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Record of Decision System (RODS)
EAGLE MINE
Abstract
| Site Name: | EAGLE MINE |
| Address: | W OF US HWY 24 |
| City & State: | MINTURN/REDCLIFF CO 81657 |
| County: | EAGLE |
| EPA ID: | COD081961518 |
| EPA Region: | 08 |
| NPL Status: | Currently on the Final NPL |
| ROD Type: | Record of Decision |
| ROD ID: | EPA/ROD/R08-93/068 |
| ROD Date: | 03/29/1993 |
| Operable Unit(s): | 01 |
| Media: | GW |
| Contaminant: | VOCs |
| Abstract: | The Eagle Mine site is an abandoned mining and milling facility located near Minturn, Eagle County, Colorado. The boundaries of the site are defined as the areas of past mining activity between the towns of Red Cliff and Minturn. The site includes the Eagle Mine Workings; the town of Gilman; the mine tailings pond areas of Rex Flats, Rock Creek Canyon, and waste rock; and roaster pile areas. The site borders the White River National Forest, which includes the Holy Cross Wilderness Area, to the south and west and lies along the banks of the Eagle River, which also has been affected by contamination from the site. Rex Flats, a former wetland, lies across from an area known as the Old Tailings Pile (OTP). Another tailings disposal pile, the New Tailings Pile, is known as the Consolidated Tailings Pile (CTP). The Maliot Park wetland, which is along Cross Creek, also has been affected by surface water and ground water flowing from the site. Residents of Minturn use both area wells and Cross Creek for their drinking water supply. Mining operations at the site began in the 1870s. In the early 1900s, the New Jersey Zinc company consolidated a number of these workings and operated these as Eagle Mine. In 1966, the company merged with Gulf Western. Eagle Mine workings are underground and, at the turn of the century, ores were processed by roasting. Residues from this process were left in five roaster piles, three of which are located on the west side of Eagle River and two on the east side. Later a mill was constructed to process ores. Mine tailings were slurried down valley and deposited at the OTP and the Rex Flats area, and some were left under the slurry line, probably as the result of accidental spillage. When the OTP area was filled, the slurry line was extended northwest, and the CTP was created. Tailings and polluted water runoff from the CTP deposited metals in the adjacent Maliot Park wetlands. As a result of this runoff, ground water in Rex Flats, the Old and New Tailings Piles and the Maliot Park wetlands area have been contaminated; and the Eagle River has been impacted by site contaminants. In 1983, the property was sold, and then subsequently in 1984, the mining operations were abandoned. In 1981, fluid containing PCBs was drained from three transformers located in an abandoned portion of the mine; however an estimated 28 lbs of PCB remained. In 1984, EPA conducted an emergency removal at the site for all but the three previously noted transformers from the mine. In 1988, the State ordered several PRPs to conduct site remediation under a remedial action plan (RAP), which included the following major provisions: plugging the mine audits and grouting fracture zones to flood the mine working to stop the generation of acid mine drainage; removing roaster piles; removing tailings from Rex Flats, the pipeline corridor, the toes of CTP, and the Old Tailings Pile; removing, consolidating, and capping contaminated Maloit Park wetland soil in the CTP; temporary ground water pumping at the CTP; and long-term monitoring of surface water, ground water, vegetation, soil, CTP settlement, and erosion; installing run-on diversion ditches at the waste rock piles; sitewide treatment of underlying soil for pH adjustment; removing or isolating soil with high lead levels, with re-vegetation of disturbed areas; implementing temporary surface runoff and run-on controls at Rex Flats, OTP, and CTP along with an upgradient ground water diversion ditch at CTP; removing the historic pond on top of CTP, and constructing a lined surge pond at CTP; diverting lower Rock Creek; disposing of contaminated water at the site; regrading and stabilizing the CTP; installing an Eagle River gauging station; and connecting the Pierson house to the municipal water supply. In 1989 and early 1990, concentrations in the Eagle River were extremely high. Later in 1990, the State and the PRP amended the RAP and added a chemical water treatment plant; a second lined surge pond; a mine seepage collection system; expanded ground/surface water monitoring; annual contaminant loading report; temporary sludge disposal at CTP; Rock Creek grouting and evaluation; and OTP ground water reduction. Additionally, the State continues to pursue additional cleanup measures under a Consent Decree, including improvement of mine seep collection, removal of additional roaster material, and revegetation of disturbed areas. In 1991, EPA notified the State about site violations to the Clean Water Act stemming fromvarious mine seeps and discharge from the Roaster Pile. This ROD addresses the principal sources of mine waste pollution, including the onsite tailing material, contaminated ground water, and surface water, as OU1. A future ROD will evaluate and address the potential health risks at the site, including the potential windblown metals deposition in the south end of Minturn and the Minturn Middle School area, the potential future risk of metals in