Colorado city looks to tap water from abandoned mines
The city of Aurora, CO released details of a plan for a $125 million purchase of underground water at the defunct London Mine complex south of Breckenridge. If the plan is approved it would help supply water to a fast growing metro area while helping the state deal with environmental problem of old mines draining acid metals-laced muck into streams.
The Denver Post reported that discharges from that mine for years have contaminated Denver’s and Aurora’s South Park watershed with cadmium and zinc.
The deal, if Aurora council members approve it, would give Aurora up to 5,400 acre-feet of fresh water — enough for 30,000 new residents. Aurora Water would pump the water up from an underground reservoir that holds 100,000 acre-feet of water beneath the mine, perched along the Continental Divide, using two 1,000-feet-deep stainless steel wells.
By lowering the clean water in that reservoir and preventing it from reaching exposed rock in mine tunnels, which creates a sulfuric acid mix that leaches out cadmium and zinc, Aurora could prevent further degradation of streams and fish life.
In Colorado, mountains and rivers on the heavily mined western half of the state carry 80 percent of total water. Less than 20 percent of Colorado residents live in the western half. People are concentrated on the eastern side of the mountains, where nature allocated 20 percent of the water.
Denver Water for more than a century has changed the balance by using tunnels to divert water from west to east, moving it under mountains. Aurora Water relies on a similar system to serve a growing urban expanse east of Denver, delivering 50,000 acre-feet of water. Aurora has pioneered advanced water cleaning, building a $250 million treatment plant, and reuse of water discharged below Denver into the South Platte River and blended with mountain water stored in a dozen reservoirs.
For years, the London Mine was a major producer of gold along with silver, lead and zinc from 1874 into the 1940s. It closed in 1991.
Colorado Department of Public Health and Environment officials cited the London Mine for violating discharge permit limits in 2009, 2011 and 2013. CDPHE and state natural resources officials previously had intervened to try to stop the contamination by installing a water treatment plant — but it failed. In 2016, CDPHE officials hit the estate of the deceased mine owner with a $1.1 million fine for polluting South Mosquito Creek.
Denver-based MineWater took over the ownership and obligations that year and began work to reduce the pollution. MineWater water president Joe Harrington, who also worked to contain the Gold King Mine disaster after a U.S. Environmental Protection Agency crew triggered a blowout in 2015, said he saw similarities at the London Mine.
MineWater workers rerouted a flow from behind a concrete bulkhead plug previously installed in the mine, separating water from exposed rock.
“We went into the mine and changed the plumbing,” Harrington said.
By October 2017, concentrations of cadmium and zinc were reduced significantly so that water flowing from the mine helps, rather than hurts, the creek.