Department of Environmental Quality work crews have cleared a new tunnel collapse at the Triumph Mine in East Fork and released 30,000 gallons of toxic water into a surge pond reservoir.
It is the latest of efforts to secure 200 million gallons or more of toxic mine drainage in numerous tunnels in the abandoned mine.
A recent federal court case will ensure that more regular monitoring of mine waste discharge is undertaken by state agencies
From 1882 until 1957, the Triumph Mine—northeast of Hailey—produced silver, zinc and lead, and left tailings and water discharge from the mine tunnel contaminated with the heavy metals. In 1988, the DEQ found elevated levels of arsenic, zinc and manganese in nearby surface water.
In 2003, a 16-foot-thick plug was built 1,175 feet deep in the mine tunnel. But despite the plug, 10-20 gallons per minute continued to leak from the tunnel in 2016, more than twice the four gallons per minute measured by DEQ in 2004.
DEQ installed a second plug in 2016 after discovering a tunnel collapse about 285 feet deep in the mine that backed up more than 1 million gallons of water from the tunnel entrance, making inspection of the 2003 plug impossible.
“Ultimately, we would like to completely eliminate the flow of water,” said DEQ Mine Waste Program Specialist Don Carpenter in 2016. “If we can’t do that, then we want to improve the quality of water that flows out.”
Carpenter, now serving as DEQ mine waste program scientist, said Tuesday that the new tunnel collapse occurred 125 feet from the tunnel entrance. He said clearing the collapse released about 30,000 gallons into a 1.7 million-gallon surge pond.
“We were concerned that if we did not remove the collapse, the water could have come surging out,” he said. “Clearly, the pond would have captured the water, but flows would have increased from the mine.”
Carpenter said the surge pond has an excess capacity of 250,000 gallons during normal operations. He said he now thinks it would be “next to impossible” to stop all the toxic drainage from leaking through rock fissures around the plugs.
Carpenter said work is continuing at the mine through Dec. 21 to push concrete into fissures to reduce leakage, and the second plug is working “as expected.” He said the current level of discharge from the mine is seven gallons per minute.
The Idaho Conservation League filed a lawsuit in federal court in September asking that the DEQ and the Idaho Department of Lands be prohibited from discharging polluted water from the Triumph Mine unless it obtains a permit under the federal Clean Water Act.
Bryan Hurlbutt, a staff attorney for Advocates for the West, said a settlement was reached in the case in October that requires DEQ to acquire a National Pollutant Discharge Elimination System permit that establishes acceptable levels of discharge from the mine.
Hurlbutt said DEQ is in the process of acquiring the permit, installing two new groundwater wells for water testing and starting more regular testing of water from the tunnel. DEQ and the Department of Lands are also required to post warning signs about contaminated water at the site and consider building fences in certain areas.
After the settlement was reached, the case was dismissed, Hurlbutt said.
Some work to meet the settlement requirements have begun. Carpenter said no metals typically found at the mine site were detected in the East Fork of the Big Wood River on Oct. 23.
Carpenter said water was tested on Oct.17 in the surge pond for arsenic, the only substance of human health concern tested for on that day.
“The water from the surge pond met groundwater quality standards,” he said.