Study GW18: Groundwater Protection List Monitoring for 2,4-Dichlorophenoxyacetic Acid Herbicide
Abstract
This study was conducted in 2018 to determine if 2,4-dichlorphenoxyacetic acid (2,4-D) had migrated into groundwater in areas of California with moderate to high reported agricultural use or in areas identified as vulnerable to groundwater contamination. The California Department of Pesticide Regulation’s (DPR) Groundwater Protection Program (GWPP) sampled 60 wells located in eight California counties (Butte, Fresno, Kings, Merced, San Joaquin, Solano, Stanislaus, and Tulare). Of the 60 wells sampled, no wells had detectable concentrations of 2,4-D above the method detection limit (MDL).
Wells were also analyzed for other pesticides and degradates, resulting in 22 wells with detections of one or more known groundwater contaminants listed in Title 3 California Code of Regulations (3CCR section 6800[a]). Nineteen of these wells are located within Ground Water Protection Areas (GWPAs) and will not be investigated further since use of the detected pesticides is already regulated in these areas to protect groundwater. DPR will evaluate the three detections that are in areas where their use is not currently regulated to determine if further monitoring or regulatory action is required. All detections were below established drinking water quality standards.