Results of the Wisconsin Department of Agriculture, Trade and Consumer Protection Groundwater Monitoring for Pesticides

The objective of this study is to determine the extent of groundwater contamination resulting from pesticide use in highly and moderately susceptible areas of Wisconsin. In this study highly susceptible areas are defined as having sandy soils, less than 25 feet to groundwater, and irrigation. Areas of moderate susceptibility are defined as having loamy soils and 15 to 50 feet to groundwater, with or without irrigation. The pesticides of interest are atrazine, alachlor, aldicarb, metolachlor, metribuzin, and several other compounds that have chemical characteristics and use patterns which make them relatively susceptible to leaching.

This study utilizes monitoring wells to evaluate the occurrence of pesticides in groundwater. Monitoring wells allow the investigation of pesticides in groundwater to be expanded beyond the limited zones of groundwater accessible by drinking water wells. This is consistent with the Wisconsin Groundwater Law which directs agencies to look at all groundwater, not just drinking water, when assessing contamination problems.

The results from this study are compared to the groundwater quality standards established in chapter NR 140 of the Wisconsin Administrative Code. A determination can then be made on which pesticides have the potential to enter groundwater at concentrations above groundwater standards. Under the Groundwater Law, the Department of Agriculture, Trade and Consumer Protection (DATCP) must adopt preventive rules, within its jurisdiction, to limit the presence of pesticide substances in groundwater. In order to fulfill this directive, DATCP must know the nature and extent of the problem.