Past Drainage Manuals - 2009
Sections of the 2009 Drainage Manual

Volume 5: Stormwater Best Management Practices


Alternative Paving Surfaces (PDF)

Closed-circuit Television Inspection (PDF)

Subdivision Land Area Calculations (PDF)


Administrator Memos

Mechanical Equipment (PDF)

Rural Large Lots (PDF)

Salmon Creek Basin (PDF)


Errata No. 1. August 2012 (PDF)

Modeling Information

The 2009 Drainage Design and Erosion Control Manual for Thurston County requires the use of the Western Washington Hydrologic Model, Version 3 (WWHM3) with Thurston County enhancements for BMP design. The Thurston County enhancements include the use of additional rain gage stations and 15-minute time steps and also include a recharge calculator to demonstrate minimum infiltration requirements for projects. 

WWHM3 website

Recharge Calculation Guide with Thurston Co. Enhancements (PDF)

Department of Ecology approval of WWHM3 with Thurston Co. Enhancements (PDF)

Design Guides for Best Management Practices

Bioretention (PDF)

Detention Ponds (PDF)

Post-Construction Soils Quality and Depth (PDF)

Roof Downspout Runoff Controls (PDF)

Wet Ponds (PDF)

Fact Sheets

What You Need to Know About Abbreviated Drainage Plans (PDF)

How to Determine Whether You Can Submit An Abbreviated Drainage Plan (PDF)

Sample Abbreviated Drainage Plan (PDF)

What is in the 2009 Drainage Manual? (PDF)

Differences Between the 1994 and 2009 Drainage Manuals? (PDF)

Stormwater Problems and Impacts: Why the Fuss? (PDF)

Differences between the County's 2009 Drainage Manual and Ecology's 2005 Stormwater Management Manual for Western Washington? (PDF)

Twelve Minimum Requirements & When They Apply (PDF)

Single Family Residential Projects -- On a Single Lot (PDF)

The Drainage Scoping Report -- A New Requirement (PDF)

Project Documents/Templates

Complete and submit these documents as part of your stormwater maintenance agreement with Thurston County.

Most projects typically require these

Checklist for Agreement to Maintain (PDF)

Engineers Construction Inspection Report (PDF)

Facility Summary Form (PDF)

Standard Stormwater Notes (PDF)

Stormwater Conveyance Connection Application (PDF)

Commercial & Subdivision-Residential

Agreement to Maintain Commercial  Fillable Word Form  |  PDF

Agreement to Maintain Subdivision-Residential  Fillable Word Form  |  PDF

Bond Quantities Worksheet  Fillable Excel Worksheet 

Checklist - Final Acceptance Requirements (Due prior to release of Financial Guarantees)  (PDF)

Drainage Marking Detail (PDF)

Low Pressure Air Test Report Form (PDF)

Operation & Maintenance Cost Estimate Worksheet (PDF)

Source Control Plan for Commercial  Word  |  PDF

Source Control Plan BMPs  Word  |  PDF

Single Family Residential

Agreement to Maintain  Fillable Word Form  |  PDF

Source Control Manual, Residential Stormwater Pollution Prevention (PDF)