USGS Washington Water Science Center
|U.S. Department of the Interior
U.S. Geological Survey
Release: February 7, 2001
253-428-3600, ext. 2644
The quality of ground water in the Puget Sound Basin generally meets U.S. Environmental Protection Agency drinking water standards, according to a new report published today by the U.S. Geological Survey.
Overall, nitrate concentrations in 30 shallow ground water wells randomly sampled throughout the Puget Sound Basin were quite low, with a median concentration of 1.0 milligram per liter (mg/L). Only one well had a nitrate concentration that was above the drinking water standard of 10 mg/L.
In contrast, the concentration of nitrate in 64 percent of 22 wells sampled specifically in an agricultural area in Whatcom County was above the drinking water standard. The median concentration of nitrate in 27 shallow ground water wells sampled specifically in urban residential areas in Pierce and Thurston Counties was slightly more than 4 mg/L, which was greater than nitrate concentrations in randomly sampled wells from throughout the Puget Sound Basin, but less than those in the agricultural area.
"The presence of nitrate in ground water at concentrations above a few milligrams per liter is a good indication that ground water has been affected by human activities," said Emily Inkpen, lead author of the report and hydrologist with the USGS National Water-Quality Assessment program. "Sources of nitrate in the agricultural area are mostly manure and fertilizers, and sources in the urban residential areas include lawn and garden fertilizers as well as septic systems."
"Although some pesticides were detected in shallow ground water, the good news is that all concentrations were below drinking-water standards and guidelines," said Inkpen. "An exception was the fumigant-related compound 1,2-dichloropropane (1,2-DCP), which was found at concentrations above drinking water standards in 2 of 22 wells sampled in the Whatcom County agricultural area."
Soil fumigants are used to kill nematodes in the soil before planting certain crops, such as raspberries or potatoes. Because soil fumigants currently used contain very small amounts of 1,2-DCP, it is likely that the concentrations above drinking-water standards were due to past applications of soil fumigants, which contained higher concentrations of 1,2-DCP.
Methyl tert-butyl ether (MTBE), a fuel oxygenate which is added to gasoline to reduce air pollution, was rarely found in ground water in the Puget Sound Basin. MTBE, the most widely used fuel oxygenate in the United States, is frequently found in ground water in areas where it is used. However, ethanol, not MTBE, is the primary fuel oxygenate used in the Puget Sound Basin.
The report, "Ground-water quality in regional, agricultural, and urban settings in the Puget Sound Basin, Washington and British Columbia, 1996-1998," is published as a USGS Water-Resources Investigations Report 00-4100. A copy is available for reading at the U.S. Geological Survey, 1201 Pacific Avenue, Suite 600, Tacoma, Washington 98402, (253) 428-3600. Copies can also be purchased from the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225-0286, telephone (303) 202-4700.
As the Nation's largest water, earth and biological science, and civilian mapping agency, the USGS works in cooperation with more than 2,000 organizations across the country to provide reliable, impartial scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to the sound conservation and the economic and physical development of the nation's natural resources, and enhance the quality of life by monitoring water, biological, energy, and mineral resources.
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