2025-03-14_PERMIT FILE - M2025016 (17)

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// PAGE 1 GEOTECHNICAL STABILITY Raptor Materials, LLC Cogburn Sand, Gravel, and Reservoir Project February 2025 A Regular Impact (112) Construction Permit Application – Colorado Division of Reclamation Mining and Safety, Office of Mined Land Reclamation GEOTECHNICAL STABILITY EXHIBIT SECTION 1 THROUGH 4 On a site-specific basis, an Applicant shall be required to provide a geotechnical evaluation of all geologic hazards that have the potential to affect any proposed impoundment, slope, embankment, highwall, or waste pile within the affected area. A geologic hazard is one of several types of adverse geologic conditions capable of causing damage or loss of property and life. The Applicant may also be required to provide a geotechnical evaluation of all geologic hazards, within or in the vicinity of the affected lands, which may be de-stabilized or exacerbated by mining or reclamation activities. On a site-specific basis, an Applicant shall be required to provide engineering stability analyses for proposed final reclaimed slopes, highwalls, waste piles and embankments. An Applicant may also be required to provide engineering stability analyses for certain slopes configuration as they will occur during operations, including, but not limited to embankments. Information for slope stability analyses may include, but would not be limited to, slope angles and configurations, compaction and density, physical characteristics of earthen materials, pore pressure information, slope height, post-placement use of site, and information on structures or facilities that could be adversely affected by slope failure. Where there is the potential for off-site impacts due to failure of any geologic structure or constructed earthen facility, which may be caused by mining or reclamation activities, the Applicant shall demonstrate through appropriate geotechnical and stability analyses that off-site areas will be protected with appropriate factors of safety incorporated into the analysis. The minimum acceptable safety factors will be subject to approval by the Office, on a case-by-case basis, depending upon the degree of certainty of soil or rock strength determinations utilized in the stability analysis, depending upon the consequences associated with a potential failure, and depending upon the potential for seismic activity at each site. At sites where blasting is part of the proposed mining or reclamation plan, the Applicant shall demonstrate through appropriate blasting, vibration, geotechnical, and structural engineering analyses, that off-site areas will not be adversely affected by blasting. To assure the stability of any significant, valuable, and permanent man-made structures that may exist within 200 feet of planned extraction activity, a complete and thorough stability analysis was performed by American Water Engineering Services, LLC. (AWES). Their report from October 2024 is based upon on-site samples collected from the intended areas of extraction. Copies of the AWES reports are included at the back of this exhibit. The included AWES report verifies that the maximum planned extraction slopes of 1.25H:1V will not pose a hazard to such structures. To the extent practical, operational setbacks will be observed consistent with those detailed under Exhibit D: Extraction Plan. Grading and reclamation of completed areas of extraction will reduce extracted slopes to a minimum of 3H:1V, or flatter, over a majority of the extraction area, in conformance with Rule 3.1.5(7).