Updated Oct. 1, 2019, 9:28 a.m. ET
Half a dozen men in hard hats watch as their construction rig rises more than 100 feet. On top, an American flag flutters in the sun. At the work site in Adams County, Colo., northeast of Denver, the crew is preparing to close off an abandoned well.
Instead of drilling a mile beneath the surface to extract oil, they're about to rip pipe out of the ground. In its place, they'll leave concrete plugs strong enough to seal the hole permanently.