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<br />INTRODUCTION <br />• <br />A soil and rock slope stability evaluation was conducted by engineering geologists from <br />LACHEL 8 Associates, Inc., Golden, Colorado at the Deer Creek Canyon Quarry located <br />in the NE 1 /4, Section 12, Township 6 South, Range 70 West, (Figure 1), about 3.9 miles <br />west from the Kipling Parkway exit off of Highway C-470. The study was conducted at <br />the request of Rocky Mountain Rock Products Company, Inc., a Western Mobile <br />Company, lessee of the quarry, under State of Colorado, Permit No. M-79214 to comply <br />with the State of Colorado requirement for periodic review the stability of the quarry. A <br />field investigation was undertaken on May 30 and 31, 1995 to evaluate the rock and soil <br />stability within the environs of the quarry and, if unstable, the types of failures most likely <br />to occur. <br />GEOLOGIC SETTING <br />Regional Geology <br />The ancestral Colorado Front Range is the result of the complex physical history of the <br />area involving the deposition of a great thickness of sedimentary rocks of variable <br />resistance, the intrusion of dikes and small stocks, the out-pouring of lava flows, and the <br />development of a great anticlinal uplift, the Laramide Orogeny. There were repeated <br />erosion cycles following renewed uplifts (Leroy, 1946). <br />During the Laramide Orogeny, the large arch developed at the same time as the <br />downwarping of the Denver Basin to the east in Late Cretaceous and Early Tertiary time. <br />Deep truncation of the anticline exposed a core of crystalline rocks, mostly Precambrian <br />in age. The core is a long block of hard igneous and metamorphic rock, granite, gneiss, <br />and schist, 1,000 to 1,750 million years old. This core rose 15,000 to 25,000 feet during <br />the Laramide (Van Tuyl, 1955).. <br />The Laramide Orogeny was accompanied by intense folding and faulting of the <br />metamorphic formations. The dominant tectonic pattern has a northwest trend. The <br />