The thiobencarb exceedances at the Colusa Basin Drain 5 (CBD5) site north of Highway 20 are beginning to decline. Two special monitoring events took place north of the CBD5 site as a result of the five drain exceedances on May 19, 21, 26, 28 and June 2. On May 27, the City of West Sacramento had a detection of thiobencarb below the secondary maximum contaminant level. All remaining city intake and Sacramento River results were non-detect through June 4.
We will evaluate the thiobencarb monitoring results and the final water hold release dates before determining whether to wrap-up the monitoring season the end of this month, later into July. The increase in thiobencarb use as a result of severe drought conditions along with the impact of less water in the drains adds to the challenge of managing the Rice Pesticide Program.