Water Supply Source Development

(Vashon-Maury Island, WA)  King County Water District 19 (District), the largest water purveyor on Vashon-Maury Island, hired Landau Associates to help develop a water source in compliance with an agreement between a local citizens group, the Washington State Department of Ecology (Ecology), and the District that resolved litigation over the transfer of a surface water right to a groundwater source. A major issue in developing a new source was the difficulty in finding adequate yield in the deep aquifer system where dry wells have been encountered on a number of occasions.

In accordance with provisions of Ecology’s final Report of Examination (ROE), the new water source is required to be screened in the deep aquifer system. Landau Associates developed a conceptual model of the deep aquifer system based on regional well logs and other geologic data. A well location was recommended to the District and Landau Associates’ staff oversaw well drilling and installation. The subsequent 560 ft deep well produced adequate yield to meet the District’s need. Landau Associates also assisted the District in implementing a six-day pumping test that included monitoring of six nearby domestic wells for associated impacts. We collected water samples from wells screened below sea level to establish baseline conditions for seawater intrusion and assisted the District with establishing a long-term sustainable pumping rate for the well. 

Additional services provided to the District include analysis and recommendations on long-term maintenance procedures for their main wellfield to optimize yield and the preparation of a watershed control plan for the Beall and Ellis Creek watersheds as a part of a 2008 Water System Plan.