California Water Code Clean up & Abatement
Agricultural and Food Processing Facility, Central Valley, California
JJ&A is the primary environmental contractor responsible for addressing the requirements of a Clean Up and Abatement Order (CAO) for a 77-acre agricultural and food processing facility in the San Joaquin Valley, California. Facility wastewater was discharged to a percolation pond and lands regulated under Waste Discharge Requirements (WDRs) issued by the Central Valley Regional Water Quality Control Board (CVRWQCB). The CAO requires delineation of the lateral and vertical extent of groundwater impact resulting from historic facility operations and evaluation of potential remedial actions to address those impacts.
JJ&A developed a preliminary conceptual site model to identify data gaps. we conducted studies and investigations to fill those data gaps supporting completion of remedial investigations, feasibility studies, and remedial action objective analyses in compliance with the CAO.
Investigation and Clean-up
The Site is underlain predominantly by unconsolidated fluvial and lacustrine deposits which contain an Upper Aquifer and Lower Aquifer separated by an Aquitard. The Upper Aquifer is impacted with elevated total dissolved solids (TDS). Irrigation practices in the area and extensive groundwater extraction from deeper aquifers has resulted in a significant downward vertical gradient in the area. The CVRWQCB required our client to evaluate the potential for historic wastewater discharges to impact the Lower Aquifer and off-site properties. JJ&A designed a comprehensive investigation to address this concern. Lower Aquifer work included:
- Age dating young groundwater through a sulfur hexafluoride and chlorofluorocarbon (SF6/CHC) study,
- Typing water quality indicating the Upper and Lower Aquifers have different geochemical signature,
- Completing a large scale comprehensive regional groundwater study including the review of 453 well completion reports and chemical data to determine regional water quality,
- Installation of lower aquifer wells to characterize vertical groundwater gradients and chemistry,
- Geophysical logging to further refine the lithologic mapping of the site,
- Evaluation of off-site potential sources, and
- Identification of the extent of impact and migration pathways.
The JJ&A data collection and analysis activities were used to refine the preliminary conceptual site model. The results indicated the facility was not the source of elevated TDS in the Lower Aquifer. This supported completion of the Lower Aquifer CAO requirements.