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Ms. Susan Morrison August 16, 1991 Page 3 1986 when aerial photography was taken to prepare a baseline topographic map. The second phase took place in May 1987 with the first longwall in progress. The third phase occurred in June 1988 when the first longwall was completely mined. The elevation data generated from the second, third, and fourth phases were compazed with those generated during the first phase to produce differential contour or subsidence maps. Maximum subsidence of less than six feet and limits of subsidence within 300 feet of the panel boundazies were noted. Foster Kirby, OSM Archeologist; Mike Selle, BLM Archaeologist; and Paul Nicksen, WFU's Consultant Archeologist visited the mine site under active subsidence on June 16, 1987. They found no significant cracks, slippage or abrupt change in ground topography due to subsidence. They all agreed that the subsidence would not cause damage to cultural resources in the ground. Pursuant to this meeting, mitigation of the archaeological site SRB859 was done by isolating it from traffic and public access rather than by excavating the artifacts. Based upon the past subsidence monitoring and results thereof, Western Fuels does not anticipate a significant impact on the cultural resources due to the longwall mining. However, as per the lease stipulation, a subsidence monitoring plan will be developed and submitted to BLM, OSM, CMLRD, SHPO, and ACHP for review and comment prior to mining in the lease area. Geoloev Section II.B of the permit discusses the geology of the mining area. Pages I[.B-4 to II.B-6 and II.B-10 to I[.B-14 of the permit have been revised to include the information on the new lease area. Maps 4, 122, 132, and 133 of the permit have also been revised to include the information for the new lease area. Map 4 is a geologic map. Map 122 shows the D Seam overburden thickness. Map 132 is an isopach map of the B Seam. Map 133 is an isopach map of the D Seam. Section II.C of the permit discusses the hydrology of the area. Due to the nature of subsidence over a longwall system, the disturbance to the hydrological flow in the drainages is expected to be minimal. Monitoring data from longwall panel No. 1 (LW-1) and No. 2 (LW-2) has shown no adverse impacts to the Red Wash floodplain. Tension cracks and basins formed as a result of subsidence are quickly filling as a result of deposition of sediments being carried by flow. These same results are expected of subsequent subsidence of longwall panels. Groundwater data collected by Western Fuels around the mined area has shown a decrease in water levels. Average depth to water in the alluvial wells of Red Wash has shown a drop from 4.8 feet to 14.7 feet below surface elevation. These impacts appear to be in the vicinity of active mining. This impact is possibly due partly to natural fluctuation and partly due to the mining influence. No additional hydrological impact is expected with the mining of the new lease. Page II.C-1 of the permit has been revised.