A total of 532 injection wells are now suspected of dumping toxic wastewater left over from oil and gas extraction into protected clean water aquifer, according to California’s Water Resources control board.

This revelation follows an investigation into this practice first exposed by NBC Bay Area in November, 2014 . The Investigative Unit showed that state officials had been allowing oil and gas companies to dump dangerous chemicals into pristine underground aquifers that are federally protected by the Environmental Protection Agency (EPA).

At the time, only nine wells were known to be dumping their wastewater into protected aquifers in violation of federal EPA guidelines.

Most of those nine wells are located in or around Bakersfield in Kern County. Now California’s Division of Oil, Gas and Geothermal Resources (DOGGR), in an e-mail to the US Environmental Protection Agency, says the questionable injection wells number in the hundreds and are located all over the state. They appear near Santa Clarita, Santa Barbara, Fresno, Paso Robles and Los Angeles as well as Kern County.

In a letter to both California’s Water Resources Control Board and California’s Division of Oil, Gas and Geothermal Resources, the EPA demands that the state come up with a workable plan to halt this practice and bring this program of wastewater injection into federal compliance by February 15, 2017.

The EPA wants to see that revised plan by February 6, 2015.

The wastewater is a by-product of several processes used to recover oil and gas from deep underground, including the use of the controversial practice of hydraulic fracturing or ‘fracking.’

Fracking uses thousands of gallons of water mixed with chemicals and abrasives such as silica to break up rocks deep underground to free oil deposits within the rocks.

The toxic wastewater re-injected at these well sites went into what the state and the EPA call “non-exempt” aquifers. “Non-exempt” aquifers are underground bodies of water that tests show are clean enough that it could have been used by humans.

When the oil is brought up to the surface, it is mixed with this water and chemical mixture, separated and recovered. The industry must then dispose of the briny water mixed with chemicals. For decades, oil and gas companies were permitted to re-inject this wastewater into aquifers that already had higher levels of solids and chemicals in them, what the EPA refers to as “exempt aquifers.”

Now, as the Investigative Unit previously revealed , it’s known that state regulators issued permits for oil and gas companies to inject that same wastewater into aquifers that the EPA considered “non-exempt” or clean enough for human consumption.

The California Division of Oil, Gas and Geothermal Resources (DOGGR) admitted back in October that oil and gas companies were issued permits by the state to dump their wastewater in those protected aquifers.

“In multiple different place of the permitting process an error could have been made,” said Marshall. “When you’re talking about wells that were permitted in 1985 to 1992, we’ve tried to go back and talk to some of the permitting engineers, and it’s unfortunate but in some cases they’re deceased.”

“The state board can now confirm that these aquifers that should have been protected are now contaminated,” said Hollin Kretzmann, a staff attorney at the Center for Biological Diversity in San Francisco. “They’ve been contaminated over a number of years and the state has done nothing to stop that.”

“It’s high quality water. This water is suitable for drinking or irrigation,” added Kretzmann. “That’s a huge concern and communities who rely on water supply wells near these injection wells have a lot of reason to be concerned that they’re finding high levels of arsenic and thallium and other chemicals nearby where these injection wells have been allowed to operate.”

The state admits that some drinking water wells located nearby these injection wells have tested positive for higher than acceptable levels of toxic chemicals such as Arsenic, Nitrates and Thallium. They say that tests so far indicate those chemicals did not come from the injection of wastewater nearby.

“We are still comparing the testing of what was the injection water to what is the tested water that came out of these wells to find out if they were background levels or whether that’s the result of oil and gas operation, but so far it’s looking like it’s background,” said DOGGR’s Jason Marshall back in November, 2014.

In a statement issued to NBC Bay Area, Western States Petroleum spokesman Tupper Hull said “There has never been a bona fide claim or evidence presented that the paperwork confusion resulted in any contamination of drinking supplies near the disputed injection wells.”

Even so, the EPA is clearly concerned. They’ve set a 2017 deadline for California to completely fix the problem.