Stormwater Code and Manual Update - Clark County Public Works
Clark County updated its Stormwater Code and Manual to comply with 2019 NPDES permit requirements, incorporating technical and policy changes for better stormwater management. Public involvement and Ecology-mandated changes were integral to the update process.
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Presentation Transcript
Stormwater Code and Manual Update DEAB Update Rod Swanson, Clark County Public Works February 4, 2021
Background Clark County created the Clark County Stormwater Manual in 2015 to have a local manual that is equivalent to the 2014 Washington Department of Ecology Stormwater Management Manual for Western Washington. The county manual is one of six municipal manuals formally approved for use in western Washington. The others are: Seattle Tacoma King Co. Pierce Co. Snohomish Co 8/9/17 2
Why Update the Code and Manual Now? The 2019 NPDES permit requirements requires updates by July 2021 Technical or policy changes needed as manual implementation proceeds Numerous minor edits and clarifications that are basically editorial housekeeping 8/9/17 3
Why Update the Code and Manual Now? The 2019 NPDES permit requirements requires updates by July 2021 Technical or policy changes needed as manual implementation proceeds Numerous minor edits and clarifications that are basically editorial housekeeping Schedule Planning Commission on March 18 Council Work Session in April Council Hearing in May 8/9/17 4
Public Involvement 2015 Clark County Stormwater Manual Extensive public involvement including a technical advisory committee providing significant input 2021 Update Draft for Ecology review placed on county web page in May 2020 with notice to stormwater stakeholders and DEAB interested parties December public review draft and a notice to the 1200+ person Planning Commission interested party list Three commenters have responded since May 8/9/17 5
Ecology-Mandated Changes Reference the most recent Ecology hydrology design model Lower the financial threshold for redevelopment from site (parcel) to project site value Provide more liberal ability to place facilities off-site Require amended soil for small projects that use the LID performance standard Completely redo requirements for discharges to wetlands Update erosion control requirements to match the current Ecology Construction Stormwater General Permit Update concrete washout BMPs for tools and equipment Add 17 source control BMPs for existing activities to Book 3 Add an approval sunset clause to Chapter 40.386 of July 2026 for projects approved before July 2021 (2015 manual) 8/9/17 6
Technical and Policy Changes to the Manual Allows use of LID List 2 for MR 1-9 home sites over five acres if not draining to county roads Allows use of CSGP SWPPP for compliance with EC requirements Does not allow permeable asphalt in county roads Requires an annual facility maintenance cost estimate for facilities dedicated to HOAs Removes the three-foot depth to water requirement from Full Dispersion Adds reference to county procedure for property conveyance to Clark County Clarifies that soil reports may require well data and not just GIS data for larger bioretention facilities 8/9/17 7
Continued Technical and Policy Changes Allows EC BMPs from the 2019 SWMMWW Updates post-construction soil testing for bioretention facilities Added WSDOT compost amended biofiltration swale Removed the use of the term commercial agriculture and its definition to simply use the term agriculture for exemptions Allows curb medallions instead of signs for biorention facilities Added a chapter on fence standards Requires a single plan sheet containing all conveyance and facility catchments for ease of mapping Added Public Works policy for land and easement conveyance to Public Works Added the standard infiltration facility vertical separation omitted from 2015 manual 8/9/17 8
Code Changes Made unpermitted connections to the MS4 a prohibited discharges under the water quality ordinance (Chapter 13.26A) Clarified code (Chapter 40.386) to require record drawings for engineered LID BMPs as is common practice now Updated the sunset language for projects that have not started construction under the 2015 manual by July 2026 Added zero rise flood plain to Chapter 40.420 Flood Hazard Areas from the manual 8/9/17 9
Other Revisions There are many minor changes for clarification or to fix errors More Information All changes are listed in the Table of Changes on the county Stormwater Code and Manual Update web page 8/9/17 10
Thank you! Comments and questions Next Steps 8/9/17 11
