EPA Region 10 Stevens County Wellpinit
5th Congressional District Other Names:
Last Update: May, 2010
Midnite Mine is an inactive open-pit uranium mine located on the Spokane Indian Reservation in rural Stevens County. Uranium-bearing rock exposed due to mining are a source of radiation, and acid rock drainage has mobilized heavy metals. EPA completed a Remedial Investigation/Feasibility Study and proposed a cleanup plan in 2005. The cleanup decision was documented in a Record of Decision in September 2006. Litigation to determine liable parties concluded in 2008. As of 2009, pursuant to a CERCLA order, the mining companies are continuing interim water management and performing pre-design studies, and they have installed a fence to restrict human and animal exposure. Negotiations for remedy design and implementation are in progress.
Dawn Mining Company ("Dawn") developed Midnite Mine in 1955 and operated it until 1981. Newmont Mining Corporation ("Newmont"), a US mining conglomerate, holds the majority interest in Dawn. Ore was hauled off the reservation by truck for processing at Dawn's mill in Ford, Washington, 25 miles east of the mine. During mine operations, about three million tons of 0.2 percent uranium oxide ore, 2.5 million tons of low grade ore (protore), and approximately 33 million tons of waste rock were dug up from six pits. Waste rock was dumped in piles and used to backfill pits, build haul roads, and contour the surface.
Today, unreclaimed piles of waste rock and stockpiles of ore and protore are visible on the more than 320 acres disturbed by mining. Two open pits contain water collected at several seeps (where water emerges at the foot of the largest waste rock pile), water flowing into the pit, and surface water runoff. The remaining pits are backfilled with waste rock from the mine.
Since 1992, to reduce impacts to surface water, Dawn has been collecting seep water, pumping it to the open pits, and treating the pit water. The water is treated on-site and discharged, under an NPDES permit, to a surface drainage. Sludge from the water treatment process is taken by truck to the mill in Ford. Until recently, the sludge was processed to extract uranium and disposed of in a lined tailings disposal area, TDA-4. The mill license was modified in 1999 to allow the sludge to be disposed directly in TDA-4 without processing. The Washington Department of Health is overseeing closure of the mill under the Uranium Mill Tailings Radiation Control Act. The mill building was demolished in 2004, and other steps in the mill cleanup are planned or in progress.
Studies by the U.S. Bureau of Mines and the U.S. Geological Survey documented that seeps, groundwater, and pit water at the mine are contaminated with heavy metals and radionuclides. In April 1998, EPA completed an Expanded Site Investigation (ESI), that confirmed elevated levels of metals and radionuclides in many on-site sources. Several seeps not currently captured by Dawn's collection system were found to contain elevated metals and radionuclides. These seeps and shallow groundwater emerge in drainages which lead to Blue Creek, which flows into the Spokane River arm of Lake Roosevelt.
Blue Creek is an important spawning and nursery area for rainbow trout and other fish, including the Paiute sculpin, a species of special concern in the State of Washington. The site is also associated with Palustrine (marshy) wetlands.
Site Responsibility: This site is being addressed through federal and potentially responsible parties' actions.
NPL Listing History
Threats and Contaminants
This site is currently being addressed by EPA under the Superfund program.
The Bureau of Land Management (BLM) scoped a mine reclamation EIS under NEPA. In 1998, while EPA finished the Expanded Site Investigation (ESI) referenced above, Newmont collected limited data under an agreement with BLM, pending negotiations for a comprehensive study. In February 1999, a fund-lead Remedial Investigation/Feasibility Study (RI/FS) began. Mining company data mostly collected on-site under an agreement with BLM was still being gathered and evaluated. For this reason, the first phase of EPA's study focused on establishing background conditions for ground water, surface water, and stream sediments, and on potential off-site impacts to these media. Data were collected for the first phase in fall 1999 and spring 2000.
The second phase of RI data collection started in fall 2000, and was completed in fall 2001. Mining company data were incorporated in scoping the work. Field work included surface material sampling for metals and radionuclides, gamma radiation surveys, radon and radon flux measurements, geotechnical data collection, and limited additional samples to provide adequate basis for statistical analyses of Phase 1 data. Evaluation of the data included slope stability reports, an evaluation of radiological equilibrium, determination of background levels for comparison to site data, and calibration of a groundwater model.
EPA worked with the Spokane Tribe on scoping the assessments for both human health and ecological risk. Tribal exposure scenarios required adjustments to many exposure assumptions typically used. EPA developed and screened site remediation alternatives with stakeholder input. In summer 2004, following a formal dispute raised by the Spokane Tribe, EPA initiated a facilitated process to resolve the disputed issues with the Tribe. A series of facilitated meetings were concluded in May 2005.
