Upper Blackfoot Mining Complex
The Upper Blackfoot Mining Complex (also known as the Heddleston district), 15 miles east of Lincoln, is an inactive mining district, greater than 50 acres in size, which was mined intermittently from 1889 to the 1950s and explored intermittently through the 1980s. Tailings and waste rock dumps and acid mine drainage from old adits have contaminated surface water, sediments, soils and groundwater. The main workings in the district are the Mike Horse Mine, which was a major contributor to surface water contamination; the Anaconda, Carbonate, Edith, Mary P and Paymaster mines; and a tailings impoundment on Beartrap Creek. In 1975, the impoundment failed during heavy rains and washed metal-laden tailings down the drainage into the upper Blackfoot River.
The mining district is located in a fairly remote area on and near national forest land which is used by hunters and other recreationists. One residence with a domestic well is located on Beartrap Creek above the tailings impoundment. No other residences are present within several miles. The mines are located in the headwaters of the Blackfoot River. The town of Lincoln, about 15 miles downstream, uses the Blackfoot River as a drinking water source.
The Montana Department of State Lands (DSL) completed an environmental assessment (EA) on the area in 1991. A 1991 state legislative action then transferred regulatory authority for the mining area from DSL to the MDHES CECRA program.
An August 1991 CERCLA preliminary assessment by MDHES summarized available information about site history and contamination.
In February 1992 MDHES notified ASARCO and ARCO that they are potentially liable persons (PLPs) for the site and directed them to conduct a remedial investigation/feasibility study (RI/FS). Consultants for the PLPs began conducting surface water monitoring and conducted a Phase I RI/FS sampling event in September 1992.
ASARCO and ARCO began a five year voluntary interim remedial action program at the UBMC in September 1993. The overall approach was to amend, revegetate and/or remove mine wastes and tailings and passively treat acid mine drainage in a wetland treatment system, which includes a pretreatment pond. The purpose of the pretreatment pond is to precipitate iron and associated metals so the iron will not plug the wetland treatment cells.
In 1993 the PLPs' contractors removed 14,000 cubic yards of mine waste and tailings from the Lower Carbonate Mine area, limed the wastes and placed them in a repository at the Upper Carbonate Mine. They built a stream diversion along the upper reach of Mike Horse Creek and began construction of the Mike Horse Mine treatability pond. They also reclaimed a reach of Mike Horse Creek adjacent to the treatability pond.
In 1994 the PLPs' contractors completed the Upper Carbonate repository and nearly completed reclamation of the Lower Carbonate area. Construction of the treatability pond continued, with installation of the pond liner and building of the pond spillway. A 318-foot section of Mike Horse Creek was relocated. Excavation and removal of hydrocarbon-contaminated soils at the Mike Horse Mine was completed. Preparation of the Mike Horse Mine repository base was completed. Approximately 7,300 cubic yards of waste material was removed from the Lower Anaconda Mine area and relocated to the Mike Horse Mine repository site. New monitoring wells were installed at the Anaconda, Carbonate and Mike Horse Mine sites.
Remediation activities completed from 1995 through 1997 include the following:
- Removal of the remaining Lower Anaconda mine waste and tailings.
- Removal of the Edith waste piles to the Mike Horse repository and revegetation of the Edith area.
- Completion of the Mike Horse repository.
- Completion of the Mike Horse treatability pond.
- Installation of alkaline drains and hydraulic seals in the Mike Horse and Anaconda adits.
- Construction of the Phase I wetland treatment cells at the Anaconda Mine site.
- Reclamation of the Upper Anaconda Mine and Middle Mike Horse Mine waste piles.
- Installation of a pipeline from the treatability pond to the wetland treatment cells.
- Treatment of acid mine drainage from Paymaster Mine with a small wetland treatment cell.
- Removal of mine wastes in lower Paymaster Creek to a repository.
- Revegetation of the Upper Mike Horse Mine area.
- Remediation of the Tunnel #3 area
- Remediation of the Capitol and Constallation mine areas.
The Montana Department of Environmental Quality Site Response Section has ranked the UBMC a high priority site.
During the fall of 1999 ASARCO petition the Montana Board of Environmental Review for temporary water quality standards for reaches of Mike Horse and Beartrap creeks and a portion of the upper Blackfoot River. Temporary standards for a period of 10 years were granted in May 2000.
The USDA Forest Service (FS) began negotiations for an Administrative Order on Consent with ASARCO to address the remaining contamination on FS lands within the UBMC area. The FS is now the lead agency for the site. Questions should be directed to Beth Ihle, Townsend Ranger District at (406) 266-3425.
