This project looked at a study area encompassing about 260 square miles in the areas draining to Lake Washington from the Kelsey Creek / Mercer Slough drainage north to the Sammamish River drainage. In this area there are six major transportation projects planned, for which we specifically looked for potential mitigation sites. This is an area with lots of state, local and private development; the potential site list could be used to identify mitigation for any of these projects. The list offers a scientifically developed and prioritized set of natural resource restoration sites in the watershed which could be used for watershed recovery, fish enhancement, and more.
The report is available through the links below. Other supporting files including GIS data and metadata are available on request.
This was the third watershed characterization completed by the WSDOT watershed program. The ultimate intent is to create lists of potential landscape-scale mitigation sites for the environmental impacts of transportation improvement projects. Find further information on the methodology used, and reports summarizing the all three characterization projects at
watershed characterization.
I-405 / SR-520 Watershed Characterization Report
Adobe Acrobat .pdf format;
designed for double-sided printing
For more information contact:
Richard Gersib
360-705-7477
gersibd@wsdot.wa.gov