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SAN FRANCISCO- Almost 3 billion gallons of oil industry wastewater have been illegally dumped into central California aquifers that supply drinking water and farming irrigation, according to state documents obtained by the Center for Biological Diversity. The wastewater entered the aquifers through at least nine injection disposal wells used by the oil industry to dispose of waste contaminated with fracking fluids and other pollutants.

The documents also reveal that Central Valley Water Board testing found high levels of arsenic, thallium and nitrates – contaminants sometimes found in oil industry wastewater – in water-supply wells near these waste-disposal operations.

“Clean water is one of California’s most crucial resources, and these documents make it clear that state regulators have utterly failed to protect our water from oil industry pollution,” said Hollin Kretzmann, a Center attorney. “Much more testing is needed to gauge the full extent of water pollution and the threat to public health. But Governor Brown should move quickly to halt fracking to ward off a surge in oil industry wastewater that California simply isn’t prepared to dispose of safely.”

The state’s Water Board confirmed beyond doubt that at least nine wastewater disposal wells have been injecting waste into aquifers that contain high-quality water that is supposed to be protected under federal and state law.

Thallium is an extremely toxic chemical commonly used in rat poison. Arsenic is a toxic chemical that can cause cancer. Some studies show that even low-level exposure to arsenic in drinking water can compromise the immune system’s ability to fight illness. “Arsenic and thallium are extremely dangerous chemicals,” said Timothy Krantz, a professor of environmental studies at the University of Redlands. “The fact that high concentrations are showing up in multiple water wells close to wastewater injection sites raises major concerns about the health and safety of nearby residents.”

The Center obtained a letter from the State Water Resources Control Board to the Environmental Protection Agency. The letter says that the Central Valley Regional Water Board has confirmed that injection wells have been dumping oil industry waste into aquifers that are legally protected under the federal Safe Drinking Water Act. The state Water Board also concedes that another 19 wells may also have contaminated protected aquifers, and dozens more have been injecting waste into aquifers of unknown quality.

The Central Valley Water Board tested eight water-supply wells out of more than 100 in the vicinity of these injection wells. Arsenic, nitrate and thallium exceeded the maximum contaminant level in half the water samples.

While the current extent of contamination is cause for grave concern, the long-term threat posed by the unlawful wastewater disposal may be even more devastating. Benzene, toluene and other harmful chemicals used in fracking fluid are routinely found in flowback water coming out of oil wells in California, often at levels hundreds of times higher than what is considered safe, and this flowback fluid is sent to wastewater disposal wells. Underground migration of chemicals like benzene can take years.