Laserfiche WebLink
May Day Idaho Mine Complex 112 (d) Permit Application <br />Surface water analytical results are presented in Section 6.4.20(11). Two surface water <br />samples are located immediately down gradient of either a mine rock deposit (Location <br />DG-2) or an historic tailings deposit (Location SW-2). The results are summarized <br />below: <br />• Surface water sample DG-2 was collected from Little Deadwood Gulch <br />immediately below mine rock on the out slope below the bench at the May Day <br />No.2 Operational Area. Concentrations of dissolved and total metals are below <br />Chronic Aquatic Life Standards. <br />• Surface water sample SW-2 is collected from the La Plata River immediately <br />down gradient of historic tailings deposited within the floodplain of the La Plata <br />River. Two samples collected from this location indicate that Total <br />Recoverable Aluminum may be a potential contaminant of concern from historic <br />tailing leachate. <br />• Results indicate that when tailings are in direct contact with surface water, <br />elevated concentrations of Total Recoverable Aluminum may be encountered. <br />The weathering of mine rock, however, does not appear to have any direct impact <br />to surface water uali . Additionally, no run of mine rock or tailings that is <br />acid or toxic producing will be disposed of in locations in direct contact with <br />surface water. <br />The geochemical characterization is in agreement with what would be predicted from the <br />general geology of the area. Sulfide minerals have been reported in several of the ore- <br />bearing porphyry veins (Christensen, 2007) and would account for the acid-potential. <br />The presence of ore within calcite replacement veins accounts for the greater neutralizing <br />potential. Thus while there is the potential for acid generation, the naturally occurring <br />calcite neutralizes any such acid. Additionally, there is the potential for aluminum above <br />Chronic Aquatic Life Standards and arsenic above drinking water standards to be <br />generated by leachate from the tailings. <br />Dry-tailings are planned to be placed within the dry stope within the May Day No. 1 <br />portal. Based on observations by Dr. David Gonzales, Fort Lewis College (pers. comm.), <br />there is no water within this stope, limiting leachate generation. Additionally, the tailings <br />will be managed such that 75% of the process water will be recycled; again limiting the <br />amount of leachate that potentially can be generated. <br />As there is no leachate being generated, the fate of the chemicals will reside with the dry <br />tailings. This will be further evaluated during the milling optimization phase. <br />(e) Measure to Prevent Unpermitted Discharges <br />The following measures will be undertaken for handling of the tailings to prevent <br />unpermitted discharges: <br />REVISED June 5, 2011 <br />May Day Idaho Mine Complex 112(d) Permit Application <br />September 21, 2010 <br />16 <br />i