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August 2002 -] 0- 003-2203 <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 Basting), 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 3306 <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 soi]/bedrock interface. The surface of the <br />CSB was compacted using the shovel from a CAT 3306 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 />two~zzoawaomcwcmosoz~ao~zzoa.oaoo.on~aon~ao~ Golder QS50Clot25 <br />