Extracting fossil fuels from underground reservoirs requires so much water a Chevron scientist once referred to its operations in California’s Kern River Oilfield “as a water company that skims oil.” Fracking operations use roughly 1.5 million to 16 million gallons per well to release oil and gas from shale, according to the U.S. Geological Survey. All that water returns to the surface as wastewater called flowback and produced water, or FPW, contaminated by a complex jumble of hazardous substances in fluids injected to enhance production, salts, metals and other harmful elements once sequestered deep underground, along with their toxic breakdown products.