But measures that control the toxic discharge are in place, according to an EPA report given in Dolores last week.
And based on known mine data, safety officials say the risk of a major blowout due to a backup – like what happened at the Gold King Mine into the Animas River – is relatively low.
Mining at the Argentine Mine Complex is long abandoned, but the hard-rock tunnels are still there reaching miles back into the Rico Mountains.
Year after year, rain and snowmelt pass through the passages accumulating unnaturally high levels of heavy metals from the rock.
Known as acid mine drainage, the polluted water flows out the collapsed St. Louis Tunnel just north of Rico, then enters into a series of 11 settling ponds that effectively drop out the heavy metals.
When the water is released back to the river, it is within federal clean water safety standards for fish and humans, reports show.
EPA project manager Steve Way explained that all of the mine tunnels in the Argentine complex are directed to flow out the St Louis tunnel exit.
“A lot of work has been done to manage the mine drainage there over the last 15 years,” he said. “Controls are in place, and are being improved.”
For example, a concrete plug at the nearby by Blaine tunnel was installed that directs drainage to the St. Louis exit point, instead of into Silver Creek.
Still, officials estimate there is between 1.2 million gallons and 1.7 million gallons of water within the mine tunnel complex. However, much of the water is in tunnels below the elevation of the river and is naturally filtered through the ground.
The rate of flow out of the St. Louis Tunnel averages 600 gallons per minute, and can peak at 1,000 gallons per minute.
How do you know there is not a back-up of mine waste occurring? is a common question.
To determine if that is happening, Way said the agency monitors the rate of discharge from the St. Louis tunnel. They compare it with past years to determine if there is a major change indicating a back-up somewhere in the tunnels.
Flow meters and pressure monitors have also been installed at the St. Louis mine exit that measure if a back-up might be occurring. The devices broadcast conditions via satellite to safety officials.
“We know in real time if there are any changes,” Way said. “The flows are consistent with long standing historic monitoring. We don’t see evidence of blockage creating a large impoundment.”
Flows out of St. Louis go up during spring snowmelt and heavy rain periods. Officials would be alerted if flows suddenly went below historic levels, indicating a possible back-up or collapse.
To handle a back up of water and prevent a blowout, two high capacity well pumps, each able to pump 1,250 gallons per minute, will be installed this summer at the St. Louis tunnel. A smaller pump is already in place.
“Should the need arrive, we will be able to extract water,” Way said. “The goal is to have them set on a trigger, where at a certain level they will automatically fire up.”
Reclamation of the mine and the settling ponds is ongoing, he said, and is mostly being paid for by Atlantic Richfield Company.
Meanwhile in nearby Ophir, the Carbonero Mine has been leaking 1-4 cubic feet per second of toxic acid waste, according to the Colorado Department of Natural Resources.
The Denver Post reports that flows from the Carbonero mine spread zinc at levels up to 8,000 parts per billion. Officials plan to install a $500,000 bulkhead the would prevent a blowout and stop 75 percent of the metals leaking into a creek, a tributary of the San Miguel River.
jmimiaga@the-journal.com
