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• Section 2.04.5 General Description of Hydrology and Geology. <br />(1) A description and map of the geology, surface and ground water <br />systems, including water quality and quantity. <br />Grand Mesa Coal Company's Red Canyon A 1 Diine and proposed # 2 <br />Mine are located on the southern flank of Grand Mesa approximately <br />3~ miles northwest of Cedaredge, Colorado. The southern slopes <br />of Grand Mesa represent the southern boundary of the Piceance Creek <br />structural basin, the largest structural basin in western Colorado. <br />Slopes upon which the mine permit boundaries exist were eroded through <br />glacial and fluvial action during the recent geologic past. <br />This erosional action in the vicinity of the mine site has exposed <br />sediments of Cretaceous Age contained within the geologic unit known <br />as the Mesaverde Group. Other units exposed in the immediate area <br />of the permit are the Mancos Shale (which underlies the Mesaverde <br />Group) and Quaternary Age glacial outwash deposits derived from <br />the upper elevations of Grand Mesa to the north. A9 can be seen on <br />• the Geology Map, 2.04.5-1, this glacial outwash material covers a <br />large portion of the permit area to oaring depths. <br />All of the geologic units exposed in the immediate area of the <br />Red Canyon ~ 1 Mine and proposed i 2 Mine are either Cretaceous <br />or Quaternary in age. The oldest geologic unit in the area is <br />the Mancos Shale exposed to the south of the permit area. This <br />shale is a marine, deep basin, carbonaceous and calcareous black <br />shale. Overlying the Mancos Shale is the Mesaverde Group. <br />subdivided into the Iles and Williams Fork Formations. The Williams <br />Fork Formation is further subdivided into the lower Bowie Shale <br />Member and the upper Paonia Shale Member. These two members contain <br />the majority of the commerical coal deposits in this region. <br />Separating the Williams Fork Formation from the Mancos Shale is the <br />most predominant sandstone unit in the entire area, referred to as <br />the Rollins Sandstone. This unit is considered to be the uppermost <br />tranitional sandstone unit in the Iles Formation (lower unit of the <br />Mesaverde Group). <br />• <br />~1 <br />