“We all live downstream,” as the saying goes, and that becomes more of a concern when abandoned mines are upstream, which is the case near the headwaters of the Dolores River.
North of Rico along the river is the Rico-Argentine Mine complex, left over from gold and silver mining efforts in the 1930s and ’40s.
For decades rain, groundwater and snowmelt laced with heavy metals have been flowing out of the St. Louis Tunnel, a collapsed entrance connected to mines on Telegraph Hill.
The primary contaminates of concern are elevated levels of cadmium and zinc, a health hazard for humans and wildlife, according to the Environmental Protection Agency.
The toxic water is supposed to flow through a series of 18 settling ponds, designed to separate out concentrated heavy metals. But the ponds, which parallel the Dolores River, have suffered from neglect and disrepair for years, until recently.
Beavers blocked culverts connecting the ponds in 2000, causing untreated mine waste to back up and overflow directly into the Dolores River. And the contaminated sludge that has settled to the bottom of the ponds has not been removed.
LEAK CONTAINED
Now, after years of environmental lawsuits, the EPA is leading a sustained cleanup project to ensure that Rico residents and the downstream communities of Dolores, Cortez, Towaoc and Dove Creek have a safe water source.
“We’re pushing forward and it has been progressing well. We’re learning a lot,” said Steven Way, EPA’s on-scene coordinator for the project. “The ultimate end-point for the completion of the water treatment system is the latter part of 2015.”
The massive cleanup operation has been ongoing since 2010, and involves three main components.
First, engineers implemented a plan to redirect water flowing through a network of mine tunnels and into the main St. Louis Tunnel, Way explained. It then flows out to the settling ponds and back to the river in a much cleaner state.
Other mine entrances have proven problematic. A coffer dam installed in 1983 inside the nearby Blaine Tunnel to the south was breached and at one point was draining water contaminated with heavy metals directly into Silver Creek, a tributary of the Dolores.
Rico draws its municipal water from Silver Creek at a point upstream from the leak, but it is considered a safe distance from the mine entrance.
The coffer dam is designed to direct flows to the lower St. Louis tunnel network and on to the settling ponds.
Way explained that blockages inside the Blaine Tunnel were causing water to pool, threatening to overwhelm the dam.
“It was contained, and the risk of (untreated mine discharge) was hopefully eliminated. But the dam could continue to deteriorate, so we will continue working on a solution there this summer,” he said.
WETLANDS FILTER
Another phase of the project is treatment of water before it flows out of the St. Louis Tunnel.
The in-situ treatment method is a process where engineers add solutions to mine water in the tunnel in an attempt to modify the chemical makeup of the water.
Original environmental mitigation had mine water flowing through a lime-filled silo to reduce acidity. Heavy metals were precipitated out before the water entered the pond system. However, the lime tower has been out of operation since 1996.
“The lime treatment is expensive to operate and maintain, and it generates a lot of waste,” Way said. “So we came up with another solution by creating wetlands that treat the water using bacteria. It is a reduction of heavy metals using natural biological processes.”
The results are promising, he said. Testing wells show the wetlands lower contaminates to near or within EPA clean water standards. However, more testing is ongoing to ensure the process will be effective.
“The challenge is to have it function year round,” Way said.
A third component of the project is dredging the ponds, drying the sludge and depositing it into a soil containment repository to be built on site.
“Removing the solids from the ponds increases their storage capacity,” he said. “Construction on the soil repository will begin next year. Right now sites are being evaluated. It will look more like a landfill, with different layers.”
According to EPA documents, a temporary drying facility was constructed at the site and 7,500 cubic yards of pond sludge were deposited there.
Plans show the dried solids will be removed to a temporary storage facility, with the goal of construction a permanent one.
Regarding the previous breached flood berm separating the settling pond from the river, Way said it has been reinforced with riprap and is being monitored.
Vulnerable zones in the flood dike have been identified for fortification as well.
During its mining heyday a century ago, Rico sported 5,000 residents and the streets were lined with bars and brothels. Now about 200 year-round residents call this quiet mountain town home and they live every day with mining wastes nearby.
“We are so used to it by now, but is shows what a bad track record mining has for cleaning up,” says James Kahn, Rico town trustee. “It is nice to see it being dealt with. I hope they do it right and it is a long-term solution.”
