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West Elk Mine 2001 Annual Hydrology Report 4.3 Sedimentation Ponds • There are 7 sediment ponds at the Project utilized to manage mine water, stormwater runoff, and wastewater treatment effluent. All ponds but MB-5, MB-3 and 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 WY2001, five ponds discharged water to the North Fork, MB-2R (112 ac-ft), MB-1 (5 ac-ft), and ponds MB-3, 4, and 5 (collectively about 1 ac-ft). Pond SG-1 discharged about 1 ac-ft of water to Sylvester Gulch. Ponds RPE and FW-1 had no dischazge. Table 9 summarizes the water quality of all CDPS discharges, including sedimentation pond (SG- 1), for WY-2001. Table 10 shows the CPDS discharge limitafion values for the sediment ponds. Figure 3 illustrates the mine water balance including the pond dischazges. Table 10 Summary of Sediment Pond CDPS Discharge Limits LJ Parameter and Time Period Sedimentation Pond Discharge Limits TSS (mg4) • 30-Day Average 35 • 7-day average n.a. • Maximum 70 TDS (mg4) • 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 Tota] Iron (mg4) • 30-Day Average 3.5 • 7-day average n.a. • Maximum 7.0 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 10 mg/l 4.3.1 Ponds MB-1 and MB-2R Pond MB-1 collects the Project's surface operafions water and diverted stormwater runoff. MB-1 can be discharged to either the North Fork or pond FW-1. Pond MB-2R receives surface operafions 20 water, storm runoff, and effluent from the WWTP. Discharge from MB-2R is typically routed to the North Fork, but can be diverted to FW-1, if necessary. Both MB-1 and MB-2R retain water so Project#oo3o1 HydroGeo, Inc.