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south of downtown Golden (Figure 1). The natural topography of the property <br />increases significantly in elevation to the west, with elevations varying from <br />approximately 6,250 feet along the eastern boundary to 7,110 feet on the <br />western boundary. The quarry currently consists of three distinct mining areas: <br />the main pit, the middle level that is adjacent to but above and south of the main <br />pit, and the upper level of excavation in the southem expansion area (Figure 2). <br />Currently, the floor of the main pit is at elevation 6,340 feet; the middle level is <br />being excavated from 6,515 feet to 6,480 feet; and the third and fourth benches <br />of the southem quarry expansion are being advanced at elevations of 7,045 and <br />7,010 feet respectively. <br />This region of the Rocky Mountain Front Range was formed structurally during <br />the Laramide orogeny in the Late Cretaceous and early Tertiary period. The <br />gneissic bedrock within the quarry is believed to have undergone two to three <br />episodes of deformation during Precambrian time (Gable, 1968). During this <br />time, the bedrock material was intruded by several distinct igneous bodies and <br />dikes. The gneisses are mapped as a series of folds, which are oriented roughly <br />east-west and have been broken and displaced by faults believed to range in <br />age from Precambrian to Tertiary. The two dominantly mapped regional fault <br />orientations are to the north to northwest, and west to northwest. <br />The granitic gneiss found in the quarry is generally hard and relatively <br />competent. The gneiss varies in color from grayish orange to dark gray, with <br />occasional banding visible along the foliation of the rock. The term foliation <br />refers to the realignment of minerals into a parallel orientation as a result of the <br />intense heat and/or pressure of metamorphism. The rock mass tends to be <br />weakest along the foliation planes, which ultimately results in a discontinuity set <br />that is parallel to the orientation of the foliation. The foliation orientation is the <br />most prominent discontinuity set identified in the quarry and is readily visible in <br />the east and west walls of the quarry; revealing a rock foliation that undulates in <br />a synclinal and anticlinal fashion, with noticeable variation in dip angles across <br />each wall. <br />-3- <br />