Pesticide Contamination Prevention Act Review Process Triggered by Detections of Bentazon in Ground Water

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Formal Review Process and Regulatory Changes

The Director suspended all products containing bentazon in March 1989, following its detection in ground water throughout the rice-growing region of the Sacramento Valley. Concurrent with cancellation proceedings, the department also initiated the Pesticide Detection Response Process. Following public hearings in 1989 and 1990, the PREC subcommittee found that bentazon use had polluted ground water and, to prevent further pollution, recommended banning its use on rice, limiting its use on the remaining labeled crops, and listing it as a restricted material. In June 1990, the Director concurred with the subcommittee’s findings and, among other actions, banned the use of bentazon on rice as well as in Humboldt and Del Norte counties. In 1991, the Director modified the suspension order to allow use of specified products provided that use complied with the newly adopted bentazon regulations.

Current Regulatory Status

While the use prohibitions on rice and in Humboldt and Del Norte counties continue, in 2004, DPR expanded the areas where certain pesticides, including bentazon, were regulated and adopted mandatory mitigation measures to protect ground water. Called “ground water 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 ground water, 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 ground water. In addition, pesticides regulated as ground water 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 Ground Water Protection Areas