DENVER — The U.S. Environmental Protection Agency on Thursday laid out the next steps it will take to clean up wastewater flowing from dozens of old mines in southwestern Colorado, including dredging contaminated sediment from streambeds and digging ditches to divert water away from tainted rocks and soil.
The work is part of the EPA's interim plan to keep toxic heavy metals from flowing into rivers while the agency searches for a more permanent solution under the Superfund program.
The interim plan concentrates on controlling or removing contaminants at 26 sites including campgrounds, mine waste piles, ponds and rivers. It will cost about $10 million and take up to five years, the agency said.
Five of the locations are recreation sites where people could be exposed to arsenic or lead, the agency said.
"EPA is interested in expediting cleanup so that we can show improvements in water quality wherever possible," said Christina Progess, manager of the Superfund project.
The cleanup was prompted by a 2015 wastewater spill at the inactive Gold King mine near Silverton. An EPA-led contractor crew was using heavy equipment to excavate at the mine entrance when it inadvertently triggered a blowout of 3 million gallons (11.4 million liters) of wastewater.
Rivers in Colorado, New Mexico and Utah were affected, as were Native American reservations.
The Gold King is not on the list of 26 sites chosen for interim work. The EPA said that's because a temporary treatment plant was installed two months after the spill and is cleaning up wastewater from the mine.
The Superfund cleanup will eventually cover 48 mining sites, but the EPA said it chose 26 for interim work to reduce human and environmental risks while a long-term solution is studied.
The EPA said the 26 sites have elevated levels of aluminum, cadmium, copper, iron, lead or zinc.
Two of the recreation sites on the list are campgrounds and three are parking areas or locations where people meet for tours, the EPA said. The plan calls for covering mine waste piles and contaminated soil with gravel or plant growth to reduce human exposure and keep the contaminants from being kicked into the air.
The other work includes dredging contaminated sediment from streams and from ponds near mine openings, and digging ditches and berms to keep water from flushing contaminants out of waste piles and into streams.
The EPA is seeking public comment on the plan. The deadline for comments is July 16.
The 2015 spill released a bright yellow-orange plume laden with arsenic, lead and other toxic metals into rivers. Municipal water suppliers and farmers temporarily stopped using the rivers, and some waterways were placed off-limits to anglers and boaters.
The EPA said the rivers quickly returned to pre-spill conditions, but state and local governments, businesses and homeowners have filed claims totaling more than $2 billion against the EPA for economic and property damage. The agency is reviewing the claims.