2013-01-29_HYDROLOGY - M1979191 - Laserfiche WebLink

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Site Name T X W S East Rigden Pit 55,000 2,500 5,800 0.2 Three Bells Pit 45,000 1,900 4,800 0.2 Kyger Pit 45,000 1,800 5,200 0.2 Shields Mine 55,000 3,700 8,000 0.2 Mr. Jared Dains Lafarge Middle Poudre Combined SWSP January 28, 2013 Page3of8 evaporation of 39 inches from the exposed water surface, with a credit of 8.8 inches for effective precipitation. You have assumed an ice covered period to occur during the months of December through February and have reduced the computation of evaporation accordingly. 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 through February) 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. A stream depletion model using the Glover method was used to calculate the lagged depletions to the Cache La Poudre River. The alluvial aquifer model uses four aquifer input parameters for each site as follows: 1) X- distance from centroid of exposed ground water to river, 2) W- distance from the aquifer boundary through the well to the river channel, 3) T- transmissivity of the alluvial aquifer (in gallons per foot /day) between the well and the river, and 4) S- specific yield - 0.2 was used for all wells. The following parameters for each site listed in the table below were used in the model: TABLE C — IDS AWAS LAGGING PARAMETERS The total lagged mining depletions for all four sites are 128.52 acre -feet. Including the credits that are dedicated to the Weitzel and Port of Entry Pits, the total projected depletions that are to be paid in 2013 are 228.36 acre -feet (see Table 1). Dewatering The East Rigden, Kyger, and Three Bells Pits are assumed to have been continuously dewatered and to be in a steady state condition where dewatering accretions equal the lagged depletions. Lafarge estimates that the three pits are dewatered at a rate of 800 to 1,000 gpm for approximately 12 hours per day. Lafarge plans to maintain these operations throughout this SWSP approval period. Once dewatering ceases or is reduced in its flow, lagged depletions will immediately hit the river. At least three years prior to a modification in dewatering operations, the Applicant must provide a plan showing how lagged post - pumping depletions will be replaced in the proper time and amount. All volumes pumped for dewatering must be metered by a Totalizing Flow Meter and be reported on the accounting submitted monthly. As required in the 2012 SWSP renewal, the Applicant has confirmed that meters have been installed on all dewatering systems. Replacements Replacement water for this combined plan will come from the following sources: accretion credits from recharge of 5 shares of the Box Elder Ditch and leases of augmentation water provided by the Lake Canal Reservoir Company ( "LCRC) and the City of Aurora ( "Aurora "). Lafarge previously owned and dedicated to this plan 8.5 shares in the Box Elder Ditch. As a part of a stipulated agreement with Stoner & Company ( "Stoner ") regarding the sale of the Weitzel Pit, Lafarge conveyed 2 of its 8.5 shares to Stoner, and is leasing an additional 1.5 shares to Stoner in 2013 with an option to renew the lease through 2016. The remaining 5 shares controlled by Lafarge will be used as a replacement source in this plan and will be diverted into a recharge pit (WDID 0302002) through an