The Department of Agriculture, Trade & Consumer Protection (DATCP) has conducted several surveys of pesticides in groundwater and has consistently found atrazine to be the most commonly detected pesticide in groundwater. A survey of randomly selected Grade A dairy farm wells in 1989 detected atrazine in 12% of the wells tested. The latest statewide survey completed in 1996 detected atrazine residues in 5.2% to 12% of Wisconsin wells. This survey also showed that about 1% of Wisconsin wells exceed the atrazine enforcement standard of 3 parts per billion (ppb). The Wisconsin Agricultural Statistics Service (WASS) has collected information on the use of agricultural pesticides in Wisconsin. According to WASS surveys, atrazine use peaked in the mid-1980’s at over 5.1 million pounds of active ingredient used per year. Atrazine was used at an average rate of 1.6 pounds of active ingredient/acre/year.