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000 <br /> Office(303)688-6611 6374 S. Racine Circle• Centennial, Colorado 80111 <br /> Fax(303) 688-6685 <br /> www.castierockconstructionco.corn <br /> Engineering Evaluation of Impacts to Utility Structures Due to <br /> Proposed Mining <br /> The following analysis is being provided in accordance with the 111(1)(a) Reclamation Permit <br /> requirements for the proposed Stoker Borrow Pit approximately 1 mile North of Eads, Colorado <br /> on US -287. On the East side of US-287 approximately 190 feet from the proposed mining limits <br /> there is a Lumen Fiber Optic Cable and two telephone cables owned by Eastern Slope Rural <br /> Telephone Company. All three of the existing lines are buried underground at approximately 30 <br /> to 36 inches of depth based off existing utility locate data. The existing farm road which will be <br /> used to access the proposed mine has an existing asphalt field approach above all three utility <br /> structures believed to be 4 to 6 inches thick. The below data and analysis demonstrate that there <br /> will be no impact to these buried facilities due to the proposed mining operations. <br /> The two potential impacts to these utility structures would be undermining/destabilization due to <br /> mining excavation and crushing due to truck traffic over the existing line, each impact is <br /> addressed below. <br /> Undermining or Line Destabilization: <br /> On the East side of US-287 approximately 190 feet from the proposed mining limits there <br /> is a Lumen Fiber Optic Cable and two telephone cables owned by Eastern Slope Rural <br /> Telephone Company. All three of the existing lines are buried underground at <br /> approximately 30 to 36 inches of depth. The proposed depth of excavation adjacent to <br /> these lines is 10 feet deep (see contours from reclamation plan in Appendix C)with a <br /> maximum 4:1 slope. Soil data collected from the site showed that the soil is <br /> predominantly classified as an AASHTO A-2-4(0). Typically, A-2-4(0) soils exhibit an <br /> internal angle of friction somewhere between 30 and 34 degrees which is steeper than a <br /> 4:1 (25 degrees)thus the 4:1 slope should provide a safety factor 1.36 for a structure not <br /> exerting ground pressure at the top of slope. This top of slope will be a minimum of 190 <br /> feet from the 3 utilities and thus there is absolutely no potential for undermining or <br /> destabilization of the structures due to mining excavation. <br /> Crushing From Mine Traffic Loading: <br /> The proposed mine entrance crosses the structures with an existing asphalt field <br /> approach. This field approach is believed to be 4 to 6 inches thick based off pavement <br /> cores taken along the highway between mileposts 114 and 116. The material beneath this <br /> asphalt should be classified as an AASHTO A-2-4(0)based off soil samples taken nearby <br /> (see Appendix A). CDOT testing for the pavement design on US-287 adjacent to the <br /> proposed mine shows a resilience modulus of 21,500 psi, a Poison's Ratio of 0.35, and a <br /> coefficient of lateral earth pressure of 0.5 for this material (see Appendix B Page 13 of <br />