL.
Dust and Debris
• Dust released from demolished sidewalks, buildings, or structures 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
Surface Pollution Prevention Measures (BMP C152)
List and describe BMPs: BMP C140: Dust Control
BMP C152: Sawcutting and Surfacing Pollution Prevention
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B.
Responsible Staff: Project CESL
Petroleum
• No fuel or chemicals will be stored on site.
• Fueling shall be provided by a fueling truck. No fuel shall be stored on site.
• All vehicle maintenance and repairs shall be done offsite.
Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site?
No
List and describe BMPs: BMP C153: Material Delivery, Storage and Containment
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B.
Cyprus Lane 9
Responsible Staff: Project CESL.
Will wheel wash or tire bath system BMPs be used during construction?
Yes
List and describe BMPs: BMP C106: Wheel Wash
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B.
Responsible Staff: Project CESL
Will pH-modifying sources be present on-site?
Yes
Table 3 – pH-Modifying Sources
None
X Bulk cement
Cement kiln dust
Fly ash
X 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
X Other – Quicklime, See BMPs as outlined by project geotechnical engineer memo in
Appendix B.
List and describe BMPs: BMP C151: Concrete Handling
BMP C252: High pH Neutralization Using CO2
BMP C253: pH Control for High pH Water
Installation Schedules: April 1, 2023
Inspection and Maintenance plan: See BMP information provided in Appendix B.
Responsible Staff: Project CESL
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.
Cyprus Lane 10
2.1.10 Element 10: Control Dewatering
No dewatering is anticipated to be required. If any dewatering does need to occur, water will be
discharged through a stabilized channel to the proposed Temporary Sediment Pond.
Table 4 – Dewatering BMPs
Infiltration
Transport off-site in a vehicle (vacuum truck for legal disposal)
Ecology-approved on-site chemical treatment or other suitable treatment technologies
Sanitary or combined sewer discharge with local sewer district approval (last resort)
Use of sedimentation bag with discharge to ditch or swale (small volumes of localized
dewatering)
List and describe BMPs: N/A
Installation Schedules: N/A
Inspection and Maintenance plan: N/A
Responsible Staff: N/A
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
Cyprus Lane 11
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.
Table 5 – Management
X Design the project to fit the existing topography, soils, and drainage patterns
X Emphasize erosion control rather than sediment control
X Minimize the extent and duration of the area exposed
X Keep runoff velocities low
X Retain sediment on-site
X Thoroughly monitor site and maintain all ESC measures
X Schedule major earthwork during the dry season
Other (please describe)
2.1.13 Element 13: Protect Low Impact Development (LID) BMPs
Cyprus Lane 12
3.0 Pollution Prevention Team
Table 7 – Team Information
Title Name(s) Phone Number
Certified Erosion and
Sediment Control Lead
(CESCL)
TBD
Resident Engineer Sheri Murata 425-885-7877
Emergency Ecology
Contact
Washington Emergency Management
Division
1-800-258-5990
Emergency Permittee/
Owner Contact
TBD
Non-Emergency Owner
Contact
Bob Wenzl 206-714-6707
Monitoring Personnel TBD
Ecology Regional Office Northwest 425-649-7000
Cyprus Lane 13
4.0 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
A blank form has been provided in Appendix D.
The site log book must be maintained on-site 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.
Complete the following paragraph for sites that discharge to impaired waterbodies for fine
sediment, turbidity, phosphorus, or pH:
All stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su
for pH and/or 25 NTU for turbidity.
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 8 – Turbidity Sampling Method
Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size)
Cyprus Lane 14
X 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.
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.
https://www.ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue
• Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima):
(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 (King, Kitsap, Island, San Juan, Skagit, Snohomish,
Whatcom): (425) 649-7000
• Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis,
Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300
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
Cyprus Lane 15
• 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 or recycled concrete over the life of the project).The use of 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 continues 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.
Method for sampling pH:
Table 8 – pH Sampling Method
X pH meter
pH test kit
Wide range pH indicator paper
Cyprus Lane 16
5.0 Discharges to 303(d) or Total Maximum Daily Load (TMDL)
Waterbodies
5.1 303(d) Listed Waterbodies
Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH?
No
List the impairment(s):
None
All stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su
for pH and/or 25 NTU for turbidity.
List and describe BMPs:
None
5.2 TMDL Waterbodies
Waste Load Allocation for CWSGP discharges:
None
List and describe BMPs:
None
Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point
of discharge.
The Construction Stormwater General Permit Proposed New Discharge to an Impaired Water
Body form is included in Appendix F.
Cyprus Lane 17
6.0 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.
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.
Cyprus Lane 18
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.
• Central Region at (509) 575-2490 for Benton, Chelan, Douglas, Kittitas, Klickitat,
Okanogan, or Yakima County
• Eastern Region at (509) 329-3400 for Adams, Asotin, Columbia, Ferry, Franklin,
Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, or Whitman
County
• Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit,
Snohomish, or Whatcom County
• Southwest Region at (360) 407-6300 for Clallam, Clark, Cowlitz, Grays Harbor,
Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, or Wahkiakum
Include the following information:
1. Your name and / Phone number
2. Permit number
3. City / County of project
4. Sample results
Cyprus Lane 19
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.
Cyprus Lane 20
Appendix/Glossary
Cyprus Lane 21
A. Site Map
5
10
25
2
ORCAS PL NENE 4TH PL
NILE PL NENILE AVENUE NEORCAS AVENUE NEPASCO AVENUE NECYPRUS LANE CIVIL CONSTRUCTION PERMITIN COMPLIANCE WITH CITY OF RENTON STANDARDS PR22-XXXXXXC22-XXXXXXLUA-22-XXXXXXDESIGN
12100 NE 195th St, Suite 300 Bothell, Washington 98011 425.885.7877
CIVIL ENGINEERING
LANDSCAPE ARCHITECTURE
PLANNING
SURVEYING
PROJECT NO. 20134 8-11-22
CYPRUS LANE CIVIL CONSTRUCTION PERMITIN COMPLIANCE WITH CITY OF RENTON STANDARDS
8-11-22 PR22-XXXXXXC22-XXXXXXDESIGN
12100 NE 195th St, Suite 300 Bothell, Washington 98011 425.885.7877
CIVIL ENGINEERING
LANDSCAPE ARCHITECTURE
PLANNING
SURVEYING
PROJECT NO. 20134 LUA-22-XXXXXXTREE PROTECTION FENCING
TREE PROTECTION MEASURES DURING CONSTRUCTION
Cyprus Lane 23
B. BMP Detail
The following BMP detail sheets are provided:
BMP C103: High Visibility Fence
BMP C105: Stabilized Consturction Access
BMP C106: Wheel Wash
BMP C120: Temporary and Permanent Seeding
BMP C121: Mulching
BMP C140: Dust Control
BMP C151: Concrete Handling
BMP C152: Sawcutting and Surfacing Pollution Prevention
BMP C153: Material Delivery, Storage, and Containment
BMP C154: Concrete Washout Area
BMP C200: Intercepter Dike and Swale
BMP C207: Check Dams
BMP C220: Storm Drain Inlet Protection
BMP C233: Silt Fence
BMP C241: Temporary Sediment Pond
BMP C252: Treating and Disposing of High pH Water
BMP C253: pH Control for High pH Water
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 marking with survey tape may not provide
adequate protection.
Conditions of Use To establish clearing limits plastic, fabric, or metal fence may be used:
• At the boundary of sensitive areas, their buffers, and other areas
required to be left uncleared.
• As necessary to control vehicle access to and on the site.
Design and Installation Specifications
High visibility plastic fence shall be composed of a high-density polyethylene material and shall be at least four 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 six inches with a polyethylene tie. On long continuous
lengths of fencing, a tension wire or rope shall be used as a top stringer to prevent sagging between posts. The fence 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.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C105: Stabilized Construction Entrance / Exit
Purpose Stabilized Construction entrances are established to reduce the amount of sediment transported onto paved roads by vehicles or equipment. This is
done 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 be entering or leaving a construction site if paved roads or other paved areas are
within 1,000 feet of the site.
For residential construction 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 4.1.1 for details. Note: the 100’ 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’).
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, 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:
Grab Tensile Strength (ASTM D4751) 200 psi min.
Grab Tensile Elongation (ASTM D4632) 30% max.
Mullen Burst Strength (ASTM D3786-80a) 400 psi min.
AOS (ASTM D4751) 20-45 (U.S. standard sieve size)
• Consider early installation of the first lift of asphalt in areas that will paved; this can be used as a stabilized entrance. Also consider the
installation of excess concrete as a stabilized entrance. During large concrete pours, excess concrete is often available for this purpose.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Fencing (see BMP C103) shall be installed as necessary to restrict
traffic to the construction entrance.
•Whenever possible, the entrance shall be constructed on a firm,
compacted subgrade. This can substantially increase the effectivenessof the pad and reduce the need for maintenance.
•Construction entrances should avoid crossing existing sidewalks andback of walk drains if at all possible. If a construction entrance must
cross a sidewalk or back of walk drain, the full length of the sidewalkand back of walk drain must be covered and protected from sediment
leaving the site.
Maintenance
Standards
Quarry spalls shall be added if the pad is no longer in accordance with
the specifications.
•If the entrance is not preventing sediment from being tracked onto
pavement, then alternative measures to keep the streets free ofsediment shall be used. This may include replacement/cleaning of the
existing quarry spalls, street sweeping, an increase in the dimensionsof the entrance, or the installation of a wheel wash.
•Any sediment that is tracked onto pavement shall be removed byshoveling or street sweeping. The sediment collected by sweeping
shall be removed or stabilized on site. The pavement shall not becleaned by washing down the street, except when high efficiency
sweeping is ineffective and there is a threat to public safety. If it isnecessary to wash the streets, the construction of a small sump to
contain the wash water shall be considered. The sediment would thenbe washed into the sump where it can be controlled.
•Perform street sweeping by hand or with a high efficiency sweeper. Donot use a non-high efficiency mechanical sweeper because this creates
dust and throws soils into storm systems or conveyance ditches.
•Any quarry spalls that are loosened from the pad, which end up on the
roadway shall be removed immediately.
•If vehicles are entering or exiting the site at points other than the
construction entrance(s), fencing (see BMP C103) shall be installed tocontrol traffic.
•Upon project completion and site stabilization, all constructionaccesses intended as permanent access for maintenance shall be
permanently stabilized.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.1.1 – Stabilized Construction Entrance
Approved as
Equivalent Ecology has approved products as able to meet the requirements of BMP
C105. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not
to accept this product approved as equivalent, or may require additional
testing prior to consideration for local use. The products are available for
review on Ecology’s website at
http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html
Driveway shall meet the requirements of the permitting agency
It is recommended that the entrance be crowned so that runoff drains off the pad
Provide full width of ingress/egress area
12” min. thickness
Geotextile
4’ – 8” quarry spalls
Install driveway culvert if there is a roadside ditch present
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C106: Wheel Wash
Purpose Wheel washes reduce the amount of sediment transported onto paved
roads by motor vehicles.
Conditions of Use When a stabilized construction entrance (see BMP C105) is not preventing sediment from being tracked onto pavement.
•Wheel washing is generally an effective BMP when installed with
careful attention to topography. For example, a wheel wash can be
detrimental if installed at the top of a slope abutting a right-of-way
where the water from the dripping truck can run unimpeded into thestreet.
•Pressure washing combined with an adequately sized and surfaced pad
with direct drainage to a large 10-foot x 10-foot sump can be very
effective.
•Discharge wheel wash or tire bath wastewater to a separate on-sitetreatment system that prevents discharge to surface water, such asclosed-loop recirculation or upland land application, or to the sanitary
sewer with local sewer district approval.
•Wheel wash or tire bath wastewater should not include wastewater
from concrete washout areas.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Design and Installation Specifications
Suggested details are shown in Figure 4.1.2. The Local Permitting
Authority may allow other designs. A minimum of 6 inches of asphalt
treated base (ATB) over crushed base material or 8 inches over a good
subgrade is recommended to pave the wheel wash.
Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance.
Keep the water level from 12 to 14 inches deep to avoid damage to truck
hubs and filling the truck tongues with water.
Midpoint spray nozzles are only needed in extremely muddy conditions.
Wheel wash systems should be designed with a small grade change, 6- to 12-inches for a 10-foot-wide pond, to allow sediment to flow to the low
side of pond to help prevent re-suspension of sediment. A drainpipe with a
2- to 3-foot riser should be installed on the low side of the pond to allow
for easy cleaning and refilling. Polymers may be used to promote
coagulation and flocculation in a closed-loop system. Polyacrylamide (PAM) added to the wheel wash water at a rate of 0.25 - 0.5 pounds per
1,000 gallons of water increases effectiveness and reduces cleanup time. If
PAM is already being used for dust or erosion control and is being applied
by a water truck, the same truck can be used to change the wash water.
