SAN FRANCISCO (AP) -- A top California oil and gas regulator has resigned amid questions about oilfield contamination of the state's water supplies.
Mark Nechedom, head of the Department of Conservation during an intensifying review of his agency's oilfield permitting by the U.S. Environmental Protection Agency, submitted his resignation Wednesday, and the state confirmed it Friday.
Nechedom gave no reason in his resignation letter but spoke of directing the department during a "difficult time."
Nechedom's three-year term at the department saw a federal investigation into improper state permitting of oil-industry operations in what were supposed to be off-limits water aquifers.
State officials acknowledged this year that the improperly permitted oilfield operations had contaminated federally protected drinking-water aquifers in Central California.
State officials had no immediate comment Friday.
Gov. Jerry Brown appointed Nechedom to lead the department in January 2012, at a time when oil companies were complaining that the state was slowing down permitting of oil-field operations with extended environmental reviews.
Brown later boasted publicly that his removal of Nechedom's predecessors had led to a speeding up of state permits for oilfield drilling.
An Associated Press analysis of state drilling records earlier this year showed that state regulators during Nechedom's tenure improperly granted hundreds of permits for oil companies to inject production fluids and wastewater into the federally protected water aquifers. The aquifers were supposed to be off-limits to oilfield activity because they were current or potential sources of water for drinking and irrigation.
The U.S. Environmental Protection Agency said the permits were granted in violation of federal safe-drinking water laws. The EPA this spring approved a state plan to gradually shut down all oilfield injections into protected water aquifers.
Nechedom's resignation came the same week that a group of Kern County farmers filed a federal lawsuit accusing oil companies and state officials, including Nechedom, of knowingly bypassing environmental laws so as to ease the way for oilfield permitting.
Evidence submitted with the lawsuit included an email between Nechedom and Kern County's planning director, as the state and local official allegedly talked of cooperating on handling environmental regulations and oilfield permitting in Kern County, according to the lawsuit.
In the email to the Kern County official, Nechedom joked he was happy "to have you and Kern Co. as a partner (unindicted co-conspirator?)."
State officials did not respond to questions Friday about the email, or whether it was related to the timing of Nechedom's resignation.
Farmers in the lawsuit allege that loosely regulated oilfield activities have polluted the groundwater supplies they use for irrigating crops.
State officials say they have no evidence that contaminants from the improperly permitted drilling have yet reached any active drinking-water wells.
This story has been corrected to show the state confirmed the resignation on Friday, not Thursday