2015-05-14_HYDROLOGY - M1977151 - Laserfiche WebLink

Home Browse Search

Mr. Jared Dains, P.E. Page 2 of 9 May 7, 2015 office recognizes a total of 40.2 acres at the Greeley Pit as being pre -81 exposure. Accordingly, for the 71.8 acres of ground water currently exposed at the Greeley Pit, replacement of evaporative depletions is only required from the 31.6 acres exposed after December 31, 1980. Per the State Engineer's General Guidelines for Substitute Supply Plans for Sand and Gravel Pits as updated April 1, 2011, pre -81 areas are tied to the physical location at which the groundwater was exposed prior to January 1, 1981. The applicant has provided a map showing the specific location of the pre -81 area. The credits for the pre -81 area are tied to the location identified in the 1980 Aerial Photograph shown in the attached Figure 2 (Pre/Post 1981 Exposed Area) and may not be re -allocated to other areas of ground water exposure within the gravel pit boundary. The current exposed surface area is shown on the attached Figure 2 (Exposed Area Map). The net depletion of ground water due to evaporation from the surface area of the Greeley Pit exposed after December 31, 1980 was calculated to be 87.19 acre-feet for this plan period, as shown on the attached Table 1. Based on monthly average temperatures reported for the Greeley UNC weather station, ice cover was assumed for the months of December and January. 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 2015 -January 2016) 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 Applicant has estimated that a total of 1.00 acre-foot of water will be used for dust control purposes from April through September. A monthly breakdown of the estimated dust control use is shown in the attached Table 2. The total consumptive use of ground water at the Greeley Pit is estimated to be 88.19 acre- feet for the approval period of this plan. The Alluvial Water Accounting System ("AWAS"), which uses the Glover method, was used to determine the lagged depletions to the Cache la Poudre River from past and projected evaporation and operational losses at the site. The infinite aquifer boundary condition was selected because a parallel no -flow boundary could not be identified based on information from the USGS Hydrologic Atlas HA -746A. The following parameters were used in the model: a distance (X) of 1,120 feet from the centroid of the 39.7 -acre exposed ground water surface to the river; a transmissivity (T) of 120,000 gallons per day per foot; and a specific yield (S) of 0.2. The estimated lagged stream depletions due to past and projected operations at the Greeley Pit will total 85.99 acre-feet for this plan period, as shown on the attached Table 3. Replacements The sources of replacement water to be used for this SWSP are: 1) consumptive use credits associated with the historical irrigation use of 3.0 shares of the Greeley Irrigation Company; 2) leased excess augmentation credits from the Bucklen Equipment Company; and 3) a non -irrigation season lease with the City of Aurora. The attached Table 5 shows the estimated monthly depletions and replacements for this plan period. Greeley Irrigation Company ("GIC") Shares Hiner owns three (3.0) shares of the Greeley Irrigation Company ("GIC") under the following certificates: