Drainage Design and Erosion Control Manual

2016 Drainage Design and Erosion Control Manual

Consistent with the 2013-2018 Western Washington Phase II Municipal Stormwater Permit, the City of Olympia has adopted a revised Drainage Design and Erosion Control Manual (DDECM) along with other revisions to sections of the Olympia Municipal Code and Engineering Design and Development Standards (Ord. 7027).

The revised 2016 DDECM makes low impact development the “preferred and commonly-used approach to site development” and applies to all permit applications deemed complete after December 1, 2016. Low Impact Development (LID) is an approach to site development (or re-development) that emphasizes the use and conservation of vegetation, soils, and natural processes to manage stormwater runoff.

Some sections of the manual have changed significantly or include new requirements that affect thresholds for site development and road projects. The most notable of these changes is the requirement of low impact development practices for managing stormwater runoff from hard surfaces. Other requirements including preparation of drainage plans, report content, soils investigations, and permanent stormwater facility inspection/maintenance have also been revised. The included Summary of Changes table provides a comprehensive listing of changes and updates from the 2009 DDECM to the 2016 edition.

The following information should assist in determining applicable stormwater requirements for new development and redevelopment projects under the 2016 City of Olympia Drainage Design and Erosion Control Manual (DDECM).  Guide sheets are provided below for permit applicants, engineers, contractors, and designers to assist in preparation of plans and reports for all types of projects. 

These guide sheets are not intended to replace related sections of the DDECM.  If there is discrepancy between these sheets and language in the DDECM, the requirements of the DDECM shall prevail.

Stormwater Review and Project Submittal Requirements

Construction Stormwater Pollution Prevention

Stormwater Site Management Plans and Facility Maintenance

The following templates shall be used when preparing Stormwater Site Management Plans for projects required to comply with Core Requirement #9 - Operation and Maintenance (DDECM, Volume I, Section 2.5.9). A content checklist for Stormwater Site Management Plan preparation can be found in Guide Sheet 1C.

2009 Drainage Design and Erosion Control Manual

Projects with complete Building or Engineering Permit applications submitted before December 1, 2016 are vested to the 2009 DDECM.

  • Table of Contents  
  • Volume I  An introduction, minimum requirements, and several other key elements of developing the Stormwater Site Plan.
  • Volume II  Covers best management practices (BMPs) for short-term stormwater management at construction sites (temporary erosion and sediment control)
  • Volume III  Covers hydrologic analysis and BMPs to control flow volumes from developed sites.
  • Volume IV  Addresses BMPs to minimize pollution generated by potential pollution sources at developed sites.
  • Volume V Presents BMPs to treat runoff that contains sediment or other pollutants from developed sites.


Contact Steve Thompson at 360.753.8397 or sthompso@ci.olympia.wa.us.