Oil and gas drilling can usually protect groundwater when enough effort is taken to install well casings and cement them properly. But even those safeguards may fail in karst formations, as the Bureau of Land Management's experience in New Mexico shows.
"Rancher Stacey Mills realized something was wrong when his cattle started falling sick and dying. Half of his 70,000 acres in the southwestern corner of New Mexico drew from an aquifer that had the cleanest, sweetest water. But tests in 2006 revealed that his water well was contaminated with brine.
A month earlier, EOG Resources Inc. had begun disposing of brine, a waste product of drilling oil and gas wells, in an abandoned oil well nearby. It was never established that the EOG brine had polluted the aquifer; the leak was sealed before officials tested for links between the well and the aquifer, Mills said. An EOG spokeswoman stressed that tests did not show communication between the brine well and aquifer. But in an effort to be a good neighbor, the company built Mills a new water well on his property and the infrastructure to go along with it."