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Geotechnical Stability Exhibit ��� <br /> Engineering Evaluation of Highwall Design for the South Quarry of the Morrison Quarry <br /> 1 Introduction <br /> Purpose and Scope <br /> This Geotechnical Stability Exhibit (Exhibit) presents the results of HDR Engineering, Inc.'s <br /> (HDR's) geotechnical evaluation for the highwall configurations in the Holcim Morrison Quarry <br /> mine near Morrison, Colorado. The work completed has been performed under HDR's Scope of <br /> Work agreement with Holcim (previously Aggregate Industries) dated May of 2022. This quarry <br /> is currently operating under Permit M-1973-021 from the Colorado Division of Reclamation <br /> Mining and Safety (DRMS), with the existing Permit M-1973-021 Amendment No. 7 (AM-07). <br /> The Geotechnical Stability Exhibit prepared by GEI, Inc., dated November of 2020, is included <br /> as an appendix to the existing permit. This Exhibit has been prepared to supplement the DRMS <br /> Permit M-1973-021 Technical Revision No. 9 (TR-09) and summarizes stability analyses <br /> performed to evaluate proposed quarry configurations in relation to the minimum required <br /> Factor of Safety (FoS) for rock slope stability per DRMS's Mined Land Reclamation Boards <br /> (M LRB) Policy 30, dated 2018. <br /> The following Scope of Work (SOW) was executed by HDR as part of the South Quarry <br /> evaluation. <br /> • Perform a subsurface exploration of the South Quarry to confirm historic subsurface <br /> data. <br /> • Develop a 3D model of the South Quarry using available data from previous subsurface <br /> explorations and data collected recently by HDR. <br /> • Review and provide additional laboratory testing results. <br /> • Conduct geotechnical analysis to determine FoS for various anticipated bench <br /> configurations for mining of the South Quarry from elevations 6600' to 6200'. <br /> Site Description <br /> The Morrison Quarry is a hard rock aggregate mine located west of Colorado Highway 8 and is <br /> approximately 0.5 miles north of U.S. Highway 285 in Morrison, Colorado. The mine location is <br /> shown in Figure 1, below, and is located west of the Dakota hogback along the Colorado Front <br /> Range, west of Denver. The quarry consists of three mining cells, which include the North, <br /> Central, and South Quarries. The North and Central Quarries are currently in the reclamation <br /> phase, whereas the South Quarry is active. The approximate extents of these mining cells are <br /> shown in Figure 2, below. <br /> May 2023 1 3 <br />