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Final West Elk Mine 2005 Annual Hydrology Report 32 i• 4.3 Sedimentation Ponds There are 7 sedimentation ponds (Map 2 and Figure 8) at the Project that are utilized to manage mine water, storm water runoff, and wastewater treatment effluent. All of the ponds except MB-5 and MB-3 are re lined to prevent seepage. There is also a "freshwater" pond (FW-1) that is used to equalize diversions from the North Fork and provide storage. Pond FW-1 serves as the raw fresh water supply for the mine's domestic water use and in-mine water needs. In WY 2005, six ponds discharged water to the North Fork, ponds, MB-1 (106.0 ac-ft), MB-2R (174.5 ac-ft), MB-3, 4, and 5 (1.0 ac-ft), and SG-1 (1.0 ac-ft). Ponds RPE and FW-1 had no discharge in WY 2005. Table 9 summarizes the water quality of all CDPS discharges, including sedimentation pond (SG-1), for WY 2005. Table 10 shows the CDPS discharge permit parameters and limits for the sedimentation ponds. Figure 8 illustrates the mine water balance including the sedimentation pond discharges. Table 10 Summary of Sedimentation Pond CDPS Discharge Permit Limits • Parameter and Time Period Sedimentation Pond Dischar a Limits TSS (mgA) • 30-Day Average 35 • 7-day average n.a. • Maximum 70 TDS (mg/I) • 30-Day Average n.a. • 7-day average n.a. • Maximum Report Oil and Grease (1) • 30-Day Average No Sheen • 7-day average No Sheen • Maximum No Sheen Total Iron (mg/1) • 30-Day Average 3.5 • 7-day average n.a. • Maximum ~~0 pH (S.U.) • 30-Day Average 6.5-9.0 • 7-day average 6.5-9.0. • Maximum 6.5-9.0 1 No Sheen or less than ] 0 m /1 4.3.1 Ponds MB-1 and MB-2R Pond MB-1 collects the Project's surface operations water and diverted storm water mnoff. Water • from Pond MB-1 can be discharged into either the North Fork or Pond FW-1. Pond MB-2R September 2006 HydrOGeq Inc.