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• The Park Range Uplift has been interpreted as a product of the Laramide orogeny, which probably began in <br /> early Cretaceous time and reached its peak in Paleocene time. The Park Range uplift is anticlinal in nature <br /> with a core of igneous and metamorphic rocks flanked by sedimentary rocks of Upper Cretaceous age east <br /> of the project area. The Williams Fork Mountains are at the southeastern end of the Sand Wash Basin and <br /> contain upper Cretaceous rocks. <br /> Specifically, the near surface bedrock in the project site is mapped as the Cretaceous Williams Fork <br /> Formation. The Williams Fork Formation consists of light brown to white sandstone, gray shale and coal <br /> beds from 1,000 to 2,000 feet in thickness. Gray claystone -shale bedrock materials have been encountered <br /> in previous subsurface investigations in the project area. Sandstone outcroppings were observed north of <br /> the project site and along the north side of Routt County Road #27, as well as to the west- southwest of the <br /> project site. <br /> Overlying the bedrock in undisturbed areas, residual and colluvial clay soils are the products of chemical <br /> and mechanical erosion processes, which continue. These colluvial deposits appear to be relatively old in <br /> age, based on their consistency and density. These overburden soils and the upper bedrock materials have <br /> been removed and replaced over a majority of the project site during the mining and reclamation processes. <br /> Structural features including folding and fa sting in the region are commonly associated with the Park <br /> Range Uplift and the Laramide Orogeny Three northwest trending faults are mapped within or near the <br /> project site. A syncline (fold) structure is indicated by regional mapping just east of the project site. <br /> • Movement in these structures has been inferred in Tertiary time. <br /> Seismic activity in the project area is considered to be low. According to the Uniform Building Code <br /> (1997) all of Colorado is located in Zone 1. This classification implies the following seismic risk: "minor <br /> damage; distant earthquakes may cause damage to structures with fundamental periods greater than 1.0 <br /> second; corresponding to intensities V and VI on the Modified Mercalli Intensity Scale" (Algermissen, <br /> 1969). Based on the UBC definitions, levels of peak horizontal ground acceleration should not exceed <br /> 0.04g with a 90 percent probability level. Two earthquakes of significance have been recorded in the <br /> Steamboat Springs area since 1870. Both earthquakes, March 1895 and February 1955, corresponded to <br /> Modified Mercalli Intensities of V (Kirkham and Rogers, 1981). Based on the subsurface conditions <br /> encountered across the site and our review o1' the available literature, a Site Class of D would be used for <br /> this area in accordance with Table 1615.1.1 of the IBC 2003. <br /> Field Investigation <br /> The field investigation for this project was completed in two phases. The first phase consisted of the <br /> drilling of five (5) test holes and was completed on March 3 and 4, 2008. The second phase consisted of <br /> the excavation of seven (7) test pits and was completed on March 11, 2008. The test holes and test pits <br /> were advanced at the approximate locations shown in Figure #2 to determine the subsurface conditions for <br /> the foundation of the proposed CRDA. The client, using an instrument survey, determined locations and <br /> elevations of the test holes and test pits. <br /> • <br /> Job Number: 08 -7915 NWCC, Inc. Page 3 <br /> Revised 10/12/09 <br />