Groundwater monitoring initiatives in the 1980s and 1990s in Wisconsin discovered that the herbicide atrazine and its chlorinated metabolites are present in a variety of wells and aquifers around the state. The atrazine in groundwater was believed to have resulted from the legal use of atrazine (non-point source) and from improper handling, storage and disposal (point source). The distribution of atrazine detections in the state is still widespread. The most recent random statewide survey conducted by the department in 2001 estimated that about 12% of the groundwater in the state contains atrazine or its chlorinated metabolites. And about 1% of the groundwater is over 3.0 µg/L, the health based Enforcement Standard (ES) for atrazine.