“Injection wells have proliferated over the last 60 years, in large part because they are the cheapest, most expedient way to manage hundreds of billions of gallons of industrial waste generated in the U.S. each year. Yet the dangers of injection are well known: In accidents dating back to the 1960s, toxic materials have bubbled up to the surface or escaped, contaminating aquifers that store supplies of drinking water. There are now more than 150,000 Class 2 wells in 33 states, into which oil and gas drillers have injected at least 10 trillion gallons of fluid. The numbers have increased rapidly in recent years, driven by expanding use of hydraulic fracturing to reach previously inaccessible resources.”