soil and waste rock in the Town of Gilman, and the potential contamination of private drinking water wells in the Minturn area, as OU2. The primary contaminants of concern affecting the debris, ground water, and surface water are metals, including arsenic, chromium, and lead. SELECTED REMEDIAL ACTION: The selected remedial action for this site includes installing a system to collect additional mine seepage along Rock Creek; diverting Rock Creek upgradient of the contaminated mine seepage; completing the cap on the CTP and installing engineering controls to divert surface water; relocating the Town of Minturn drinking water wells; continuing treatment of contaminated mine seepage and leachate/ground water from the CTP at the wastewater treatment plant; dewatering the resultant sludge from the treatment process, with onsite disposal in cells on the CTP; removing onsite contaminated soil and sediment from wetland areas, with addition of top soil and revegetation; monitoring ground water, surface water, biota, and the mine pool; conducting leachability tests on the waste rock; and implementing institutional controls, including deed restrictions. The estimated present worth cost for this remedial action is $17,374,400, which includes an estimated annual O&M cost of $ 1,922,623 for 10 years. PERFORMANCE STANDARDS OR GOALS: Soil remediation goals for lead are based on the EPA Interim Guidance for Establishing a Soil Level for Lead of 1,000 mg/kg. Chemicalspecific ground water cleanup goals are based on State standards, and includearsenic 50 ug/l; cadmium 10 ug/l; chromium 50 ug/l; lead 50 ug/l; and mercury 2 ug/l. Surface water cleanup goals are based on State standards, and include cadmium 1.1 ug/l; copper 12 ug/l; lead 4 ug/l; silver 0.07ug/l; and zinc 106 ug/l. INSTITUTIONAL CONTROLS: Deed and ground water use restrictions will be implemented to ensure the long-term integrity of onsite structures and facilities and to prevent ground water use at the Rex Flats area. |
| Remedy: |
This Operable Unit, one of two designated for the Site, addresses the principal sources of mine waste pollution that are impacting the Eagle Riverand certain ground water resources. The purpose of this Operable Unit (OU- 1) is to control the transport of toxic metals originating from various sources to the Eagle River and to Site ground waters. The identified sources include the Eagle Mine, the Roaster Pile area, the Waste Rock Piles, Rex Flats, the Old Tailings Pile (OTP), the Consolidated Tailings Pile (CTP) and the Maloit Park Wetlands. The environmental receptors of concern are the fresh-water biota, particularly the Eagle River aquatic life. Human health concerns include potential impacts and possible re-entrained soils contamination from the CTPto children and employees attending the Minturn Middle School and to full- time residents who live adjacent to the school from wind-blown particulate matter from the Consolidated Tailings Pile (CTP). There are also human health concerns related to potential future contamination of the Town of Minturn drinking water wells. The major components of the selected remedy include: . Installation of a system to collect additional mine seepage along Rock Creek . Diversion of Rock Creek upgradient of contaminated mineseepage . Expediting revegetation in the area of Roaster Pile 1 and associated drainage, and monitoring of seep water quality below the Roaster Pile 1 area . Surface water run-off and ground water monitoring at the Waste Rock Piles, leachability tests on the waste rock, with evaluation of the data for possible future action . Development of an inspection and maintenance plan to ensure the long-term integrity of structures and facilities associated with the Eagle Mine Site . Implementation of use restrictions for ground water at the Rex Flats and OTP and accelerated revegetation at Rex Flats . Rapidly complete the cap on the CTP, drain and cap the historic pond, extract and treat leachate/ground water from the CTP extraction trenches, enhance CTP extraction trenches, construct a new up-gradient ground water diversion structure and relocate the Town of Minturn drinking water wells . Continue the treatment of contaminated mine seepage and leachate/ground water from the CTP at the Water Treatment Plant (WTP) until Site cleanup goals can be met without such treatment, dewater the treatment sludge, and dispose of the dewatered sludge in on-site lined cells on the CTP . Remove the contaminated soils and sediments from the Maloit Park Wetlands, control seepage from the CTP, and rapidly add topsoil and revegetate . Conduct regular monitoring of surface water, groundwater, mine pool, and biota at key locations on the Site and downstream of the Site to determine progress toward cleanup goals The components noted above represent the current selected remedy. EPA recognizes that there is ongoing research into alternate remedies and encourages the responsible party to continue this research. A separate Operable Unit, OU-2, has been established to evaluate additional potential human health risks at the Eagle Mine Site. These concerns relate to: the potential wind-blown metals deposition in the south end of Minturn and in the Minturn Middle School area; the potential future risk from metals in soils and waste rock in the Town of Gilman and; the potential contamination of private drinking water wells in the Minturn area. |
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