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<br />Sills and dikes associated with Tertiary volcanism intrude the Yermejo <br />and Raton Formations and are visible in the Picketwire Valley. They <br />range in thickness from a few inches to greater than 20 feet and are <br />primarily composed of basalt. <br />Quaternary deposits consist primarily of river terrace and floodplain <br />deposits associated with the Purgatoire River and its tributaries. The <br />study area contains two levels of rock benches that formerly may have <br />been referred to in the literature as Beshoar and Barilla pediments. The <br />applicant's consultant has interpreted these as strath terraces with an <br />alluvial veneer. These strath terraces are located approximately 90 to <br />170 feet above the river in the study area. They have been eroded from <br />shale and siltstone containing thin interbeds of fine to very fine, silty <br />sandstone. The overlying alluvium has a maximum thickness of <br />approximately 35 feet and is composed of predominantly silt and sand <br />containing pebbles and occasional boulders. <br />Two levels of alluvial terraces were identified adjacent to the <br />Purgatoire River. These terraces are located 5 to 10 feet and 40 to <br />50 feet above the river in the study area and have been investigated by <br />Powell, 1952. They are composed of relatively unweathered, gray to light <br />tan alluvium overlain by medium to dark brown sandy overbank deposits. <br />These terraces support typical hydrophytic vegetation characteristic of <br />floodplains and contain ground water hydrologically connected to the <br />river. Absolute dates on the alluvial deposits are not available; <br />however, in analogous areas of the Rocky Mountain Region, the strath <br />terraces are of Pleistocene age and the alluvial terraces of Holocene age. <br />B. Ground Water = Bedrock Aquifers <br />The Trinidad Sandstone is a significant regional aquifer given its <br />250 feet thickness and regional extent. This sandstone is the first <br />major aquifer below the lowest coal seam to be mined and is separated <br />from the coal seam by up to 900 feet of interbedded and lenticular <br />shales, siltstone s, and sandstones. The Trinidad Sandstone, however, may <br />be impacted by the Golden Eagle 14ine. Early in 1988, a substantial <br />artesian flow of water was encountered in conjunction with a fracture <br />zone in the Second Right entry area of the mine. The source of this <br />water is uncertain, but the Trinidad Sandstone is a possibility. <br />The coal seams and most of the overburden in the permit area are part of <br />the Raton Formation. Sandstones in the formation are interbedded and <br />lenticular. These characteristics of the formation inhibit the vertical <br />and horizontal flow of ground water through it. <br />Little or no ground water has been encountered in the Raton Formation <br />during the exploration phases at the New Elk and Golden Eagle Mines. <br />Small amounts of water are encountered in.the coal seams during mining. <br />Minor amounts of water were encountered within minor coal beds that were <br />intersected during mine development. Small amounts of ground water may <br />generally be found in the sandstone units and fractures occurring in the <br />formation. <br />-13- <br />