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The site lies along the westerly flank of the West Elk Mountains within the drainage <br />' basin of the North Fork of the Gunnison River. Both Sylvester Gulch, to the east, <br />and "No Name" Gulch, to the west of the plant site, drain into the river. The <br />average annual precipitation is ten inches along the river. Most of the precipita- <br />tion falls as snow during the winter months, while the sparse summer precipitation <br />consists of isolated thunderstorms. Temperatures range from 10°F in the winter to <br />90°Ft in the summer, with the mean temperature about 70°F. Depth of surface- <br />=freezing is approximately 54 inches. The plant site is densely covered with tall <br />grasses and shrubs, consisting primarily of Gambol oak and Saskatoon serviceberry. <br />B. Soils Investigations: <br />An estensive subsurface soils investigation was performed by Chen and Associates <br />during the early summer of 1980. This investigation included the drilling of <br />approximately fifty (50) exploratory test holes and the setting oP approximately <br />sixteen (16) piezometers. Tests were performed to determine shear strength, <br />bearing capacity, permeability, compaction, compressability and swelling <br />characteristics of the various materials. Chen and Associates submitted a report <br />on both the initial investigation end a subsequent boring program. Refer to <br />Geotechnical Site Evaluation, Job No. 20,240, dated July 31, 1980. <br />C. Landslide Investigations: <br />A geotechnical investigation into possible landslide areas at the site was conducted <br />by Geo-Hydro, inc., during the Summer of 1980. Their findings indicate that the <br />prime area for potential landslides is in the area above the natural bench at <br />elevation 6,400 plus or minus. Their investigation was centered primarily on the <br />requirements for construction of the Portal Bench, Access Road, Substation pad, <br />and shop warehouse pad. It was their conclusion that the stability of any cuts <br />within the landslide boundary is directly related to the saturation state in the upper <br />fifteen (15) feet of the soils. As such, a dewatering system was designed and will <br />' be constructed to lower the water levels and, thus, stabilize the existing ground and <br />the planned construction within these areas. <br />The landslide report did not address the reclamation procedures to be followed for <br />the facilities within the landslide boundary. However, information contained in <br />that report was utilized for the investigations included in the report herein. <br />D. Piezometer Monitoring Program: <br />The ARCO Coel Company has contracted with the WATEC Company to perform <br />periodic measurements on the piezometers installed by Chen and Associates. The <br />WATEC Company will be continuing their monitoring operations throughout the <br />construction of the Mt. Gunnison Project to ensure that the dewatering system is <br />t operating properly. Such monitoring should be continued throughout the <br />operational life of the mine. <br />1 <br /> <br />