A group of 21 scientists from around the country has told Gov. Jerry Brown that California is on the right track with proposed regulations to allow fracking of the state's shale oil reserves.

The letter sent to Brown on Wednesday follows last month's release of proposed stimulation/hydraulic fracturing regulations for public comment. The governor in September signed a law that laid out parameters for the regulations.

Fracking, or the injection of a mixture of water, sand and various chemicals at very high pressure, is used to extract otherwise hard-to-reach oil and gas in shale and rock formations. The new regulations require drillers to notify neighboring landowners at least 30 days before using hydraulic fracturing techniques and to test their water wells upon request. Drillers also must do other groundwater monitoring and disclose chemicals used.

"California has always been at the forefront of environmental protection, and the state’s recent passage of new regulations governing the safe use of hydraulic fracturing technology is certainly part of that tradition," said a letter in favor of the proposed regulations. Signers include UC-Berkeley climate scientist Richard Muller and Stephen Holditch, head of the Department of Petroleum Engineering at Texas A & M, and a past member of a U.S. Department of Energy's advisory board on the safety of shale development.

"The key, in our view, to leveraging the opportunity of shale into a “win-win” for both the economy and the environment is to insist that stringent regulation govern development at each and every stage of the process," the letter says. "We believe the balance that you and the Legislature have worked to strike in California represents a model that can be replicated all across the country."

Tom Williams, a retired oil field specialist and fracking critic, said he had not yet seen the full text of the scientists' letter. But he questions the group's contention that the draft regulations offer adequate environmental protections in areas where fracking would take place.

The regulations "are too timid," said Williams, who as a member of the energy committee of the Sierra Club's local chapter has lobbied for tougher regulations. "The problem is that these regulations don't do enough to ensure that, because (drillers) don't want to spend the money."

The public comment period ends Jan 15.

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Councilmen Propose L.A. Moratorium on Fracking