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T <br /> TETRA TECH Updated Tucson South Proposed Gravel Mine Slope Stability Analysis <br /> N <br /> November 9, 2018 <br /> 4.3 MODEL RESULTS <br /> The model results are given in Table 2. The setbacks listed are the minimum setbacks required. Resulting <br /> sections from the model are presented as Figures 2 through 17. <br /> Tucson • Aggregate <br /> StabilityModels <br /> Section Structure Mud Static Factor Seismic Factor Required Setbacks <br /> Lens of Safety of Safety Based on Model Results <br /> (Y/N) (ft) <br /> 1 Tucson St. (from West Pit) Y 1.5- 1.6 1.3 - 1.4 75 <br /> 2 Tucson St. (from East Pit) N 1.6- 1.7 1.3- 1.4 75 <br /> 3 South Platte River N 1.5- 1.6 1.3- 1.4 90 <br /> 4 Water Pipeline N 1.5- 1.6 1.3- 1.4 110 <br /> 5 Gas Well Y 1.8- 1.9 1.3- 1.4 70 <br /> 6 Power Pole N 1.5- 1.6 1.4- 1.5 150 <br /> 7 Brighton Ditch N 1.6- 1.7 1.3- 1.4 160 <br /> 8 Highway 7 (from closest N 1.7- 1.8 1.3- 1.4 85 <br /> mine limits to road) <br /> 5.0 LIMITATIONS <br /> The findings presented in this Report are based on previous studies of the site and strength parameters for the <br /> various materials modeled provided by the Colorado Division of Minerals and Geology in 2004. Tetra Tech should <br /> be contacted if the mining plans change or if the subsurface conditions vary from their portrayal in this study to <br /> reevaluate the potential effects of any changes on the factors of safety for the critical structures. Factors of safety <br /> were only considered at the critical structure and were not considered close to the highwall. <br /> Please do not hesitate to reach out with any questions or comments. <br /> Sincerely, <br /> Michelle Franke, El Justin Stoeber, PE <br /> Geotechnical Engineer Tetra Tech <br /> Tetra Tech Geotechnical and Dams Group Leader <br /> 1560 Broadway, Suite 1400 1560 Broadway, Suite 1400 <br /> Denver, CO 80202 Denver, CO 80202 <br /> 720-931-9307 720-931-9344 <br /> michelle.franke(aMetratech.com iustin.stoeber aatetratech.com <br /> Page 515 <br />