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May Day Idaho Mine Complex 112 (d) Permit Application <br />(iii) Off-site Impact Prevention <br />The following measures will be taken to prevent off-site impacts: <br />• Use of designated chemicals occurs approximately 0.5 mile inside <br />permit boundary; <br />• Only small quantities of designated chemicals (as defined by EPA will <br />be used at any given time; <br />• Spill prevention measures include bermed storage areas and paved floors <br />within storage and processing areas; <br />• Distance to water courses, and depth to groundwater (Section 6.4.20(8)) <br />allow for immediate containment during spill response of small volumes <br />minimizing exposure risk through off-site migration to these receptors; <br />• Monitoring programs will be implemented (Section 6.4.20(7)) at the <br />initiation of the milling phase. <br />(c) Assessment of Potential Acid-Forming Materials <br />An assessment of the acid forming potential of the mine rock is presented in Section <br />6.4.20(14). Based on this assessment, a favorable Acid-Base Potential was reported <br />indicating potentially acid-neutralizing material. Specific tailings analysis will be <br />undertaken during mill optimization, as described in Section 6.4.20(7)(d). <br />6.4.20(7) Facilities Evaluation <br />(a) Site-Specific Conditions <br />The following site-specific conditions lead to favorable Environmental Protection: <br />• Small concentrations of designated chemicals are used at any time, <br />minimizing the impact of any accidental release of designated chemicals; <br />• All operations are undertaken in a underground, allowing for effective <br />response to any release of designated chemicals and no off-site migration; <br />• The designated chemicals are stored approximately 400 feet from a water <br />course; <br />• Groundwater is estimated to be 1,000 feet below the level of use and storage <br />of the designated chemicals (Section 6.4.20(8)); <br />• Tailings will be prepared to reduce moisture available for leaching, and <br />stored within a dry underground workings; <br />• Moisture will be removed using a vacuum or belt filter press (or suitable <br />alternative) and if moisture content is elevated (saturation limits are exceeded) <br />cement or suitable alternative will be added to stabilize the filter cake; and <br />• The mine rock has a greater degree of neutralizing capacity compared with <br />its acid generation potential. <br />(b) Materials Storage <br />REVISED June 5. 2011 <br />May Day Idaho Mine Complex 112(d) Permit Application <br />September 21, 2010 <br />6