Geology and ground-water resources of northwestern King County, Washington

King County, in the west-central part of the State of Washington, includes about 2,135 square miles. The eastern part of the county lies in the Sierra-Cascade Mountains province and the remainder is in the Puget Trough of the Pacific Border province. The area covered by the present investigation is almost entirely within the Puget Trough and includes about 450 square miles.