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Lyons Quarry ��` <br /> 112d Reclamation Permit Operations 7` <br /> Technical Revision <br /> proposes to perform as-needed rock bolting of the exposed dacite formation in place of backfilling <br /> along the northeast and northwest-facing slopes of Quarry 1. <br /> 3.4 Rockfall Catchment Basin and Berms <br /> Scaling and rock bolting as mentioned above will remove or stabilize the highest risk blocks within <br /> the dacite highwalls. However, due to the columnar jointing of the dacite formation, the potential for <br /> development of rock blocks to fall out of the highwalls will always remain. As a result, an <br /> appropriately sized rockfall catchment basin and/or berm coupled with restricted access to the toe <br /> areas of the highwalls are necessary. The joint orientations and spacings in the dacite presented in <br /> the Kleinfelder report indicate a high potential to form elongated blocks that could range in size from <br /> about 2 to 6 feet in all dimensions, based on the reported spacing of the joint sets. <br /> Aggregate Industries proposes to connect the existing backfill at the east end of Quarry 1 with the <br /> ramp that leads to Quarry 2. This will require backfilling of the existing swale that allows access to <br /> Quarry 1, creating a 30-foot high berm across the swale as shown in Figure 6. By filling this swale, a <br /> large rockfall catchment basin will be formed at the toe of the northeast-facing highwall in Quarry 1. <br /> An updated rockfall evaluation using a Colorado Rockfall Simulation Program (CRSP) model (Jones <br /> et al., 2000) was used to verify that the catchment basin shown in Figure 6 is adequate to catch <br /> 100% of the modeled potential rockfall from both the dacite and Fountain Formation sandstone with <br /> an adequate factor of safety. The CRSP evaluation report is included as Attachment E-2. <br /> March 2021 1 10 <br />