2015-10-30_HYDROLOGY - M1982147 - Laserfiche WebLink

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Thomas A. Williamsen, P.E. October 21, 2015 Page 2 with the water commissioner prior to installation of the measuring and recording devices and obtain approval of the measuring and recording devices from the water commissioner after installation. In addition, the Applicant must provide accounting as required by the division engineer and water commissioner to show that water is not stored in Nyholt-Mann Lake out - of -priority. Depletions The depletions that will be covered by this SWSP are limited to evaporation from the ground water exposed to the atmosphere, after December 31, 1980. According to the decree granted in case no. 05CW146 the water surface area of the Nyholt-Mann Lake is 65.5 acres of which 14 acres was exposed prior to January 1, 1981. Pursuant to 537-90-137(11)(b), C.R.S., and Case No. 2009CW49, a gravel pit operator or property owner does not need to replace depletions that occur due to evaporation from ground water exposed prior to January 1, 1981 ("pre -81 ") as a result of open mining of sand and gravel, regardless of whether mining continued after December 31, 1980 ("post -1980"). The applicant provided a report dated April 16, 2012 in order to meet the burden of proof required under 537-90-137(11)(b), C.R.S., and claim pre -81 credits at this site. The pre -81 credit is tied to this physical location and may not be reallocated to other areas within, or outside of, the mining boundary. The groundwater surface area that will be considered under this SWSP is the 51.5 acres exposed after December 31, 1980. Depletions from past mining operations have already depleted the stream system. In accordance with the decree granted in Case No. 05CW146, the average annual gross evaporation rate is 45 inches. The average monthly gross evaporation rate was determined by distributing this annual rate according to the monthly factors given in the General Guidelines for Substitute Water Supply Plans for Sand and Gravel Pits (updated April 1, 2011) for elevations below 6500 feet msl. The average gross monthly evaporation was reduced by the average monthly effective precipitation. The annual gross precipitation rate for this location is approximately 14.47 inches, based on average annual precipitation from 1973 through 2003, taken from the Brighton weather station. The effective precipitation is 10.13 inches (14.47 inches X 70%). The anticipated consumptive use for this SWSP is 149.8 acre-feet per year, as shown on the attached Table 1. In accordance with the decree in Case No. 05CW146, depletions resulting from evaporation wilt be lagged to the stream using the Glover equation with the following model parameters: Transmissivity 100,000 gallons per day per foot, Specific Yield 0.20, and distance from the lake to the river 140 feet. The monthly lagged depletions are shown on the attached Table 1. Replacements A lease of 158.6 acre-feet of fully consumable water provided by the City of Aurora ("Aurora") will be used to make replacements during the SWSP plan period. The releases will be made from the Metro Waste Water Reclamation Facility (WDID 0200700) located on the South Platte River approximately 11 miles upstream of Nyholt-Mann Lake. The Applicant has leased adequate water to account for a 5.5% (0.5% per mile) river transit loss.