Maintenance Standards The wheel wash should start out the day with fresh water.
The wash water should be changed a minimum of once per day. On large
earthwork jobs where more than 10-20 trucks per hour are expected, the
wash water will need to be changed more often.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.1.2 – Wheel Wash
Notes:
1. Asphalt construction entrance 6 in. asphalt treated base (ATB).2. 3-inch trash pump with floats on the suction hose.
3. Midpoint spray nozzles, if needed.
4. 6-inch sewer pipe with butterfly valves. Bottom one is a drain. Locate top pipe’s invert 1
foot above bottom of wheel wash.
5. 8 foot x 8 foot sump with 5 feet of catch. Build so the sump can be cleaned with atrackhoe.
6. Asphalt curb on the low road side to direct water back to pond.
7. 6-inch sleeve under road.
8.Ball valves.
9. 15 foot. ATB apron to protect ground from splashing water.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
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 Use seeding throughout the project on disturbed areas that have reached
final grade or that will remain unworked for more than 30 days.
The optimum seeding windows for western Washington are April 1
through June 30 and September 1 through October 1.
Between July 1 and August 30 seeding requires irrigation until 75 percent
grass cover is established.
Between October 1 and March 30 seeding requires a cover of mulch with straw or an erosion control blanket until 75 percent grass cover is
established.
Review all disturbed areas in late August to early September and complete
all seeding by the end of September. Otherwise, vegetation will not
establish itself enough to provide more than average protection.
•Mulch is required at all times for seeding because it protects seeds
from heat, moisture loss, and transport due to runoff. Mulch can beapplied on top of the seed or simultaneously by hydroseeding. See
BMP C121: Mulching for specifications.
•Seed and mulch, all disturbed areas not otherwise vegetated at final
site stabilization. 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 preventerosion.
Design and Installation
Specifications
Seed retention/detention ponds as required.
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 blanketsover hydroseed. Before allowing water to flow in vegetated
channels, establish 75 percent vegetation cover. If vegetated
channels cannot be established by seed before water flow; install sod
in the channel bottom—over hydromulch and erosion control
blankets.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Confirm the installation of all required surface water control measures
to prevent seed from washing away.
•Hydroseed applications shall include a minimum of 1,500 pounds per
acre of mulch with 3 percent tackifier. See BMP C121: Mulching forspecifications.
•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 on the disturbed soil
surface before application.
•When installing seed via hydroseeding operations, only about 1/3 of
the seed actually ends up in contact with the soil surface. This reducesthe ability to establish a good stand of grass quickly. To overcome this,
consider increasing seed quantities by up to 50 percent.
•Enhance vegetation establishment by dividing the hydromulch
operation into two phases:
1.Phase 1- Install all seed and fertilizer with 25-30 percent mulch
and tackifier onto soil in the first lift.
2.Phase 2- Install the rest of the mulch and tackifier over the first lift.
Or, enhance vegetation by:
1. Installing the mulch, seed, fertilizer, and tackifier in one lift.
2. Spread or blow straw over the top of the hydromulch at a rate of800-1000 pounds per acre.
3.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:
•Irrigation.
•Reapplication of mulch.
•Repair of failed slope surfaces.
This technique works with standard hydromulch (1,500 pounds per acre minimum) and BFM/MBFMs (3,000 pounds per acre minimum).
•Seed may be installed by hand if:
•Temporary and covered by straw, mulch, or topsoil.
•Permanent in small areas (usually less than 1 acre) and coveredwith mulch, topsoil, or erosion blankets.
•The seed mixes listed in the tables below include recommended
mixes for both temporary and permanent seeding.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Apply these mixes, with the exception of the wetland mix, at a rate
of 120 pounds per acre. This rate can be reduced if soil
amendments or slow-release fertilizers are used.
•Consult the local suppliers or the local conservation district fortheir recommendations because the appropriate mix depends on avariety of factors, including location, exposure, soil type, slope,
and expected foot traffic. Alternative seed mixes approved by the
local authority may be used.
•Other mixes may be appropriate, depending on the soil type andhydrology of the area.
•Table 4.1.2 lists the standard mix for areas requiring a temporary
vegetative cover.
Table 4.1.2 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
•Table 4.1.3 lists a recommended mix for landscaping seed.
Table 4.1.3 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
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Table 4.1.4 lists a turf seed mix for dry situations where there is no
need for watering. This mix requires very little maintenance.
Table 4.1.4
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
Colonial bentgrass
Agrostis tenuis
5 98 90
•Table 4.1.5 lists a mix for bioswales and other intermittently wet areas.
Table 4.1.5 Bioswale Seed Mix*
% 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
*Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Table 4.1.6 lists a low-growing, relatively non-invasive seed mix
appropriate for very wet areas that are not regulated wetlands. Apply
this mixture at a rate of 60 pounds per acre. Consult Hydraulic Permit
Authority (HPA) for seed mixes if applicable.
Table 4.1.6 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
* Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix
•Table 4.1.7 lists a recommended meadow seed mix for infrequently
maintained areas or non-maintained areas where colonization by nativeplants is desirable. Likely applications include rural road and utility
right-of-way. Seeding should take place in September or very early
October in order to obtain adequate establishment prior to the winter
months. Consider the appropriateness of clover, a fairly invasive
species, in the mix. Amending the soil can reduce the need for clover.
Table 4.1.7 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
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
• Roughening and Rototilling:
• The seedbed should be firm and rough. Roughen all soil no matter
what the slope. Track walk slopes before seeding if engineering
purposes require compaction. Backblading or smoothing of slopes greater than 4H:1V is not allowed if they are to be seeded.
• Restoration-based landscape practices require 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 soil amendments to achieve
organic matter and permeability performance defined in
engineered soil/landscape systems. For systems that are deeper
than 8 inches complete the rototilling process in multiple lifts, or
prepare the engineered soil system per specifications and place to achieve the specified depth.
• Fertilizers:
• Conducting soil tests to determine the exact type and quantity of
fertilizer is recommended. This will prevent the over-application
of fertilizer.
• Organic matter is the most appropriate form of fertilizer because it
provides nutrients (including nitrogen, phosphorus, and potassium)
in the least water-soluble form.
• In general, use 10-4-6 N-P-K (nitrogen-phosphorus-potassium)
fertilizer at a rate of 90 pounds per acre. Always use slow-release fertilizers because they are more efficient and have fewer
environmental impacts. Do not add fertilizer to the hydromulch
machine, or agitate, more than 20 minutes before use. Too much
agitation destroys the slow-release coating.
• There are numerous products available 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 provides a good
source of long-term, slow-release, available nitrogen.
• Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix:
• On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically
Bonded Fiber Matrix (MBFM) products. Apply BFM/MBFM
products at a minimum rate of 3,000 pounds per acre of mulch
with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during application. Numerous products are available commercially. Installed products per manufacturer’s
instructions. Most products require 24-36 hours to cure before
rainfall and cannot be installed on wet or saturated soils.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Generally, products come in 40-50 pound bags and include all
necessary ingredients except for seed and fertilizer.
•BFMs and MBFMs provide good alternatives to blankets in most
areas requiring vegetation establishment. Advantages overblankets include:
•BFM and MBFMs do not require surface preparation.
•Helicopters can assist in installing BFM and MBFMs in remoteareas.
•On slopes steeper than 2.5H:1V, blanket installers may requireropes and harnesses for safety.
•Installing BFM and MBFMs can save at least $1,000 per acrecompared to blankets.
Maintenance
Standards
Reseed any seeded areas that fail to establish at least 80 percent cover
(100 percent cover for areas that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such as sodding,
mulching, or nets/blankets. If winter weather prevents adequate grass
growth, this time limit may be relaxed at the discretion of the local
authority when sensitive areas would otherwise be protected.
•Reseed and protect by mulch any areas that experience erosion afterachieving adequate cover. Reseed and protect by mulch any eroded
area.
•Supply seeded areas with adequate moisture, but do not water to the
extent that it causes runoff.
Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C120. The products did not pass through the Technology Assessment
Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to
accept this product approved as equivalent, or may require additional testing
prior to consideration for local use. The products are available for review on
Ecology’s website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C121: Mulching
Purpose Mulching soils provides immediate temporary protection from erosion.
Mulch also enhances plant establishment by conserving moisture, holding
fertilizer, seed, and topsoil in place, and moderating soil temperatures. There is an enormous variety of mulches that can be used. This section
discusses only the most common types of mulch.
Conditions of Use As a temporary cover measure, mulch should be used:
•For less than 30 days on disturbed areas that require cover.
•At all times for seeded areas, especially during the wet season andduring the hot summer months.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•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: cottonseed
meal; fibers made of wood, recycled cellulose, hemp, kenaf; compost;
or blends of these. Tackifier shall be plant-based, such as guar or alpha
plantago, or chemical-based such as polyacrylamide or polymers. Any
mulch or tackifier product used shall be installed per manufacturer’sinstructions. Generally, mulches come in 40-50 pound bags. Seed and
fertilizer are added at time of application.
Design and
Installation
Specifications
For mulch materials, application rates, and specifications, see Table 4.1.8.
Always use a 2-inch minimum mulch thickness; increase the thickness
until the ground is 95% covered (i.e. not visible under the mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive
areas or other areas highly susceptible to erosion.
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
Minimum Percent passing 3” sieve openings 100%
Minimum Percent passing 1” sieve openings 90%
Minimum Percent passing ¾” sieve openings 70%
Minimum Percent passing ¼” sieve openings 40%
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 Hydraulic Permit Authority (HPA) for mulch mixes if applicable.
Maintenance
Standards
•The thickness of the cover must be maintained.
•Any areas that experience erosion shall be remulched and/or protected
with a net or blanket. If the erosion problem is drainage related, thenthe problem shall be fixed and the eroded area remulched.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Table 4.1.8 Mulch Standards and Guidelines
Mulch Material Quality Standards Application Rates Remarks
Straw Air-dried; free from
undesirable seed and
coarse material.
2"-3" thick; 5
bales per 1,000
sf or 2-3 tons per
acre
Cost-effective protection when applied with adequate thickness.
Hand-application generally requires greater thickness than
blown straw. The thickness of straw may be reduced by half
when used in conjunction with seeding. In windy areas straw
must be held in place by crimping, using a tackifier, or covering
with netting. Blown straw always has to be held in place with a tackifier as even light winds will blow it away. Straw, however, has several deficiencies that should be considered when selecting mulch materials. It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits. It should also 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 ¾-1 inch clog hydromulch equipment.
Fibers should be kept to less than ¾ inch.
Compost No visible water or
dust during
handling. Must be produced per WAC 173-350, Solid Waste Handling Standards, but may have up to 35% biosolids.
2" thick min.;
approx. 100 tons
per acre (approx. 800 lbs per yard)
More effective control can be obtained by increasing thickness
to 3". Excellent mulch for protecting final grades until
landscaping because it can be directly seeded or tilled into soil as an amendment. Compost used for mulch has a coarser size gradation than compost used for BMP C125 or BMP T5.13 (see Chapter 5 of Volume V of this manual) It is more stable and practical to use in wet areas and during rainy weather conditions. Do not use 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" thick min.; This is a cost-effective way to dispose of debris from clearing and grubbing, and it eliminates the problems associated with burning. Generally, it should not be used on slopes above
approx. 10% because of its tendency to be transported by
runoff. It is not recommended within 200 feet of surface waters.
If seeding is expected shortly after mulch, the decomposition of
the chipped vegetation may tie up nutrients important to grass
establishment.
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” thick min.; approx. 100 tons per acre (approx. 800 lbs. per cubic yard)
This material is 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” 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 ⅜-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))
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C140: Dust Control
Purpose Dust control prevents wind transport of dust from disturbed soil surfaces
onto roadways, drainage ways, and surface waters.
Conditions of Use • In areas (including roadways) subject to surface and air movement of dust where on-site and off-site impacts to roadways, drainage ways, or
surface waters are likely.
Design and
Installation
Specifications
•Vegetate or mulch areas that will not receive vehicle traffic. In areas
where planting, mulching, or paving is impractical, apply gravel or
landscaping rock.
•Limit dust generation by clearing only those areas where immediate
activity will take place, leaving the remaining area(s) in the original
condition. Maintain the original ground cover as long as practical.
•Construct natural or artificial windbreaks or windscreens. These may
be designed as enclosures for small dust sources.
