Stormwater Manual

On July 7, 2005, Yakima County and the Cities of Yakima, Union Gap and Sunnyside formally entered into an Interlocal Governmental Agreement (ILA) for coverage under the Eastern Washington Phase II Municipal Stormwater Permit. The ILA was formed based upon previous studies indicating that there would be reduced costs and less confusion if a regional approach to stormwater management was adopted. As part of that process a regional manual was identified as providing benefits to reflect local conditions in a semi-arid environment.

This Manual is for managing stormwater runoff from new development and redevelopment projects in order to protect receiving body water quality, the conveyance systems, minimize local flooding, and lessen impacts to down-gradient properties as more urban development occurs. This Manual has been developed to reduce cost for stakeholder and community compliance with the MS4 discharge permit requirements.

The purpose of this Manual is to provide guidelines, procedures and local information for the planning, design and maintenance of stormwater facilities located in areas identified in the Regional Stormwater Management Program (RSMP) for Yakima County, City of Yakima, City of Union Gap and City of ,Sunnyside. The guidance outlined in this manual is fashioned to have direct applicability to these urban areas.

The WA Department of Ecology approved the Yakima County Regional Stormwater Manual in 2010.