The U.S. Environmental Protection Agency announced three long-term goals Wednesday for cleaning up the Bonita Peak Mining District Superfund site in southwestern Colorado.

The goals call for improving water quality in four sections of rivers and streams, stabilizing mine waste piles to keep more pollutants from leaching into waterways and preventing big releases of tainted water from mine shafts.

The Superfund site was established after the EPA inadvertently triggered a massive spill of 3 million gallons (11 billion liters) of wastewater from the Gold King Mine in 2015, tainting rivers in Colorado, New Mexico and Utah with a yellow-orange plume carrying toxic metals. The Gold King is one of 48 mining-related sites included in the Superfund cleanup.

The goals are preliminary and could change, said Rebecca Thomas, the EPA’s team leader for the Bonita Peak district. The EPA will develop more specific objectives later, she said.

The water quality cleanup target areas include portions of the Animas River, the South Fork of Mineral Creek and Upper Mineral Creek. The goal includes meeting or exceeding state water quality standards and improving the habitat for fish and other aquatic life, said Doug Benevento, EPA’s regional administrator based in Denver.

The EPA has already outlined techniques it could use to waste sites from bleeding more contaminants into rivers. They include stopping erosion of waste piles, blocking rain and snowmelt from seeping through them, removing waste rocks from stream banks, dredging sludge from settling ponds and capping waste rock piles that people camp or hike on.

Stopping future blowouts from mine shafts is the toughest of the three goals, Thomas said. The options include installing bulkheads or barriers inside the mines to block or regulate the drainage.

Wastewater sometimes pulses out of old mines, but it’s impossible to predict when, Thomas said. The bursts could be caused by tunnel collapses or other events, she said.

Benevento said the EPA compiled the goals after meetings with community members in the district, which lies north of Silverton. He said he’s confident the agency will have enough money to continue the work.