Over the last several decades, U.S. industries have dumped more than 30 trillion gallons of toxic waste - a volume roughly four times that of Utah's Great Salt Lake -- into injection wells deep beneath the earth's surface. These wells epitomize the notion of out of sight, out of mind, entombing chemicals too dangerous to discard in rivers or soil. The Environmental Protection Agency is responsible for overseeing this invisible disposal system, setting standards that, above all, are supposed to safeguard sources of drinking water at a time when water has become increasingly precious. Abrahm Lustgarten's series, “Injection Wells: the Hidden Risks of Pumping Waste Underground,” lays out in frightening detail just how far short regulators have fallen in carrying out that mission. His analysis of hundreds of thousands of inspection records showed that wells often fail mechanical integrity tests meant to ensure contaminants aren't leaking into water supplies and that companies repeatedly violate basic rules for safe disposal. EPA efforts to strengthen regulation of underground injection have been stymied time and again by the oil and gas industry, among the primary users of disposal wells. As the number of wells for drilling waste has grown to more than 150,000 nationwide, regulators haven't kept pace, leaving gaps that have led to catastrophic breakdowns. And Lustgarten's most surprising finding was that the EPA has knowingly permitted the energy industry to pollute underground reservoirs, handing out more than 1,500 “exemptions” allowing companies to inject waste and other chemicals into drinking water aquifers.