2020-12-09_REVISION - M1977300 - Laserfiche WebLink

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Waste Rock Pile Cap This work scope is not necessary due to the placement of the excavated materials in the Minnesota and Black Forest Mines. The top of the waste rock piles will not be disturbed. Consequently, CLL is requesting that the $88,389 included in the current bond be released. "Denver Water Contingency" During the permit transfer process in February 2018, DRMS, CLL and Denver Water had extensive discussions regarding the operation of the water treatment system at the mine. Because the mine pool was pumped down to a level that would maintain the compliance point of 150 feet below the Steve Adit, CLL did not need to operate the system for 12 months a year. Rather, the level was adequate for CLL to operate only 6 months out of the year and maintain the compliance level. The result of the joint discussions was to have CLL further evaluate that the 6- month operation time was adequate. As a"contingency"DRMS included another$1,187,529 to the bond calculation for potential increased annual operating time. DRMS stated that the amount could be released upon making an adequate demonstration that 6 months operation was adequate. CLL is intending to provide the full justification in the upcoming Amendment No. 6 to the mine permit in 2021. However, CLL has taken additional actions to ensure that the 6-month operation timeframe was fully in compliance with the permit conditions. Based on over 3 years of water level data in the mine, CLL calculated that lowering the dewatering pump down to 348 feet below the Steve Adit would provide a wide margin of safety for compliance. CLL located the alternate pumping location in 2018. A down-hole camera inspection was conducted in the Jeffrey Air Shaft to approximately 488-feet below the Sunshine Adit (approximately 348 feet below the Steve Adit). The successful camera inspection supported relocating the mine pool dewatering pump to the air shaft. The new submersible pump (50HP Goulds Model 7CSLC)was lowed to approximately 550 feet below the Sunshine Adit (approximately 410 feet below the Steve Adit)on a custom fabricated housing sled via a winch system (Figure 7). The housing sled protected and supported the pump during installation. The dedicated winch system was installed adjacent to the vent shaft on a concrete footer. The new winch system allows above-ground access to the pump for maintenance and repair, which supports the long-term health and safety goal of eliminating all underground work onsite. CLL operated the new larger pump throughout 2020. When the pump was turned off on October 29, 2020, the mine pool had been dropped down to 345 feet below the Steve Adit. Looking at the mine recharge data collected for over 3 years shows that the mine pool will not rebound past the compliance point if the water treatment plant is operated between 5 to 6 months. Consequently, CLL is requesting that the $250,000 of the"Denver Water contingency" amount included in the current bond be released. This amount was needed to design, construct, and install the new higher horsepower pump deeper in the mine through the Jeffrey Air Shaft. Moreover, the revised operational approach for dewatering the mine pool clearly demonstrates that the water treatment plant can safely operate for 6 or less months per year.