•Sprinkle the site with water until surface is wet. Repeat as needed. To
prevent carryout of mud onto street, refer to Stabilized Construction
Entrance (BMP C105).
•Irrigation water can be used for dust control. Irrigation systems should
be installed as a first step on sites where dust control is a concern.
•Spray exposed soil areas with a dust palliative, following the
manufacturer’s instructions and cautions regarding handling and
application. Used oil is prohibited from use as a dust suppressant.
Local governments may approve other dust palliatives such as calcium
chloride or PAM.
•PAM (BMP C126) added to water at a rate of 0.5 lbs. per 1,000
gallons of water per acre and applied from a water truck is more
effective than water alone. This is due to 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. AddingPAM may actually reduce the quantity of water needed for dust
control. Use of PAM could be a cost-effective dust control method.
Techniques that can be used for unpaved roads and lots include:
•Lower speed limits. High vehicle speed increases the amount of dust
stirred up from unpaved roads and lots.
•Upgrade the road surface strength by improving particle size, shape,
and mineral types that make up the surface and base materials.
•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.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Use geotextile fabrics to increase the strength of new roads or roads
undergoing reconstruction.
•Encourage the use of alternate, paved routes, if available.
•Restrict use of paved roadways by tracked vehicles and heavy trucksto prevent damage to road surface and base.
•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.
•Pave unpaved permanent roads and other trafficked areas.
•Use vacuum street sweepers.
•Remove mud and other dirt promptly so it does not dry and then turn
into dust.
•Limit dust-causing work on windy days.
•Contact your local Air Pollution Control Authority for guidance andtraining on other dust control measures. Compliance with the local AirPollution Control Authority constitutes compliance with this BMP.
Maintenance
Standards
Respray area as necessary to keep dust to a minimum.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
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, utilize these management practices. Concrete
construction projects include, but are not limited to, the following:
•Curbs
•Sidewalks
•Roads
•Bridges
•Foundations
•Floors
•Runways
Design and
Installation
•Assure that washout of concrete trucks, chutes, pumps, and internals is
performed at an approved off-site location or in designated concrete
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Specifications washout areas. Do not wash out concrete trucks onto the ground, or
into storm drains, open ditches, streets, or streams. Refer to BMP
C154 for information on concrete washout areas.
•Return unused concrete remaining in the truck and pump to theoriginating batch plant for recycling. Do not dump excess concrete onsite, except in designated concrete washout areas.
•Wash off hand tools including, but not limited to, screeds, shovels,
rakes, floats, and trowels into formed areas only.
•Wash equipment difficult to move, such as concrete pavers in areasthat do not directly drain to natural or constructed stormwaterconveyances.
•Do not allow washdown from areas, such as concrete aggregate
driveways, to drain directly to natural or constructed stormwater
conveyances.
•Contain washwater and leftover product in a lined container when no
formed areas are available. Dispose of contained concrete in a manner
that does not violate ground water or surface water quality standards.
•Always use forms or solid barriers for concrete pours, such as pilings,
within 15-feet of surface waters.
•Refer to BMPs C252 and C253 for pH adjustment requirements.
•Refer to the Construction Stormwater General Permit for pH
monitoring requirements if the project involves one of the following
activities:
•Significant concrete work (greater than 1,000 cubic yards pouredconcrete or recycled concrete used over the life of a project).
•The use of engineered soils amended with (but not limited to)
Portland cement-treated base, cement kiln dust or fly ash.
•Discharging stormwater to segments of water bodies on the 303(d)
list (Category 5) for high pH.
Maintenance Standards
Check containers for holes in the liner daily during concrete pours and
repair the same day.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C152: Sawcutting and Surfacing Pollution Prevention
Purpose Sawcutting and 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 created
through sawcutting or surfacing from entering waters of the State.
Conditions of Use Utilize these management practices anytime sawcutting or surfacing
operations take place. Sawcutting and surfacing operations include, but are not limited to, the following:
•Sawing
•Coring
•Grinding
•Roughening
•Hydro-demolition
•Bridge and road surfacing
Design and
Installation
Specifications
•Vacuum slurry and cuttings during cutting and surfacing operations.
•Slurry and cuttings shall not remain on permanent concrete or asphalt
pavement overnight.
•Slurry and cuttings shall not drain to any natural or constructed
drainage conveyance including stormwater systems. This may require
temporarily blocking catch basins.
•Dispose of collected slurry and cuttings in a manner that does not
violate ground water or surface water quality standards.
•Do not allow process water generated during hydro-demolition,
surface roughening or similar operations to drain to any natural or
constructed drainage conveyance including stormwater systems.
Dispose process water in a manner that does not violate ground water
or surface water quality standards.
•Handle and dispose cleaning waste material and demolition debris in a
manner that does not cause contamination of water. Dispose of
sweeping material from a pick-up sweeper at 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 vacuum trucks.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C153: Material Delivery, Storage and Containment
Purpose Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses from material delivery and storage.
Minimize the storage of hazardous materials on-site, store materials in a designated area, and install secondary containment.
Conditions of Use These procedures are suitable for use at all construction sites with delivery and storage of the following materials:
•Petroleum products such as fuel, oil and grease
•Soil stabilizers and binders (e.g., Polyacrylamide)
•Fertilizers, pesticides and herbicides
•Detergents
•Asphalt and concrete compounds
•Hazardous chemicals such as acids, lime, adhesives, paints, solvents,and curing compounds
•Any other material that may be detrimental if released to theenvironment
Design and Installation Specifications
The following steps should be taken to minimize risk:
•Temporary storage area should be located away from vehicular traffic,near the construction entrance(s), and away from waterways or stormdrains.
•Material Safety Data Sheets (MSDS) should be supplied for allmaterials stored. Chemicals should be kept in their original labeledcontainers.
•Hazardous material storage on-site should be minimized.
•Hazardous materials should be handled as infrequently as possible.
•During the wet weather season (Oct 1 – April 30), consider storing
materials in a covered area.
•Materials should be stored in secondary containments, such as earthen
dike, horse trough, or even a children’s wading pool for non-reactivematerials such as detergents, oil, grease, and paints. Small amounts of
material may be secondarily contained in “bus boy” trays or concretemixing trays.
•Do not store chemicals, drums, or bagged materials directly on theground. Place these items on a pallet and, when possible, and within
secondary containment.
•If drums must be kept uncovered, store them at a slight angle to reduce
ponding of rainwater on the lids to reduce corrosion. Domed plasticcovers are inexpensive and snap to the top of drums, preventing water
from collecting.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Material Storage Areas and Secondary Containment Practices:
•Liquids, petroleum products, and substances listed in 40 CFR Parts110, 117, or 302 shall be stored in approved containers and drums and
shall not be overfilled. Containers and drums shall be stored intemporary secondary containment facilities.
•Temporary secondary containment facilities shall provide for a spillcontainment volume able to contain 10% of the total enclosed
container volume of all containers, or 110% of the capacity of thelargest container within its boundary, whichever is greater.
•Secondary containment facilities shall be impervious to the materialsstored therein for a minimum contact time of 72 hours.
•Secondary containment facilities shall be maintained free ofaccumulated rainwater and spills. In the event of spills or leaks,
accumulated rainwater and spills shall be collected and placed intodrums. These liquids shall be handled as hazardous waste unless
testing determines them to be non-hazardous.
•Sufficient separation should be provided between stored containers to
allow for spill cleanup and emergency response access.
•During the wet weather season (Oct 1 – April 30), each secondary
containment facility shall be covered during non-working days, priorto and during rain events.
•Keep material storage areas clean, organized and equipped with anample supply of appropriate spill clean-up material (spill kit).
•The spill kit should include, at a minimum:
•1-Water Resistant Nylon Bag
•3-Oil Absorbent Socks 3”x 4’
•2-Oil Absorbent Socks 3”x 10’
•12-Oil Absorbent Pads 17”x19”
•1-Pair Splash Resistant Goggles
•3-Pair Nitrile Gloves
•10-Disposable Bags with Ties
•Instructions
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C154: Concrete Washout Area
Purpose 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 ground water.
Conditions of Use Concrete washout area best management practices are implemented on
construction projects where:
•Concrete is used as a construction material
•It is not possible to dispose of all concrete wastewater and washoutoff-site (ready mix plant, etc.).
•Concrete trucks, pumpers, or other concrete coated equipment are
washed on-site.
•Note: If less than 10 concrete trucks or pumpers need to be washed out
on-site, the washwater may be disposed of in a formed area awaitingconcrete or an upland disposal site where it will not contaminate
surface or ground water. The upland disposal site shall be at least 50
feet from sensitive areas such as storm drains, open ditches, or water
bodies, including wetlands.
Design and Installation Specifications
Implementation
The following steps will help reduce stormwater pollution from concrete
wastes:
•Perform washout of concrete trucks at an approved off-site location or
in designated concrete washout areas only.
•Do not wash out concrete trucks onto the ground, or into storm drains,open ditches, streets, or streams.
•Do not allow excess concrete to be dumped on-site, except in
designated concrete washout areas.
•Concrete washout areas may be prefabricated concrete washout
containers, or self-installed structures (above-grade or below-grade).
•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.
•If self-installed concrete washout areas are used, below-grade
structures are preferred over above-grade structures because they areless prone to spills and leaks.
•Self-installed above-grade structures should only be used if excavation
is not practical.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Education
•Discuss the concrete management techniques described in this BMP
with the ready-mix concrete supplier before any deliveries are made.
•Educate employees and subcontractors on the concrete wastemanagement techniques described in this BMP.
•Arrange for contractor’s superintendent or Certified Erosion and
Sediment Control Lead (CESCL) to oversee and enforce concrete
waste management procedures.
•A sign should be installed adjacent to each temporary concretewashout facility to inform concrete equipment operators to utilize theproper facilities.
Contracts
Incorporate requirements for concrete waste management into concrete
supplier and subcontractor agreements.
Location and Placement
•Locate washout area at least 50 feet from sensitive areas such as storm
drains, open ditches, or water bodies, including wetlands.
•Allow convenient access for concrete trucks, preferably near the area
where the concrete is being poured.
•If trucks need to leave a paved area to access washout, prevent track-
out with a pad of rock or quarry spalls (see BMP C105). These areas
should be far enough away from other construction traffic to reduce
the likelihood of accidental damage and spills.
•The number of facilities you install should depend on the expecteddemand for storage capacity.
•On large sites with extensive concrete work, washouts should be
placed in multiple locations for ease of use by concrete truck drivers.
On-site Temporary Concrete Washout Facility, Transit Truck
Washout Procedures:
•Temporary concrete washout facilities shall be located a minimum of
50 ft from sensitive areas including storm drain inlets, open drainage
facilities, and watercourses. See Figures 4.1.7 and 4.1.8.
•Concrete washout facilities shall be constructed and maintained in
sufficient quantity and size to contain all liquid and concrete wastegenerated by washout operations.
•Washout of concrete trucks shall be performed in designated areas
only.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Concrete washout from concrete pumper bins can be washed into
concrete pumper trucks and discharged into designated washout area
or properly disposed of off-site.
•Once concrete wastes are washed into the designated area and allowedto harden, the concrete should be broken up, removed, and disposed ofper applicable solid waste regulations. Dispose of hardened concrete
on a regular basis.
•Temporary Above-Grade Concrete Washout Facility
•Temporary concrete washout facility (type above grade) should beconstructed as shown on the details below, with a recommendedminimum length and minimum width of 10 ft, but with sufficient
quantity and volume to contain all liquid and concrete waste
generated by washout operations.
•Plastic lining material should be a minimum of 10 milpolyethylene sheeting and should be free of holes, tears, or otherdefects that compromise the impermeability of the material.
•Temporary Below-Grade Concrete Washout Facility
•Temporary concrete washout facilities (type below grade) should
be constructed as shown on the details below, with a recommendedminimum length and minimum width of 10 ft. The quantity and
volume should be sufficient to contain all liquid and concrete
waste generated by washout operations.
•Lath and flagging should be commercial type.
•Plastic lining material shall be a minimum of 10 mil polyethylenesheeting and should be free of holes, tears, or other defects thatcompromise the impermeability of the material.
•Liner seams shall be installed in accordance with manufacturers’
recommendations.
•Soil base shall be prepared free of rocks or other debris that maycause tears or holes in the plastic lining material.
Maintenance Standards Inspection and Maintenance
•Inspect and verify that concrete washout BMPs are in place prior to the
commencement of concrete work.
•During periods of concrete work, inspect daily to verify continued
performance.
•Check overall condition and performance.
•Check remaining capacity (% full).
