The State Water Resources Control Board (SWRCB), in collaboration with the U.S. Geological Survey (USGS), has published new reports from the ongoing Regional Groundwater Monitoring Program (RGMP), focusing on the Placerita oil field and Elk Hills-Coles Levee areas. These reports aim to investigate potential groundwater contamination related to oil field operations, using data collected since 2018.
The report on Elk Hills-Coles Levee evaluated samples from 34 wells and found minimal evidence of contamination, particularly from thermogenic gases or hydrocarbon volatile organic compounds (VOCs). However, it raised concerns about legacy waste disposal practices, where old surface discharge methods could have residual impacts on shallow groundwater. These practices, once common and legally permissible, may require further study to fully understand their long-term effects.
The report in its entirety can be viewed here.
In the Placerita Oil Field, groundwater sampling detected low levels of petroleum hydrocarbon VOCs in 4 of the 13 samples collected. Importantly, these concentrations were well below drinking water standards, with none exceeding 0.5 µg/L.
The reports call for additional monitoring, including more sampling and new monitoring wells, to provide a clearer picture of whether oil field activities, particularly fluid migration, are affecting groundwater. These efforts will help determine the overall impact of oil extraction operations on groundwater quality.
The RGMP was established under SB 4 and has been collecting data since 2018 to assess the influence of oil field operations on groundwater. More details on the program can be found here.