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i -'- • 2. IF, DURING TFIE COURSE OF MINING OPERATIONS, PREVIOUSLY UNIDENTIFIED CULTURAL RESOURCES ARE DISCOVERED, SENECA COALS LTD. SHALL INSURE THAT THE SITE ZS NOT DISTURBED AND SHALL NOTIFY THE DIVISION. TtiE OPERATOR SHALL INSURE THAT THE RESOURCE IS PROPERLY EVALUATED IN TERMS OF THE NATIONAL HISTORIC PLACES ELIGIBILITY CRITERIA (36 CFR60.6)). SHOULD A RESOURCE BE DETERMINED ELIGIBLE FOR LISTING IN CONSULTATION WITX TXE SHPO, BLM, OSM, AND MLRD, THE OPERATOR SHALL CONFER WITH AND OBTAIN THE APPROVAL OF THE SXPO, BLM, OSM AND MLRD CONCERNING THE DEVELOPMENT AND IMPLEMENTATION OF MITIGATION MEASURES AS APPROPRIATE. IV. GEOLOGY The Geology section is found in Volume ZI, Tab 6 of the application. The Seneca SI mine is located in the southern section of the Tow Creek Anticline, a structural feature of the Washakie Basin in the tJyoming Basin Physiographic Province of southcentral Wyoming and northern Colorado. The coal seams of interest, the Lennox, wadge, and wolf Creek, are contained in the Middle Coal Group of the Williams Fork Formation, Mesa Verda Croup, Upper Cretaceous Series, between the Trout Creek Sandstone and the Twenty Mile Sandstone. The Lennox is the top seam of the three, Lying 50 feet above the Wadge. It is 2.5 to 5.5 feet thick with the poorest quality coal of the three seams. Overburden is a thin sandstone unit overlain by a thick marine shale. Neither the Lennox coal seam or it's overburden are considered aquifers. Due to the relatively poor quality of the Lennox, the seam will only be recovered when operationally and economically feasible. The next seam stratigraphically downward, the Wadge, is the principal reserve to be recovered. This seam, 9 to 10 feet thick and of uniform quality, outcrops mid- way up the flank of the Tow Creek Anticline West and South of the permit area. The seam rises 6 to Z9 degrees to the East, except in the South end of the permit area, where, as it rounds the toe of the anticline, the rise becomes northward and finally westward. The Wadge overburden is a moderately thick sequence of very fine grained, low porosity sandstones and siltstones with thin interbedded shales. This strata together with the coal seam is considered to be an aquifer. The Wolf Creek Seam is the lowest to be mined and Lies 150 feet below the wadge. It averages 15 feet thick and outcrops near the crest of the Tow Creek Anticline in the northeast part of the permit area. It is overlain by a sequence of lenticular sandstones, siltstones, shales, and thin coal beds. Neither the coal seam nor the Wolf Creek overburden are considered to be aquifers. The floor of this seam is a black carbonaceous shale followed by sandstones, siltstones, and shales. The Trout Creek Sandstone lies roughly 70 feet below the Wolf Creek seam and is con- sidered to be the first aquifer below the coal. It is a thick (120 Feet), massive, well to very well sorted, fine grained, glauconitic sandstone which forms prominent cliffs . A series of four normal faults, one with a displacement of SO to 60 feet, occur North of the permit area. These appear on the extreme northern edge of the area and may have some effect on groundwater in the mine site. Mining originally began along the western limb of the anticline with coal striking primarily South with dips ranging from 6o to Igo to the West. Mining is now preceding around the toe of the an ticZine where the strike of the coal is to the East.