2010-12-01_HYDROLOGY - M1982131 - Laserfiche WebLink

Home Browse Search

Mr. Jared Dains Page 2 November 23, 2010 According to the Applicant, the distance from the surface of the exposed ground water area to the Cache La Poudre River was measured based on the down gradient extent of the exposed ground water surface (nearest point). For purposes of this SWSP, the method used to measure the distance to estimate the lagged depletions will be accepted, however any future SWSP must measure the distance from the exposed ground water surface area to the Cache La Poudre River based on the centroid of the exposed ground water surface. Computation of evaporation under this plan was reduced during the ice covered period. You have assumed the ice covered period to occur during the months of December and January based on the average monthly temperatures of 29.4°F for December, and 28.6°F for January. Temperature data were obtained from the Greeley UNC weather station (053553) for the time period of 1967 through 2005. The ice covered periods may be used to reduce the amount of evaporative losses that need to be replaced; however, for the purpose of this SWSP, the Applicant shall replace the net evaporation depletions from the exposed ground water surface area that may occur during the assumed ice covered period (December and January) for any time that the pit is not completely covered by ice. Computation of the net evaporation during any time that the pit 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 State Engineer's General Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro-rata amount of the effective precipitation for that period. The attached Table 1 identifies the estimated monthly depletions from evaporation. You have provided a monthly breakdown of the annual depletions totaling 49.14 acre-feet of evaporative loss from 17.81 acre of exposed surface area, 4.51 acre-feet of water used and consumed for dust control, and 0.74 acre-feet of water lost with 50,000 tons of mined product. Prior to dewatering, the material to be mined was located below the water table; however since this site has been dewatered, the material to be mined will be in a dewatered state. Since the material will not be washed, pursuant to the State E'ngineer's Guidelines for Substitute Water Supply Plan for Sand and Gravel Pits, the assumed moisture content is 2% by weight. The estimated monthly depletions due to operational losses are shown on the attached Table 2. Replacements The sources of replacement water to be used for this SWSP are: 1) consumptive use credits associated with the historical irrigation use of five shares of the Greeley Irrigation Company ("GIC"), 2) a lease of 12.9 acre-feet of augmentation water provided by the Platte River Power Authority, and 3) a lease of 1.3 acre-feet of augmentation water provided by the City of Greeley. 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 ground water. The DRMS letter identifies four approaches to satisfy this requirement. The 4t' approach requires documentation to identify what water rights or other permanent water source will