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Slope Stability and Setback Exhibit – Windsor East Mine September 21, 2022 <br />TETRA TECH 5 <br />Table 4. Factors of Safety for proposed reclamation slope with stockpile <br />Location Factor of Safety <br />(Static) <br />Factor of Safety <br />(Pseudostatic) Object Measured From <br />Section 1 1.7 1.3 Edge of ROW <br />Section 2 1.7 1.3 Edge of ROW <br />Section 9 1.9 1.5 Edge of ROW <br />4.0 LIMITATIONS <br />The findings presented in this memorandum are based on information from previous investigations at the site and <br />strength parameters of the modeled materials assumed from typical published values. Tetra Tech should be contacted if <br />the mining plans change or if the subsurface conditions vary from the descriptions here as reevaluation may be <br />necessary to investigate the potential effects of the changes on the factors of safety for the critical structures determined <br />in this evaluation. Factors of safety for this evaluation were limited to effects at the critical manmade structures and were <br />not an evaluation of the overall mining highwall or mine slopes. <br /> <br />Prepared By: Reviewed By: <br /> <br /> <br />Aric Hotaling, P.E. Caleb Stock, P.E. <br />Geotechnical Engineer Senior Geotechnical Engineer <br /> <br />Attachments <br />Attachment A – Geotechnical Data from Deere & Ault, 2017 <br />Attachment B – Geotechnical Data from Martin Marietta, 2019 <br />Attachment C – Figure A - Location of Slope Stability Cross Sections <br />Attachment C - Figures 1 through 12 – Slope Stability Analysis Results <br />O:\Projects\Longmont\8741\117-8741006\SupportDocs\Calcs\Stability\Stability Analysis Tech Memo_final 2022 0921.docx