Laserfiche WebLink
• generally low infiltration rates associated with the ECOSA footprint area, the <br />ECOSA will be engineered and constructed with a low-permeability cover to <br />minimize water infiltration and oxygen diffusion into the placed overburden. <br />Construction <br />The total capacity of the MLE ECOSA will be approximately 66 million tons at <br />the design configuration. The maximum elevation of the OSA will be <br />approximately 10,565 feet once completed. Initial site preparation will include <br />vegetation and growth medium salvage, followed by removal of clay materials <br />from select areas in the footprint for use in the VLF liner system and as a low- <br />permeability cover for the ECOSA. Following clay removal, additional surface <br />preparation will include roughing the base of the ECOSA to enhance infiltration <br />drainage into the underlying diatreme rock. Sediment and drainage control <br />measures will be installed downgradient of the OSA as appropriate prior to <br />surface disturbance. <br />The facility will be constructed in 50-foot lifts to maximize compaction with <br />outslopes graded to 2.5H:1 V. The exposed end-dumped area will be minimized <br />• with an average of 9.1 acres exposed at any one time. Each lift outslope will be <br />graded to final grade after placement. A 10-foot bench will be constructed at the <br />toe of each 50-foot lift, sloped to direct runoff from the surface of the lift. Once a <br />lift is complete and the outslope has been graded to final contour, the outslope <br />will be covered with two feet of clayey gravel from the clay borrow area to serve <br />as a base course. The clayey gravel will be proof rolled prior to placement of the <br />compacted clay layer. The compacted clay layer will consist of clay from the clay <br />borrow area that has a plasticity index of not less than 15% and has been screened <br />to eliminate material greater than 2 inches in diameter. The compacted clay layer <br />will be 12 inches thick and will be compacted to 95% of optimum after <br />placement. Six inches of plant growth medium will be placed over the clay <br />followed by seeding during the next available planting season. This process will <br />be repeated lift by lift until the final configuration is achieved. <br />The low permeability cover for the ECOSA is designed to minimize infiltration <br />through the facility; minimize air entry to the covered overburden; and minimize <br />the potential for flow from the base of the ECOSA to Grassy Valley. Upon <br />completion of the low-permeability cover and revegetation, the initial infiltration <br />will be retained in the storage area until field capacity of the placed overburden is <br />• Cripple Creek & Victor Gold Mining Company <br />Cresson Project Mine Life Extension <br />5-18