From The Denver Post (Bruce Finley):
This re-engineering along headwaters of the Dolores River requires replanting wetlands with native grasses and laying in soil to mimic natural processes — an innovative approach that may be deployed more widely across the water-challenged West, where tens of thousands of toxic mines foul rivers and streams. So far, the experiment is working, removing fish-killing zinc, manganese linked to birth deformities and cancer-causing cadmium from muck flowing from the Argentine Mine complex uphill from Rico.
“Mining is what brought communities to life at the turn of the 19th century, but now residents and visitors would like to see these scars restored as much as possible — especially focusing on water cleanup,” San Miguel County commissioner Hilary Cooper said from her perch in Telluride, 22 miles north of the mess. “For many of these areas, human intervention is required to initiate the cleanup. But planning, which ultimately allows native vegetation, restored natural floodplains and the engineering skills of beavers to assist with the cleanup is generally preferred when possible. In the end, we will find it is more effective.”
Wildlife, including river otters, may be reviving in Rico because multiple factors favor environmental recovery.
First, federal agencies enforced laws. The Environmental Protection Agency in 2011 issued an emergency order compelling action to stop contamination of Dolores headwaters after state regulators and mine owners failed to get a grip. Then, EPA officials swiftly identified and enlisted a private company legally responsible for the mess — something agency officials haven’t done at other sites, including the Gold King Superfund district, where a potentially responsible corporation is fighting the EPA in court.
And the company, Atlantic Richfield — now owned by global energy giant BP — resolutely embarked on a cleanup, investing tens of millions of dollars. This compares with less than $5 million that the EPA has mustered for cleanup of the 48-site Gold King district above Silverton. For another Superfund disaster that the EPA declared in 2008 in Creede, federal funds have been so scarce that cleanup has barely begun.
In 2012, Atlantic Richfield contractors at Rico faced rising water inside mine tunnels that threatened a ruinous blowout. The St. Louis Tunnel, within a few hundred yards of the Dolores River, had collapsed and was oozing as much as 1,300 gallons a minute of toxic muck. A lime water treatment plant installed to neutralize sulfuric acid in the flow, churning out thousands of cubic yards a year of waste solids, wasn’t working. (The acid, private contractors later determined, is mostly neutralized by natural calcium deposits inside the tunnel before the muck flows out.) Cleanup crews also had to deal with eroding, unlined tailings ponds where rain and melting snow leached toxic metals into the river…
The innovative cleanup by Atlantic Richfield modernizes the standard approach of installing water treatment plants in the high country along with bulkhead plugs to try to control leaks. Contractors scooped out and lined the old ponds, planted grasses interspersed with stones and put in a sediment mix of manure, hay, alfalfa and woodchips — all aimed at filtering out toxic metals…
This massive experiment now covers 55 acres, closed inside fences and berms, below the newly dammed St. Louis Tunnel. The toxic muck still flows at rates fluctuating from 700 to more than 1,000 gallons a minute but now is channeled through three black tubes that carry the muck through the engineered ponds and wetlands.
In one pond, the toxic mine water seeps down vertically 2.5 feet through sediment, where chemical reactions help break out the manganese, zinc and cadmium. Native sedge and rush grasses are starting to grow atop that sediment layer. In other ponds, water is pushed through wetlands created using stones and grasses that grow naturally in the San Juan Mountain to filter out and chemically extract toxic metals.
Once contractors figure out which method or combination works best, they say they’ll seek EPA approval and then fully install engineered wetlands, eventually removing fences and roads.