Driving the highway between Loving and Carlsbad on May 19, Jackie Onsurez noticed something unusual rising above an oilfield site operated by NGL Energy Partners. As he got closer, he realized the 70-foot plume was not smoke but a geyser of toxic oil field wastewater — known as produced water — erupting from a pipe. Onsurez, an engineer and member of New Mexico’s State Emergency Response Commission, immediately began calling NGL, 911, the New Mexico Environment Department and local officials. A roughneck arrived moments later and tried unsuccessfully to stop the spray. “The only people with protective gear were the...