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2002 -11- 003-2203 <br />finished grade. The excavations were either backfilled with CSB to <br />approximately 10 feet below the finished grade or shaped for the CP at a <br />workable depth below 10 feet. The surface of the CSB or existing material <br />was compacted using the shovel from a CAT 330b excavator. A 3-foot <br />minimum CP was cast into the shaft and allowed to cure for a minimum of <br />7 days. A minimum 7-foot thick layer of CR was then placed onto the CP. <br />After the CR was allowed to cure, SF was then placed to the final grade, as <br />needed. In some cases, the excavation did not require placement of CSB <br />prior to placement of the CP and CR. <br />- For collapsed workings extending deeper than 25 feet and where the depth <br />to competent bedrock was greater than 7 feet to the final SLF subgrade <br />surface, the collapsed materials were excavated to a depth of 25 feet below <br />finished grade. The excavations were either backfilled with CSB to <br />approximately 3 feet below the soil/bedrock interface or shaped for <br />placement of the CP. The surface of the CSB was compacted using the <br />shovel from a CAT 330b excavator. A 3-foot minimum CP was cast into <br />the shaft and allowed to cure for a minimum of 7 days. A minimum 7-foot <br />thick layer of CR was then placed onto the CP. After the CR was allowed <br />to cure, SF was then placed to the final grade, as needed. <br />• - Shallow surface pits that were less than 25 feet deep below the final SLF <br />subgrade surface were excavated to bedrock or pit termination. The pits <br />were then backfilled with compacted SSF and SF to the final subgrade <br />elevation. <br />- In some cases, shallow surface pits were completely removed during slope <br />recontouring and required no further remediation. <br />2.1.2 Remediation of Laterals/Inclines/Adits <br />A number of laterals and adits were identified within the Phase IVa Area. As per the <br />remediation recommendations, underground workings that were identified within 50 feet of <br />the finished grade elevation were remediated. Workings that were deeper than 50 feet below <br />the final grade elevation did not require any remediation. <br />Remediation for laterals and adits consisted of drilling nominal 3-inch diameter blast holes into <br />the 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 <br />isI0012203taQOJICertRep060210032203.a400.a1940u~doc Golder Associates <br />