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By ATL Date 1011112020 Client Aggregate Industries Sheet 3 of 7 <br /> Updated Rockfall Evaluation—Lyons Quarry:Technical Review <br /> Chkd.By NA Date 10/21/2020 Description Update Job# 10246984-002 <br /> Table • - by • • • <br /> Slope Type Surface Tangential Normal <br /> Roughness Coefficient Coefficient <br /> Sandstone 2:1 cut slope 0.35 0.85 0.3 <br /> Dacite Wall 0.25 0.9 0.25 <br /> High Anqle Talus 0.8 0.85 0.25 <br /> Low Anqle Talus 1 0.8 0.2 <br /> Catchment Area (Soil) 0.5 0.8 0.15 <br /> • <br /> Rock Type Density Shape Rock Sizes Simulated <br /> (feet) <br /> Sandstone 150 Spherical 2,4, 6, 8, and 12 foot <br /> diameter <br /> Dacite 180 Cylindrical 1x4, 2x4, 2x6, 3x6, and <br /> 6x12 (diameter x length) <br /> 3.0 RESULTS: <br /> Northeast Facing Dacite Wall <br /> Since the swale berm shown in Figure 1 was already part of the reclamation plan regardless of rockfall <br /> potential, results of this evaluation were used to determine whether the catchment berm that is created <br /> will be adequate to catch 100% of all modeled rock sizes as listed in Table 2. Section A, shown in <br /> Figure 2, was evaluated for the northeast-facing dacite wall as the critical section because it is the <br /> highest and steepest slope. The first step was to evaluate the necessary length of the runout area <br /> without a berm. Several iterations were simulated with the analysis point at various distances from the <br /> toe of the slope. The results shown in Table 3 indicate that a runout length of 170 feet will catch 100% <br /> of even the largest rock sizes simulated. <br /> The eastern extent of the northeast highwall has only about 30 feet of runout length available at the <br /> toe but has an opposite facing slope at 1 H:1 V across the runout area. To evaluate the maximum <br /> height along the slope that would stop 100% of all modeled rock sizes the location of the analysis <br /> point was varied. The results are shown in Table 4 and indicate that 100% of all rock sizes will be <br /> caught at a height of 9 feet along the opposite facing slope. The opposite slope at the east end of the <br /> highwall is 50 feet high which provides a factor of safety of 5.6 relative to the slope height, as in actual <br /> slope height divided by required slope height. <br /> These two evaluations bracket all situations. The lowest height of an opposite slope within the <br /> catchment basin is 20 feet which has a runout length of about 130 feet. The catchment berm as <br /> planned will catch 100% of all modeled rock sizes with a factor of safety. <br />