2010-04-20_REVISION - M1977300 (6)

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Environmental Protection Plan, Schwartzwalder Mine 9-5 • Increases in sulfate and uranium concentrations in alluvial groundwater that were observed in Fall 2008 and Spring 2009, suggest that the flooded mine could contribute 0.8 to 8% of the alluvial flow. However, increases in chloride concentrations cannot be explained by hydraulic connection with the mine because concentrations in mine water are about half the concentrations in alluvial groundwater. Drill holes, near-surface fractures, or rock foliation could provide potential conduits for low rates of flow from the mine to the valley floor alluvium. Fifteen boreholes were plugged in May 2000 with a mixture of Portland cement and bentonite (7%), including 11 long holes at the Montana (Atlantic) adit, and four surface core holes (DHH#3, L-1, L-4, L-5). A targeted search was conducted for an additional 33 exploration holes drilled from pre-1956 to 1977 (White, 2000). The boreholes could not be located, and some or all of them may have been left unplugged. Flow from boreholes and fractures is believed to be low, based on the mixing calculations performed in Table 9-2 and the observation that flow in Ralston Creek did not decrease noticeably by capture from the boreholes when the mine was fully dewatered" to 2,200 feet. Either the boreholes act as "one-way valves" or groundwater flow along these pathways was so low as to be unrecognizable. Table 9-2. Mixing Calculation to Determine Maximum Contribution of Mine Water to Alluvial Water Quality .7 Sample Results - Alluvial Well MW-9 Mixing Calculation Avg Final Conc.in Ratio of flow Parameter 12/29/04 6/23/05 9/6/07 3/25/08 10/29/08 Initial Increase mine from mine water Conc. Conc. water to cause increase pH (std units) 7.26 7.41 Total dissolved solids (mg/L) 352 334 366 356 494 350.7 494 143.3 3,290 4.9% Bicarbonate (mg/L as HCO3) 120 115 153 131 148 129.3 148 18.7 471 5.5% Alkalinity, total (mg CaC03/L) 98 94 126 107 121 Calcium, dissolved (m 59.8 56.4 73.5 89.4 58.1 89.4 31.3 428 8.5% Calcium, total (mg/L) 64.7 Magnesium, dissolved (mg/L) 20.3 19 25.3 30.6 19.65 30.6 10.95 256 4.6% Sodium, dissolved (mg/L) 17.9 13.5 15.1 18.9 23.7 15.5 23.7 8.2 256 Potassium, dissolved (mg/L) 3.1 4 3.4 4.2 Sulfate (m 132 131 112 151 183 125 183 58 2,050 3.0% Chloride (mg/L) 26 15 27 31 43 22.67 43 20.3 21 -1220.0% Aluminum, dissolved (mg/L) <0.2 <0.2 <0.2 <0.2 <0.1 Aluminum, total (mg/L) <0.1 <0.1 <0.2 <0.2 <0.2 Antimony, dissolved (mg/L) <0.001 <0.001 <0.001 <0.001 <0.05 Antimony, total (mg/L) <0.05 <0.05 <0.001 <0.001 Arsenic, total (mg/L) <0.001 <0.001 <0.1 <0.1 <0.1 Copper, dissolved (mg/L) <0.005 <0.005 <0.005 <0.005 <0.01 Copper, total (mg/L) <0.005 <0.01 <0.005 <0.005 <0.005 Iron, dissolved (mg/L) <0.03 <0.03 0.09 <0.03 <0.03 Iron, total (mg/L) 0.03 <0.03 0.08 <0.03 <0.03 Lead, total (mg/L) <0.05 <0.05 <0.005 <0.005 <0.005 Manganese, diss. (mg/L) <0.01 <0.01 <0.01 <0.01 <0.01 Manganese, total (mg/L) <0.01 <0.01 <0.01 <0.01 <0.01 Mercury, total (mg/L) <0.0001 <0.001 <0.0001 <0.0001 <0.001 Molybdenum, diss. m 0.053 0.052 0.046 0.04 <0.1 Silver, total (mg/L) <0.01 <0.01 <0.001 <0.001 <0.001 Thallium, dissolved (mg/L) <0.001 <0.001 <0.001 <0.001 <0.1 Thallium, total (mg/L) <0.05 <0.1 <0.001 <0.001 Zinc, total (m 0.008 <0.01 0.006 0.006 0.008 Uranium, dissolved (mg/L) 0.593 0.43 0.601 0.481 0.849 0.541 0.849 0.308 41 0.8% Uranium, total (mg/L) 0.635 Radium-226, dis. (Ci/L 0.8 0.2 0.4 0.15 0.05 0.05 • 18 During the last four years of mining, at its total maximum depth of 2,200 feet, groundwater inflow to the Schwartzwalder mine was only 189 gpm. 4109C.100419 Whetstone Associates