Oil drilling in Los Angeles has been associated with asthma, heart disease and low-birthweight babies. Close to 300,000 people in Kern County reside within a mile of an oil well.

If you were to parachute into Kern County about 40 miles west of Bakersfield, you might doubt California’s status as a national leader on climate. Pumpjacks spread out in every direction across a hellscape scraped bare of anything green. Scattered at irregular intervals, spires of latticed steel reach up more than a hundred feet, secured with guy-wires: evidence of hydraulic fracturing, a practice sufficiently infamous that its household nickname, fracking, invokes images of tap water so toxic you can light it on fire.

Fracked oil wells are everywhere on this southeastern extreme of the San Joaquin Valley, hard by the leeward side of the San Andreas fault. Big oil companies such as Chevron and Mobil began hydraulically fracturing wells here in earnest during the late 1970s, after the OPEC embargo made oil expensive and scarce. Drillers learned that by injecting a powerful slurry of chemical-laden water and sand into sedimentary rock, they could blast under played-out conventional wells and squeeze out oil left trapped in fissures, or could access reserves that traditional drilling otherwise couldn’t. (They could also inject acid into a certain kind of petroleum-bearing rock to dissolve it, another “well stimulation” method less common, but just as controversial, as hydraulic fracturing.)

Environmentalists and community activists have long lobbied for a statewide ban on fracking, arguing that the unique chemical cocktails that make up fracking fluids present novel risks to human health. “Given what we know about fracking’s dangers, [banning it] is just a no-brainer,” says Hollin Kretzmann, a staff attorney with the Center for Biological Diversity. But up until two year ago, no one but the drillers even knew where fracking was happening.