Senate Bill 4, authored by state Sen. Fran Pavley, D-Agoura Hills, proposes disclosure measures and permitting of the decades-old practice of pumping acid down an oil well, sometimes at high pressure, for maintenance or production purposes.

The bill is partly a response to environmentalists’ questions about acidization’s safety and potential impacts on groundwater.

“The public knows very little about the use of acidization to stimulate oil production, in fact, less than we know about hydro-fracking,” Bill Allayaud, director of government affairs for the Washington-based nonprofit Environmental Working Group, wrote in an email.

Pavley’s bill, passed by the state Senate in late May and now working its way through the Assembly, is essentially an extension of the Legislature’s efforts to regulate fracking, even as state officials craft new rules on the controversial practice.

The discussion is important to Kern County’s economy not only because acidization is used here in the heart of West Coast oil production, but also because it has been cited by local operators as a potential key to unlocking the vast Monterey Shale oil formation beneath the southern Central Valley.

Oil industry trade groups say they are unaware of any risks related to acidization beyond the need for proper handling of the corrosive liquid. They note that hydrochloric and hydrofluoric acid are commonly used to clean out oil wells.

Apart from well maintenance, acid is sometimes poured down oil wells to make petroleum-bearing rock formations more permeable and, therefore, more productive. Some companies also pump it underground at high pressure to crack open oil deposits, similar to fracking.

Only in the latter case of pressurized “acid fracturing,” industry representatives say, should the practice be regulated under the bill.

“Hundreds of businesses use acid for routine maintenance. It is used in thousands of public pools every day. The acid is neutralized when it comes into contact with the reservoir and is no longer acid or hazardous and does not pose a risk,” California Independent Petroleum Association CEO Rock Zierman wrote in an email.

State regulators have reacted to the proposed rules on acidization much as they did when the Legislature first considered regulating fracking a few years ago. That is, they emphasize that although they don’t track the technique’s use, they ensure wells are built so that anything going up or down a bore doesn’t enter groundwater.

In a July 22 letter to lawmakers, the director of the state Department of Conservation, Mark Nechodom, described a number of oil field “well stimulation” techniques, including some involving the use of acid. He noted that while the department’s Division of Oil, Gas and Geothermal Resources does not collect data on well stimulation techniques, that may change as the department weighs new rules on fracking and other procedures.

Separately, DOGGR chief Tim Kustic wrote in an email Tuesday that his agency has “no reported evidence of damage or harm” caused by acidization.

Regardless, Pavley’s bill would treat acidization the same way it would fracking, which injects water, sand and sometimes toxic chemicals underground at high pressure to release hard-to-get petroleum deposits.

As currently proposed, the bill would require an independent scientific study of well stimulation, “specifically including acidization and fracking,” by Jan. 1, 2015. It would mandate full disclosure of fluids used in such procedures, though not their precise concentrations so as to protect trade secrets. This information would be made available publicly.

The bill would also force oil companies to obtain a permit for well stimulation, and require DOGGR to notify the public and regional water boards of well stimulation plans at least 30 days in advance.

It would institute follow-up water quality testing on water wells and surface water and impose fines of between $10,000 and $25,000 a day for violations.

Tupper Hull, vice president of the Western States Petroleum Association, called Pavley’s bill “a work in progress.” He wrote in an email that the trade group will stay involved in discussions about what types of well stimulation techniques the legislation would cover.