2014-06-20_HYDROLOGY - M1983090 - Laserfiche WebLink

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Poudre Pits Combined SWSP Page 4 of 9 June 18, 2014 discharged directly to the river creating no lagged accretions. The operator installed meters at this site site by January 2013 and starting January 2013 the actual meter readings are used in the dewatering analysis. Dewatering that occurred throughout 2013 was returned directly to the river. The site is projected to be dewatered at an average rate of 75 gpm during this plan period, with dewatering water water returned directly to the river through an unnamed slough located above the Whitney Ditch. Combining the lagged depletions and net accretions from the stated recharge (prior to 2012) with projected dewatering depletions and accretions, dewatering activities will create a net depletion of 14.46 acre-feet during 2014. Dewatering operations at the La Poudre Pit occurred from January 1995 through December 2002. With the stated recharge that occurred, the lagged depletions to be replaced replaced in 2014 equal 0.72 acre-feet. Combined, the dewatering operations at the North La Poudre and La Poudre pits will result in a net depletion of 15.18 acre-feet. For this SW S P and any future approvals, actual monthly meter readings must be used to determine the true dewatering rate, and to determine how much water was delivered to recharge versus being directly returned to the river. Table D below summarizes the impacts past and projected dewatering operations at each pit will have on the stream system during this S W S P period. Table D - Summary of Dewatering Impacts (acre-feet) Site Name 2014 Direct 2014 Lagged 2014 Lagged Net Balance Accretions Accretions Depletions Firestein 0.60 -0.79 -0.19 Tigges 15.02 -31.92 -16.90 Roberts - 3.30 -4.39 -1.09 North La Poudre 117 0.36* -131.82 -14.46 La Poudre - 2.17 -2.89 -0.72 Total 117 21.45 -171.81 -33.36 * Excludes accretions from any dewatering recharge that may have occurred in 2012 AWAS was used to determine the lagged depletions to the Cache La Poudre River from past and projected dewatering operations at each site. The following parameters were used in the model with the infinite aquifer boundary condition: the distance (X) from the centroid of the exposed ground water surface to the river; the transmissivity (T); and the specific yield (S). The Glover parameters used for each pit are shown in the table below. Table E - Glover Parameters (Dewatering) Site Name X (ft) T (gpd/ft) S Firestein 1,035 120,000 0.20 Tigges 3,600 120,000 0.20 Roberts 3,435 120,000 0.20 La Poudre 1,500 50,000 0.20 North La Poudre 2,500 50,000 0.20 The lagged combined evaporative and operational depletions in 2014 will be 228.07 acre-feet. The lagged combined post dewatering depletions and accretion from the stated recharge creates a net