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Cripple Creek & Victor Gold Mining Company Squaw Gulch Valley Leach Facility Design <br />Appendix D presents a site reconnaissance of the underground mine workings within <br />the Squaw Gulch VLF area. Remediation of underground workings will be required to <br />ensure the stability of the foundation of the VLF, similar to that completed for Phase 5 <br />and submitted as Amendment No. 9. A site reconnaissance of the Squaw Gulch VLF <br />area was completed by Golder in February 2007, SWC in 2008, and again as part of <br />this design by AMEC in May of 2010. The primary activities that were completed <br />included the following: <br />• A detailed review of the available historical records, including the historical mining <br />plans filed at CC &V and in the public record. <br />• A detailed surface reconnaissance program undertaken to further characterize the <br />surface disturbance features. Surface disturbances were photographed and <br />documented. <br />These data, combined with the experience gained during the construction of the <br />current Cresson Project VLF, were used to develop the mine working remediation <br />guidelines. The general approach to remediate the mine workings is as follows: <br />• Shaft/stope remediation (Detail 12 on Drawing A270): <br />o For open excavations where the depth to bedrock is less than 7 feet below the <br />final SLF subgrade surface: Backfill open shafts with coarse shaft backfill to <br />approximately 10 feet below the SLF subgrade surface and then place a <br />concrete plug, cemented rock fill, and structural fill to achieve SLF subgrade <br />surface. <br />o For open excavations where the depth to bedrock is greater than 7 feet below <br />the final SLF subgrade surface: Backfill the open shafts with coarse shaft <br />backfill to 3 feet below the soil /bedrock interface. Then place a concrete plug, <br />cemented rock fill, and structural fill to achieve SLF subgrade surface. <br />o For collapsed excavations where the depth to bedrock is less than 7 feet below <br />the final SLF subgrade surface: Excavate collapsed material from shafts to a <br />depth of 25 feet below the SLF subgrade surface, then backfill with coarse <br />shaft backfill to approximately 10 feet below the SLF subgrade surface and <br />then place a concrete plug, cemented rock fill, and structural fill to achieve SLF <br />subgrade surface. <br />o For collapsed excavations where the depth to bedrock is greater than 7 feet <br />below the final SLF subgrade surface: Excavate collapsed materials from <br />shafts to a depth of 25 feet below the SLF subgrade surface, then backfill with <br />coarse shaft backfill to approximately 3 feet below the soil /bedrock interface, <br />and then place a concrete plug, cemented rock fill, and structural fill to achieve <br />SLF subgrade surface. <br />• Excavate shallow surface pits to rock or to 25 feet below the SLF subgrade surface <br />(whichever is less), then backfill with compacted select structural fill and /or <br />Project No.: 74201125G0 Page 11 <br />1 September 2011 <br />amec0 <br />