(LATimes) - The agencies charged with overseeing oil production and protecting California's ever-dwindling water sources from the industry's pollution all fell down on the job, one state official told a panel of peeved lawmakers Tuesday.

During a testy two-hour oversight hearing, officials from the California Department of Conservation, the department's Division of Oil, Gas and Geothermal Resources and the state Water Resources Control Board promised senators a top-down overhaul of their regulation of the disposal of oil field wastewater.

But after a handful of recent embarrassing revelations about the division's history of lackluster regulation, lawmakers questioned how they could trust agency officials to follow through, characterizing longstanding agency practices as corrupt and inept.

Sen. Hannah-Beth Jackson (D-Santa Barbara) called the division's failings "endemic" and said that just reading background materials to prepare for Tuesday's hearing caused her blood pressure to soar.

"There has been a serious imbalance between the role regulating the oil and gas industry and the role of protecting the public," Jackson said.

Division of Oil, Gas and Geothermal Resources officials admitted last summer that for years they inadvertently allowed oil companies to inject wastewater — from fracking and other oil production operations — into hundreds of disposal wells in protected aquifers, a violation of federal law. Disclosures by oil drillers show high levels of benzene, a carcinogen, in the water that comes out of the ground with oil. Benzene is naturally occurring but extremely dangerous.

So far, the state has shut down 23 of the hundreds of injection wells that are in aquifers not approved for waste injection.