On Thursday, the Center for Biological Diversity urged California officials to release results from an investigation into thousands of oil industry injection wells in the Los Angeles area that may be contaminating water and threatening public health.

“State oil officials need to come clean about this dirty threat to L.A.’s water supplies,” said Hollin Kretzmann, a Center attorney. “Gov. Brown’s administration has already admitted allowing other oil wells to dump waste into clean water. But this new investigation suggests an even wider oil pollution risk during the worst drought in state history. It makes no sense to sit on information that’s so vital to the public health. The results should be made public immediately.”

The state’s scandal-plagued oil agency recently assessed more than 2,000 injection wells in the “Cypress District” — composed mainly of L.A.-area oilfields — for risks to public safety and water and other natural resources, according to a letter last week from the state to the U.S. EPA. The Cypress District was studied first because oil industry injections in this area pose the highest risk, state officials told the federal government.

But the assessment is being held for administrative review, shielded from public view, even as oil companies continue injecting oil waste and other fluid into the wells under investigation. Oil wastewater commonly contains high levels of cancer-causing benzene, according to oil companies’ own tests.

The L.A. injection well investigation was mentioned by state oil officials in a July 15 letter to the EPA. The letter sought to explain the Brown administration’s efforts to bring California’s regulation of the oil industry back into compliance with the federal Safe Drinking Water Act. California officials have admitted that thousands of other injection wells across the state are operating in protected aquifers, in violation of federal and state law.

In the new letter to the EPA, state officials reveal they’ve investigated whether L.A.-area injection wells have been drilled into protected water supplies, have been properly assessed for mechanical integrity to safeguard against leaks, or have fractures or other conduits that would allow toxic injection fluids to migrate to underground water. But the letter says nothing about the investigation’s results.

The investigation also tried to assess whether staff at the Division of Oil, Gas and Geothermal Resources have the proper training, tools and resources to enforce the federal Safe Drinking Water Act and protect water supplies from toxic oil waste.

A recent California Council of Science and Technology study found “significant concerns” regarding the state’s protection of underground sources of drinking water from oil industry pollution.

The state also admitted in the letter that it mistakenly stripped federal protections for 10 of 11 aquifers that contain high-quality groundwater. Nonetheless, state officials intend to allow illegal injection into these aquifers to continue until December 2016. The state’s top oil official resigned several weeks ago in the wake of lawsuits over his failure to prevent oil companies from contaminating protected aquifers.

“Californians deserve to know what’s going on with these injection wells in L.A.,” Kretzmann said. “It doesn’t do anyone any good to keep the results secret but, instead, becomes simply another disturbing chapter in the Brown administration’s scandalous failure to protect California’s water from oil industry pollution. The more we learn the worse things look for our state.”

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