Stormwater & Site Development Manual

The Pierce County Stormwater Management and Site Development Manual (Manual) was created to establish design and analysis criteria for almost all types of development activity. The intent of the Manual is to:
  • Establish criteria for review and analysis of developments and;
  • Manage stormwater to minimize contact with contaminants and;
  • Mitigate the impacts of increased runoff due to urbanization and;
  • Manage runoff from developed property and property being developed.
Pierce County began regulating stormwater runoff in 1984 and there have been periodic updates through the years as technology changed, environmental impacts were recognized, and state or federal laws took effect.

The Development Engineering section coordinates updates to the Stormwater and Site Development Manual (Title 17A).
Stormwater Manual Updates
Updates are required by the Washington State Department of Ecology, typically on a five-year cycle. The Manual was last updated in 2015. It made Low Impact Development Principles and Best Management Practices the preferred and commonly used approach for development.

Pierce County must update the 2015 Manual by July 1, 2021.

In addition to incorporating some minor staff and industry-requested changes, there are nine significant changes required for this update in the following areas:

  1. Continuous Simulation Modeling
  2. Replaced Hard Surfaces Redevelopment Threshold
  3. Equivalent Areas
  4. Minimum Requirement 2
  5. Minimum Requirement 5
  6. Minimum Requirement 7
  7. Concrete Washout Best Management Practices
  8. Source Control Best Management Practices
  9. Wetlands Guidance
Ecology Requirements:
Comment on draft changes by June 1
The draft updates are available to download below as Word documents in a track changes format. There are also two spreadsheets that summarize the changes. Please review the drafts and submit comments, suggestions or questions by June 1.

Proposed Amendments
The Planning Commission will review and consider proposed amendments to the Pierce County Stormwater Management and Site Development Manual.

Adopted Manual

Adopted Stormwater Manual PDF, 29 MB,
Effective Dec. 5, 2015

Adopted Stormwater Manual by Volume 
A directory of the volumes. Includes AutoCad files.

Library of Supporting documents and historic manuals

Other resources:

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Stormwater Manual Update

Dawn Anderson, Project Manager
(253) 798-2291