Publication Summary

From December 1993 to February 1994, 27 wells were sampled near Walla Walla, Washington for pesticides and nitrate+nitrite as N. Field measurements of water temperature, pH, and specific conductance were also made. Wells were located in the Walla Walla Surficial Aquifer underlying the Walla Walla River valley.

From December 1993 to February 1994, 27 wells were sampled near Walla Walla, Washington for pesticides and nitrate+nitrite as N. Field measurements of water temperature, pH, and specific conductance were also made. Wells were located in the Walla Walla Surficial Aquifer underlying the Walla Walla River valley.

Eight pesticides were detected in the initial samples: dacthal (DCPAs), atrazine, simazine, prometon, picloram, oxamyl, and methiocarb. However, only atrazine, simazine, and prometon were confirmed by the verification sampling. An additional pesticide, aldicarb, was detected in one well during the verification sampling. Pesticides were detected in 14 of the 27 study wells, with more than one pesticide found in seven wells. Concentrations of all pesticides were below the Maximum Contaminant Level (MCL) or Lifetime Health Advisory Level set by the EPA for public drinking water.

In seven wells, the nitrate+nitrite as N concentration exceeded the 10.0 mg/L drinking water standard for nitrate. Four wells also had specific conductance values greater than or equal to the 700 umhos/cm MCL for drinking water. Two of these four wells were also included in the seven wells with high nitrates.

Link to EIM data for User Study ID WALLA WA