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News Release

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

Release: March 20, 1998
Luis A. Fusté, Information Officer
(253) 428-3600, ext 2653

Snohomish ground water quality is good; no widespread problems found

Water from western Snohomish County wells is generally good quality for drinking, and the few problems that can be found are generally due to natural processes, according to a report issued by the U.S. Geological Survey (USGS), Department of the Interior.

The report presents the results of a ground-water study by the USGS, in cooperation with Snohomish County, to help this rapidly growing county meet its needs for drinking water.

Hydrologists collected and examined data for more than 1,300 wells to determine the water-bearing layers, called aquifers. Then water samples from nearly 300 wells were analyzed to determine the quality of the water in these aquifers.

"The ground-water quality in western Snohomish County is generally good for drinking," said Blake Thomas, USGS hydrologist and principal author of the report. "We looked for contamination from septic systems, animal wastes, and fertilizers, but we didn't find any widespread problems."

Hydrologists looked for indicators of human impact, such as nitrate and fecal-coliform bacteria in water, with good results. The median concentration of nitrate was less than 0.05 ppm (parts per million), and fecal-coliform bacteria were present in only 2 percent of the samples. Only four samples exceeded the U.S. Environmental Protection Agency (EPA)'s drinking water standard of 10 ppm for nitrate.

Hydrologists found a few elevated concentrations of nitrate and bacteria in isolated areas; no regional patterns of contamination were found.

Naturally occurring arsenic was found in 63 percent of the water samples (186 out of 297), but only five samples (2 percent) exceeded the EPA's drinking water standard for arsenic of 50 ppb (parts per billion).

In scattered areas, hydrologists found high concentrations of iron and manganese, elements that occur naturally in ground water and are typical of western Washington ground water. Twenty percent of the water samples exceeded 300 ppb of iron, and 41 percent exceeded 50 ppb of manganese. Although not a health concern, these high concentrations are mostly a nuisance by making water taste unpleasant and staining laundry and plumbing fixtures.

The report "The Ground-Water System and Ground-Water Quality in Western Snohomish County," by B.E. Thomas, J.M. Wilkinson, and S.S. Embrey, is published as U.S. Geological Survey Water-Resources Investigations Report 96-4312. The report is available for reading at the U.S. Geological Survey, WRD, 1201 Pacific Avenue, Suite 600, Tacoma, Washington 98402-4384. It can be purchased from the U.S. Geological Survey, Branch of Information Services, Box 25286, Denver, Colorado 80225, telephone (303) 202-4610.

The report is also available from the Snohomish County Department of Planning and Development Services, Planning Division, on the 4th floor of the Administration Building, 3000 Rockefeller Avenue, Everett, Washington, telephone (425) 388-3311, extension 2203. Additionally, the report may be viewed at the Everett Public Library, 2702 Hoyt Avenue, Everett, Washington.

*** USGS ***

Note to Editors: Snohomish County is preparing a ground water management plan. For more information, contact the Snohomish County Department of Planning and Development Services at the address and telephone listed above.

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