Laserfiche WebLink
October 2004 -10- 043-2170 <br />• 2.1.2 Remediation of Laterals/Inclines/Adits <br />Laterals and adits identified within 50 feet of fmished grade in the Phase IVc OSA were remediated <br />according to approved remediation specifications. Workings that were deeper than 50 feet below the <br />final grade elevation did not require any remediation. <br />Remediation for laterals and adits consisted of drilling nominal 3-inch diameter blast holes into the <br />crown pillar (the rock between the ground surface and the roof of the working) using an <br />Ingersoll-Rand EMC-660 pneumatic-hammer track drill rig. The blast holes were loaded and the <br />crown pillars blasted into the mined void. If the blasted lateral or adit could not be fully and safely <br />excavated, two layers of geogrid sepazated by a layer of Select Structural Fill was placed 15 feet <br />(laterally) beyond the mine working limits. <br />All blast holes that did not intercept the underground working or were not incorporated in the blast <br />were completely grouted with bentonite slurry prior to blasting the crown pillar and remediating the <br />working. <br />• Underground working remediation activities for the Phase Nc OSA were performed during the <br />construction seasons from 3uly 2001 through June 2004. <br />2.2 Underdrains <br />Ames constructed approximately 1,348 lineaz feet of Secondary Underdrain (SU) in the Phase Nc <br />OSA. Record Drawing No. 2 shows the location of the SU. The cross-sectional dimensions of the SU <br />was nominally 4 feet wide by 2 feet deep, providing across-sectional area of 8 square feet, as shown on <br />IFC Drawing 13, Detail 2. Ames excavated each SU trench to the minimum dimensions, and placed <br />geotextile and OF in the trench. Ames placed SSF over the geotextile to a minimum depth of 6 inches. <br />The SU geosynthetic installation is discussed further in Section 3.1. Approximately 400 cubic yards of <br />UF, 100 cubic yards of SSF, and 17,500 square feet of geotextile were used to construct the SU. <br />2.3 Leak Detection System <br />Ames constructed approximately 6,5601inear feet of LDT and 745 linear feet of LDT extension in the <br />• Phase IVc OSA, at the location shown in Record Drawing No. 4. <br />~:w+vnmwoman~eexiv~-~oww~in,u.aan,ws.a~.enrv~na Golder Associates <br />