•If using self-installed washout facilities, verify plastic liners areintact and sidewalls are not damaged.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•If using prefabricated containers, check for leaks.
•Washout facilities shall be maintained to provide adequate holding
capacity with a minimum freeboard of 12 inches.
•Washout facilities must be cleaned, or new facilities must beconstructed and ready for use once the washout is 75% full.
•If the washout is nearing capacity, vacuum and dispose of the waste
material in an approved manner.
•Do not discharge liquid or slurry to waterways, storm drains or
directly onto ground.
•Do not use sanitary sewer without local approval.
•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.
•Remove and dispose of hardened concrete and return the structureto a functional condition. Concrete may be reused on-site or hauledaway for disposal or recycling.
•When you remove materials from the self-installed concrete washout,
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 Temporary Concrete Washout Facilities
•When temporary concrete washout facilities are no longer required for
the work, the hardened concrete, slurries and liquids shall be removed
and properly disposed of.
•Materials used to construct temporary concrete washout facilities shall
be removed from the site of the work and disposed of or recycled.
•Holes, depressions or other ground disturbance caused by the removal
of the temporary concrete washout facilities shall be backfilled,
repaired, and stabilized to prevent erosion.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.1.7a – Concrete Washout Area
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.1.7b – Concrete Washout Area
Figure 4.1.8 – Prefabricated Concrete Washout Container w/Ramp
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C200: Interceptor Dike and Swale
Purpose Provide a ridge of compacted soil, or a ridge with an upslope swale, at the
top or base of a disturbed slope or along the perimeter of a disturbed
construction area to convey stormwater. Use the dike and/or swale to
intercept the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can prevent storm runoff from entering the
work area or sediment-laden runoff from leaving the construction site.
Conditions of Use Where the runoff from an exposed site or disturbed slope must be conveyed
to an erosion control facility which can safely convey the stormwater.
•Locate upslope of a construction site to prevent runoff from entering
disturbed area.
•When placed horizontally across a disturbed slope, it reduces the
amount and velocity of runoff flowing down the slope.
•Locate downslope to collect runoff from a disturbed area and directwater to a sediment basin.
Design and Installation
Specifications
•Dike and/or swale and channel must be stabilized with temporary or
permanent vegetation or other channel protection during construction.
•Channel requires a positive grade for drainage; steeper grades require
channel protection and check dams.
•Review construction for areas where overtopping may occur.
•Can be used at top of new fill before vegetation is established.
•May be used as a permanent diversion channel to carry the runoff.
•Sub-basin tributary area should be one acre or less.
•Design capacity for the peak volumetric flow rate calculated using a10-minute time step from a 10-year, 24-hour storm, assuming a Type
1A rainfall distribution, for temporary facilities. Alternatively, use 1.6
times the 10-year, 1-hour flow indicated by an approved continuous
runoff model. For facilities that will also serve on a permanent basis,
consult the local government’s drainage requirements.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Interceptor dikes shall meet the following criteria:
Top Width 2 feet minimum.
Height 1.5 feet minimum on berm.
Side Slope 2H:1V or flatter.
Grade Depends on topography, however, dike system minimum is 0.5%, and maximum is 1%.
Compaction Minimum of 90 percent ASTM D698 standard proctor.
Horizontal Spacing of Interceptor Dikes:
Average Slope Slope Percent Flowpath Length 20H:1V or less 3-5% 300 feet
(10 to 20)H:1V 5-10% 200 feet
(4 to 10)H:1V 10-25% 100 feet
(2 to 4)H:1V 25-50% 50 feet
Stabilization depends on velocity and reach
Slopes <5% Seed and mulch applied within 5 days of dike
construction (see BMP C121, Mulching).
Slopes 5 - 40% Dependent on runoff velocities and dike materials.
Stabilization should be done immediately using either sod
or riprap or other measures to avoid erosion.
•The upslope side of the dike shall provide positive drainage to the dike
outlet. No erosion shall occur at the outlet. Provide energy dissipation
measures as necessary. Sediment-laden runoff must be released
through a sediment trapping facility.
•Minimize construction traffic over temporary dikes. Use temporarycross culverts for channel crossing.
Interceptor swales shall meet the following criteria:
Bottom Width 2 feet minimum; the cross-section bottom shall be
level.
Depth 1-foot minimum.
Side Slope 2H:1V or flatter.
Grade Maximum 5 percent, with positive drainage to a
suitable outlet (such as a sediment pond).
Stabilization Seed as per BMP C120, Temporary and Permanent Seeding, or BMP C202, Channel Lining, 12 inches thick riprap pressed into the bank
and extending at least 8 inches vertical from the
bottom.
•Inspect diversion dikes and interceptor swales once a week and after
every rainfall. Immediately remove sediment from the flow area.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Damage caused by construction traffic or other activity must be
repaired before the end of each working day.
Check outlets and make timely repairs as needed to avoid gully formation.
When the area below the temporary diversion dike is permanently
stabilized, remove the dike and fill and stabilize the channel to blend with
the natural surface.
BMP C207: Check Dams
Purpose Construction of small dams across a swale or ditch reduces the velocity of concentrated flow and dissipates energy at the check dam.
Conditions of Use Where temporary channels or permanent channels are not yet vegetated,
channel lining is infeasible, and/or velocity checks are required.
•Check dams may not be placed in streams unless approved by the State
Department of Fish and Wildlife. Check dams may not be placed inwetlands without approval from a permitting agency.
•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 juvenilesalmonids and emergent salmonid fry.
•Construct rock check dams from appropriately sized rock. The rock
used must be large enough to stay in place given the expected design
flow through the channel. The rock must be placed by hand or by
mechanical means (no dumping of rock to form dam) to achievecomplete coverage of the ditch or swale and to ensure that the center
of the dam is lower than the edges.
•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 costefficient.
•Place check dams perpendicular to the flow of water.
•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.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Before installing check dams impound and bypass upstream waterflow away from the work area. Options for bypassing include pumps,
siphons, or temporary channels.
•Check dams in association with sumps work more effectively at
slowing flow and retaining sediment than just a check dam alone. A
deep sump should be provided immediately upstream of the checkdam.
•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 furthersediment from leaving the site.
•The maximum spacing between the dams shall be such that the toe of
the upstream dam is at the same elevation as the top of the downstream
dam.
•Keep the maximum height at 2 feet at the center of the dam.
•Keep the center of the check dam at least 12 inches lower than the
outer edges at natural ground elevation.
•Keep the side slopes of the check dam at 2H:1V or flatter.
•Key the stone into the ditch banks and extend it beyond the abutmentsa minimum of 18 inches to avoid washouts from overflow around the
dam.
•Use filter fabric foundation under a rock or sand bag check dam. If a
blanket ditch liner is used, filter fabric is not necessary. A piece of
organic or synthetic blanket cut to fit will also work for this purpose.
•In the case of grass-lined ditches and swales, all check dams and
accumulated sediment shall be removed when the grass has matured
sufficiently to protect the ditch or swale - unless the slope of the swale
is greater than 4 percent. The area beneath the check dams shall be
seeded and mulched immediately after dam removal.
•Ensure that channel appurtenances, such as culvert entrances below
check dams, are not subject to damage or blockage from displaced
stones. Figure 4.2.7 depicts a typical rock check dam.
Maintenance
Standards
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.
•Anticipate submergence and deposition above the check dam and
erosion from high flows around the edges of the dam.
•If significant erosion occurs between dams, install a protective riprap
liner in that portion of the channel.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C207. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not
to accept this product approved as equivalent, or may require additional
testing prior to consideration for local use. The products are available for
review on Ecology’s website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html
Figure 4.2.7 – Rock Check Dam
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C220: Storm Drain Inlet Protection
Purpose Storm drain inlet protection prevents coarse sediment from entering
drainage systems prior to permanent stabilization of the disturbed area.
Conditions of Use Use storm drain inlet protection at inlets that are 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 conveying runoff entering catch basins to a
sediment pond or trap.
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 4.2.2 lists several options for inlet protection. All of the methods for
storm drain inlet protection tend to plug and require a high frequency of
maintenance. Limit drainage areas to one acre or less. Possibly provide
emergency overflows with additional end-of-pipe treatment where
stormwater ponding would cause a hazard.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Table 4.2.2 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. Sediment settles out of the stormwater prior to entering the
storm drain.
•Provide a depth of 1-2 ft as measured from the crest of the inlet
structure.
•Slope sides of excavation no steeper than 2H:1V.
•Minimum volume of excavation 35 cubic yards.
•Shape basin to fit site with longest dimension oriented toward the
longest inflow area.
•Install provisions for draining to prevent standing water problems.
•Clear the area of all debris.
•Grade the approach to the inlet uniformly.
•Drill weep holes into the side of the inlet.
•Protect weep holes with screen wire and washed aggregate.
•Seal weep holes when removing structure and stabilizing area.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Build a temporary dike, if necessary, to the down slope side of thestructure to prevent bypass flow.
Block and Gravel Filter - A barrier formed around the storm drain inlet
with standard concrete blocks and gravel. See Figure 4.2.8.
•Provide a height of 1 to 2 feet above inlet.
•Recess the first row 2-inches into the ground for stability.
•Support subsequent courses by placing a 2x4 through the block
opening.
•Do not use mortar.
•Lay some blocks in the bottom row on their side for dewatering the
pool.
•Place hardware cloth or comparable wire mesh with ½-inch openings
over all block openings.
•Place gravel just below the top of blocks on slopes of 2H:1V or flatter.
•An alternative design is a gravel donut.
•Provide an inlet slope of 3H:1V.
•Provide an outlet slope of 2H:1V.
•Provide a1-foot wide level stone area between the structure and the
inlet.
•Use inlet slope stones 3 inches in diameter or larger.
•Use gravel ½- to ¾-inch at a minimum thickness of 1-foot for theoutlet slope.
Figure 4.2.8 – Block and Gravel Filter
Gravel and Wire Mesh Filter - A gravel barrier placed over the top of the
inlet. This structure does not provide an overflow.
•Use a hardware cloth or comparable wire mesh with ½-inch openings.
•Use coarse aggregate.
•Provide a height 1-foot or more, 18-inches wider than inlet on allsides.
•Place wire mesh over the drop inlet so that the wire extends a
minimum of 1-foot beyond each side of the inlet structure.
•Overlap the strips if more than one strip of mesh is necessary.
Ponding Height
Notes: 1. Drop inlet sediment barriers are to be used for small, nearly level drainage areas. (less than 5%)2. Excavate a basin of sufficient size adjacent to the drop inlet.3. The top of the structure (ponding height) must be well below the ground elevation downslope to prevent
runoff from bypassing the inlet. A temporary dike may be necessary on the downslope side of the structure.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Place coarse aggregate over the wire mesh.
•Provide at least a 12-inch depth of gravel over the entire inlet opening
and extend at least 18-inches on all sides.
Catchbasin 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
catchbasin filter with another type of inlet protection. This type of inlet
protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights-of-way.
•Provides 5 cubic feet of storage.
•Requires dewatering provisions.
•Provides a high-flow bypass that will not clog under normal use at a
construction site.
•Insert the catchbasin filter in the catchbasin just below the grating.
Curb Inlet Protection with Wooden Weir – Barrier formed around a curb
inlet with a wooden frame and gravel.
•Use wire mesh with ½-inch openings.
•Use extra strength filter cloth.
•Construct a frame.
•Attach the wire and filter fabric to the frame.
•Pile coarse washed aggregate against wire/fabric.
•Place weight on frame anchors.
Block and Gravel Curb Inlet Protection – Barrier formed around a curb inlet with concrete blocks and gravel. See Figure 4.2.9.
•Use wire mesh with ½-inch openings.
•Place two concrete blocks on their sides abutting the curb at either side
of the inlet opening. These are spacer blocks.
•Place a 2x4 stud through the outer holes of each spacer block to alignthe front blocks.
•Place blocks on their sides across the front of the inlet and abutting the
spacer blocks.
•Place wire mesh over the outside vertical face.
•Pile coarse aggregate against the wire to the top of the barrier.
Curb and Gutter Sediment Barrier – Sandbag or rock berm (riprap and
aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure
4.2.10.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Construct a horseshoe shaped berm, faced with coarse aggregate if
using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet.
•Construct a horseshoe shaped sedimentation trap on the outside of the
berm sized to sediment trap standards for protecting a culvert inlet.
Maintenance Standards
•Inspect catch basin filters frequently, especially after storm events.
Clean and replace clogged inserts. For systems with clogged stone
filters: pull away the stones from the inlet and clean or replace. An
alternative approach would be to use the clogged stone as fill and put
fresh stone around the inlet.
