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The original Pierce adit bulkhead location was constrained by a weak altered <br />• zone on the south rib, which terminates about 35 feet outby from the stope <br />intersection. Placement of a bulkhead within that alteration affected zone would <br />have at a higher risk of perimeter leakage, and therefore the bulkhead was <br />located outby from that altered zone, and also outby any areas of the sill (floor) <br />being undermined significantly. Thus, in the original calculations, a tentative <br />location (inby side) of 304 feet from the portal was selected. <br />It was noted on an examination from the bridge over the stope area farther inby <br />in the Pierce adit that there was a possible stope area under the adit. <br />r~ <br />To investigate the thickness of the sill pillar (adit floor) above the suspected stope <br />area, probe hole drilling was conducted to verify that there was adequate sill <br />thickness. The probe hole drilling verified that there was at least 30 feet of rock <br />pillar, however there was a fractured and rubbellized zone encountered below <br />Figure 2: Area of possible stope <br />