A group of Yakima Valley dairies have agreed to reduce runoff pollution that's tainting the area's groundwater, officials announced Wednesday.

The agreement between the dairies and the Environmental Protection Agency comes more than five months after the agency published a study that said the dairies were likely to be one of the sources of nitrate pollution in nearby private water wells. The study was followed up by lawsuit threats from public interests groups.

"These are family farmers who have lived and worked in this community for decades," said Paul Queary, a spokesman for the dairies, in a statement. "They are committed to responsible business practices and working with the EPA to protect the health and safety of their neighbors."

Under the agreement, the dairies will provide alternative water sources for neighbors within a one-mile radius whose drinking sources have been tainted. The dairies also agree to take steps to control sources of nitrogen, such as manure and commercial fertilizer. They also will conduct soil and groundwater testing at each dairy.

The dairies in the agreement are the Cow Palace, George DeRuyter and Son Dairy, D&A Dairy, Liberty Dairy — all located north of Granger and Outlook, the EPA said.

The agreement ends the threat of enforcement action by the EPA and lays a foundation for ongoing scientific testing of groundwater in the area and appropriate mitigation of any problems that testing finds, Queary said.

About 24,000 people use wells for their drinking water in that area.

The state Department of Ecology applauded the agreement, highlighting that elevated nitrate levels are a problem in many drinking water wells in the Yakima Valley.

"These agreements are an important step," said EPA Regional Administrator Dennis McLerran. "We expect to continue our work with state and local partners and the (Groundwater Management Area) process to build on this collaborative effort to better understand and control other sources of nitrates in a meaningful manner."

The EPA began its study after a 2008 Yakima Herald-Republic series detailing how as many as 1 in 5 of the wells in the area were contaminated by nitrates.

Excessive exposure to nitrates can harm infants and people with compromised immune systems. Nitrates can also indicate the presence of other contaminants such as bacteria and pesticides. odds

The report singled out dairies, including several with lagoons estimated to have leaked millions of gallons of manure into the ground each year. But the report did not blame the region's entire nitrate problem on the dairies.

-- The Associated Press