2021-02-24_HYDROLOGY - M1997054 - Laserfiche WebLink

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��--dbiiruaiiry 24, 2021 � e Depletions resulting from granite mining operations, such as dust control, material washing, or product moisture loss, will not be approved pursuant to §37-90-137(11), C.R.S. Depletions occurring as a result of granite mining operations must be included in a SWSP approved pursuant to §37-92-308, C.R.S. In accordance with the letter dated April 30, 2010 from the Colorado Division of Reclamation, Mining, and Safety ("DRMS"), 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 for $1,145.,736 through DRMS to assure that depletions from groundwater evaporation do not occur in the unforeseen event, or events, which would lead to the abandonment of the Pit. In addition, Martin Marietta Materials owns and has dedicated five shares of Twin Lakes Reservoir and Canal Company to cover these potential long term depletions. Martin Marietta Materials must continue to commit those shares to this plan until such time as the State Engineer authorizes the release of this commitment. DEPLETIONS The depletions that result from the mining operation over the period of this SWSP include evaporation from exposed groundwater, dust suppression, dewatering, and water lost with the mined product. Evaporation losses will result from the exposure of groundwater in the settling ponds, an aggregate washing pond, and dewatering trenches. The maximum exposed water surface area during this SWSP period will be 5.0 acres. Gross annual evaporation at the mining operation is estimated to be 46.0 inches per year and the monthly distribution is as depicted on the attached Table 1. Net evaporation is defined as gross evaporation less the consumptive use of water by vegetation that naturally occurred at the site prior to construction of the pit. The historical consumptive use was assumed to be equal to the effective precipitation, which was estimated as 70% of the 12.51 inches of average annual precipitation based on data from the Canon City weather station over the period 1893 through 2016. The net evaporation for the exposed water surface is 37.32 inches per year with a monthly distribution as shown on the attached Table 1. The total annual stream depletion resulting from the exposure of groundwater is estimated to be 15.53 acre-feet, which includes months of potential ice cover (December, January, and February). Ice covered periods may include the months of December, January, and February based on the Canon City weather station average temperatures of 22.5°F for December, 26.23°F for January, and 24.13°F for February. However, for the purpose of this SWSP, the Applicant shall replace the net evaporation depletions from the exposed groundwater surface area that may occur during the potential ice covered period (the months of December, January, and February) for any time that the exposed ground water in the pit is not completely covered by ice. Computation of the net evaporation during any time that the pond is not completely covered by ice shall be determined as the pro-rata amount of the monthly gross evaporation rate distribution amount identified in the