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• - 2.0 GEOLOGIC ASSESSMENT <br />~r~~~~ <br />2.1 GEOLOGIC ASSESSMENT <br />Prior to drilling, the Colorado Office of the State Engineer, Division of Water Resources, was <br />contacted to obtain drilling permits. Copies of the correspondence and permits aze included in <br />Appendix I. <br />The drilling for the surface wells commenced on June I0, 1997, and was completed on June 16, <br />1997. The drilling for the underground wells commenced on June 10, 1997, and was completed <br />on June 26, 1997. Delays in drilling the underground wells occurred due to the competence of <br />the sandstone encountered. The surface monitoring wells were drilled using a rotary drill rig <br />utilizing an 8 5/e-inch outside diameter (OD) rotary bit to set surface casing and completing the <br />remainder of the boring utilizing a 5'/e-inch OD rotary bit. The underground borings were drilled <br />using a 2-inch core bit to set surface casing and utilizing a 1.5-inch OD bit to complete the <br />boreholes. A well could not be set in the RSS and RSN boreholes due to the small diameter of the <br />boreholes. Therefore, the RSS and RSN well were completed open borehole. <br />2.2 LITHOLOGY <br />• The project area is located in an area of the Cretaceous age Mesaverde Group. -The Rollins <br />Sandstone is the most continuous sandstone in the azea and is the focus of this study. The Rollins <br />Sandstone can generally be described as deltaic and beach front sandstone consisting of a <br />coarsening-upward regressive sequence (Collins, 1996). <br />The lithology encountered in the UTL boring consisted of gravel and sand alluvial material, <br />associated with the Colorado River, to a depth of 35 feet. Shale and interbedded carbonaceous <br />shale and sandstone was encountered below the alluvial material to a depth of 87 feet. Alternating <br />siltstone and sandstone was encountered to a depth of 117 feet. A two foot coal bed was <br />encountered at 105 feet. Shale and interbedded carbonaceous shale and coal were encountered to <br />130 feet followed by a fine grained, poorly sorted sandstone to 144 feet. The Cameo B-seam was <br />encountered at 144 feet and extended to 152 feet below grade. Shale and siltstone were <br />encountered to the top of the Rollins Sandstone at 175 feet. The Rollins Sandstone consisted <br />predominantly of a fine grained, light gray sandstone with varying degrees of cementation and <br />hardness. Interbedded shale was encountered in portions of the formation. The Rollins extended <br />to a depth of 275 feet and the bottom of the boring. The available ground water increased with <br />depth within the Rollins appazently due to fracturing and subsequent influence from the Colorado <br />River. <br />The N-Decline well consisted of 72 feet of talus and alluvial material followed by a dazk gray <br />shale to 110 feet below grade. A one-foot thick coal seam was encountered at 106 feet below <br />• grade. Siltstone with interbedded shale was encountered to 139 feet below grade. The Cameo-B <br /> <br />