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APPENDIX D <br />March 2000 -9 993-2099.150 <br />? Underground workings of moderate to shallow depth may have been <br />mined up close to surface. Holes were drilled across the alignment of <br />such workings. <br />? Some areas that had been mined or caved through to surface locally <br />indicated that shallow stopes extended away from the area. Holes were <br />drilled to provide an indication of how far such stopes might extend <br />away from the open surface features. <br />? Areas indicated on the mining plans as having been excavated as wide <br />open stopes, or where multiple openings appeared to be very close <br />together, and that may have been shallow or deep, may have caved up to <br />close to surface. Holes were drilled vertically down into these areas to <br />determine if open voids close to surface were present. <br />? Lateral extensions that were observed extending from open shafts or <br />shafts that were excavated are inherently shallow and may represent <br />potentially unstable excavations. Holes were drilled across such features <br />to determine the approximate geometry of such features and the <br />thickness of the crown pillar. <br />• <br />Specific discussions on what was encountered as part of the field investigation are <br />identified in Section 4. All holes indicated above as being drilled "across" features or <br />known openings were drilled at an angle to increase the potential of intersecting the feature <br />along the wall exposure. Such holes were drilled at an initial angle of approximately <br />60 degrees. Targets were established for each hole, and the objective was to "hit" the <br />target approximately 50 feet below ground surface, except where the overburden was more <br />than about 15 feet deep, in which case the target depth was correspondingly deeper. The <br />inclined holes were generally 100 feet long, and hence each hole extended past the <br />specified target area by about 40 feet or more. Holes which intersected stopes or level <br />workings were drilled again at angles that were progressively flatter to determine the <br />approximate depth of the back of the excavation below surface. <br />The vertical holes were drilled into areas where the mine plans indicated wide stope spans. <br />. Such wide spans require greater crown pillar thicknesses to ensure stability. Hence, some <br />1:19V%2D 4 INAL REPORrOMAMD.DW Golder Associates