Separately from the RI/FS, EPA initiated a non-time-critical removal action to dig up uranium ore spilled in past years along the public road used to haul ore from Midnite Mine to Dawn Mill. Dawn excavated the roadside ore and backfilled with clean material in September and October 2004, removing the material from the public right of way. The work was performed under EPA and Tribal oversight, pursuant to an administrative order on consent. The excavated ore at Midnite Mine will be handled with other mine waste as part of the overall site cleanup.
In September 2005, EPA published the Remedial Investigation and Feasibility Study reports, as well as the ecological and human health risk assessments. In addition, EPA issued the "Proposed Plan" summarizing the RI/FS and indicating EPA's preferred alternative. The initial 30-day public comment period was extended to a total of 105 days, ending January 18, 2006. Several meetings were held during the comment period to answer questions about the Proposed Plan and to take public comment.
The preferred alternative described in the Proposed Plan was a modification of Feasibility Study Alternative 5a.
EPA's cleanup plan (called the Selected Remedy) was documented in a Record of Decision dated September 29, 2006, with concurrence from the Spokane Tribe. The Selected Remedy calls for excavation of waste (including waste rock, ore and protore, gravel, and sediments) from the site surface and containment of the waste in the two large open pits. The two pits will include wells, an engineered drainage layer, and low permeability liners, and the backfilled waste will be covered with a vegetated soil cover. An existing area of waste-rock filled pits will also be graded and covered, and wells installed. Covering the waste will prevent direct contact and reduce radiation and radon levels at the surface, and will minimize surface water infiltration through the waste. Groundwater entering the pits will be removed and pumped to a water treatment system, to minimize the formation of acid drainage. Contaminated water will be treated using barium chloride and lime precipitation to remove metals and radionuclides, then discharged to the Spokane River Arm of Lake Roosevelt under a NPDES permit. Sludge from the treatment process will be disposed at a commercial facility off site. Institutional controls will permanently restrict certain activities in waste containment areas, while health advisories will be needed until cleanup objectives are met in groundwater, sediments, and surface water.
Prior to the Record of Decision, EPA held public meetings at the reservation at least twice annually to update community members on site progress and to hear their concerns. Since then, informal meetings have been held to discuss community concerns. Many of EPA's actions have been in the context of enforcement (litigation, order for interim water management, and RD/RA negotiations) and updates have been limited to media releases to the Spokane Indian Tribe’s newspaper, Rawhide. A local community group, the SHAWL Society, worked with support from TOSNAC (Technical Outreach Services for Native American Communities) and others on raising community awareness of radiation impacts and site cleanup plans.
In 2005, the United States Department of Justice filed a claim against Dawn Mining Company (Dawn) and Newmont USA Limited (Newmont) for EPA study costs. The trial took place in July 2008 and concluded with a judicial order finding Dawn, Newmont, and the United States each liable for one third of study and cleanup costs. EPA issued a CERCLA 106 Order in November 2008 requiring interim water management and other actions. This measure was necessary in part because a provision in the license for Dawn's nearby mill site, which allowed water treatment waste to be disposed of in the mill's tailings disposal area, was scheduled to expire at the end of 2008. The Washington Department of Health has since extended the provision through 2010, at which time mill closure is expected to preclude further use of the tailings disposal area. In 2009, however, in compliance with the 106 Order, Dawn and Newmont installed fencing around the mined area to reduce human and game animal exposure to radiation and contaminated water. In addition, Dawn and Newmont undertook testing of water treatment processes which may remove uranium from the water, generating waste that does not require disposal as low-level radioactive waste. The 106 Order calls for interim measures to reduce contaminant loading and for implementation of priority pre-design investigations.
Work under the 106 Order is ongoing. Ion exchange pre-treatment was tested to take uranium out of the water before the lime precipitation process (to produce a sludge that does not require disposal as low-level radioactive waste) and modifications to the treatment process are anticipated. In addition, field work begins in 2010 for design investigations and for interim improvements to the water management systems, to reduce impacts to Blue Creek.
In May 2009, EPA sent "special notice letters" to initiate negotiations with the responsible parties. The letter included a draft CERCLA consent decree and statement of work for remedial design and remedial action (RD/RA). If successful, negotiations will lead to design and implementation of the Selected Remedy. Negotiations are ongoing as of May 2010.
Public meetings and more frequent updates will resume once remedial design is underway.