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Kern County's South Belridge Oil Field is among the most productive in California.

A new study by the U.S. Geological Survey concludes oilfield activity has lowered the quality of groundwater in western Kern County, making it saltier and possibly affecting nearby irrigation sources but not harming drinking water.

The findings published this month in a technical journal of the American Association of Petroleum Geologists raise a red flag about local oil industry practices but do not point to any imminent government action on what has for years been a hot topic among California anti-oil activists.

Based on research required under a 2013 state law, the report by local geologist Janice Gillespie suggests local groundwater has mixed with waste fluid known as produced water, the naturally occurring saltwater that comes up from the ground with crude oil. It attributes the mixing to the common industry disposal means of surface ponds and injection wells.

Intermingling of wastewater and groundwater in the Lost Hills, North Belridge and South Belridge oil fields would appear to contravene federal and state regulations designed to protect aquifers containing groundwater deemed suitable for irrigation.

"This is the first time in this study we've seen direct evidence of disposed water migrating outwards from oilfield underground injection disposal wells in California," Gillespie, a former Cal State Bakersfield geology professor who has done consulting work for local oil companies, wrote in a news release from the State Water Resources Control Board.

The oil industry viewed the findings with varying degrees of skepticism. Two oil trade groups asked whether other factors may have contributed to the higher levels of salinity.

Data for the study were drawn from three kinds of wells: those used for oil production, others used for injecting produced water and groundwater monitoring wells.

A follow-up study expected to be released next year will use different methods to examine salinity in shallow groundwater near local oil fields and agricultural areas, the water board's news release said.

The water board's chief deputy director, Jonathan Bishop, said Gillespie's study may lead to additional studies.

"This study provides us with new information that the agencies will use to evaluate if additional groundwater investigations are warranted," he stated in the release.

Surface disposal of produced water puts the fluid into unlined pits, a seep-and-evaporate technique that has largely been phased out in California, with some exceptions in western Kern.

Injection wells, the leading alternative to surface disposal, are generally regarded as environmentally sound as long as an oilfield operator can demonstrate the aquifer where the waste is injected into is of relatively poor quality.

A major implication of the new study is that neither method has been entirely successful at keeping wastewater from spreading into areas where it's not wanted.

The U.S. Geological Survey, where Gillespie works, was contracted to perform the research by the water board, which was obligated to create a regional groundwater monitoring program by 2013's Senate Bill 4.

The Western States Petroleum Association said by email it supports scientific reviews of its operations and the environment and that the trade group is looking over the report to see if further analysis might be in order. President Catherine Reheis-Boyd emphasized groundwater near the three oil fields is not of high enough quality to be considered a source of drinking water.

Another oil trade group, the California Independent Petroleum Association, was more critical. Its CEO, Rock Zierman, faulted the methodology Gillespie used, saying the report failed to repeat warnings contained in other studies cited in her work.

He said the report did not consider whether other sources contributed to the elevated salinity. He added that it was unclear why the study did not cite extensive data gathered during the oil fields' history.

"Our heavily regulated industry operates responsibly under the toughest environmental protections in the world," Zierman said by email. "We support increased regulations when supported by strong science, but these overly generalized conclusions deserve further study rather than broad conclusions that will only result in unfounded public fear and confusion."

The study can be found online here:

John Cox can be reached at 661-395-7404. Follow him on Twitter: @TheThirdGraf. Sign up at for free newsletters about local business.

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