Tom Knudson / The Sacramento Bee

SHAFTER, Calif. — One afternoon last fall, Tom Frantz cradled a videocamera in his hand and pointed it at an oil well on the edge of this San Joaquin Valley farm town.

Workers shuffled amid tanks and trucks, preparing the site for hydraulic fracturing — fracking, for short — the controversial drilling method that has the potential to spark an economic boom in California and perhaps even free the state from foreign oil.

But Frantz recorded something less promising: oily-brown waste spilled from a pipe into an unlined pit near an almond grove, followed by a stream of soapy-looking liquid.

“That was kind of shocking,” said Frantz, 63, a fourth-generation farmer. “We can’t live without fresh groundwater. It doesn’t take much to ruin that.”

This is not the first time oil companies have fracked wells in California.

Today, though, they are doing it more often and in more places to try to tap an enormous buried treasure called Monterey shale.

Stretching from Los Angeles north along the coast and into the San Joaquin Valley, the formation is not just another potential new source of domestic oil. It is the grand prize, the richest oil shale formation in America. If it can be fully exploited — and that is not yet clear — it is estimated to hold enough oil to create hundreds of thousands of jobs, flood the state with tax revenue and halt oil imports to California for a half-century.

But here in the manicured, mint-green farm country around Shafter — a modern-day Sutter’s mill on California’s new fracking frontier — that promise is already being clouded by conflict, pollution and fear.

Along once-quiet rural roads, residents complain about dust and noise from trucks and drilling equipment. Large metallic flares dot the countryside, burning off methane and other gases into one of the most polluted air basins in America.

Last year, one flare roared for months close to Walt Desatoff’s home outside Shafter. “I called it my loud, expensive porch light,” he said.

“We’d have to get away for a few days just to get to quiet. It was very unfortunate.”

The biggest concern is what can’t be seen: the high-pressure injection of fluids, some toxic, under aquifers and some of the richest farmland on earth. “If you ruin the water, who’s going to buy the crops?” asked Frantz.

The industry says there’s no reason for worry. “We can say — and say it confidently — that we’re not aware of any risk to California from this technology,” said Tupper Hull, spokesman for the Western States Petroleum Association.

Others, though, advise caution. “There is tremendous (scientific) uncertainty,” said Michael Kiparsky, associate director of UC Berkeley’s Wheeler Institute for Water Law and Policy and co-author of a recent report that found gaping holes in California’s regulation of fracking.

“California has historically been a leader in the governance of environmental issues” — but not fracking, Kiparsky said. “There is the opportunity to learn from other states and try not repeat their learning experiences.”

The report cited many possible remedies, such as banning the underground injection of liquid drilling wastes near risky earthquake faults and requiring that companies give advance notice before fracking and disclose all chemicals used in the process.

State lawmakers are scrambling to fill the void. This year, they introduced 10 fracking-related bills. Only one — focusing on public notice, disclosure and better monitoring — remains alive. The others died for a mix of reasons, including opposition from both the industry and environmentalists.

For some, including Desatoff, change can’t come soon enough. A retired businessman, he moved to rural Shafter in the early 1990s for its quiet pace of life. Now, he can smell the gassy odors and hear the million-mosquito drone of diesel equipment from his front porch.

“I’m not opposed to it,” he said. “We just need more control. Let’s do it right. Let’s do it safe. Let’s do where it’s monitored and (companies) are not just given carte blanche to do whatever they want.”

In response to growing national controversy, Occidental Petroleum Corp. and other companies began posting some details about fracking on an industry website,, in 2011. That site, which is voluntary, shows Kern County is the epicenter of fracking in California and the pace of activity is accelerating. In the first three months this year, more than 170 wells were fracked, mostly in Kern County, more than double the same period in 2012.

“Folks are looking eagerly at that resource,” Hull said.

Whether the shale can be fully tapped is uncertain because its geology is complex. But if so, fracking’s boom-time promise could spread more widely.

That’s because what lies beneath California is an oil shale whale, a 1,750-square-mile river of rock estimated to hold more than 15 billion barrels of oil — four times more than the Bakken formation in North Dakota, which has ignited a frenetic drilling boom and helped reduce the nation’s import of foreign oil to 45 percent in 2011.

California’s reliance on foreign oil, though, continues to climb. Last year, a record 51 percent of crude oil delivered to California refineries — about 314,000 barrels a day — came from Saudi Arabia, Iraq, Ecuador and other countries, according to California Energy Commission figures.

Hull said tapping the Monterey shale not only could reverse that trend but actually make California energy independent.

“The numbers are quite straightforward,” he said. “If you take 15 billion barrels and produce it at 600,000 barrels a day, there is enough to replace everything we import for about 50 years.”

Such a boom would deliver “huge benefits to California,” Hull said, including tens of thousands of jobs and billions in tax revenue.

But many wonder at what cost? High on the list of concerns are the chemicals companies inject into the shale, along with large volumes of water and sand, to free up its oil. They include compounds ranging from “generally harmless to extremely toxic,” the UC Berkeley study reported, including some known or suspected of causing cancer.

The industry’s Hull said the risk of contamination is low because fracking typically occurs more than a mile beneath the surface, far below the water table. What’s more, he said, fracking has a good environmental track record in the state.

“The technology has been in use in California for 60-some odd years,” he said. “There has never been an assertion or claim that we are aware of that hydraulic fracturing has posed a risk or harmed the environment in any way.”

Environmentalists say the industry’s clean slate comes with a caveat: Before reporting on “fracfocus” began in 2011, no one knew where wells were being fracked.

“They did this for five decades with basically no oversight,” said Bill Allayaud, California director of government affairs for the Environmental Working Group. “People could have pollution in their groundwater and we would have no idea.”

The controversial drilling method has experienced a boom on the West Coast — thanks to a vast shale deposit beneath the state — but farmers and environmentalists are worried.