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The operation is located in the Colorado Piedmont section of the Great <br />Plains. Mining will extract the No. 7 coal seam of the Laramie Formation, <br />Geologic information contained in Appendix F, G and H of the application <br />characterizes the unique geology of this mine site. The flat lying coal seam <br />is overlain by 60-100 feet of overburden consisting of yellow-brown and gray <br />to blue gray soft carbonaceous shale and clay interbedded with sand and shaley <br />sand, It contains some cross bedded gray to buff sandstone which is slightly <br />to well cemented, The bedrock is overlain by 10 to 25 feet of Aeolian {wind <br />blown) sand. <br />The operator conducted an extensive drilling program to characterize the <br />physical and chemical properties of the overburden, <br />The information on physical and chemical characteristics can be found in <br />Appendices G and H of the application. The permittee adequately considered <br />the overburden characteristics on the backfilling and grading operations and <br />the revegetation plan {see Appendices L-1, Q-1, Q-3 and pages 47, 105 and <br />113-116 of Volume 1 of the application), In addition, the applicant <br />considered the overburden chemical characteristics on the potential for ground <br />water quality degradation. A discussion of these affects can be found in <br />Appendix I of the application, <br />The permittee is in compliance with the requirements of this section, <br />Ground Water Hydrology - Rules 2.04:5, 2.04.7, 2.05.613) and-4.05. <br />Information regarding Ground Water Hydrology is found in Section 2.04,5 and <br />2.04.7 and Appendix I and J of the permit application. <br />Baseline Discussion: <br />The applicant determined the probable hydrologic consequences of the surface <br />coal mining operations on four aquifers identified in or adjacent to the <br />operation (Appendix I and Volume 1 Section 2.04.7). <br />The aquifers and aquicludes that are identified as important to the <br />geohydrologic regime in the area of the Keenesburg Mine are as follows. The <br />bottom aquiclude is the Pierre shale. This formation is a thick sequence of <br />marine shales that have been identified regionally as a barrier to ground <br />water movement. <br />Above this formation is the Fox Hills sandstone. This sandstone is recognized <br />regionally as an important aquifer. It is approximately 65 to 100 feet <br />thick. The water quality of this aquifer locally considered poor for domestic <br />use because of exceedances in several primary drinking water standards. Total <br />dissolved solids of this water generally are approximately 1000' mg/1 in the <br />area of the Keenesburg Mine. However, the Keenesburg Mine currently uses this <br />water for domestic use. The water is characterized as a sodium bicarbonate <br />type with a very high sodium hazard to crops. The Keenesburg Mine has 2 <br />production wells in this formation; however, only well LFH-1 is being actively <br />used. In December of 1985 a chemical analysis of a sample from well LFH-2 <br />showed total dissolved solids of 6627 mgjl which is a marked rise in TDS from <br />previous samples. This well was used to obtain irrigation water for the 1985 <br />reclamation areas. <br />-9- <br />