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News Release

U.S. Department of the Interior
U.S. Geological Survey

Release: May 21, 2002
R.C. Lane
253-428-3600, ext. 2604

Shoalwater Bay Indian Reservation aquifers studied

Results of a study of ground water on the Shoalwater Bay Indian Reservation and nearby areas in Pacific County are published today in a report by the U.S. Geological Survey (USGS), in cooperation with the Shoalwater Bay Indian Tribe, under a grant from the Bureau of Indian Affairs.

Knowledge of the geologic layers under the reservation is important for understanding the factors influencing ground water flow and quality. USGS scientists studied geologic data for 38 wells in the reservation and nearby areas, measured water levels, and sampled ground water during 1998-99. Data indicate that there are two aquifers--a shallow aquifer and an artesian aquifer--separated by a clay-and-silt layer.

The artesian aquifer (water-bearing rocks or sediments containing water under pressure) under the reservation is the Tribe's primary source of drinking water. Tribal concerns for the aquifer included seawater intrusion, nitrate and bacterial contamination from septic systems, and seawater possibly entering the aquifer.

Ground-water samples generally meet established standards for safe drinking water. Samples were analyzed for metals, nitrate, pesticides, and other compounds. Of the 93 measured properties and chemical analyses of water samples, none of them exceeded EPA drinking water standards. Low chloride concentrations indicate that seawater is not entering the artesian aquifer.

The report, "Hydrogeologic and Water-Quality Reconnaissance of the Artesian Aquifer Under the Shoalwater Bay Indian Reservation and Tokeland Peninsula, Pacific County, Washington, 1998-99," by R.C. Lane and J.C. Ebbert, is published as U.S. Geological Survey Water-Resources Investigations Report 01-4023. Copies of the report are available for reading at the U.S. Geological Survey, 1201 Pacific Avenue, Suite 600, Tacoma, WA 98402. Copies can be purchased from the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225-0286, telephone 303-202-4200. The report can also be viewed at

The USGS, a bureau within the Department of the Interior, serves the nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.

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