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CESARE,INC. <br /> 3. HAZARD ANALYSIS <br /> During the site visit on June 16, 2022, the CMTTS engineering geologist observed the area, measured <br /> the fracture sets, measured the rock mass rating (RMR) value for the rock mass, and created a <br /> stereonet of the fracture sets for kinematic analysis. <br /> 3.1 FIELD RMR VALUE CALCULATION <br /> For the obsidian outcrops: <br /> Weathering grade: I to II, fresh rock is exposed on the cut face <br /> Strength: weak to medium strong rock, estimated field value of 25 to 50 MPa <br /> Groundwater: completely dry except at the bottom of the pits <br /> Fracture sets: VII— 3 main joint sets with random fractures <br /> Fracture spacing: close spacing <br /> Low to medium persistence of fractures <br /> Aperture: "closed", 3 to 20mm <br /> No infilling <br /> Roughness: 2 to 4 <br /> Rock quality designation (RQD): field estimated value of < 50% <br /> RMR calculation: <br /> JA1=4, JA2=8, JA3=10, JA4=25, JA5=15, JB=(-25) <br /> RMR value 37 Class IV, Poor Rock <br /> RMR values for the rhyolite were not calculated because of its discontinuous nature and inconsistent <br /> character. It is concluded to be very poor rock overall. <br /> 3.2 STEREONET SURVEY <br /> A kinematic stereonet analysis of the fracture data was completed (Exhibit 4). The interpretation of <br /> the slope stability for this data set is that the cut face will be stable within plus or minus 200 of the <br /> present slope direction. If the high wall continues to follow the present strike, or within 200 of the <br /> present cut face, slope stability will be maintained. The multitude of fracture sets at close spacing <br /> and variable directions makes a large wedge failure or plane failure unlikely in the high wall. <br /> 22.6084 Obsidian Quarry Slope Consultation Letter 06.29.22 4 <br />