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b. Freeboard reserve of 1.2 inches has been specified in the Tailings Impoundment. For more detail <br />• <br />and analysis, refer to revised Exhibit C and T. <br />18. Exhibit C and T have been changed to reflect that the existing use of groundwater in this vicinity is <br />surface water recharge. <br />19. Concerning the ground water aspects of this review: <br />a. A schematic of the monitoring well construction detail has been included in a revised Exhibit C <br />and D. <br />b. Denture Resources has clarified that any water sampling and testing should analyze the following <br />metals: Al, As, Ba, Cd, Cr, Cu, Pb, Mn, Hg, Se, Ag, and Zn. See revised Exhibit C. <br />c. Sampling procedures in Exhibit C have been modified to include field pH testing accurate to <br />1/101h of a standard unit. <br />d. Sampling procedures in Exhibit C have been modified to include a well purging sequence as <br />recommended by the DRMS. <br />e. Sampling procedures in Exhibit C have been modified to include DRMS sample reporting <br />requirements. <br />f. 'Venture Resources acknowledges the DRMS requirement to approach this operation using <br />practice-based permit conditions protective of groundwater quality. As a result, the entire scope <br />of the permit has been re-vamped to include a composite liner system. A GeoComposite layer on <br />top of an impermeable HDPE liner will provide a continuous underdrain, thereby limiting the <br />hydrostatic head to less than three feet. Refer to revised Exhibit C, D, E, and T. <br />g. DRMS has determined that practice-based groundwater protection shall be applied to this <br />operation through the implementation of a composite liner system. Numeric protection limits <br />will not be applicable. Exhibits C, D, and T have been revised. <br />• 20. Exhibit T has been revised concerning the use of the phrase "extractive metallurgical process". The <br />language has been changed to read: "There are no hydrometallurgical extractive processes proposed as <br />part of this operation, only gravity and flotation concentration methods". <br />21. Exhibits C, E, and T have been thoroughly revised concerning stormwater management. <br />a. Drainage analysis has been revised to more accurately reflect the NRCS soil survey determination <br />of Cathedral-Rock Outcrop complex hydrologic soil group D. A new runoff curve number of 73 <br />has been used in the new analysis. DRMS mentions that a small percentage of Mammoth <br />Ohman soil is present in the vicinity. This is true, however, that soil type is not in the immediate <br />drainage basin but on the other side of the defining ridge. <br />b. Exhibit C and E have been revised to clarify the sequence of installation of stormwater diversion <br />ditches. <br />c. Following the revised drainage analysis done with the correct soil profiles, a new peak flow has <br />been determined. This analysis can be found in revised Exhibit C. Using the new peak flow <br />data, ditch profile and riprap revetment analysis was done. This analysis was based on design <br />guidance provided by the Federal Highway Administration Hydraulic Engineering Circulars <br />RFC-11 & HEC-1 S and the Urban Drainage & Flood Control Criteria. Exhibits C, E, and T <br />have been revised with this information. <br />d. The stormwater narrative found in Exhibits C & T and the stormwater design elements in the <br />drawings of Exhibit E have been more accurately correlated to reflect the relationship between <br />the diversion ditches and sediment collection pond. DRMS may feel this sediment pond <br />arrangement is not sound stormwater management practice; however, the CO WQCD has been <br />consulted and they find it acceptable. Because of the "bowl" shaped nature of the tailings <br />impoundment vicinity, it was determined that the sediment pond design element would be <br />acceptable. Ultimately the CO WQCD is responsible for issuing the SWMP permit. <br />• e. Following the revised drainage analysis done: with the correct soil profiles, a new peak flow has <br />been determined. This analysis can be found in revised Exhibit C. Using the new peak flow <br />Page 4 of 7