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EPA completes second round of groundwater sampling in Lower Yakima Valley

Release Date: 04/26/2010
Contact Information: Michael Cox, EPA Office of Environmental Assessment, (206) 553-1597,, Tony Brown, EPA Public Affairs, (206) 553-1203,

(Yakima, Wash. - April 26, 2010) The U.S. Environmental Protection Agency has just completed a second round of sampling in the Lower Yakima Valley in an attempt to link the high nitrate levels in groundwater and private wells to possible sources of contamination. EPA sampled over 330 residential drinking water wells between February 22nd and March 6th and finished collecting a second set of water and soil samples on April 22nd.

Residents who participated in the first round have been notified of their results and given information on how to reduce the risk from nitrate in their drinking water. EPA found 21 percent of the wells sampled had nitrate levels greater than the EPA drinking water standard of 10 parts per million. In total, eight wells tested positive for bacterial contamination and of these, three were also high in nitrate.

EPA used first round sampling results to identify locations for the second, more focused round of sampling. The second round included taking water from 29 wells to test for a wide array of contaminants including nitrate, isotopes of nitrogen, bacteria, pesticides, general chemistry parameters, and a variety of pharmaceuticals and hormones. Soil samples were taken from crop fields and dairies. Manure and lagoon water samples were taken from dairies, and samples were collected at wastewater treatment plants. In total, over 1,000 sample bottles were collected and sent to seven laboratories for analysis.

Over the next few months, EPA will analyze and evaluate these samples, which may help link the high nitrate levels in the Valley's groundwater with possible sources of contamination. The results should be available in late summer of 2010. EPA hopes that these results will help provide the information needed to determine how to best reduce nitrate levels in groundwater.

“The families and business owners participating in the study have performed a valuable public service,” said Tom Eaton, Director of EPA’s Washington State Office. “We appreciate the community's continued support of our efforts.”

The EPA is conducting the study in response to community concern over high nitrate levels in groundwater throughout the Lower Yakima Valley. EPA’s study is one part of a multi-agency approach to ensure that local families have access to safe drinking water. EPA is working with: the Yakama Nation; the Washington departments of Ecology, Agriculture, and Health; local governments; and the community to manage the problem. EPA and agency partners will be staffing a booth at the Sunnyside Cinco de Mayo celebration on May 1st and 2nd from 10AM to 4PM to answer questions about the study and drinking water in general.

Nitrate is a compound that forms naturally when nitrogen combines with oxygen or ozone. High levels of nitrate-nitrogen in drinking water can be harmful to health, especially for infants and pregnant women. Sources of nitrate that can enter wells include fertilizers, septic systems, animal feedlots, industrial waste, and food-processing waste.

More information and a copy of the recently released report outlining options for addressing high levels of nitrate and bacteria found in shallow aquifers throughout the Lower Yakima Valley is available online at:

For a hard-copy of the Report, contact Ryan Anderson at 509-575-2642 or by email at

Important information about drinking water safety for people on private wells is available on the Department of Health Web site:

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