Crumbling mine tunnels awash with polluted waters perforate the Colorado mountains, and scientists may one day send robots creeping through the pitch-black passages to study the mysterious currents that sometimes burst to the surface with devastating effects. One such disaster happened at the inactive Gold King Mine in southwestern Colorado in 2015, when the Environmental Protection Agency accidentally triggered the release of 3 million gallons (11 million liters) of mustard-colored water laden with arsenic, lead and other toxins. The spill tainted rivers in three states.

Now the EPA is considering using robots and other sophisticated technology to help prevent these types of "blowouts" or clean them up if they happen. But first the agency has to find out what's inside the mines, some of which date to Colorado's gold rush in the 1860s. Wastewater laden with toxic heavy metals has been spewing from hundreds of inactive mines nationwide for decades, the product of complicated and sometimes poorly understood subterranean flows. Mining creates tainted water in steps: Blasting out tunnels and processing ore exposes long-buried, sulfur-bearing rocks to oxygen. The sulfur and oxygen mix with natural underground water flows to create sulfuric acid. The acidic water then leaches heavy metals out of the rocks. To manage and treat the wastewater, the EPA needs a clear idea of what's inside the mines, some of which penetrate thousands of feet into the mountains. But many old mines are poorly documented. Investigating with robots would be cheaper, faster and safer than humans.

"You can send a robot into an area that doesn't have good air quality. You can send a robot into an area that doesn't have much space," said Rebecca Thomas, project manager for the EPA's newly created Gold King Superfund site, officially known as the Bonita Peak Mining District. Instruments on the robots could map the mines and analyze pollutants in the water.

They would look more like golf carts than the personable robots from "Star Wars" movies. Hao Zhang, an assistant professor of computer science at the Colorado School of Mines, envisions a battery-powered robot about 5 feet (1.5 meters) long with wheels or tracks to get through collapsing, rubble-strewn tunnels. Zhang and a team of students demonstrated a smaller robot in a mine west of Denver recently. It purred smoothly along flat tunnel floors but toppled over trying to negotiate a cluttered passage.

"The terrain is pretty rough," Zhang said. "It's hard for even humans to navigate in that environment."

A commercial robot modified to explore abandoned mines - including those swamped with acidic wastewater - could cost about $90,000 and take three to four years to develop, Zhang said.