Dawn Mining Company (State of Washington)
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1.0 Site Identification
|Type of Site:||Uranium Recovery Facility|
2.0 Site Status Summary
The Dawn Mining Company uranium millsite is about 800 acres. Dawn Mining Company operations for processing uranium ore at the Dawn Mining Company millsite ended in 1982. After the decommissioning and closure plan was approved in early 1995, progress has been made to decommission the site consistent with the approved plan. The mill building was decommissioned and buried in a lined tailings impoundment in 2003. Most of contaminated soil clean up has been completed. The only buildings that remain are part of the original office and shop complex. Demolition and burial of the remaining buildings is scheduled for 2014. The site is being decommissioned with concentration based criterion established 10 CFR Part 40, Appendix A and in Washington State uranium and thorium milling regulations, WAC 246-252. Based upon the approval date of the decommissioning plan, the soil regulatory standard, averaged over areas of 100 square meters, which, as a result of by-product material, does not exceed the background level by more than: 5 picocuries per gram radium-226 averaged over the first 15 centimeters below the surface or 15 picocuries per gram radium-226 averaged over 15 centimeters thick layers more than 15 centimeters below the surface. However, based on ALARA site specific dose risk analyses have been conducted to establish appropriate uranium soil cleanup levels.
As part of closure and reclamation, five passive evaporation ponds were constructed in 1995 over 110 acres over old tailings areas and constructed with 60 mil High Density Polyethlene (HDPE). Initially the five ponds contained a total of 600 acre feet of contaminated process solutions. Approximately 90 acre feet of contaminated water remains. In order for construction of the final radon barrier to proceed on schedule over the old tailings areas, a new lined evaporation pond was constructed off of the old tailings areas and the 90 acre feet of contaminated water transferred to the new pond summer of 2013. Three of the five evaporation ponds have been decommissioned and construction of the final radon barrier should be completed over the three ponds October 2013. The remaining two evaporation ponds over the old tailings will be decommissioned and final radon barrier completed summer of 2014.
3.0 Major Technical or Regulatory Issues
Two separate ground water contaminant plumes have been identified at the site. One plume is associated with the old unlined tailings, and the other plume is associated with ore stockpile area. The tailings plume is well characterized. The characterization of the ore stockpile plume is in progress. Once characterization of the ore stockpile plume is complete then remedial alternatives can be reviewed. The ground water plumes are hydraulically connected to Chamokane Creek, owned by the Spokane Tribe of Indians. The Spokane Tribe was granted authority by EPA to be treated as a State and set their own surface water quality standards. The Spokane Tribe's uranium standard for surface water is .3 pCi/l above natural conditions. Even though the uranium values in the creek are below drinking water standards established in the Safe Drinking Water Act, the uranium values exceed the .3 pCi/l standard. It is premature to set a final closure date for the Dawn Mining Company millsite until the remaining ground water and surface water issues are resolved.