Lake Washington Area Regional Background

Ecology evaluated existing data from surface sediments in the Lake Washington area to establish regional background values for select bioaccumulative chemicals.  The Lake Washington Area Regional Background Sediment Characterization  Data Evaluation and Summary Report is complete.  Please click on the link below under "Documents" to access the report.

The Lake Washington area is located in Water Resources Inventory Area 8 and is an area where multiple freshwater sediment cleanup site work is occurring. Much of this work includes implementing the Sediment Management Standards (SMS) rule, Chapter 173-204 WAC.   A key provision in the SMS rule is the concept of regional background, the concentration of a contaminant that exists in an area due to diffuse sources of pollution rather than a specific source.

Regional background values can be used to establish the upper cap for sediment cleanup levels, inform cleanup decisions, and identify potential areas of sediment contamination that may require cleanup.  You may find more information on the SMS rulemaking and other regional background work here.

Regional background established for the Lake Washington Area will apply to urban lakes in King County WRIA 8, including Lake Union, Lake Washington, Lake Sammamish, as well as the Lake Washington Ship Canal area east of the Hiram Chittenden Locks. Regional background established in this report is not applicable to river systems, or less developed suburban or rural lakes.


Additional Resources

Thumbnail map of Washington showing King County


King County

En espanol

For information on  Regional Background  contact:
Chance Asher
Sediment Program Policy Lead
Chance Asher
(360) 407-6914

For site information contact:
Ching-Pi Wang
(425) 649-7134

Repository Locations:
Ecology Northwest Regional Office
3190 – 160th Ave. SE Bellevue, WA 98008-5452
(425) 649-7000