A draft of the third five-year review report for the Triumph Mine tailing piles site indicates that remedies for addressing contaminated soils and standing water on the two tailings piles are functioning as planned and that nearby wells are not being impacted by mine waste.
The site in the East Fork valley consists of two mill tailings piles associated with former lead, zinc and silver production that occurred from 1882 to 1957. During processing, the ore was crushed and ground, and the residual waste material was conveyed as slurry into two piles.
The two tailings piles are located on the valley floor immediately north of the East Fork of the Wood River. Also included in the site are a mine portal and a former processing area adjacent to the tailings piles.
Under an agreement with the U.S. Environmental Protection Agency, the Idaho Department of Environmental Quality is required to issue reviews of site cleanup efforts every five years because contaminants remain on-site and may pose potential risk. The agreement was reached as an alternative to placing the site on the EPA’s Superfund list.
According to the report, the piles were graded to ensure runoff and capped with a minimum of 6 inches of soil. The cap was then seeded to create a vegetative cover. The vegetated soil cap serves as a barrier to reduce exposures to people and the environment and contaminant migration. A 12-inch soil cap buffer was created on the tailings piles that are directly adjacent to residential yards and where there is no physical barrier such as a road or fence between the residential yard and the tailings pile.
Excavation of contaminated soil materials and replacement with uncontaminated materials was performed on nearby yards and on unpaved roads and road shoulders.
The report also states that a mine plug aimed at reducing the load of arsenic and manganese moving from the mine into the wetlands and groundwater continues to limit water discharge volumes and is generally functioning as intended, though additional work is needed to ensure long-term functionality.
In a news release issued last week, the DEQ stated that the remedies are expected to protect human health and the environment upon completion of all remedial actions, and in the interim, exposure pathways that could result in unacceptable risks are being controlled.
The draft report is available for public review at DEQ’s state office in Boise and on the DEQ’s website.
The DEQ is seeking public comment on the draft report by May 28. Submit comments or questions online or by mail or email to Rob Hanson, mine waste program manager, Idaho Department of Environmental Quality, 1410 N. Hilton, Boise, ID 83706 or email firstname.lastname@example.org.