2012-08-21_REVISION - M1980244 (32)

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1) Where is the neutralization capacity in the overburden coming from? Is Cripple Creek & Victor (CC &V) going to apply a buffering agent as part of the placement of the overburden in ECOSA? Please explain. The Grassy Valley drainage is connected to the Wilson Creek drainage, which eventually reports to Four Mile Creek. The surface water quality for the two drainage areas that could be impacted is generally considered to be good. Additional ground water quality and quantity evaluation for Grassy Valley drainage area was submitted under this amendment. Based on the additional data submitted and the similarity of the water quality to the other drainage areas in the district, the Division believes the drainage area to be within the diatreme. As a result, if the ground water preferential flow path joins the Carlton Tunnel drainage, impacts from acid generating potential should be buffered by the abundant calcium carbonate at depth. However, the Division has expressed some concern about the lack of additional deep drill core data to demonstrate if this area is indeed within the diatreme's footprint. Despite the obvious overwhelming acid - neutralization capacity of the rock at depth within the diatreme, it is the Division's responsibility to require detailed geochemical characterization of the Overburden (OB) to be placed in ECOSA, from basic Acid Base Accounting (ABA) through leach testing. In addition, CC & V has raised some doubt about the potential for the preferential flow path to be circumvented, which could adversely impact the surface and shallow perched ground water in Grassy Valley. In order to mitigate this occurrence, the Division believes the addition of a three foot inert low infiltration layer above the overburden would limit moisture contact, thereby minimizing impact to the prevailing hydrologic balance. 2) CC &V must commit to place a minimum of three feet of inert low infiltration soil as part of the reclamation plan for ECOSA. Please revise the reclamation plan for ECOSA, adding three feet of inert low infiltration cover as part of the final reclamation plan. 3) If the potential exists for the preferential flow path to be circumvented in ECOSA, it stands to reason the same low probability could exist in the other existing and proposed overburden storage areas that will be expanded under the proposed amendment. If it is CC &V's assertion that the same condition will not exist in other overburden storage areas as previously accepted by the Division, CC &V must explain the reasons in detail. If not, CC &V must also place a minimum of three feet of low infiltration cover in all current and proposed overburden storage areas as part of the final reclamation plan. Please provide a detailed response explaining how CC &V will address this concern. 4) In the event of leachate release to the environment, it is always useful to have some knowledge of the expected geochemical interactions between the leachate and the material underlying the pile, whether it is bedrock or unconsolidated material, to assess the attenuation properties of these materials. The Carlton Tunnel drainage system and the overburden stockpiles are in significantly different environments. One being an underground flow system that has been flowing for many decades and appears to have established some level of equilibrium as evidenced by the relatively consistent water quality of the tunnel discharge, the other is a pile of freshly mined and crushed rock that will be exposed to a new environment of weathering and oxidizing conditions. It is unlikely the two sites will weather and leach similarly. The Carlton Tunnel has been in place draining the underground workings for over 60+ years. If an assumption is made that the ground water flow system feeding it has established some kind of stasis or equilibrium, then it might give doubt about the existence of preferential flow paths causing selective dissolution and depletion of available minerals along those flow paths. Additional and ongoing geochemical testing will provide data to help minimize future concerns. a. Therefore, the Division requires the operator conduct sequential batch leach tests continually, using ASTM approved methods to document results of such tests. The results must be submitted on a quarterly basis or when enough representative sample data is collected. The tests must be an ongoing process throughout the life of the operation. b. Please provide the type(s) of ongoing sequential batch leach tests the operator plans to implement throughout the life of the operation.