2003-07-15_REVISION - M1980037HR

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j. Mining Evaluation lfercaon Ingleside Quarry Highway 287, Larimer County, Colorado Terracon Project No. 20035106 Page 2 evidenced by large areas of Precambrian (six hundred million (600,000,000) years old or older) igneous and metamorphic rocks. The crystalline Precambrian basement complex was formed at great depths within the earth's crust and was once covered with thick sedimentary strata. The sediments were uplifted, along with the basement rocks, and folded during the large-scale, crustal movements known as the "Great Laramide Orogeny." Since this Late Cretaceous mountain building period (sixty-five million (65,000,000) to one hundred million (100,000,000) years ago), extensive weathering and erosion have removed the overlying sedimentary rocks, leaving the present-day topography. The Lower Permian Ingleside Formation forms the ridge currently being quarried. The Ingleside Formation in the area is approximately 240 feet thick. The formation consists of alternating beds of gray sandy limestone and dolomitic limestone and red fine grained quartzose sandstone well cemented with quartz or calcite. The youngest portion of the formation at the site located at the top of the ridge consists of a 2 to 3-foot layer of gray sandy limestone underlain by red cross bedded sandstone approximately 15 feet thick. The sandstone is underlain by another gray sandy limestone layer approximately 15 feet thick. Below the limestone is a thick red sandstone stratum. The red sandstone is underlain by another gray limestone. This limestone appears to form the contact with the younger Fountain Formation of Lower Permian and Upper to Middle Pennslyvanian Age. The Fountain Formation consists of reddish brown arkosic wnglomerate, sandstone, siltstone and shale. The road along the east edge of the site forms the boundary with the younger Lower Permian Owl Canyon Formation. The Owl Canyon formation consists of red siltstone and fine-grained sandstone. Across section of the quarry showing the bedrock fonnations and orientation is included in Figure 2 of this letter. Seismic activity in the area is anticipated to be low. The closest potentially active fault to the project area is the Livermore fault located several miles to the northwest. According to Kirham and Rodgers (1981) this fault has displayed no movement in the last 10,000 years. Braddock (1988) has mapped faults several miles north of the quarry, including the North and West Livermore faults. None of these faults other than the Livermore fault have been determined to have undergone recent movement by Widmann, Kirkham and Rodgers (1998). An epicenter of an earthquake of 2 to 2.9 on the Richter scale is noted west of the quarry in the Poudre Canyon on the Colorado Earthquake Hazards Map (Colorado Office of Emergency Management, 1999). This study indicates the earthquake occurred between 1962 and 1996. In November of 1882 an earthquake occurred in northern Colorado, Wyoming, Utah and Kansas. According to Kirkham and Rodgers (1986) the epicenter was located in the Northern Colorado, Southern Wyoming area. In 1986 Colorado Geological Survey scientists determined the earthquake center was located about ten miles north of Estes