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58. Memo <br />Date: August 7, 2012 <br />To: Tim Cazier <br />From: Berhan Keffelew <br />Re: Cresson Project; DRMS File No. M -1980 -244; AM -10 (MLE2) Geochemistry and <br />Groundwater Adequacy Review <br />Per your request, I have completed the review of my assigned sections for the amendment. <br />The amendment application Volumes I thru VII appear to have been submitted in the same format as <br />previous amendments. The amendment proposes to increase the current permit area of 5862.4 acres to <br />5989.7 acres by adding 127.3 acres. The new proposed leach pad in Squaw Gulch will be constructed <br />with a triple liner design. The operator also proposes to place a large mill for high grade ore recovery <br />in the existing permit area. <br />As requested, I did a cursory review of the entire application to make sure references to past approvals <br />reflect what was previously approved. The Environmental Protection Plan is in compliance with Rule <br />6.4.21(5). The list of designated chemicals and the materials handling plan are in compliance with <br />Rule 6.4.21(5). All of the monitoring included for the solution collection systems is in compliance <br />with Rule 6.4.21(5). The amendment is also in compliance with Rule 6.4.21(16). A detailed Quality <br />Assurance and Quality Control Plan, with material specification, is included in the application <br />(Volume V appendix H, Technical Specifications). The detoxification process of the new proposed <br />valley heap leach pad (phase VI) consists of two pore volumes of water and one pore volume of <br />hydrogen peroxide. The numeric limit for the decommissioning of the pad remains at 0.2 mg/1 wad <br />CN (weak acid dissociable cyanide). Once this is achieved, the liner will be punctured so it will free <br />drain. The puncturing of the liner serves three purposes: 1) it will allow the Division to detect any <br />metal releases from the pad by monitoring the ground water compliance points during reclamation, 2) <br />it will allow root zones to properly establish below the liner and 3) it will help eliminate build up of <br />hydrostatic head. <br />Geochemistry Evaluation and Rules 6.4.21(5) and (6 <br />The geochemistry of the District has been extensively investigated, as it relates to ground water <br />hydrology. The past and ongoing evaluations include, total sulfur and carbonate content, total metal <br />content, Net Acid Generation Potential (NAGP) tests and long term accelerated tests, like the humidity <br />cell tests. The long term geochemistry evaluation includes all areas covered under previous approvals <br />in addition to the current proposed ore processing and overburden placement areas that will be <br />expanded under the proposed amendment. The Division agrees that impacts to the probable <br />hydrologic balance will be negligible if the following conditions exist. Drainage, from all areas <br />previously permitted and currently proposed, is within the diatreme and passes through the preferential <br />flow path, ultimately discharging at the Carlton Tunnel. This is due to the abundant Net Neutralization <br />Potential (NNP) at depth (within the diatreme) which limits the release of additional metals. <br />However, in Volume IV, under East Cresson Overburden Storage Area ( ECOSA) Evaluation, Section <br />4.2, Groundwater Potential Impact, the operator states, "In the event that the neutralizing capacity of <br />the overburden materials is exhausted, the water seeping from the base of ECOSA will become acidic, <br />and the concentrations of calcium sulfate, iron, zinc and other metals may increase ". The operator <br />continues, "The potential for impact arises as a result of the fate of the water after it flows out of the <br />base of the ECOSA. If the water proceeds down through the diatremal volcanic rocks, contacts the <br />abundant carbonate in the Diatreme and joins the regional ground water system that flows from the <br />Carlton Tunnel, there will be no net impact, as this is the same fate that it would have had naturally. If <br />however, the water does not follow the path, but emerges at the toe of the ECOSA and joins the <br />surface water system in Grassy Valley, then dissolved constituents in it resulting from sulfide <br />oxidation have the potential to cause impact to surface water and shallow ground water resources in <br />Grassy Valley ". Assuming the average total sulfur content of the overburden is approximately 1.36 %, <br />as stated in section 4.2, the Division has the following comments. <br />