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RECEIVE® <br /> Black Obsidian Pit—Permit M-1987-026 <br /> 112c Conversion Application (rev 7/14/22) ��� 9 2022 <br /> DIVISION OF RECLAMATION <br /> Rule 6.5 MINING AND SAFETY <br /> Geotechnical Stability Exhibit <br /> A key feature of the proposed mining and reclamation plans for this 112c conversion includes a steep <br /> highwall configuration, composed of vertical walls alternating with level benches. The overall final <br /> highwall gradient will be 0.5H:1.OV. The operator believes this gradient is stable for the mining stages as <br /> well as for the long-term post-mining stage. <br /> To support this,the operator engaged the services of Cesare Inc./CMT Technical Services to investigate <br /> the site and produce a geotechnical stability report. The following report states that a benched highwall <br /> in this obsidian quarry,with an overall slope as steep as 0.5H:1.OV, is considered stable. <br /> Please see the following report. <br />