2010-08-02_REVISION - M1977300 (28)

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Environmental Protection Plan, Schwartzwalder Mine 14-3 • on these theses results, material in the East and West Waste Rock Piles, and the fill adjacent to Ralston Creek have low potential to generate acidic drainage. Table 143. Summary of Acid-Base Accounting Results Years Depth ANP AGP NNP Sample Location eft) Exposed to t CaC03/kt t CaCO3/kt t CaC03/kt ANP/AGP Weathering North Waste Rock Pile • South End, Central Bench 1.5 <1* 214 8 206 28.5 South End, Central Bench 6 10-17 175 23 152 7.5 South End, Central Bench 11 10-17 179 14 165 12.7 North End, Central Bench 1.7 <1* 188 8 180 22.7 North End, Central Bench 6 10-17 123 38 86 3.3 North End, Central Bench 11.5 10-17 160 22 138 7.4 South Waste Rock Pile * = moved in six months prior to ABA testing North End, Top 1.5 15-17 186 29 158 6.5 North End, Top 6 15-17 162 38 124 4.3 North End, Top 10.5 15-17 174 33 141 5.3 South End, Top 1 13-18 229 28 201 8.2 South End, Toe 2.5 13-15 157 68 89 2.3 Average 177 28 149 10 (iii)Acid Consumption Tests An evaluation of the potential for acid-leach reprocessing of the waste rock piles was performed in 1986 by Colorado School of Mines Research Institute (Chlumsky, 1986). Results of the study indicated that the acid consumption per ton of waste rock was between 400 and 420 pounds of sulfuric acid. This neutralizing potential is equivalent to about 160 t CaC03/kt assuming 40% solution of sulfuric acid, and is in good agreement with the results of ABA testing. (iv) Impact Analysis Waste rock from the mine was placed in two external dumps that are located adjacent to Ralston Creek upstream of the mine (Figure 2-1). The stability of the waste rock piles was investigated by McDermid (1983a, 1983b) and hydraulic control structures were constructed to protect the piles from the 100-year flood event (Shepherd Miller, 1999). The control structures include an energy dissipater located in the ephemeral drainage near the east waste rock pile and rip rap on the side slopes. Additionally, the waste rock piles were recontoured to a stable 2H: IV slope configuration. R.G. Otto & Associates (1984) performed a detailed survey of surface and groundwater quality to assess the impact of runoff and seepage from the waste rock piles on the water quality in Ralston Creek. Surface water samples were collected upstream and downstream of the waste rock piles and groundwater samples were collected down-slope of the disposal site from September 1983 through August 1984. The study concluded that the waste rock piles had no measurable impact on water quality in the stream, with the possible exception of stream uranium levels. The uranium data were inconclusive for determining impact, and the uranium levels in Ralston Creek downstream of the waste rock piles were below the Colorado Basic Stream Standards. Subsequent water quality monitoring on Ralston Creek from 1984 to 2009 has not indicated impacts to • water quality in the creek. Laboratory data and the E.C. survey conducted in November 2008 (Section 8(e)(ii)) showed no impact from the waste rock piles on Ralston Creek (Figure 8-22). 4109C.100731 Whetstone Associates •