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West Elk Mine 2006 Annual Hydrology Report <br />36 <br />4.4 Sedimentation Ponds <br />There are 7 sedimentation ponds (Map 2 and Figure 8) at the Project that are utilized to manage <br />mine water, storm water runoff, and wastewater treatment effluent. All of the ponds except MB-5 <br />and MB-3 have been re lined to prevent seepage. There is also a "freshwater" pond (FW-1) that is <br />used to equalize diversions from the North Fork and provide storage. Pond FW-1 serves as the raw <br />fresh water supply for the mine's domestic water use and in-mine water needs. <br />In WY 2006, four ponds discharged water to the North Fork, ponds, MB-1 (106 ac-ft), MB-2R <br />(174.5 ac-ft), MB-4 (1 ac-ft), and SG-1 (MCC, 2007). Ponds MB-3, MB-5, RPE, and FW-1, had <br />no discharge in WY 2006 (MCC, 2007). Table 10 summarizes the water quality of all CDPS <br />discharges for WY 2006. Table 11 shows the CDPS discharge permit parameters and limits for the <br />sedimentation ponds. Figure 8 illustrates the mine water balance including the sedimentation pond <br />discharges. <br />Table 11 <br />Summary of Sedimentation Pond CDPS Discharge Permit Limits <br />• <br /> <br />Parameter and Time Period Sedimentation Pond <br /> Dischar a 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 (mg/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 />~~ No Sheen or less than ]0 mg/1 <br />December 2007 <br />HydroGeo, Inc. <br />