WASHINGTON STATE REGISTER

WSR 01-19-046

DEPARTMENT OF ECOLOGY

[ Filed September 14, 2001, 1:26 p.m. ]

Ecology Issues Revised Stormwater Management Manual for Western Washington

аааа Background: Stormwater is the water that runs off surfaces such as rooftops, paved streets, highways, and parking lots. It can also come from hard grassy surfaces like lawns, play fields, and from graveled roads and parking lots.

аааа Urban development causes significant changes in patterns of stormwater flow from land into receiving waters. Water quality can be harmed when runoff carries contaminants such as oil, metals or pesticides into streams, wetlands, lakes, and marine waters or into ground water. Better managing stormwater runoff helps to reduce this significant pollution problem that makes waterways unhealthy for people and fish.

аааа Stormwater management involves careful application of site design principles, construction techniques to prevent sediments and other pollutants from entering surface or ground water, source controls, and treatment of runoff to reduce pollutants and the harm of altered hydrology.

аааа In preparing this revision to the 1992 Stormwater Manual, the Department of Ecology has relied heavily on contributions from advisory committees. There were five separate advisory committees, with nearly one hundred members, representing a broad range of expertise and interests. Their insights and practical knowledge - gained from years of experience in the field - have been particularly valuable.

аааа Two public review drafts were prepared and presented at public workshops. Ecology staff reviewed numerous public comments and in consultation with the advisory committees and national experts, incorporated many of those comments into the final document.

аааа Why did the Department of Ecology Revise the Manual? There are several reasons why the Washington Department of Ecology (ecology), with assistance from local governments, other state agencies, and industries, revised the manual.

Х Ecology published the Stormwater Management Manual for the Puget Sound Basin in 1992, drawing from research done in the 1980s. This update was necessary to include new information and standards that are more protective of the waters in Washington state.

Х Recently adopted federal stormwater regulations will require many local governments to manage stormwater within their jurisdiction. The manual will provide technically sound and appropriate stormwater management practices.

Х The manual was originally written for the Puget Sound area, although it has been used for construction and industrial activities statewide since it was written. The revised manual is more appropriate and useful for application throughout western Washington.

аааа Key Changes in the Revised Manual:

Х Thresholds for the selection of best management practices (BMPs) are written to allow for the most appropriate sizing and placement of flow control and treatment BMPs. Fewer projects will require engineered structures, but all projects will be required to use appropriate BMPs.

Х Runoff flow control requirements will now address problems of both increased peak flow and the duration of high flows. This will require the use of more sophisticated stormwater runoff models and will generally result in the construction of larger runoff control facilities.

Х Higher levels of treatment will be required to remove and reduce pollution from runoff to lakes and smaller streams to provide more assurance that the treated stormwater runoff is not harmful to fish and other aquatic life and is protective of the environment.

Х New BMPs have been added for controlling runoff from construction sites and for preventing stormwater pollution at the source. These BMPs will help to further remove contaminants from runoff.

Х Ecology proposes to establish a Technical Review Committee to evaluate new treatment technologies and to maintain an updated list of approved treatment technologies.

аааа How to Get Printed Copies of the Stormwater Manual: If you have a credit card, you may order printed copies of the manual at the following Internet address: https://wws2.wa.gov/prt/printwa/wsprt/default.asp.

аааа You may also use this Internet site to get price information (approximately $60) and then send a check or money order payable to "Department of Printing" at the following address: Department of Printing, P.O. Box 798, Olympia, WA 98507-0798.

аааа Include your name, mailing address, phone number, and the name of the publication (Stormwater Manual). Allow about two weeks for delivery. If you have questions about ordering the Stormwater Manual, please call the Department of Printing at (360) 753-6820.

аааа How to Find the Stormwater Management Manual on the Internet: The Stormwater Management Manual for Western Washington is also available on ecology's stormwater homepage. The Internet address is: http://www.ecy.wa.gov/programs/wq/stormwater/index.html.

Х	Ecology published the Stormwater Management Manual for the Puget Sound Basin in 1992, drawing from research done in the 1980s. This update was necessary to include new information and standards that are more protective of the waters in Washington state.
Х	Recently adopted federal stormwater regulations will require many local governments to manage stormwater within their jurisdiction. The manual will provide technically sound and appropriate stormwater management practices.
Х	The manual was originally written for the Puget Sound area, although it has been used for construction and industrial activities statewide since it was written. The revised manual is more appropriate and useful for application throughout western Washington.

Х	Thresholds for the selection of best management practices (BMPs) are written to allow for the most appropriate sizing and placement of flow control and treatment BMPs. Fewer projects will require engineered structures, but all projects will be required to use appropriate BMPs.
Х	Runoff flow control requirements will now address problems of both increased peak flow and the duration of high flows. This will require the use of more sophisticated stormwater runoff models and will generally result in the construction of larger runoff control facilities.
Х	Higher levels of treatment will be required to remove and reduce pollution from runoff to lakes and smaller streams to provide more assurance that the treated stormwater runoff is not harmful to fish and other aquatic life and is protective of the environment.
Х	New BMPs have been added for controlling runoff from construction sites and for preventing stormwater pollution at the source. These BMPs will help to further remove contaminants from runoff.
Х	Ecology proposes to establish a Technical Review Committee to evaluate new treatment technologies and to maintain an updated list of approved treatment technologies.

й Washington State Code Reviser's Office