2021-09-27_REVISION - M1990057 - Laserfiche WebLink

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Mr. Dustin Czapla 7 CDRMS September 24, 2021 • The slurry will next be pumped back into the building for dewatering to separate our value carrying pregnant solution from the tailings. ■ Processed material then splits, with the pregnant solution going to the Merrill Crowe circuit for metals recovery, and the dewatered tailings goes to detoxification. ■ The Merrill Crowe area will be well contained, spill protected by an area sump, and by floor sumps. • The detoxification area is where we turn the tailings back into a slurry, to facilitate the cyanide detoxification. The tails will be mixed with process water and then Ferric Sulfite will be added to combine with any remaining cyanide to produce a benign material. The detoxified slurry will then again be dewatered, and conveyed out to the TSF. ■ These areas being protected by primary and secondary containment afford us strong control of our material to prevent any emissions into the environment at large. ■ Our TSF is designed with a primary containment layer, then a leak detection/conveyance layer, and finally a Geosynthetic Clay Liner (GCL). The leak detection layer reports to a sump, which will be monitored. (c) naturally occurring geological and geochemical conditions, and alterations of these conditions by the mining and metallurgical process. Response Geology The permit area (See Figure 9-1) and the adjacent properties are underlain by Till of Pinedale glaciation (late Pleistocene) (subangular to subrounded). The till is characterized as unconsolidated, pebble to boulder sized clasts in a clayey, silty sand matrix with an estimated thickness of 10-200 feet. Deposits generally poorly sorted to unsorted. Clasts range up to 30 feet in diameter and are competent, with very little weathering. Deposit is characterized by steep-crested lateral moraines and undrained hummocky depressions within terminal and recessional moraine complexes, deposited directly by glacial ice. Locally it has sorted and bedded lenses of sandy gravels deposited by subglacial streams. Convoluted and disturbed bedding due to minor glacial advances is locally preserved. (Madole, 1986; Nelson and Shroba, 1998; Benson and others, 2004, 2005, Brugger, 2007). A general stratigraphic section is illustrated on Figure 9-2. Representative geologic sections are presented in mill and adjacent landowner well logs (See attached Appendix 7-1). Faults/Fracture Systems Glacial tills and outwash sands and gravels make up the geologic foundation within two miles of the Leadville mill with depths exceeding 200 feet. (See attached Appendix 7-1 Diedrich well is located upgradient and East of the Leadville Mill) Seismic Activity Geologic mapping by the United States Geological Survey (USGS) indicates that the property is underlain by alluvium. Our subsurface investigation encountered material consistent with this interpretation. The surface and near surface soils are vulnerable to erosion especially from concentrated flows. (See Appendix 21-1-Stormwater Management Plan Erosion Control-BMPs in permit). Faults are mapped in the Leadville area. A map published by the Colorado Office of Emergency Management in 1999 shows the most recent movement of the faults occurred in the late to middle Quaternary (130 thousand to 750 thousand years ago) The area is considered by the 1997 Uniform Building Code (UBC) its least active zone designation.