BY

In August of 1981, the Central Valley Regional Water Quality Control Board detected the herbicide bentazon (Basagran’) in a water well located at a pesticide applicator washdown site in Glenn County. This detection was reported to the California Department of Food and Agriculture (CDFA) in 1986 as required by the Pesticide Contamination Prevention Act of 1985. As part of its policy to investigate such historical data as time and resources permit, the CDFA sampled to verify the presence of bentazon residues in well water and determine whether they were due to legal agricultural use of bentazon. After it was determined that residues resulted from agricultural use, expanded monitoring was conducted to determine the extent of contamination. Samples were collected from 190 wells between December of 1988 and April of 1989. Wells were sampled in 14 rice growing counties with reporte