2009-12-22_HYDROLOGY - M2001085 - Laserfiche WebLink

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Mr. Jacob Bauer December 18, 2009 Page 2 Depletions The annual depletion resulting from evaporation from the 2 acres of exposed ground water is 5.7 acre -feet. During the remainder of the mining period (September 1, 2009 through December 31, 2009) the water lost in mined product will be 4.4 acre -feet from 300,000 tons of mined product. Stream depletions were calculated by using the Alluvial Water Accounting System ( "AWAS ") model with the "Alluvial Aquifer" boundary condition option. The following table shows the input data. X ft W ft T d/ft) Specific Yield 2,295 3,836 63,000 0.2 To determine the timing of stream depletions resulting from the pumping of tributary groundwater by the wells, the AWAS model was used with the alluvial aquifer boundary condition option. The AWAS — alluvial aquifer model uses four aquifer input parameters for each well as follows: 1) X- distance from well 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 location of the stream depletion is assumed to be perpendicular to the river. An analysis showed that 98% of the total depletions impacting the South Platte River will occur within 15 months starting August 1, 2009. Therefore, a small portion of the lagged depletions will impact the South Platte River after December 31, 2010. Those lagged depletions were wrapped into the depletions in the prior months. Therefore, for purposes of the SWSP, it will be assumed that all lagged depletions impact the South Platte River by December 31, 2010. Replacements The replacement source for this plan is 22.01 acre -feet of fully consumable water from the City of Brighton ( "Brighton "). The Applicant has an agreement with Brighton whereby Brighton will release the fully consumable water during the period of September 2009 through December 2010. A copy of the agreement is attached. The fully consumable water will be released to the South Platte River from Brighton's Midland augmentation station or Brighton's 124 Avenue or Ken Mitchell Lake storage facilities. The replacement schedule for September 2009 through December 2010 is shown in the attached Table 4. Conditions of Approval I hereby approve this substitute water supply plan, in accordance with Section 37 -90- 137(11), C.R.S., subject to the following conditions: 1. This SWSP shall be valid for the period of September 1, 2009 through April 30, 2010, unless otherwise revoked, modified, or superceded by decree. If the applicant provides evidence to the State Engineer's office that the liner has been approved, prior to April 30, 2010, this plan shall be extended until December 31, 2010. If the pit is not lined and all lagged depletions