Remediation measures at the Triumph Mine have functioned as anticipated to reduce heavy-metals pollution in groundwater, from tailings piles and in local soils, but liquid discharge from the tunnel still does not meet water quality standards, the Idaho Department of Environmental Quality stated in a five-year review report released this month.
“At this time, mine water disposal alternatives are being evaluated,” the department stated. “This work should continue in order to discharge the mine water according to the requirements of the Clean Water Act.”
The mine along the East Fork of the Big Wood River in central Blaine County operated from 1882 until 1957, producing silver, zinc and lead, then left tailings and water discharge contaminated with heavy metals, including arsenic, zinc and manganese.
In 1993, the U.S. Environmental Protection Agency proposed to designate the area as a Superfund cleanup site. However, following opposition to that idea from local residents, the project was taken over the next year by the Idaho Department of Environmental Quality. An agreement between the two agencies includes a requirement for a review of the effectiveness of remediation measures every five years.
In 2003, a 16-foot-thick concrete plug was installed deep in the mine tunnel to block the flow of debris and metal-contaminated water. In 2016, DEQ installed a second plug closer to the tunnel entrance to further reduce the flow of water and the concentration of pollutants.
According to the recent report, discharge from the mine tunnel has decreased from 90 to 190 gallons per minute before the first plug was installed to 6 to 8 gallons per minute now.
That water flows through a pipe into an underground rock-lined “infiltration basin,” though it sometimes rises to the surface. Water also enters the basin from a pond east of the lower tailings pile. It is then discharged to a channel that connects to the East Fork of the Big Wood River during spring runoff.
In September 2018, the Idaho Conservation League filed a lawsuit against DEQ and the Idaho Department of Lands, which owns some of the land at the site, alleging violations of the federal Clean Water Act, which prohibits the “discharge of any pollutant” into rivers unless authorized by a National Pollutant Discharge Elimination System permit. Under a settlement arranged on Oct. 1, 2018, the two agencies agreed to install two new wells for monitoring groundwater.
In October 2018, water samples showed that levels of antimony, arsenic, iron and lead exceeded Idaho’s groundwater quality standards and federal drinking water standards. However, in January 2019, samples showed metals concentrations at or below Idaho’s groundwater quality standards, the federal drinking water standards and the Triumph Mine remediation goal.
Sampling of the East Fork of the Big Wood River is also required by the ICL settlement agreement. In October 2018 and June 2019, samples were collected from a location upstream of the site and a location downstream of the site below the alleged discharge. The review report stated that downstream metals concentrations were not significantly different than the upstream concentrations, and did not exceed Clean Water Act standards.
“These results suggest the site and alleged discharge are not impacting the East Fork Wood River at the downstream sample location,” the DEQ stated in the report.
As part of the settlement agreement, DEQ and the Department of Lands submitted an application to the EPA for a pollution-discharge permit on Sept. 24, 2019. The permit application is being processed at this time, DEQ stated in the review report.
“Monitoring the mine pool Triumph Mine tailings piles site, tunnel discharge, ground water and surface water quality, and new seeps or discharges will be necessary over the long term,” the report states. “Additional evaluations are needed to identify and select an approach to complete tunnel closure.”
In an emailed statement, the ICL expressed satisfaction with the monitoring process.
“We believe that the settlement agreement ICL reached with DEQ and IDL last October has put the state on the right path to remediating the Triumph mine site,” ICL Central Idaho Conservation Associate Josh Johnson said. “As DEQ’s five-year review document details, DEQ and IDL have applied to EPA for a permit for the discharge of mining-impacted waters and have been doing additional monitoring at the site to ensure that the local ground and surface water is being adequately protected. We have confidence that those additional remediation measures are a significant step in the right direction at Triumph.”
Johnson said ICL will continue to monitor the state’s remediation efforts.
In addition to the water discharge, soil contamination has also been a matter of concern at Triumph.
Thirty homes adjacent to the mine complex make up the unincorporated town of Triumph, which has about 65 residents.
An upper tailings pile occupies about six acres and a lower tailings pile occupies about 22 acres, with an estimated total volume of 680,000 cubic yards of mine waste.
According to the review report, people were being exposed to heavy metals by ingesting soil, breathing dust, drinking water and eating homegrown vegetables, or through dermal exposure. Contaminated soil was removed from 19 residential yards, three community roads and six road shoulders. Tailing deposits in wetlands were removed. Tailings and waste-rock piles were graded and capped.
“The remedy for residential soils is functioning as intended,” the report states. “Contaminated soils have been removed and disposed of on site, and barriers have been created that encapsulate contaminated material remaining at the site. These actions have broken the exposure pathway from contaminated soil to humans. Inspection found no evidence of damage to barriers in residential properties.
“The tailings capping remedy is functioning as intended. Inspections of the upper and lower tailings piles ensure that the barrier stays in place. When problems are identified, repairs are completed to maintain the integrity of the clean soil cap. No significant deficiencies in the barriers were noted despite the extended period of permanent pond overflow during the 2017 spring snowmelt.”
The DEQ is seeking public comments on its five-year review. The report is available on the agency’s website, deq.idaho.gov/news-archives/waste-triumph-five-year-review-1019/.
Comments can be submitted on DEQ’s website or by mail or email to:
Don Carpenter, Senior Mining Scientist, Idaho Department of Environmental Quality, DEQ State Office, 1410 N. Hilton St., Boise, ID 83706
Email: don.carpenter @deq.idaho.gov
Comment deadline is Nov. 8.