Recycled oil field wastewater is clean, Chevron test results show

Results of the most recent testing of recycled oil field wastewater that Chevron sells to Kern County farmers for irrigation showed no traces of methylene chloride, an industrial solvent that had appeared in previous testing conducted by a clean water advocacy group.

Chevron sells 21 million gallons of treated oil field wastewater per day to the Cawelo Water District, which provides water to 90 Kern County farmers. Before releasing it to the district, Chevron treats the wastewater in settling ponds and other processes designed to remove contaminants.

Chevron officials have said that the recycled water is clean and complies with state regulations. On Wednesday, the company said its program provides water for the “benefit of California agriculture.”

Samples collected by the water advocacy group, Water Defense, raised concern that methylene chloride, which is a toxic chemical, was present in water used on thousands of acres of farmland in the Central Valley. The group’s tests detected significant levels of methylene chloride in samples collected both in 2014 and last March from the water district’s distribution canal. Acetone, also a solvent, was also detected in samples taken in 2014.

The company, however, contested Water Defense’s testing methods and the results of its analysis, which used water collected from various depths and taken over a long period of time. Scott Smith, who collected the sample for Water Defense, has said his methods provide a more complete analysis than standard tests.

In April, the Central Valley Regional Water Quality Control Board, which oversees Chevron’s oil field wastewater recycling program, ordered comprehensive screening of the irrigation water to check for the presence of chemicals used in oil production.

Chevron’s test results were provided to the board in reports submitted June 15 and June 26 and in a subsequent report this week that specifically contained data about methylene chloride.

Chevron’s previous lab results showed the recycled water contained small amounts of potentially harmful chemicals, including acetone and benzene, a carcinogen. This week’s results reported that the lab did not detect methylene chloride in any of the samples provided.

In a statement Wednesday, Chevron said the presence of acetone in earlier tests was probably the result of natural biological processes. “We know of no operational source of acetone within Chevron’s oil field processes in the San Joaquin Valley,” said Chevron spokesman Cam Van Ast.

All test results to date, including those conducted by Water Defense, show that water supplied by Chevron to the Cawelo Water District is in compliance with the company’s permit from the water board.

julie.cart@latimes.com