Publication Summary

This document is in five downloads. In this file you will find:
Chapter 5 - Runoff Treatment Facility Design
Chapter 6 - Flow Control Facility Design
See below for links to the other files.

Urban development causes significant changes in patterns of stormwater flow from land into receiving waters. Water quality can be affected when runoff carries sediment or other pollutants into streams, wetlands, lakes, and marine waters or into groundwater. Stormwater management can help to reduce these effects. Stormwater management involves careful application of site design principles; construction techniques and source controls to prevent sediment and other pollutants from entering surface or groundwater; treatment of runoff to reduce pollutants; and flow controls to reduce the impact of altered hydrology.

The objective of this Manual is to provide guidance in stormwater design and management for eastern Washington. The Manual aims to provide a commonly accepted set of technical standards, in addition to presenting new design information and new approaches to stormwater management. The Department of Ecology believes that when the standards and recommendations of this Manual are properly applied, stormwater runoff should generally comply with water quality standards and protect beneficial uses of the receiving waters. Ecology recognizes that individual circumstances vary greatly, and in some instances compliance with the Manual may not ensure compliance with water quality standards.

Many guidance manuals for stormwater have been written to address national, regional and local characteristics and management needs. In Washington, several guidance manuals have been prepared, used, and updated to address regional and local requirements. The Department of Ecology published the Stormwater Management Manual for Western Washington in August 2001 as an update to a predecessor manual prepared in 1992. Ecology initially proposed that the Manual could be updated to cover the entire state of Washington. Eastern Washington representatives requested that Ecology instead create a separate manual for the eastern portion of the state. Based upon these requests and upon recognition of the significantly different hydrology and geology of eastern Washington, Ecology agreed to create a separate manual.

Discussions continued at various conferences, meetings and forums to determine the best method to accomplish this effort. A chartering meeting was held in June 2001 to formalize the structure and process for preparing the Manual for eastern Washington. The meeting was attended by more than 70 representatives of 17 cities, 11 counties and five Federal and State agencies with interests in stormwater management in eastern Washington. The chartering meeting established a ten-person Steering Committee with several alternate members to lead the overall effort; it also created two Subcommittees: one for leading the preparation of the Technical Stormwater Manual, and another for leading the preparation of a Model Municipal Stormwater Program. Ecology agreed to fund the hiring of a consultant team to support the development and preparation of the documents and to assist the Steering Committee and Subcommittees with meeting coordination, public involvement and related project tasks. Proposals were received by four consultant teams in October 2001; the Steering Committee selected the team lead by Tetra Tech/KCM of Spokane.

A project kick-off meeting was held on November 7, 2001 with members of the Steering Committee, Ecology, and the consultant team. The scope of work for the project and a proposed production schedule were prepared; a corresponding budget was prepared and the work began. A stakeholder workshop was held on November 29, 2001 to inform interested parties about the project efforts, the regulatory requirements, the schedule for meetings, and the document production format. After the introductory sessions, concurrent meetings of the Subcommittees were held to begin the development of the Manual and the Model Program. Meetings were held at least once per month to review drafts and updates for each chapter of each document. Periodic presentations were made to address special stormwater management issues. These efforts resulted in draft documents being submitted for public review in fall 2002.

Following the public comment period, the subcommittees reviewed all of the comments received on both of the documents and agreed to minor revisions to the Model Program and substantive revisions to the Manual. The final Model Program will be published in summer 2003. The public comment period on the Final Draft Manual is from early June through mid August 2003.