2015-07-09_HYDROLOGY - M1977439 - Laserfiche WebLink

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Upper Poudre Combined SWSP Page 3 of 11 June 26, 2015 SWSPs (prior to January 1, 2011) approved the pre -81 area without specific mention of its location. Therefore, the State Engineer's Office allowed the pre -81 area to be re -allocated and memorialized under the May 11, 2011 SWSP approval. The applicant provided a map (Figure 1 - Home Office Pit) showing the specific location of the pre -81 area (including the 22.1 acres of ground water exposed in Lamb Lake A). The credits for the pre -81 area are tied to the location identified on Figure 1 - Home Office Pit and may not be re -allocated to other areas of ground water exposure within the gravel pit boundary. Evaporative depletions were calculated using a gross annual evaporation of 38 inches, with a credit of 10.56 inches for effective precipitation (based on an average annual precipitation of 15.08 inches for Fort Collins weather station 053005, Western Regional Climate Center). You have estimated that there are a total of 240.9 acres of exposed ground water surface within the permit boundary of the Home Office Pit. Of this amount, 100 acres are considered to be pre -81 and do not require replacement and 125.2 acres are included in the Partners Combined SWSP (note that this amount includes 37.8 acres associated with Treiber Pond A, which has been lined), leaving depletions from 15.7 acres which must be replaced under this SWSP. The 15.7 -acre pond is known as the Curry Pit. You have estimated the total surface area of ground water exposed in the North Taft Hill Expansion Site as 3.05 acres for this plan period. You have stated that no ground water will be exposed at the Overland Ponds Site during this plan period. As previously noted, any water exposed within the lined perimeter of cell 5 must be treated as ground water with evaporation losses assessed until the liner is approved by this office. The estimate of evaporative losses under this combined plan was reduced during the ice covered period. You have assumed the ice covered period occurs from December through February, based on the average temperatures of 29.04° F for December, 27.59 ° F for January and 30.61 'F for February; taken from the Fort Collins weather station (053005) using available data for the period of 1893-2012. 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 (January, February, and December 2015) for any time that the pits are not completely covered by ice. Computation of the net evaporation during any time that the pits are 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. You have estimated that a total of 29.46 acre-feet of water will be pumped from the Curry Pit at the Home Office Site for dust control purposes at the Home Office Pit, Overland Ponds Sites, and North Taft Hill Expansion Site during this plan period. Water pumped for dust control purposes is considered to be 100% consumed. All pumping for dust control purposes must be metered. You have estimated that 264,000 tons of aggregate will be mined at the Overland Ponds Site during this plan period. Of this amount, 116,150 tons is anticipated to be crushed and 147,850 tons is anticipated to be washed. You have estimated that an additional 637,000 tons of aggregate will be mined at the North Taft Hill Expansion Site during this plan period, of which 261,400 tons is anticipated to be crushed and 375,600 tons is anticipated to be washed. The material is mined below the ground water table, but in a dewatered state, therefore the water retained in the crushed product is considered to be 2.0% of the mined material by weight, and the water retained in the washed product is considered to be 4.0% of the mined material by weight. 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 each site. The following parameters were used in the model with the