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• eliminated during the natural filtering process. This percolation should have a positive hydrologic <br />impact on the area as the natural runoff will be retained in the area for a longer period of time and <br />recharge the groundwater system where it is less subject to evaporative losses. <br />Direct evaporation from the pond surface is the least desirable means of dewatering as the water is <br />lost without beneficial results. Under the worst conditions possible (i.e., there is always water in the <br />pond available for evaporation), an estimated 12.8 acre-feet of water could be lost to evaporation <br />each year. However, prior to the construction of any ponds, water storage rights, which recognize <br />this evaporation problem, will be obtained. <br />The sedimentation pond in the D Portal Area (DP-1) collects water from a total area of 1 percent of <br />Scullion Gulch's watershed. The ponds in the Refuse Disposal Area are adjacent to a tributary <br />stream to Red Wash. The total area collected by these ponds is 1-1/2 percent of the total water <br />shed of this tributary. The hydrologic effects, either positive or negative, of these ponds will be <br />minor and localized. <br />V.B.3 Disposal Site Characteristics There are two disposal sites used during operation: (1) <br />Halandras Trash Dump area and (2) Coal Refuse Area. The Halandras Trash Dump is near the top <br />of a drainage area. Water is diverted around the actual dump. On-site water is collected and <br />filtered in a local sediment trap. Halandras Reservoir No. 1 is further downstream and will also act <br />• as a sediment trap. No hazardous materials are disposed of at this dump. The area will be <br />continually reclaimed as new dumps are opened. At the end of the mine life, the final open cut <br />dump will be filled, topsoiled and revegetated. Map 136 shows the sanitary landfill operation. <br />The coal refuse banks are located in one area. The disposal area is divided into smaller sub-areas. <br />Through experience, it has become necessary to use more than one sub-area at the same time to <br />allow more surface area and more time for drying of the coal refuse. Runoff from the waste banks <br />will continue to be trapped in the sedimentation ponds and thus will not affect the surface hydrology <br />of the area. <br />Neither seeps, springs, nor groundwater have been identified as existing in the disposal area. See <br />Illustration 17. <br />The compacted coal waste banks will be more pervious than the natural soil, therefore, the <br />existence of these banks will not adversely affect the recharge of the groundwater system. Since <br />evapotranspiration exceeds precipitation for revegetated sites in this area, it is anticipated that very <br />little precipitation will infiltrate to the compacted coal waste layers, <br />The coal to be mined has an average sulfur content of 0.5 percent. This low-sulfur content, <br />together with the low rainfall amounts in the area and net acid neutralizing potential, indicates that <br />acid drainage problems should not develop from the coal waste banks. In addition, if seepage were <br />to occur, it would be buffered by the calcareous materials in the area. For this reason, no <br />• impervious blanket is provided between the waste bank and the natural foundation material. The <br />Mid-Term Review 2002 (8/2002) V-7