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December 27, 2023 Page 8-1 <br />Agapito Associates, Inc. <br />8 CONCLUSION <br />Agapito has considered the typical pillar extraction approaches and methods best suited for the <br />Sunset Mains South pillars between crosscuts 2 and 30. Based on the considerations listed below, <br />the full extraction approach using the Christmas tree extraction method has been recommended. <br /> Pillar extraction mining will begin at crosscut 30. <br /> Pillar extraction will stop one crosscut outby of the BF Fault at the outby end of Sunset <br />Mains South. <br /> In order to maintain a bleeder system around areas of gob and to inspect inby seals, a single <br />life-of-mine roadway must remain travelable during and after pillar extraction activities. <br /> The pillars will be extracted in their current state and, as such, additional development and <br />roof bolting should not be considered for preparation in the pillar extraction plan. <br /> To avoid unstable remanent pillars, the pillar extraction should aim to mine as much of the <br />pillar as safely and practically possible. <br /> If a large percentage of the pillar remains following extraction, the remaining pillar should <br />be classed as long-term stable. <br /> <br />Empirical and numerical assessments indicate that the pillars in Sunset Mains South are suitable <br />for full extraction using the Christmas tree method. The mains outcomes of the assessment are as <br />follows: <br /> The existing pillars are adequately sized to support the front abutment load to a satisfactory <br />SF. <br /> The remnant pillars that will remain following extraction will not be capable of bearing <br />any significant loads. <br /> The remaining pillars in the gateroads and chute roads will remain long-term stable with <br />SFs in excess of 1.5. <br /> The pillars next to the life-of-mine roadways have been assessed as long-term stable with <br />SFs in excess of 1.5. <br /> The maximum surface subsidence associated with the pillar extraction mining is estimated <br />to be 3.5 ft. <br /> <br />Variable roof and rib conditions are anticipated during pillar extraction activities, and the presence <br />of local geotechnical anomalies should be examined and evaluated. Particular attention should be <br />given to the roof conditions prior to pushout removal and prior to retreating up to an intersection. <br />Prior to lifting, an appropriate mine official should examine the roof and ribs and, if need be, a <br />remedial support strategy implemented. These potential areas include locally poor roof, joint <br />zones, faults, excessive rib spall, and/or overwide roadways. <br />Lastly, the gob edge should be controlled by a set of two MRS placed on the gob side of the lift. <br />The MRS should be kept as close as possible to the continuous miner during the lifts. As the lifts <br />approach the outby intersection, another set of two MRS should be installed in the mouth of the <br />intersection.