•Do not wash sediment into storm drains while cleaning. Spread all
excavated material evenly over the surrounding land area or stockpile
and stabilize as appropriate.
Approved as
Equivalent
Ecology has approved products as able to meet the requirements of BMP
C220. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional
testing prior to consideration for local use. The products are available for
review on Ecology’s website at
http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.2.9 – Block and Gravel Curb Inlet Protection
A
Plan View
Wire Screen orFilter Fabric Catch Basin
Curb Inlet
Concrete Block
Ponding Height
Overflow
2x4 Wood Stud(100x50 Timber Stud)
Concrete Block
Wire Screen orFilter Fabric
Curb Inlet
¾" Drain Gravel(20mm)
¾" Drain Gravel(20mm)Section A - A
Back of Curb Concrete Block
2x4 Wood Stud
Catch BasinBack of Sidewalk
NOTES:1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff.2. Barrier shall allow for overflow from severe storm event.3. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removedfrom the traveled way immediately.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.2.10 – Curb and Gutter Barrier
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C233: Silt Fence
Purpose Use of a silt fence reduces the transport of coarse sediment from a
construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. See Figure 4.2.12 for
details on silt fence construction.
Conditions of Use Silt fence may be used downslope of all disturbed areas.
•Silt fence shall prevent soil carried by runoff water from going
beneath, through, or over the top of the silt fence, but shall allow thewater to pass through the fence.
•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.
•Do not construct silt fences in streams or use in V-shaped ditches. Siltfences do not provide an adequate method of silt control for anything
deeper than sheet or overland flow.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.2.12 – Silt Fence
Design and
Installation
Specifications
•Use in combination with sediment basins or other BMPs.
•Maximum slope steepness (normal (perpendicular) to fence line)
1H:1V.
•Maximum sheet or overland flow path length to the fence of 100 feet.
•Do not allow flows greater than 0.5 cfs.
•The geotextile used shall meet the following standards. All geotextile
properties listed below are minimum average roll values (i.e., the test
result for any sampled roll in a lot shall meet or exceed the values
shown in Table 4.2.3):
Table 4.2.3
Geotextile Standards
Polymeric Mesh AOS
(ASTM D4751)
0.60 mm maximum for slit film woven (#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
•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 thefabric. Silt fence materials are available that have synthetic mesh
backing attached.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Filter fabric material shall contain ultraviolet ray inhibitors and
stabilizers to provide a minimum of six months of expected usable
construction life at a temperature range of 0°F. to 120°F.
•One-hundred percent biodegradable silt fence is available that isstrong, long lasting, and can be left in place after the project iscompleted, if permitted by local regulations.
•Refer to Figure 4.2.12 for standard silt fence details. Include the
following standard Notes for silt fence on construction plans and
specifications:
1.The contractor shall install and maintain temporary silt fences at
the locations shown in the Plans.
2. Construct silt fences in areas of clearing, grading, or drainage prior
to starting those activities.
3.The silt fence shall have a 2-feet min. and a 2½-feet max. heightabove the original ground surface.
4.The filter fabric shall be sewn together at the point of manufacture
to form filter fabric lengths as required. Locate all sewn seams at
support posts. Alternatively, two sections of silt fence can be
overlapped, provided the Contractor can demonstrate, to thesatisfaction 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.
5.Attach the filter fabric on the up-slope side of the posts and securewith staples, wire, or in accordance with the manufacturer's
recommendations. Attach the filter fabric to the posts in a manner
that reduces the potential for tearing.
6.Support the filter fabric with wire or plastic mesh, dependent on
the properties of the geotextile selected for use. If wire or plasticmesh is used, fasten the mesh securely to the up-slope side of the
posts with the filter fabric up-slope of the mesh.
7. 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 orgreater 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.
8.Bury the bottom of the filter fabric 4-inches min. below the ground
surface. Backfill and tamp soil in place over the buried portion ofthe filter fabric, so that no flow can pass beneath the fence and
scouring cannot occur. When wire or polymeric back-up support
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
mesh is used, the wire or polymeric mesh shall extend into the
ground 3-inches min.
9.Drive or place the fence posts into the ground 18-inches min. A
12–inch min. depth is allowed if topsoil or other soft subgrade soilis not present and 18-inches cannot be reached. Increase fence post
min. depths 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 fencedue to sediment loading.
10. Use wood, steel or equivalent posts. The spacing of the support
posts shall be a maximum of 6-feet. Posts shall consist of either:
•Wood with dimensions of 2-inches by 2-inches wide min. anda 3-feet min. length. Wood posts shall be free of defects suchas knots, splits, or gouges.
•No. 6 steel rebar or larger.
•ASTM A 120 steel pipe with a minimum diameter of 1-inch.
•U, T, L, or C shape steel posts with a minimum weight of 1.35
lbs./ft.
•Other steel posts having equivalent strength and bending
resistance to the post sizes listed above.
11.Locate silt fences 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 ofthe fence, place gravel check dams perpendicular to the back of the
fence to minimize concentrated flow and erosion. The slope of the
fence line where contours must be crossed shall not be steeper than
3H:1V.
•Gravel check dams shall be approximately 1-foot deep at theback of the fence. Gravel check dams 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.
•Gravel check dams shall consist of crushed surfacing basecourse, gravel backfill for walls, or shoulder ballast. Gravel
check dams shall be located every 10 feet along the fence
where the fence must cross contours.
•Refer to Figure 4.2.13 for slicing method details. Silt fence installationusing the slicing method specifications:
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
1. The base of both end posts must be at least 2- to 4-inches above the
top of the filter 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 filter fabric, enabling posts to
support the filter fabric from upstream water pressure.
4.Install posts with the nipples facing away from the filter fabric.
5.Attach the filter fabric to each post with three ties, all spaced
within the top 8-inches of the filter fabric. Attach each tie
diagonally 45 degrees through the filter fabric, with each puncture
at least 1-inch vertically apart. Each tie should be positioned tohang on a post nipple when tightening to prevent sagging.
6.Wrap approximately 6-inches of fabric around the end posts and
secure with 3 ties.
7. No more than 24-inches of a 36-inch filter fabric is allowed above
ground level.
Compact the soil immediately next to the filter 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. Check and correct the silt fence
installation for any deviation before compaction. Use a flat-bladedshovel to tuck fabric deeper into the ground if necessary.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.2.13 – Silt Fence Installation by Slicing Method
Maintenance Standards
•Repair any damage immediately.
•Intercept and convey all evident concentrated flows uphill of the silt
fence to a sediment pond.
•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 flowsparallel to the fence. If this occurs, replace the fence or remove thetrapped sediment.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
•Remove sediment deposits when the deposit reaches approximately
one-third the height of the silt fence, or install a second silt fence.
•Replace filter fabric that has deteriorated due to ultraviolet breakdown.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C241: Temporary Sediment Pond
Purpose Sediment ponds remove sediment from runoff originating from disturbed
areas of the site. Sediment ponds are typically designed to remove
sediment no smaller than medium silt (0.02 mm). Consequently, they usually reduce turbidity only slightly.
Conditions of Use Prior to leaving a construction site, stormwater runoff must pass through a
sediment pond or other appropriate sediment removal best management
practice.
A sediment pond shall be used where the contributing drainage area is 3 acres or more. Ponds must be used in conjunction with erosion control
practices to reduce the amount of sediment flowing into the basin.
Design and
Installation
Specifications
•Sediment basins must be installed only on sites where failure of the
structure would not result in loss of life, damage to homes or
buildings, or interruption of use or service of public roads or utilities.Also, sediment traps and ponds are attractive to children and can be
very dangerous. Compliance with local ordinances regarding health
and safety must be addressed. If fencing of the pond is required, the
type of fence and its location shall be shown on the ESC plan.
•Structures having a maximum storage capacity at the top of the dam of10 acre-ft (435,600 ft3) or more are subject to the Washington Dam
Safety Regulations (Chapter 173-175 WAC).
•See Figures 4.2.18, 4.2.19, and 4.2.20 for details.
•If permanent runoff control facilities are part of the project, they
should be used for sediment retention. The surface area requirementsof the sediment basin must be met. This may require temporarily
enlarging the permanent basin to comply with the surface area
requirements. The permanent control structure must be temporarily
replaced with a control structure that only allows water to leave the
pond from the surface or by pumping. The permanent control structuremust be installed after the site is fully stabilized. .
•Use of infiltration facilities for sedimentation basins during
construction tends to clog the soils and reduce their capacity to
infiltrate. If infiltration facilities are to be used, the sides and bottom of
the facility must only be rough excavated to a minimum of 2 feetabove final grade. Final grading of the infiltration facility shall occuronly when all contributing drainage areas are fully stabilized. The
infiltration pretreatment facility should be fully constructed and used
with the sedimentation basin to help prevent clogging.
•Determining Pond Geometry
Obtain the discharge from the hydrologic calculations of the peak flow
for the 2-year runoff event (Q2). The 10-year peak flow shall be used if
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
the project size, expected timing and duration of construction, or
downstream conditions warrant a higher level of protection. If no
hydrologic analysis is required, the Rational Method may be used.
Determine the required surface area at the top of the riser pipe with the equation:
SA = 2 x Q2/0.00096 or
2080 square feet per cfs of inflow
See BMP C240 for more information on the derivation of the surface
area calculation.
The basic geometry of the pond can now be determined using the following design criteria:
•Required surface area SA (from Step 2 above) at top of riser.
•Minimum 3.5-foot depth from top of riser to bottom of pond.
•Maximum 3H:1V interior side slopes and maximum 2H:1V exteriorslopes. The interior slopes can be increased to a maximum of 2H:1V iffencing is provided at or above the maximum water surface.
•One foot of freeboard between the top of the riser and the crest of the
emergency spillway.
•Flat bottom.
•Minimum 1-foot deep spillway.
•Length-to-width ratio between 3:1 and 6:1.
•Sizing of Discharge Mechanisms.
The outlet for the basin consists of a combination of principal and
emergency spillways. These outlets must pass the peak runoffexpected from the contributing drainage area for a 100-year storm. If,
due to site conditions and basin geometry, a separate emergency spill-
way is not feasible, the principal spillway must pass the entire peak
runoff expected from the 100-year storm. However, an attempt to
provide a separate emergency spillway should always be made. Therunoff calculations should be based on the site conditions during
construction. The flow through the dewatering orifice cannot be
utilized when calculating the 100-year storm elevation because of its
potential to become clogged; therefore, available spillway storage
must begin at the principal spillway riser crest.
The principal spillway designed by the procedures contained in this
standard will result in some reduction in the peak rate of runoff.
However, the riser outlet design will not adequately control the basin
discharge to the predevelopment discharge limitations as stated in
Minimum Requirement #7: Flow Control. However, if the basin for apermanent stormwater detention pond is used for a temporary
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
sedimentation basin, the control structure for the permanent pond can
be used to maintain predevelopment discharge limitations. The size of
the basin, the expected life of the construction project, the anticipated
downstream effects and the anticipated weather conditions during construction, should be considered to determine the need of additional
discharge control. See Figure 4.2.21 for riser inflow curves.
Figure 4.2.18 – Sediment Pond Plan View
Figure 4.2.19 – Sediment Pond Cross Section
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Perforated polyethylenedrainage tubing, diametermin. 2" larger thandewatering orifice.Tubing shall comply with ASTM F667 and AASHTO M294
Polyethylene cap Provide adequatestrapping
Dewatering orifice, schedule,40 steel stub min.Diameter as per calculations
Alternatively, metal stakesand wire may be used toprevent flotation
2X riser dia. Min.
Concrete base
Corrugatedmetal riser
Watertightcoupling
18" min.
6" min.
Tack weld
3.5" min.
Figure 4.2.20 – Sediment Pond Riser Detail
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Figure 4.2.21 – Riser Inflow Curves
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Principal Spillway: Determine the required diameter for the principal
spillway (riser pipe). The diameter shall be the minimum necessary to pass
the site’s 15-minute, 10-year flowrate. If using the Western Washington
Hydrology Model (WWHM), Version 2 or 3, design flow is the 10-year (1 hour) flow for the developed (unmitigated) site, multiplied by a factor of
1.6. Use Figure 4.2.21 to determine this diameter (h = 1-foot). Note: A
permanent control structure may be used instead of a temporary riser.
Emergency Overflow Spillway: Determine the required size and design
of the emergency overflow spillway for the developed 100-year peak flow using the method contained in Volume III.
