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West Elk Mine 2008 Annual Hydrology Report 49 <br />0 4.5 Sedimentation Ponds <br />There are nine sedimentation and treatment ponds (Map 2 and Figure 9) at the mine site that are <br />utilized to manage mine water, storm water runoff, and wastewater treatment effluent. All of the <br />ponds except MB-5 and MB-3 have been re-lined to reduce seepage. There is also a "freshwater" <br />pond (FW-1) that is used to equalize diversions from the North Fork of the Gunnison River and <br />provide storage. Pond FW-l serves as the raw fresh water supply for the mine's domestic water <br />use and in-mine water needs. <br />In WY 2008, four ponds discharged water to the North Fork: ponds MB-1 (53.51 ac-ft), MB-2R <br />(100.89 ac-ft), MB-4 (0.22 ac-ft), and RPE (1.84 ac-ft) as illustrated on Figure 9 (MCC, 2009). <br />There was no discharge from Pond MB-3, MB-5, or SG-1 in WY 2008 (MCC, 2009). Table 12 <br />summarizes the flow and water quality data for the CDPS discharges for WY 2008. Table 13 <br />shows the CDPS discharge permit parameters and limits for the sedimentation ponds. <br />Table 13 <br />Summary of Sedimentation Pond CDPS Discharge Permit Limits <br />0 <br />• <br />Parameter and Time Period Sedimentation Pond <br /> Discharge Limits <br />TSS (mg/1) <br />• 30-Day Average 35 <br />• 7-day average n.a. <br />• Maximum 70 <br />TDS (mg/1) <br />• 30-Day Average n.a. <br />• 7-day average n.a. <br />• Maximum Report <br />Oil and Grease (1) <br />• 30-Day Average No Sheen <br />• 7-day average No Sheen <br />• Maximum No Sheen <br />Total Iron (µg/1) <br />• 30-Day Average 3.5 <br />• 7-day average n.a. <br />• Maximum 7.0 <br />pH (S.U.) <br />• 30-Day Average 6.5-9.0 <br />• 7-day average 6.5-9.0. <br />• Maximum 6.5-9.0 <br />T') No Sheen or less than 10 mg/l <br />June 2009 HydroGeo, Inc.