2012-02-28_REVISION - M1980244 (65)

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Cripple Creek & Victor Gold Mining Company Squaw Gulch Valley Leach Facility Design of 2 to 4 feet of growth medium in the valley floor bounded by Highway 67, and 6 to 18 inches of growth medium up the valley slopes. The growth medium was underlain by clayey gravels, clayey sands, silty gravels, silty sands, and clay. These soils classify as GC, SC, GM, SM and CL under the Unified Soil Classification System (USCS). Underlying these soils was fractured bedrock to depths ranging from approximately 4 feet upslope of the valley to 19 feet in the valley floor, with an average depth encountered of approximately 11 feet. The encountered bedrock was predominantly fragmented breccia with large clasts, and secondarily a competent and unweathered granodiorite. During the 2007 field investigation performed by SWC, perched groundwater was encountered in 12 test pits located within the Squaw Gulch valley floor bounded by Highway 67. The groundwater was intercepted at an average depth of 5 feet and was flowing at a rate of approximately 3 to 6 gallons per minute (gpm) from the test pit sidewalls. The perched groundwater was primarily contained within alluvium present in the valley floor and is likely to be seasonal. Groundwater was not encountered in any of the test pits excavated in Squaw Gulch during the 2010 AMEC field investigation. Three core holes, SWCBH -1 through SWCBH -3, were drilled within the footprint of the proposed PSSA embankment. The location of the geotechnical borings are shown on Drawing A20. The borings were advanced until bedrock was encountered, at which point coring commenced. Standard penetration tests (SPT) were conducted in all borings to assess the in place stiffness of foundation materials. The SPT blow counts ranged from 7 to 50 (refusal), with an average of approximately 22, indicating the presence of medium to dense in -place soils. The soils encountered in the borings consisted of well - graded sands with clay and silt, clayey sands, and silty sands. These soils classify as SW -SC, SW -SM, SC, and SM under the USCS. SWCBH -1, SWCBH -2, and SWCBH -3 intercepted bedrock at depths of 20, 24, and 9 feet, respectively. The coring commenced when the borings encountered refusal at the bedrock interface. The coring was advanced at least 10 feet into competent bedrock to assess the in -place permeability of the rock and to characterize the general rock mass conditions. The bedrock encountered in all core holes consisted of unweathered, competent granodiorite with slight iron staining and thin clay gouge at the joints. Single- packer permeability tests were conducted in each core hole. Testing occurred in 10 -foot sections at the base of the core holes at completion of coring. The bedrock permeability generally ranged from 2X10 to 2.5X10 " cm /s, indicating moderate permeability. The results of the packer permeability testing are presented with the core logs and boring logs in Appendix A.1. Results from the SWC geotechnical laboratory tests conducted on the soil samples obtained within the VLF footprint are summarized in Table 3 and presented in Appendix B.1.1. Results from the AMEC geotechnical laboratory tests are Project No.: 74201125G0 Page 14 1 September 2011 amec.