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sss WYOMING FUEL COMPANY NEW ELK MINE EROSION CONTROL ANALYSIS ~~n' Erosion from the West Portal Substation and West Portal Water Tank Areas were modeled using the SEDCAD+ software package to determine if Wyoming Fuel Company's effluent standard will be met while the vegetation is becoming established. The effluent standard for Wyoming Fuel Company's New Elk Mine is 0.50 ml/L.. Based on the SEDCAD+ analyses, Wyoming Fuel Company can meet the effluent standard during reclamation. However, alternate sediment control consisting of check dams constructed of hay bales will be installed and maintained to achieve the effluent standard during revegetation of the sites. Two major assumptions were made to conduct the SEDCAD+ analyses. First, we assumed •-~_ a mulch will be applied to the sites so that total ground cover equals or exceeds 70 percent. Second, we assumed all water flows off each site through a single exit point. Because characteristics of the sites are such that this second assumption is unlikely, the assumption is essentially a worst case scenario. The SEDCAD+ analyses indicate three check dams will be needed to meet the effluent standard. One check dam will need to be installed across the entire width of the lower end of the West Portal Substation site. The other two dams will be placed on the northwest side of the West Portal Water Tank area (Area 1 ). The first of these two dams will need to be placed across the site, midway down the slope. While the second dam will need to be installed across the entire width of the lower boundary of the site. These dams will consist of standard two foot high hay bales buried 6 inches into the ground and placed end to end and anchored with steel pins. The West Portal Water Tank Area 2 will not require any further modification once the • mulch has been placed which equals or exceeds 70 percent cover.