2008-06-18_REVISION - M1980244 (7)

Home Browse Search

The proposed reclamation plan for the Valley Leach Facility (VLF) does not appear to be protective of public health, property, and the environment. Specifically, the four (4) year monitoring period following rinsing may not be sufficient to ensure long -term geochemical stabilization of the heap prior to puncturing the protective liners, and we request an analysis substantiating the sufficiency of the selected monitoring period. Further, the proposed standard of .2 mg/1 CNWAp in the rinsate from meteoric water mobility testing on representative sampling of the spent ore, or in return flows derived from the detoxified ore, or both, does not appear adequate to protect public health, property, and the environment. While this numeric standard coincides with Colorado groundwater standards, it is far in excess of area surface water quality standards. Given the location of the VLF in Arequa Gulch and the subsurface mining structures and drainage tunnels directly underlying the VLF, the final cyanide standard for the heap must ensure compliance with all surface water standards. Further, the method for demonstrating compliance with any such standard should be clarified and improved to ensure long -term protection of water quality. In particular, any amended reclamation permit should ensure proper rinsing of the VLF, including consideration for compacted layers and potential preferential flows through the heap. Lastly, in order to ensure successful reclamation, examples of other heap closure plans where rinsing and then puncturing the protective liners was successful should be required. VLF stability is not sufficiently demonstrated. Recent reports have shown some geologic instability associated with the south end of the heap via a sloughing off of material and a deterioration of the benches designed to stabilize that portion of the heap. The reclamation plan should ensure geologic stability of the heap at all times during operation and during reclamation and after closure. The application indicates that geologic stability of the pit highwalls may be suspect, particularly in the post - mining period. These stability issues should be fully resolved to ensure long -term geologic stability prior to any permit approval. The application does not sufficiently address Acid Mine Drainage issues. In particular, while the application indicates a buffering capacity of the geologic layer below the surface, the application should demonstrate the long -term impacts associated with the exposure of acid generating rock in the pits and mined lands, the waste rock storage areas, and the VLF. The application should clearly demonstrate the total buffering capacity of the relevant local geology, and provide a plan for ensuring that acid mine drainage is controlled and effectively neutralized in perpetuity. Part of this demonstration should be a comprehensive geological and water monitoring and characterization plan to ensure that all areas contained in the mine permit have been analyzed for acid mine drainage potential. While the current outflows from the Carlton Tunnel do not exceed state standards for pH, any reclamation permit should require a comprehensive demonstration that the Carlton Tunnel discharge will not degrade or become acidic over time. To this end, the application should include a long- term monitoring plan at the Carlton Tunnel to ensure long -tenn protection of Four Mile Creek and the Arkansas River watershed. Lastly, the application should fully demonstrate protection from any potential acid mine drainage associated with backfilled open pits. The application should ensure that the VLF design for any dams or berms constructed to contain leachate or other chemicals ensure geologic stability and prevent sedimentation of holding ponds. The application must identify all groundwater sources in the permit boundary, including any and all perched aquifers, in order to ensure that the reclamation plan adequately protects those existing groundwater sources. 2