Pesticide Contamination Prevention Act Review Process Triggered by Detections of Simazine in Groundwater

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Formal Review Process and Regulatory Changes

The formal review process began in August 1986, following the determination that detections of simazine in groundwater were the result of its legal agricultural use. Following a public hearing in February 1987, the PREC subcommittee found that use modifications, handler training and additional monitoring would create a high probability that simazine would not continue to pollute groundwater. In August 1987, the Director concurred with the subcommittee's findings and, among other actions, banned the use of simazine in artificial recharge areas and on rights-of-ways in Pesticide Management Zones (PMZ).

Current Regulatory Status

In 2004, DPR expanded the areas where certain pesticides, including simazine, were regulated and adopted mandatory mitigation measures to protect groundwater. Called "groundwater protection areas" (GWPA), these new areas included all former PMZs as well as sections of land with no reported detections but with soil types and depths-to-ground water that are characteristic of contaminated areas. Based on the pathway of pesticide movement to groundwater, GWPAs are designated as either leaching or runoff. In leaching GWPAs, the mandatory mitigation measures are designed to prevent over-irrigation while in runoff GWPAs, they are designed to either prevent offsite movement of contaminated runoff or manage contaminated runoff so that it does not move to groundwater. In addition, pesticides regulated as groundwater contaminants may not be applied in artificial recharge basins, inside canal or ditch banks, or on engineered rights-of-way throughout California unless applicators observe mandatory mitigation measures.

For more information, please see: Identifying and Protecting Groundwater Protection Areas