Stormwater Code and Manual

Clark County Stormwater Manual 2015
Body

Clark County has a National Pollutant Discharge Elimination System (NPDES) Phase I Municipal Stormwater permit effective August 1, 2019 through July 31, 2024. The Washington State Department of Ecology issued the permit and is responsible for enforcing the federal Clean Water Act in this state.

Clark County has operated under an NPDES permit since 1999. This permit, among other things, specifies regulations for managing the quantity and quality of stormwater discharged from the county’s stormwater system to our local creeks, streams, rivers and groundwater.

Clark County most recently updated code and manuals in 2015. The update was a two-year effort and included numerous stakeholders. The current Clark County Stormwater Manual 2015 became effective January 8, 2016. The manual has been reviewed and approved by the Department of Ecology and is considered equivalent to the 2014 Stormwater Management Manual for Western Washington.


​Stormwater Code

Clark County Code includes regulations for local land use and development, along with best management practices to minimize pollution and harmful effects of stormwater. Specific codes for stormwater include:

  • 13.26A Water Quality - sets regulations for how to protect water quality.
  • 40.386 Stormwater and Erosion Control - sets regulations for development related to stormwater.
  • Title 40 - Numerous code sections reference development practices, including the use of low impact development and requirements to minimize impacts to stormwater, including sections for landscaping, parking and building.

Clark County Stormwater Manual and Code Update

Clark County is updating its 2015 stormwater design manual and associated county code. A draft manual and associated code must be submitted to Ecology for review by June 30, 2020 and the final manual implemented by July 1, 2021.

There are several reasons for the update. The Washington Department of Ecology’s 2019 NPDES stormwater permit for Clark County has several required manual changes that are of relatively minor significance. There are many minor changes to correct errors and formatting found as Clark County implemented the 2015 manual.

There are also several policy and technical changes driven by staff requests and problems implementing the manual. Send comments to Rod Swanson at rod.swanson@clark.wa.gov

Table of Changes

Proposed Manual Revisions

Introduction

Proposed Code Revisions
Clark County Stormwater Manual 2015 

The stormwater manual is a comprehensive document to guide project applicants and developers through every step related to stormwater planning, design, construction, maintenance and operation. The manual is divided into four books for various users and took effect on January 8, 2016. Subsequently, the Clark County Board of County Councilors approved the first errata to the Clark County Stormwater Manual 2015 on November 22, 2016. All files are PDF documents.

NOTE: Applications submitted prior to December 2, 2016, will use the code in place at the time of filing.

CCSM 2015 Errata Updates 
Clark County Stormwater Manual 2015 Errata September 2016 (Effective December 2, 2016)
With strikeout/underline notations
Clark County Stormwater Manual 2015 (effective January 8, 2016) 
Supporting resources:

For required signage on stormwater features, use the applicable template with your local sign fabricator:


Western Washington Hydrologic Model

Update (March 2016) - The Washington State Department of Ecology has an update that can be downloaded at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee-guidance-resources/Stormwater-manuals/Western-Washington-Hydrology-ModelYou will need to download and install both the WWHM2012 Version 4.2.12 and Map Data for this update.

Description of the changes:  Version 4.2.12 addresses issues related to generating project reports in the PDF format, the wetland fluctuation report, the water balance report and the water quality report. This also addresses an issue related to the auto-size feature for the 3 orifice design. These issues are considered a programming bug.  According to the version numbering system in use as of October 21, 2015, the digits after the last decimal point are changed for this WWHM update. More information and instructions can be found on the Ecology web page.  Contact them directly with questions or comments.


Resources


Trainings

Visit our Low Impact Development web page for information about trainings related to stormwater planning, design, maintenance and operations. More >>


State Stormwater Permits for Development Projects

Projects disturbing one or more acres of land are required, in most cases, to have a state construction stormwater permit. More information can be found on Ecology's Construction Stormwater General Permit page. 

Projects that create industrial activities may also need a state industrial stormwater permit. More information can be found on Ecology's Industrial Stormwater General Permit page.


Historic documents

Join the email distribution list for updates to stormwater regulations

Email cleanwater@clark.wa.gov with Regulations in the subject line, your contact information in the body of the email.

Low Impact Development in Clark County:

Upcoming Trainings: