2012-08-24_REPORT - M1980244 (11)

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II) Underground Mine Workings A) Discovery During cut to fill two Underground Workings were encountered. The locations were surveyed by Ames and given a project designations of UG #4069 and #UG4070. B) Drilling Confirmatory drilling was performed at Underground Working #4001. A drill pattern was set out by an AMEC field representative. Eleven holes were drilled encountering six voids. An approximate total of 550 lineal feet was drilled. As -built survey of the drill holes was performed by Ames. Confirmatory drilling was performed at Underground Working #4031. A drill pattern was set out by an AMEC field representative. Twenty -six holes were drilled encountering thirteen voids. An approximate total of 1,300 lineal feet was drilled. As -built survey of the drill holes was performed by Ames. Confirmatory drilling was performed at Underground Working #4048. A drill pattern was set out by an AMEC field representative. Thirteen holes were drilled encountering three voids. An approximate total of 650 lineal feet was drilled. As -built survey of the drill holes was performed by Ames. Confirmatory drilling was performed at Underground Working #4052. A drill pattern was set out by an AMEC field representative. Twelve holes were drilled encountering ten voids. An approximate total of 600 lineal feet was drilled. As -built survey of the drill holes was performed by Ames. Confirmatory drilling was performed at Underground Working #4058. A drill pattern was set out by an AMEC field representative. Sixteen holes were drilled encountering nine voids. An approximate total of 800 lineal feet was drilled. As -built survey of the drill holes was performed by Ames. Grouting of missed (non -void) confirmatory drill holes was performed at Underground Workings #4007, 4051, and #4053. A grout pump and laborers were used to place bentonite grout into the "miss" drill holes. Q Remediation Remediation of Underground Working #4000 was performed with the placement of a three -layer geogrid cap extending 15 feet from the working location identified during confirmatory drilling. Approximately 25,200 square feet of geogrid was placed and accepted by an AMEC field representative prior to select structural fill placement. Approximately 365 cubic yards of select structural fill was then placed over the previously installed geogrid layer in a 6 -inch compacted lift. Prior to compaction the select structural fill material was moisture conditioned using a CAT 773 water truck. Compaction of the select structural fill was then performed using a 10 -ton smooth drum compactor using the static method. Four nuclear density tests were performed with results passing. Moisture - density relations were performed in accordance with ASTM D698 -07. Remediation of Underground Working #4016 continued as the fill progressed in the area. A CAT 345 excavator was used to place small lifts of overburden fill into the working and bucket tamp the material. This was performed due the working being too narrow for the CAT 563 vibratory smooth drum compactor to be used for compaction. Remediation will continue as the overburden fill placement progresses in the area. MEW Weekly Report WE 03.17.2012