Volatile organic compound and pesticide data in public water-supply reservoirs and wells, Texas, 1999-2001

To provide data for the Texas Source-Water Assessment and Protection Program, the U.S. Geological Survey conducted a synoptic survey of 48 public water-supply reservoirs and 174 public water-supply wells during 1999–2001. The surface-water samples were analyzed for volatile organic compounds and soluble pesticides. The ground-water samples were analyzed for volatile organic compounds and soluble pesticides, as well as nitrite plus nitrate nitrogen and tritium.

One or more volatile organic compounds were detected in 75 percent of the reservoirs and in 9 percent of the wells. Methyl tert-butyl ether was detected most frequently in reservoirs, and toluene was detected most frequently in wells. One or more pesticides were detected in 96 percent of the reservoirs and in 33 percent of the wells. Atrazine or its breakdown product deethylatrazine was the most frequently detected pesticide.

Volatile organic compounds and pesticides were not detected at concentrations exceeding the maximum contaminant level allowed in drinking water. The only constituent sampled for that exceeded its maximum contaminant level (10 milligrams per liter) was nitrate nitrogen (in 8 percent of the 174 wells).