Dewatering Orifice: Determine the size of the dewatering orifice(s)
(minimum 1-inch diameter) using a modified version of the discharge
equation for a vertical orifice and a basic equation for the area of a circular
orifice. Determine the required area of the orifice with the following equation:
5.0
5.0
3600x6.0
)2(
Tg
hAAso=
where Ao = orifice area (square feet)
As = pond surface area (square feet)
h = head of water above orifice (height of riser in feet) T = dewatering time (24 hours) g = acceleration of gravity (32.2 feet/second2)
Convert the required surface area to the required diameter D of the orifice:
ooAADx54.13x24==π
The vertical, perforated tubing connected to the dewatering orifice must be
at least 2 inches larger in diameter than the orifice to improve flow
characteristics. The size and number of perforations in the tubing should be large enough so that the tubing does not restrict flow. The orifice
should control the flow rate.
•Additional Design Specifications
The pond shall be divided into two roughly equal volume cells by a
permeable divider that will reduce turbulence while allowingmovement of water between cells. The divider shall be at least one-half the height of the riser and a minimum of one foot below the top of
the riser. Wire-backed, 2- to 3-foot high, extra strength filter fabric
supported by treated 4"x4"s can be used as a divider. Alternatively,
staked straw bales wrapped with filter fabric (geotextile) may be used.If the pond is more than 6 feet deep, a different mechanism must beproposed. A riprap embankment is one acceptable method of
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
separation for deeper ponds. Other designs that satisfy the intent of this
provision are allowed as long as the divider is permeable, structurally
sound, and designed to prevent erosion under or around the barrier.
To aid in determining sediment depth, one-foot intervals shall be prominently marked on the riser.
If an embankment of more than 6 feet is proposed, the pond must
comply with the criteria contained in Volume III regarding dam safety
for detention BMPs.
•The most common structural failure of sedimentation basins is causedby piping. Piping refers to two phenomena: (1) water seeping throughfine-grained soil, eroding the soil grain by grain and forming pipes or
tunnels; and, (2) water under pressure flowing upward through a
granular soil with a head of sufficient magnitude to cause soil grains to
lose contact and capability for support.
The most critical construction sequences to prevent piping will be:
1.Tight connections between riser and barrel and other pipe
connections.
2.Adequate anchoring of riser.
3. Proper soil compaction of the embankment and riser footing.
4.Proper construction of anti-seep devices.
Maintenance Standards
•Sediment shall be removed from the pond when it reaches 1–foot in
depth.
•Any damage to the pond embankments or slopes shall be repaired.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C252: High pH Neutralization Using CO2
Purpose When pH levels in stormwater rise above 8.5 it is necessary to lower the
pH levels to the acceptable range of 6.5 to 8.5, this process is called pH
neutralization. pH neutralization involves the use of solid or compressed carbon dioxide gas in water requiring neutralization. Neutralized
stormwater may be discharged to surface waters under the General
Construction NPDES permit.
Neutralized process water such as concrete truck wash-out, hydro-
demolition, or saw-cutting slurry must be managed to prevent discharge to surface waters. Any stormwater contaminated during concrete work is
considered process wastewater and must not be discharged to surface
waters.
Reason for pH Neutralization:
A pH level range of 6.5 to 8.5 is typical for most natural watercourses, and this neutral pH is required for the survival of aquatic organisms. Should
the pH rise or drop out of this range, fish and other aquatic organisms may
become stressed and may die.
Calcium hardness can contribute to high pH values and cause toxicity that
is associated with high pH conditions. A high level of calcium hardness in waters of the state is not allowed.
The water quality standard for pH in Washington State is in the range of
6.5 to 8.5. Ground water standard for calcium and other dissolved solids in
Washington State is less than 500 mg/l.
Conditions of Use Causes of High pH:
High pH at construction sites is most commonly caused by the contact of
stormwater with poured or recycled concrete, cement, mortars, and other
Portland cement or lime containing construction materials. (See BMP
C151: Concrete Handling for more information on concrete handling
procedures). The principal caustic agent in cement is calcium hydroxide (free lime).
Advantages of CO2 Sparging:
•Rapidly neutralizes high pH water.
•Cost effective and safer to handle than acid compounds.
•CO2 is self-buffering. It is difficult to overdose and create harmfullylow pH levels.
•Material is readily available.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
The Chemical Process:
When carbon dioxide (CO2) is added to water (H2O), carbonic acid
(H2CO3) is formed which can further dissociate into a proton (H+) and a
bicarbonate anion (HCO3-) as shown below:
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
The free proton is a weak acid that can lower the pH. Water temperature has an effect on the reaction as well. The colder the water temperature is
the slower the reaction occurs and the warmer the water temperature is the
quicker the reaction occurs. Most construction applications in Washington
State have water temperatures in the 50°F or higher range so the reaction is almost simultaneous.
Design and Installation
Specifications
Treatment Process:
High pH water may be treated using continuous treatment, continuous
discharge systems. These manufactured systems continuously monitor
influent and effluent pH to ensure that pH values are within an acceptable range before being discharged. All systems must have fail safe automatic shut off switches in the event that pH is not within the acceptable
discharge range. Only trained operators may operate manufactured
systems. System manufacturers often provide trained operators or training
on their devices.
The following procedure may be used when not using a continuous discharge system:
1. Prior to treatment, the appropriate jurisdiction should be notified in
accordance with the regulations set by the jurisdiction.
2. Every effort should be made to isolate the potential high pH water inorder to treat it separately from other stormwater on-site.
3. Water should be stored in an acceptable storage facility, detention
pond, or containment cell prior to treatment.
4.Transfer water to be treated to the treatment structure. Ensure that
treatment structure size is sufficient to hold the amount of water that isto be treated. Do not fill tank completely, allow at least 2 feet offreeboard.
5. The operator samples the water for pH and notes the clarity of the
water. As a rule of thumb, less CO2 is necessary for clearer water. This
information should be recorded.
6. In the pH adjustment structure, add CO2 until the pH falls in the rangeof 6.9-7.1. Remember that pH water quality standards apply so
adjusting pH to within 0.2 pH units of receiving water (background
pH) is recommended. It is unlikely that pH can be adjusted to within
0.2 pH units using dry ice. Compressed carbon dioxide gas should beintroduced to the water using a carbon dioxide diffuser located near
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
the bottom of the tank, this will allow carbon dioxide to bubble up
through the water and diffuse more evenly.
7.Slowly discharge the water making sure water does not get stirred up
in the process. Release about 80% of the water from the structureleaving any sludge behind.
8. Discharge treated water through a pond or drainage system.
9. Excess sludge needs to be disposed of properly as concrete waste. If
several batches of water are undergoing pH treatment, sludge can be
left in treatment structure for the next batch treatment. Dispose ofsludge when it fills 50% of tank volume.
Sites that must implement flow control for the developed site must also
control stormwater release rates during construction. All treated
stormwater must go through a flow control facility before being released
to surface waters which require flow control.
Maintenance Standards Safety and Materials Handling:
•All equipment should be handled in accordance with OSHA rules and
regulations.
•Follow manufacturer guidelines for materials handling.
Operator Records:
Each operator should provide:
•A diagram of the monitoring and treatment equipment.
•A description of the pumping rates and capacity the treatment
equipment is capable of treating.
Each operator should keep a written record of the following:
•Client name and phone number.
•Date of treatment.
•Weather conditions.
•Project name and location.
•Volume of water treated.
•pH of untreated water.
•Amount of CO2 needed to adjust water to a pH range of 6.9-7.1.
•pH of treated water.
•Discharge point location and description.
A copy of this record should be given to the client/contractor who should
retain the record for three years.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
BMP C253: pH Control for High pH Water
Purpose When pH levels in stormwater rise above 8.5 it is necessary to lower the
pH levels to the acceptable range of 6.5 to 8.5, this process is called pH
neutralization. Stormwater with pH levels exceeding water quality standards may be treated by infiltration, dispersion in vegetation or
compost, pumping to a sanitary sewer, disposal at a permitted concrete
batch plant with pH neutralization capabilities, or carbon dioxide sparging.
BMP C252 gives guidelines for carbon dioxide sparging.
Reason for pH Neutralization:
A pH level range of 6.5 to 8.5 is typical for most natural watercourses, and this pH range is required for the survival of aquatic organisms. Should the
pH rise or drop out of this range, fish and other aquatic organisms may
become stressed and may die.
Conditions of Use Causes of High pH:
High pH levels at construction sites are most commonly caused by the
contact of stormwater with poured or recycled concrete, cement, mortars,
and other Portland cement or lime containing construction materials. (See
BMP C151: Concrete Handling for more information on concrete handling
procedures). The principal caustic agent in cement is calcium hydroxide (free lime).
Design and Installation
Specifications
Disposal Methods:
Infiltration
•Infiltration is only allowed if soil type allows all water to infiltrate (no
surface runoff) without causing or contributing to a violation ofsurface or ground water quality standards.
•Infiltration techniques should be consistent with Volume V, Chapter 7
Dispersion
Use BMP T5.30 Full Dispersion
Sanitary Sewer Disposal
•Local sewer authority approval is required prior to disposal via the
sanitary sewer.
Concrete Batch Plant Disposal
•Only permitted facilities may accept high pH water.
•Facility should be contacted before treatment to ensure they can acceptthe high pH water.
Stormwater Discharge
Any pH treatment options that generate treated water that must be
discharged off site are subject to flow control requirements. Sites that
must implement flow control for the developed site must also control
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
stormwater release rates during construction. All treated stormwater must
go through a flow control facility before being released to surface waters
which require flow control.
FROM: Volume II - Construction Stormwater Pollution Prevention - December 2014
Cyprus Lane 25
C. Correspondence
Cyprus Lane 26
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:
Cyprus Lane 28
E. Construction Stormwater General Permit (CSWGP)
Issuance Date:
Effective Date:
Expiration Date:
November 18, 2015
January I, 2016
December 31, 2020
Modification Issuance Date: March 22, 2017
Modification Effective Date: May 5, 2017
CONSTRUCTION STORMW ATER
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.
her R. Bartlett
Wa r Quality Program Manager
Washington State Department of Ecology
Construction Stormwater General Permit
Page 2
TABLE OF CONTENTS
LIST OF TABLES ...........................................................................................................................3
SUMMARY OF PERMIT REPORT SUBMITTALS .....................................................................4
SPECIAL CONDITIONS ................................................................................................................5
S1. PERMIT COVERAGE ........................................................................................................5
S2. APPLICATION REQUIREMENTS ...................................................................................8
S3. COMPLIANCE WITH STANDARDS .............................................................................12
S4. MONITORING REQUIREMENTS, BENCHMARKS, AND
REPORTING TRIGGERS ................................................................................................13
S5. REPORTING AND RECORDKEEPING REQUIREMENTS .........................................20
S6. PERMIT FEES...................................................................................................................23
S7. SOLID AND LIQUID WASTE DISPOSAL ....................................................................23
S8. DISCHARGES TO 303(d) OR TMDL WATERBODIES ................................................23
S9. STORMWATER POLLUTION PREVENTION PLAN...................................................27
S10. NOTICE OF TERMINATION .........................................................................................37
GENERAL CONDITIONS ...........................................................................................................38
G1. DISCHARGE VIOLATIONS ...........................................................................................38
G2. SIGNATORY REQUIREMENTS.....................................................................................38
G3. RIGHT OF INSPECTION AND ENTRY .........................................................................39
G4. GENERAL PERMIT MODIFICATION AND REVOCATION ......................................39
G5. REVOCATION OF COVERAGE UNDER THE PERMIT .............................................39
G6. REPORTING A CAUSE FOR MODIFICATION ............................................................40
G7. COMPLIANCE WITH OTHER LAWS AND STATUTES .............................................40
G8. DUTY TO REAPPLY .......................................................................................................40
G9. TRANSFER OF GENERAL PERMIT COVERAGE .......................................................41
G10. REMOVED SUBSTANCES .............................................................................................41
G11. DUTY TO PROVIDE INFORMATION ...........................................................................41
G12. OTHER REQUIREMENTS OF 40 CFR ...........................................................................41
G13. ADDITIONAL MONITORING ........................................................................................41
G14. PENALTIES FOR VIOLATING PERMIT CONDITIONS .............................................41
G15. UPSET ...............................................................................................................................42
G16. PROPERTY RIGHTS ........................................................................................................42
Construction Stormwater General Permit
Page 3
G17. DUTY TO COMPLY ........................................................................................................42
G18. TOXIC POLLUTANTS.....................................................................................................42
G19. PENALTIES FOR TAMPERING .....................................................................................43
G20. REPORTING PLANNED CHANGES .............................................................................43
G21. REPORTING OTHER INFORMATION ..........................................................................43
G22. REPORTING ANTICIPATED NON-COMPLIANCE .....................................................43
G23. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT ..........44
G24. APPEALS ..........................................................................................................................44
G25. SEVERABILITY ...............................................................................................................44
G26. BYPASS PROHIBITED ....................................................................................................44
APPENDIX A – DEFINITIONS ...................................................................................................47
APPENDIX B – ACRONYMS .....................................................................................................55
LIST OF TABLES
Table 1: Summary of Required Submittals ................................................................................... 4
Table 2: Summary of Required On-site Documentation............................................................... 4
Table 3: Summary of Primary Monitoring Requirements .......................................................... 15
Table 4: Monitoring and Reporting Requirements ..................................................................... 17
Table 5: Turbidity, Fine Sediment & Phosphorus Sampling and Limits for
303(d)-Listed Waters .................................................................................................... 25
Table 6: pH Sampling and Limits for 303(d)-Listed Waters ...................................................... 26
Construction Stormwater General Permit
Page 4
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.C Request for Chemical Treatment Form As necessary Written approval from Ecology is required prior to using chemical treatment
(with the exception of dry ice or CO2 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
G9 Notice of Permit Transfer As necessary
G20 Notice of Planned Changes As necessary
G22 Reporting Anticipated Non-compliance As necessary
SPECIAL 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.
