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`` COLORADO LEGACY LAND <br /> $CHWARTZWALDER MINE <br /> 2 The Biological Assessment does not specify the planting rate or specific quantities of specifics that need to be <br /> planted. Therefore,for the purposes of this Amendment CLL assumes an equal distribution of each tree/shrub <br /> species shall be planted over the 7.1 acres of disturbed land shown on Figure F-1. <br /> 3 Figure F-1 shows the anticipated extent of disturbed acres that will need to be replanted, totalling 7.1 acres. <br /> Therefor the planting rate per acre is a calculated value of each Species Quantity divided by 7.1 acres. <br /> E.S. MINE POOL MITIGATION <br /> The WTP operating strategy is considered in conjunction with in-situ treatment of the mine pool to provide <br /> physical and chemical stabilization of the mine pool. During the period in which the WTP is shut down, in-situ <br /> treatment of the mine pool may at times be conducted, as necessary, to maintain chemical stabilization. A <br /> demonstration of the physical and chemical stabilization of the mine pool, including previous in-situ <br /> treatments,is discussed below. <br /> E.5.1. Physical Stabilization of the Mine Pool Demonstration <br /> Physical stabilization of the mine pool began when a 10-horsepower (hp) pump was installed in the #2 Shaft <br /> behind the Steve bulkhead. The pump was capable of dewatering the mine pool at 100 gallons per minute <br /> (gpm). The 10-hp pump was replaced with a 25-hp pump in February 2017 to increase the mine dewatering <br /> rate and speed up the process of achieving the regulatory limit.The pump was installed in the#2 Shaft behind <br /> the Steve bulkhead at 210 ft below the Steve Level and was capable of dewatering the mine pool at 190 gpm. <br /> The 25-hp pump dewatered the mine pool to below the regulatory limit by November 2017.The WTP has been <br /> operating approximately 50% of the time for the last four consecutive years and as shown in Figure E-3,the <br /> mine pool has been consistently below the regulatory limit,with the possible exception of one instance in the <br /> Winter of 2019 (January 27-29,2019). <br /> In April 2019,a 60-hp pump was installed in the Jeffrey Air Shaft at 410 ft below the Steve Level.The pump is <br /> capable of dewatering the mine pool at approximately 300 gpm. <br /> In April 2020,there was a malfunction with the 60-hp pump and the 25-hp pump was temporarily brought into <br /> operation to dewater the mine pool. Operation of just the 25-hp pump was sufficient to keep the mine pool <br /> below the regulatory limit. <br /> In October 2020,a team entered the mine to verify the mine pool elevation and calibrate the transducer used <br /> to measure the mine pool elevation. The team measured that the mine pool had been dewatered to 22 feet <br /> lower than the elevation recorded by the transducer,which caused inaccurate and higher measurements to be <br /> recorded.The transducer was lowered from 294 ft to 354 ft below the Steve Level and calibrated to accurately <br /> measure the mine pool elevation. The steep drop in October 2020 shown on Figure E-3 reflects when the <br /> calibration was performed. The fact that the transducer had been providing shallower mine pool elevation <br /> measurements indicates that the exceedance of the mine pool elevation above the regulatory limit in the Winter <br /> of 2019 may not have been an actual exceedance, and also it is possible that the mine achieved the 150 foot <br /> below Steve level sooner than November 2017. <br /> AUGUST 2022 17 AMENDMENT 6 <br />