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August 2002 40- 003.2203 <br />0 <br />2.1 Underground Workings Remediation <br />Historic underground workings within the footprint of the Phase IVa Area were remediated <br />following the recommended remediation plans presented in Drawing No. 12 of the <br />Construction Drawings. <br />A summary of the underground workings remediation is presented in Table 3. This table <br />shows the working identification, location (northing and easting), type of working, <br />remediation quantities, and comments. The following provides a summary of the general <br />remediation methods for the underground workings within the Phase IVa Area. <br />2.1.1 Remediation of Shafts Stopes and Shallow Surface Pits <br />The following is the general approach used to remediate isolated shafts and shallow surface <br />Pits: <br />► For open workings where the depth to competent bedrock is less than <br />7 feet to the final SLF subgrade surface, the excavations were backfilled <br />with CSB to approximately 10 feet below the finished surface grade. The <br />surface of the CSB was compacted using the shovel from a CAT 330b <br />excavator. A 3 -foot minimum CP was cast into the shaft and allowed to <br />cure for a minimum of 7 days. A minimum 7 -foot thick layer of CR was <br />then placed onto the CP. SF was then placed to the final grade, as needed. <br />► For open workings where the depth to competent bedrock was greater than <br />7 feet to the final SLF subgrade surface, the excavations were backfilled <br />with CSB to 3 feet below the soil/bedrock interface. The surface of the <br />CSB was compacted using the shovel from a CAT 330b excavator. A <br />3 -foot minimum CP was cast into the shaft and allowed to cure for a <br />minimum of 7 days. A minimum 7 -foot thick layer of CR was then placed <br />onto the CP. After the CR was allowed to cure, SF was then placed to the <br />final grade, as needed. <br />► For collapsed workings extending deeper than 25 feet and where the depth <br />to competent bedrock was less than 7 feet to the final SLF subgrade <br />surface, the collapsed materials were excavated to a depth of 25 feet below <br />I -VX 03W40mcalRepoAOZM2203 .0400,04740bd.eoc <br />Golder Associates <br />