Table 2: Summary of Required On-site Documentation
Document Title Permit Conditions
Permit Coverage Letter See Conditions S2, S5
Construction Stormwater General Permit See Conditions S2, S5
Site Log Book See Conditions S4, S5
Stormwater Pollution Prevention Plan (SWPPP) See Conditions S9, S5
Construction Stormwater General Permit
Page 5
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.
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 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 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
ground water, 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
S2.C).
c. Routine maintenance that is performed to maintain the original line and grade,
hydraulic capacity, or original purpose of a facility.
Construction Stormwater General Permit
Page 6
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 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 ground water 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.
Construction Stormwater General Permit
Page 7
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 ground water, are prohibited.
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.
Construction Stormwater General Permit
Page 8
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.
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.
S2. APPLICATION REQUIREMENTS
A. Permit Application Forms
1. Notice of Intent Form/Timeline
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://www.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
Construction Stormwater General Permit
Page 9
c. The operator must submit the NOI at least 60 days before discharging
stormwater from construction activities and must submit it on or before 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, based
on public comments, or any other relevant factors, coverage under the general
permit will automatically commence on the thirty-first day following receipt by
Ecology of a completed NOI, or the issuance date of this permit, whichever is
later; unless Ecology specifies a later date in writing as required by WAC173-
226-200(2).
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, it must provide notice
of the selection of an equivalent BMP to Ecology at least 60 days before
intended use of the equivalent BMP.
e. Permittees must notify Ecology regarding any changes to the information
provided on the NOI by submitting an updated NOI. 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.
f. 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. Temporary Erosion and Sediment Control (TESC) plans,
iv. Related portions of the Stormwater Pollution Prevention Plan (SWPPP)
that address the management of contaminated and potentially
contaminated construction stormwater and dewatering water,
v. Dewatering plan and/or dewatering contingency plan.
Construction Stormwater General Permit
Page 10
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 the Permittee submits a Transfer of Coverage Form in accordance with
General Condition G9. Transfers do not require public notice.
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 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 number of acres to
be disturbed.
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.
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.”
Construction Stormwater General Permit
Page 11
C. 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 5 acres and the site is not a
portion of a common plan of development or sale that will disturb 5 acres or
greater.
2. Calculation of Erosivity “R” Factor and Regional Timeframe:
a. The project’s rainfall erosivity factor (“R” Factor) must be less than 5 during the
period of construction activity, as calculated (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 additional
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/resourcesguidance.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 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.
Construction Stormwater General Permit
Page 12
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
S2.C.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.
S3. COMPLIANCE WITH STANDARDS
A. Discharges must not cause or contribute to a violation of surface water quality standards
(Chapter 173-201A WAC), ground water quality standards (Chapter 173-200 WAC),
sediment management standards (Chapter 173-204 WAC), and human health-based
criteria in the National Toxics Rule (40 CFR Part 131.36). Discharges not in compliance
with these standards are not authorized.
B. Prior to the discharge of stormwater and non-stormwater to waters of the State, the
Permittee 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:
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 technical manuals published or approved by
Ecology, including the proper selection, implementation, and maintenance of all
applicable and appropriate BMPs for on-site pollution control. (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 ground water, the ground water discharges
must also meet the terms and conditions of this CSWGP. Permittees who discharge to
ground water through an injection well must also comply with any applicable
requirements of the Underground Injection Control (UIC) regulations, Chapter 173-218
WAC.
Construction Stormwater General Permit
Page 13
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
The Permittee’s site inspections must include all areas disturbed by construction
activities, all BMPs, and all stormwater discharge points under the Permittee’s
operational control. (See Special Conditions S4.B.3 and B.4 below for detailed
requirements of the Permittee’s Certified Erosion and Sediment Control Lead [CESCL].)
Construction sites one acre or larger that discharge stormwater to surface waters of the
State must have site inspections conducted by a certified CESCL. Sites less than one
acre may have a person without CESCL certification conduct inspections.
1. The Permittee must examine stormwater visually for the presence of suspended
sediment, turbidity, discoloration, and oil sheen. The Permittee must evaluate the
effectiveness of BMPs and 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 as soon as possible,
addressing the problems no later than 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.
2. The Permittee 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 day do not require daily inspections. For
example, if a stormwater pond discharges continuously over the course of a week,
only one inspection is required that week.) The Permittee may reduce the
inspection frequency for temporarily stabilized, inactive sites to once every
calendar month.
Construction Stormwater General Permit
Page 14
3. 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.
4. The SWPPP must identify the CESCL or inspector, who must be present on site or
on-call at all times. The CESCL 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).
5. 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, the general conditions during inspection and the
approximate amount of precipitation since the last inspection, and precipitation
within the last 24 hours.
c. A summary or list of all implemented BMPs, including observations of all
erosion/sediment control structures or practices.
d. A description of the locations:
i. Of BMPs inspected;
ii. Of BMPs that need maintenance and why;
iii. Of BMPs that failed to operate as designed or intended; and
iv. Where additional or different BMPs are needed, and why.
e. A description of stormwater discharged from the site. The Permittee must note
the presence of suspended sediment, turbidity, discoloration, and oil sheen, as
applicable.
f. Any water quality monitoring performed during inspection.
g. General comments and notes, including a brief description of any BMP repairs,
maintenance or installations made following the inspection.
h. A summary report and a schedule of implementation of 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.
Construction Stormwater General Permit
Page 15
i. 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
Disturbance1
Weekly Site Inspections Weekly Sampling w/ Turbidity Meter
Weekly Sampling w/ Transparency Tube
Weekly pH
Sampling2
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 method3 Required Yes
Sites that disturb 5 acres or more Required Required Not Required4 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 poured concrete or recycled concrete 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 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.
Construction Stormwater General Permit
Page 16
C. Turbidity/Transparency Sampling Requirements
1. Sampling Methods
a. If construction activity involves the disturbance of 5 acres or more, the
Permittee must conduct turbidity sampling per Special Condition S4.C.
b. If construction activity involves 1 acre or more but fewer than 5 acres of soil
disturbance, the Permittee must conduct either transparency sampling or
turbidity sampling per Special Condition S4.C.
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) on the SWPPP 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.
Construction Stormwater General Permit
Page 17
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.
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 Phone Reporting Trigger Value
Turbidity NTU SM2130 Weekly, if
discharging
25 NTUs 250 NTUs
Transparency cm Manufacturer instructions, or Ecology guidance
Weekly, if discharging 33 cm 6 cm
5. Turbidity/Transparency Benchmark Values and Reporting Triggers
The benchmark value for turbidity is 25 NTUs or less. 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.
a. Turbidity 26 – 249 NTUs, or Transparency 32 – 7 cm:
If the discharge turbidity is 26 to 249 NTUs; or if discharge transparency is
less than 33 cm, but equal to or greater than 6 cm, the Permittee must:
i. Review the SWPPP for compliance with Special Condition S9 and make
appropriate revisions within 7 days of the date the discharge exceeded the
benchmark.
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.
Construction Stormwater General Permit
Page 18
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 management process described below.
i. 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) within 24 hours, 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
Links to these numbers and the ERTS reporting page are located on the
following web site:
http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html.
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. 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.
iv. Document BMP implementation and maintenance in the site log book.
v. Sample discharges daily until:
a) Turbidity is 25 NTUs (or lower); or
b) Transparency is 33 cm (or greater); or
Construction Stormwater General Permit
Page 19
c) The Permittee has demonstrated compliance with the water quality
limit 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
d) The discharge stops or is eliminated.
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 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. For sites with significant concrete work, the Permittee must begin the pH sampling
period when the concrete is first poured and exposed to precipitation, and continue
weekly throughout and after the concrete pour and curing period, until stormwater
pH is in the range of 6.5 to 8.5 (su).
2. 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).
3. 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.
4. During the applicable pH monitoring period defined above, the Permittee must
obtain a representative sample of stormwater and conduct pH analysis at least once
per week.
5. 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.
6. The benchmark value for pH is 8.5 standard units. Anytime sampling indicates that
pH is 8.5 or greater, the Permittee must either:
Construction Stormwater General Permit
Page 20
a. Prevent the high pH water (8.5 or above) from entering storm sewer systems or
surface waters; 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 or dry ice. The Permittee must obtain written approval from
Ecology before using any form of chemical treatment other than CO2 sparging
or dry ice.
7. 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.
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 either call the applicable Ecology
Region’s Environmental Report Tracking System (ERTS) number by phone within 24
hours of analysis or submit an electronic ERTS report (or submit an electronic report
through Ecology’s Water Quality Permitting Portal (WQWebPortal) – Permit Submittals
when the form is available). See the CSWGP web site 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 G13 (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. To find out more
information and to sign up for WQWebDMR go to: http://www.ecy.wa.gov/programs/
wq/permits/paris/portal.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 copy DMR at:
Department of Ecology
Water Quality Program - Construction Stormwater
PO Box 47696
Olympia, Washington 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 shall
Construction Stormwater General Permit
Page 21
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 issuance date to termination).
For more information, contact Ecology staff using information provided at the following
web site: 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 three 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 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 monitors any pollutant more frequently than required by this permit
using test procedures specified by Special Condition S4 of this permit, the results of 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 of fuels or other materials, catastrophic
pond or slope failure, and discharges that violate water quality standards), or exceed
Construction Stormwater General Permit
Page 22
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
www.ecy.wa.gov/programs/wq/stormwater/construction/turbidity.html
for Regional ERTS phone numbers).
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.
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.
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
2. The Permittee must address written requests for plans and records listed above
(Special Condition S5.G.1) as follows:
Construction Stormwater General Permit
Page 23
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
iii. Within 14 days of receipt of the written request, the Permittee may
submit a copy of the plans and records to Ecology for viewing and/or
copying by the 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.
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
Waterbodies
Construction Stormwater General Permit
Page 24
1. Permittees who discharge to segments of waterbodies 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, 2016, 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
Operators of construction sites that discharge to a TMDL or 303(d)-listed waterbody are
not eligible for coverage under this permit unless the operator:
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 if
Ecology issues permit coverage based upon an affirmative determination that the
discharge will not cause or contribute to the existing impairment.
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.
Construction Stormwater General Permit
Page 25
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 shall sample
discharges daily until the violation is corrected and comply with the non-
compliance notification requirements in Special Condition S5.F.
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)
1Permittees 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).
Construction Stormwater General Permit
Page 26
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
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 shall 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
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 or as 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.
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,
Construction Stormwater General Permit
Page 27
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.
2. Applicable TMDL means a TMDL for turbidity, fine sediment, high pH, or
phosphorus that is completed and approved by EPA before January 1, 2016, or
before the date the operator’s complete permit application is received by Ecology,
whichever is later. TMDLs completed after the operator’s complete permit
application is received by Ecology become applicable to the Permittee only if they
are imposed through an administrative order by Ecology, or through a modification
of permit coverage.
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 implement best management practices (BMPs) to prevent erosion and
sedimentation, and to identify, reduce, eliminate or prevent stormwater
contamination and water pollution from construction activity.
2. To prevent violations of surface water quality, ground water quality, or sediment
management standards.
3. To control peak volumetric flow rates and velocities of stormwater discharges.
B. General Requirements
1. The SWPPP 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.
Construction Stormwater General Permit
Page 28
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
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
Construction Stormwater General Permit
Page 29
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. Control street wash wastewater by pumping back on site or
otherwise preventing it from discharging into systems tributary to waters of the
State.
