2021-02-04_HYDROLOGY - M2004013 - Laserfiche WebLink

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Kirystle Eiirvihn Page 2 „f„ 2022, the total exposed groundwater will be expanded to 9.76 acres. Pond 5 will be dewatered via a dewatering trench when the cell is being actively mined. Operational losses will occur due to water retained in the mined product and water used for dust suppression. Under Scenario C, there will be no mining on this site during the approval period and evaporation will occur from exposure of a total of 9.76 acres of water in four settling and wash ponds and in the mined cell for the entirety of the approval period. No operational losses will occur under Scenario C. Under Scenario D, Pond 5 will be actively mined during March through August of 2021 and 2022. During active mining, the total exposed groundwater will be reduced to 4.57 acres. In August 2021 and 2022, the total exposed groundwater will be expanded to 9.76 acres. Pond 5 will be dewatered via a dewatering trench when the cell is being actively mined. Operational losses will occur due to water retained in the mined product and water used for dust suppression. The slurry wall will be constructed in March 2021. Under Scenario E, Pond 5 will be actively mined during March through August of 2022. During active mining, the total exposed groundwater will be reduced to 4.57 acres. In August 2019 and 2020, the total exposed groundwater will be expanded to 5.77 acres. Pond 5 will be dewatered via a dewatering trench when the cell is being actively mined. Operational losses will occur due to water retained in the mined product and water used for dust suppression. The slurry wall will be constructed in March 2022. In accordance with the letter dated April 30, 2010 (copy attached) from the Colorado Division of Reclamation, Mining, and Safety ("DRMS"), all sand and gravel mining operators must comply with the requirements of the Colorado Reclamation Act and the Mineral Rules and Regulations for the protection of water resources. The April 30, 2010 letter from DRMS requires that you provide information to DRMS to demonstrate you can replace long term injurious stream depletions that result from mining related exposure of groundwater. In accordance with approach nos. 1 and 3, you have indicated that a bond has been obtained through the Division of Reclamation, Mining, and Safety ("DRMS") to assure that depletions from groundwater evaporation do not occur in the unforeseen event, or events, that would lead to the abandonment of the Pit. According to a letter from DRMS dated November 30, 2020, you must submit a new Financial Warranty reflecting the increase to $549,,479 to DRMS by January 29, 2021. DEPLETIONS Total estimated annual aggregate production is 210,000 tons per year and the water lost with the mined product associated with 210,000 tons of aggregate is 6.18 acre-feet (4% by weight) for both 2021 and 2022. The total annual water consumption for dust suppression is estimated at 1.68 acre-feet for both 2021 and 2022. During construction of the slurry wall, dewatering of approximately 70 acre-feet of water will occur over a period of two weeks. An instantaneous credit of 70 acre-feet from dewatering to the river during the slurry wall construction was removed from stream depletions. Effective precipitation credit was applied to these plans. Under Scenario A, during the time when the cell is actively being mined, evaporation will occur from a maximum of 4.57 acres of water in the four settling and wash ponds and a dewatering trench. During the two year period, the area of exposed water surface will vary,