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• <br />• <br />Snowmelt Runoff Discharge <br />In the winter months, snow depths on the 13.43 -acre pad can exceed several feet, with water contents of 6 <br />inches or more. During spring snowmelt (assuming a water content of 6 inches), 6.7 acre -feet of runoff <br />could be realized. Since the maximum pond capacity (with 3 years of sediment already deposited) to the <br />spillway invert is only 1.246 acre -feet, discharge will occur through the spillway. The modeling results <br />demonstrate that even if the pond is full at the time spring snowmelt begins, the pond will adequately treat <br />the runoff and settle out sediment so that the discharge complies with NPDES discharge limits. <br />Pond Water Quality Data <br />Water samples collected from the pond surface during snowmelt runoff in the spring of 2006 showed the <br />following analytical results: <br />pH <br />Total Suspended Solids <br />Conductivity <br />Iron <br />Other Metals <br />8.13 <br />10 mg /L <br />993 µmhos /cm <br />340 mg/L <br />Very low to non - detectable <br />These analytical results indicate discharge water that is similar in quality to ambient conditions. They <br />also demonstrate that the pond is functioning as designed to remove sediment. <br />CERTIFICATION <br />I, Richard Spotts, state that the information presented in the 6MN Intake Shaft Facility Drainage <br />And Sediment Control System Design Report for Twentymile Coal Company was prepared by me <br />or by persons under my supervision and is correct to the best of my knowledge and information. <br />Water & Earth Technologies, Inc. <br />Richard Spotts, P.E. <br />President <br />Principal Engineer /Hydrologist <br />i <br />26155 <br />L <br />TCC 6MN Intake Shaft Facility 8 <br />Drainage and Sediment Control System Design <br />Water & Earth Technologies, Inc. <br />April 24, 2009 <br />