3. Control Flow Rates
a. Protect properties and waterways downstream of development sites from
erosion and the associated discharge of turbid waters due to increases in the
Construction Stormwater General Permit
Page 30
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 retention or detention facilities as one of the first steps in grading.
Assure that detention facilities 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 siltation 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 design, install and maintain such controls to:
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 control fabrics and matting, soil application of polyacrylamide
Construction Stormwater General Permit
Page 31
(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).
Construction Stormwater General Permit
Page 32
b. The Permittee must divert off-site stormwater (run-on) or ground water 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.
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
Construction Stormwater General Permit
Page 33
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.
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. 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 contained in 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
Construction Stormwater General Permit
Page 34
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 or concrete
handling equipment onto the ground, or into storm drains, open ditches, streets,
or streams. Washout of concrete handling equipment may be disposed of in a
designated concrete washout area or in a formed area awating concrete where it
will not contaminate surface or ground water. 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 prohibited.
Do not wash out to formed areas awaiting LID facilities.
i. Obtain written approval from Ecology before using any chemical treatment,
with the exception of CO2 or dry ice used 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, into a
controlled conveyance system before discharge to a sediment trap or sediment
pond.
b. Permittees may discharge clean, non-turbid dewatering water, such as well-
point ground water, 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.
Construction Stormwater General Permit
Page 35
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.
12. Manage the Project
a. Phase development projects to the maximum degree practicable and take into
account seasonal work limitations.
b. Inspection and monitoring – 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. Maintaining an updated construction SWPPP – 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 LID BMPs/On-site LID Stormwater Management BMPs is
to reduce the disruption of the natural site hydrology. LID BMPs are permanent
facilities.
a. Permittees must protect all 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 facilities 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.
Construction Stormwater General Permit
Page 36
b. Permittees must maintain the infiltration capabilities of Bioretention and Rain
Garden facilities 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.
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 facilities
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.
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.
Construction Stormwater General Permit
Page 37
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
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 General Condition G9),
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, Washington 98504-7696
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 thirty-first calendar day following the date Ecology
receives a complete NOT form, unless Ecology notifies the Permittee that the
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 38
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; or
4. In the case of a municipal, state, or other public facility, by either a principal
executive officer or ranking elected official.
B. All reports required by this permit and other information requested by Ecology
(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
Construction Stormwater General Permit
Page 39
knowledge and belief, true, accurate, and complete. I am aware that there
are significant penalties for submitting false information, including the
possibility of fine and imprisonment for knowing violations.”
G3. RIGHT OF INSPECTION AND ENTRY
The Permittee 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.
Construction Stormwater General Permit
Page 40
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.
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, Washington 98504-7696
Construction Stormwater General Permit
Page 41
G9. TRANSFER OF GENERAL PERMIT COVERAGE
Coverage under this general permit is automatically transferred to a new discharger,
including operators of lots/parcels within a common plan of development or sale, if:
A. A written agreement (Transfer of Coverage Form) between the current discharger
(Permittee) and new discharger, signed by both parties and containing a specific date for
transfer of permit responsibility, coverage, and liability (including any Administrative
Orders associated with the Permit) is submitted to the Director; and
B. The Director does not notify the current discharger and new discharger of the Director’s
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 submit an updated application form (NOI) to the Director
indicating the remaining permitted acreage after the transfer.
G10. REMOVED SUBSTANCES
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.
G11. 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)].
G12. OTHER REQUIREMENTS OF 40 CFR
All other requirements of 40 CFR 122.41 and 122.42 are incorporated in this permit by
reference.
G13. ADDITIONAL MONITORING
Ecology may establish specific monitoring requirements in addition to those contained in
this permit by administrative order or permit modification.
G14. 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.
Construction Stormwater General Permit
Page 42
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.
G15. 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.
G16. PROPERTY RIGHTS
This permit does not convey any property rights of any sort, or any exclusive privilege.
G17. 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.
G18. 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.
Construction Stormwater General Permit
Page 43
G19. 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.
G20. 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: for sites 5 acres or larger, a 20% or greater increase in
acreage disturbed by construction activity.
C. A change in or addition of surface water(s) receiving stormwater or non-stormwater
from the construction activity.
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.
G21. REPORTING OTHER INFORMATION
Where the Permittee becomes aware that it failed to submit any relevant facts in a permit
application, or submitted incorrect information in a permit application or in any report to
Ecology, it must promptly submit such facts or information.
G22. 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
Construction Stormwater General Permit
Page 44
unavoidable interruption of operation and degradation of effluent quality, must be scheduled
during non-critical water quality periods and carried out in a manner approved by Ecology.
G23. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT
Any discharger authorized by this permit may request to be excluded from coverage under
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.
G24. 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.
G25. 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.
G26. BYPASS PROHIBITED
A. Bypass Procedures
Bypass, which is the intentional diversion of waste streams from any portion of a
treatment facility, is prohibited for stormwater events below the design criteria for
Construction Stormwater General Permit
Page 45
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.
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.
Construction Stormwater General Permit
Page 46
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 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.
Construction Stormwater General Permit
Page 47
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, 2016, or before the date the operator’s
complete permit application is received by Ecology, whichever is later.
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.
Construction Stormwater General Permit
Page 48
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 ground water.
Construction Activity means land disturbing operations including clearing, grading or
excavation which disturbs the surface of the land. Such activities may include road construction,
construction of residential houses, office buildings, or industrial buildings, site preparation, soil
compaction, movement and stockpiling of topsoils, and demolition activity.
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 Groundwater means groundwater which contains contaminants, pollutants, or
hazardous substances that do not occur naturally or occur at levels greater than natural
background.
Contaminated Soil means soil 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.
Construction Stormwater General Permit
Page 49
2. The pollutant removal performance expected from the BMPs selected.
3. The technical basis supporting the performance claims for the BMPs selected, including
any available data concerning field performance of the BMPs selected.
4. An assessment of how the selected BMPs will comply with state water quality standards.
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 ground water 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
ground water 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 ground water 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
Construction Stormwater General Permit
Page 50
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 establishment of a
permanent vegetative cover, or equivalent permanent stabilization measures (examples of
permanent non-vegetative stabilization methods include, but are not limited to riprap, gabions or
geotextiles) which prevents erosion.
Ground Water 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 substance as defined in RCW 70.105.010(10) 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, 42 U.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
Construction Stormwater General Permit
Page 51
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.
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 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 water 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 ground
water drainage, redirecting stream natural flows, or for conveyance of irrigation water/return
flows that coincidentally convey stormwater are considered the receiving water.
Construction Stormwater General Permit
Page 52
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.
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 ground water quality or sediment
management standards.
Significant Concrete Work means greater than 1000 cubic yards 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
Construction Stormwater General Permit
Page 53
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.
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.
Construction Stormwater General Permit
Page 54
Transfer of Coverage (TOC) means a request for transfer of coverage under this general permit
as specified by General Condition G9 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.
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 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 55
APPENDIX B – ACRONYMS
AKART All Known, Available, and Reasonable Methods of Prevention, Control,
and Treatment
BMP Best Management Practice
CESCL Certified Erosion and Sediment Control Lead
CFR Code of Federal Regulations
CKD Cement Kiln Dust
cm Centimeters
CTB Cement-Treated Base
CWA Clean Water Act
DMR Discharge Monitoring Report
EPA Environmental Protection Agency
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
Cyprus Lane 30
F. 303(d) List Waterbodies / TMDL Waterbodies Information
Cyprus Lane 31
G. Contaminated Site Information
Cyprus Lane 32
H. Engineering Calculations
South Basin
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 0.102 2-Year 0.973
5-Year 0.164 5-Year 1.281
10-Year 0.214 10-Year 1.583
25-Year 0.294 25-Year 2.003
50-Year 0.370 50-Year 2.661
100-Year 0.392 100-Year 3.301
200-Year 0.627 200-Year 3.342
500-Year 0.942 500-Year 3.374
TESC Pond Surface Area Calculation
TESC Pond minimum surface area, SA, is determined by the following equation:
SA = 2080 sf/cfs * (Total Q10-developed) (page D-47, 2016 KCSWDM)
Where: SA = minimum TESC pond surface area (sf)
Q10-developed = 1.583 CFS = 10-year developed, 15-minute, peak flow
SAmin = 3,293 SF
The design surface area of the proposed detention vault is 5,104 square feet which is more than enough
to provide adequate erosion and sedimentation control.
Principal Spillway (Riser Pipe)
The riser pipe must pass the developed condition 10-year peak flow using MGSFlood 15-minute time
steps (1.583 CFS) with 0.5 ft of head. Therefore, using Figure 5.3.4.H (page 5-47 2016 KCSWDM) the
minimum riser pipe diameter is 10 inches. A 12-inch diameter riser will be provided for the temporary
sediment pond.
Cyprus Lane 33
Dewatering Orifice
The dewatering orifice diameter must be at least one inch and is sized using a three step process,
outlined on page D-48 of the 2016 KCSWDM.
1. Determine the required area of the orifice
A modified version of the discharge equation for a vertical orifice is used to determine the
required orifice surface area, as follows:
Cyprus Lane 34
𝐴𝑂=𝐴𝑆(2ℎ)0.5
0.6𝑥3600𝑥𝑇𝑔0.5
Where: AO = orifice area (sf)
AS = required pond surface area (3,293 sf)
h = head of water above orifice (10 ft, minimum per Section D.3.5.2 2009 KCSWDM)
T = dewatering time (24 hours, page D-48 2009 KCSWDM)
g = acceleration due to gravity (32.2 ft/s2)
AO = 0.05 sf
2. Convert the required surface area to the required diameter, D (inches)
The required surface area of the orifice is converted to the required diameter, D, using a basic
equation for the area of a circular orifice, as follows:
𝐷=24𝑥√𝐴𝑂
𝜋
D = 3.03” = 3 1/8 inches
3. Determine the size of the vertical, perforated tubing connected to the dewatering orifice
The minimum diameter for the perforated tubing connected to the dewatering orifice is 2 inches larger
than the orifice. Therefore, the minimum tubing diameter = 6 inches.
Cyprus Lane 35
West Basin
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 3.688E-02 2-Year 0.207
5-Year 5.513E-02 5-Year 0.276
10-Year 7.162E-02 10-Year 0.339
25-Year 8.845E-02 25-Year 0.434
50-Year 0.114 50-Year 0.578
100-Year 0.124 100-Year 0.721
200-Year 0.177 200-Year 0.727
500-Year 0.248 500-Year 0.730
TESC Pond Surface Area Calculation
TESC Pond minimum surface area, SA, is determined by the following equation:
SA = 2080 sf/cfs * (Total Q10-developed) (page D-47, 2016 KCSWDM)
Where: SA = minimum TESC pond surface area (sf)
Q10-developed = 0.339 CFS = 10-year developed, 15-minute, peak flow
SAmin = 706 sf
The design surface area of the proposed detention vault is 1,512 square feet.
Principal Spillway (Riser Pipe)
The riser pipe must pass the developed condition 10-year peak flow using MGSFlood 15-minute time
steps with 0.5 feet of head. Therefore, using Figure 5.3.4.H (page 5-47 2016 KCSWDM) the minimum
riser pipe diameter is 10 inches. A 12-inch diameter riser pipe will be provided.
Cyprus Lane 36
Dewatering Orifice
The dewatering orifice diameter must be at least one inch and is sized using a three step process,
outlined on page D-48 of the 2016 KCSWDM.
1. Determine the required area of the orifice
A modified version of the discharge equation for a vertical orifice is used to determine the
required orifice surface area, as follows:
Cyprus Lane 37
𝐴𝑂=𝐴𝑆(2ℎ)0.5
0.6𝑥3600𝑥𝑇𝑔0.5
Where: AO = orifice area (sf)
AS = required pond surface area (706 sf)
h = head of water above orifice (5.1 ft, minimum per Section D.3.5.2 2009 KCSWDM)
T = dewatering time (24 hours, page D-48 2009 KCSWDM)
g = acceleration due to gravity (32.2 ft/s2)
AO = 0.008 sf
2. Convert the required surface area to the required diameter, D (inches)
The required surface area of the orifice is converted to the required diameter, D, using a basic
equation for the area of a circular orifice, as follows:
𝐷=24𝑥√𝐴𝑂
𝜋
D = 1.21” = 1 1/8 inches
3. Determine the size of the vertical, perforated tubing connected to the dewatering orifice
The minimum diameter for the perforated tubing connected to the dewatering orifice is 2 inches larger
than the orifice. Therefore, the minimum tubing diameter = 4 inches.