2023-11-29_HYDROLOGY - M2005059 - Laserfiche WebLink

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Nelson Mining Resources SWSP November 29, 2023 Page 3 of 6 yield (SY) =0.2, the distance (X) from the centroid of the exposed ground water surface to the creek = 2,126 feet, and the distance (W) from the aquifer boundary through the well to the creek channel = 3,700 feet. The transmissivity value has been updated from the value used in the previous SWSPs based on the value identified in the Colorado Decision Support System ("CDSS") Website. The total lagged depletions were determined to be 16.41 acre-feet during the period of this SWSP, as shown on the attached Table 5, column 3. Dewatering Dewatering during this plan period will be at an average rate of 500 gpm/month and directly discharged to Saint Wain Creek. Based on this rate approximately 806.52 acre-feet will be pumped from the site during this plan period (Table 4). The dewatering activities were lagged using the same aquifer parameters as the evaporative depletions, resulting in lagged depletions to the river of approximately 805.47 acre-feet (Table 5, column 4). The net effect on the river from dewatering shows that during the period of this SWSP there is an accretion to the river of 1.05 acre-feet, as shown in Table 5 (column 2 - column 4). All dewatering activities must be metered with a totalizing flow meter that is recorded and reported on the submitted monthly accounting. Replacements Out-of-priority depletions associated with the mining operation at this site will be replaced using fully consumable municipal return flows leased from the City of Longmont ("Longmont"). A copy of the lease with Longmont for the November 2023 through October 2024 period was provided to this office on November 28, 2023 and is attached to this letter. In accordance with the lease, Longmont will provide a total of 24 acre-feet of fully consumable water during the period of November 2023 through October 2024. The Longmont wastewater treatment plant is located approximately 10.5 miles upstream of this mining operation. A 0.25 percent per mile transit loss (2.63 percent overall loss) has been accounted for in the amount of replacement water obtained from Longmont. The monthly depletions and replacement requirements are found on the attached Table 6. Long Term Augmentation In accordance with the letter dated April 30, 2010 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. The DRMS letter identifies four approaches to satisfy this requirement. In accordance with approach nos. 1 and 3, you have indicated that a bond has been obtained for $1,097,165.51 through the DRMS for lining of this site 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. In addition, according to the information previously provided you indicated that the land owner Mr. Howard Nelson has entered into a lease agreement with the applicant, which states that Lessor will grant to Lessee the water rights associated with the property for processing and augmentation during the term of the lease. The term of the lease is for a period of 20 years from the date entered into the agreement, which was April 18, 2001. If it is the Applicant's intent to dedicate water rights in order to satisfy the DRMS requirement, such water rights must be dedicated until such time as all