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APPENDIX D <br />• March 2000 -16- 993-2099.150 <br />5.2 Rmmediation of Open or Collapsed Laterals/Inclines/Adits <br />A number of laterals, inclines, or adits have been excavated in the Phase IV area to <br />provide access to various mining locations. The locations of these as determined from the <br />historical mining plans are presented in Drawing Nos. 1 and 2. The accuracy to which <br />features on the mining plans can be referenced to the surface topographic surveying and <br />physically located on surface is very good, and there is a high probability that all of these <br />will be located on surface during the remediation program. <br />Those that have been located to date or that are located in the future will have collapsed <br />material and surficial material around the portal removed as the first step of the <br />remediation process. The stability of the immediate portal area will be reviewed so that <br />any potential adverse structural features can be identified. Potential instabilities will be <br />excavated. The crown pillar of the lateral will then be blasted. The blasted material will <br />be left in-place. If a depression exists after the blast, the depression will then be backfilled <br />• with Structural Fill. The area will then be capped with geogrid at the surface to control <br />settlement. <br />Alternatively, the open lateral may be plugged via injection of a flowable fill into the <br />excavation, without further excavation or blasting. A suitable, low compressibility, inert <br />fill material will be identified prior to implementation of the remediation program. <br />5.3 Mined Slot <br />During the remediation program for the Phase III VLF, numerous mined slots were <br />identified. Mined slots are narrow, nearly vertical excavations that were created as narrow <br />veins were mined. These slots are typically less than 3 feet wide and range in depth from <br />10 to greater than 50 feet deep. <br />• <br />1:M209?"ML REPOA'rJMAM.DM Golder Associates