One-fifth of the domestic and public water supply wells in east-central Washington have been measured with unsafe levels of nitrates, according to a new federal survey.
The worst contamination is found in Grant, Adams and Franklin counties in areas where fertilizers are used intensively, said Sarah Ryker, a U.S. Geological Survey geographer and the study’s principal author.
High nitrate levels can cause health problems, state officials warn.
Nitrates are particularly dangerous to children between six months and one year because the nitrates can react with oxygen-carrying hemoglobin in the blood to cause an anemic condition known as “blue baby syndrome.”
Water with nitrate levels exceeding the EPA’s drinking water safety level of 10 milligrams per liter should not be given to infants, health officials say.
In the area USGS surveyed, some 19 percent of the 573 wells exceeded the 10-milligram level. Most of the well data came from samples taken between 1980 and 1994.
The nitrate concentrations vary widely, but generally have increased since the 1950s, according to the survey.
The worst problems are in Franklin County between Pasco and Quincy, where 29 percent of the wells exceed the drinking water safety levels in an area of large Columbia Basin Irrigation Project farms where fertilizers are used intensively.
That area has the region’s highest rate of fertilizer application, at 151 pounds per acre, according to the study. By contrast, Adams County uses 68 pounds per acre, and Whitman County farmers apply 54 pounds per acre.
The high nitrate concentrations appear in shallower ground water, but also can be carried to deeper aquifers, especially in areas of irrigated agriculture.
That finding has implications for a U.S. Environmental Protection Agency proposal to protect ground water in a 14,000-square-mile area of Eastern Washington and Idaho.
The sole-source aquifer proposal is supported by environmental groups and opposed by some farm groups and rural elected officials hostile to additional federal regulations.
One of the questions scientists are asking about the EPA’s proposed Eastern Columbia Plateau Aquifer System is whether surface contamination is reaching deeper zones in the aquifer.
“We are seeing evidence of high nitrate levels in some deep wells,” said Sandy Williamson, project chief for the Columbia Plateau water study.
The well survey is part of an ongoing USGS study of the state’s Central Columbia Plateau, an area extending from Vantage on the west to the Snake River on the south and into Idaho’s Latah County on the east. Only a small corner of southwestern Spokane County is included.
The Central Columbia Plateau is one of 60 National Water-Quality Assessment study areas nationwide. The areas include major river basins and parts of aquifer systems.
, DataTimes ILLUSTRATION: Graphic with map: Eastern Washington’s well contamination