Record of Decision System (RODS)
BUNKER HILL MINING & METALLURGICAL COMPLEX
|Site Name:||BUNKER HILL MINING & METALLURGICAL COMPLEX|
|City & State:||SMELTERVILLE ID 83837|
|NPL Status:||Currently on the Final NPL|
|Contaminant:||Antimony, arsenic, lead, cadmium, mercury|
Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.
The Bunker Hill Mining & Metallurgical Complex, non-populated areas Operable Unit 2 (OU), is located in Kellogg, Idaho. The Bunker Hill Mining and Metallurgical Complex site encompasses 21 square miles along Interstate 90 in the Silver Valley area of Shoshone County in northern Idaho. The site includes the now active Bunker Hill Mine and the inactive metallurgical and smelting facility (together called the Bunker Hill Complex), and the cities of Kellogg, Pinehurst, Smelterville, and Wardner. These cities have a combined population of over 5,000.
The site has widespread contamination from mine tilings, emissions from the Bunker Hill smelter complex, and blowing dust from tailings piles and other barren areas. Barren hillsides and open areas within the site contribute to erosion and blowing dust problems. Extensive soil contamination remains in the residential areas in the above mentioned communities as well as the surrounding non-populated areas. There are high lead levels in house dust. There is also extensive heavy metals contamination of groundwater and surface water because of historical mining activities and continued leaching of metals from mine and mill wastes.
In 1917, the Bunker Hill lead smelter began producing lead, cadmium, silver, and alloys of these heavy metals. In 1928, an electrolytic zinc plant was also put into production. Smelter and zinc plant operations resulted in fugitive and stack emissions of metals and sulfur dioxide.
In September 1973, a fire in a pollution control device (bag house) at the lead smelter operated by Gulf Resources and Chemical Corporation (Gulf) resulted in a dramatic increase in emissions. In the first three months of 1974, approximately 73 tons of lead per month were emitted into the environment.
In 1974, the average blood-lead level for children under 12 years of age within the site boundaries was 65 micrograms of lead per deciliter of blood. This average is over six times the Centers for Disease Control and Prevention (CDC) current level of concern. Excessive amounts of lead in the body has been linked to impaired neuro-behavioral development, kidney damage, anemia, and hypertension, especially in children.
Health studies were initiated and emergency measures were taken at the site in the late 1970s. The Bunker Hill facility was closed in 1981. To date, the bulk of the Smelter Complex has been demolished and the Closure Cap area is being constructed. Environmenal Protection Agenct (EPA) is beginning the removal of contaminated soils from the surrounding gulches for consolidation under the Closure Cap.
Environmental Protection Agency (EPA) selected treatment for materials exceeding the Principal Threat Material (PTM) action levels in the 1992 ROD. PTMs were defined as contaminants which would be expected to induce symptomatic health effects, requiring emergency treatment, to an exposed individual based on a 70 mg/day soil ingestion rate for a short duration. There are five metals identified as PTMs: antimony, arsenic, cadmium, lead and mercury. Materials contaminated with these metals, but at concentrations below the threshold criteria, were to be consolidated without treatment beneath the Smelter Complex Closure Cap.
The original ROD selected cement based stabilization of materials above threshold criteria. After treatment, the PTMs were to be disposed of in an on-site unlined landfill. During the remedial design process for the Industrial Complex Closure in late 1995 and early 1996, EPA identified an alternative option to stabilization/fixation of PTMs. Complete containment was identified as a possible alternative option to stabilization/fixation of PTMs. Complete containment was identified as a possible alternative which would provide long-term protectiveness and overall protection of human health and the environment. Containment satisfies all applicable or relevant and appropriate requirements. Containment has several advantages over cement based stabilization, including a 90 percent reduction in cost, faster implementation, and fewer on-site worker exposure concerns. The containment design will also allow for potential reprocessing of materials as technology develops. Since all of the above advantages can be realized without treatment, EPA is modifying the stabilization remedy of PTMs to containment in a separate, completely enclosed cell beneath the Closure Cap.
|Remedy:||This Record of Decision Amendment (RODA) changes a component of the selected remedial action for the non-populated areas operable unit of the Bunker Hill site. The ROD for this operable unit, signed on September 22, 1992, required treatment of all PTMs at the site. This RODA will require containment of all PTMs, except mercury, in a fully lined monocell rather than treatment followed by capping. Mercury contaminated material will still be treated prior to disposal. Unlike the containment proposal evaluated in the 1992 ROD which called for consolidation of PTMs and placement under a simple, surficial cap, this amended remedy will completely isolate the PTMs from the environment, including groundwater, thereby being protective of both human health and the environment. Containment satisfies all applicable or relevant and appropriate requirements. The containment design will also allow for potential future reprocessing of materials as technology develops. All other elements of the selected remedy in the original ROD are unchanged.|
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