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Richard T. Raines <br />May 21, 2009 <br />DEPLETIONS <br />Page 2 <br />During this plan year, the site excavations may expose a maximum total of 16.7 acres of <br />ground water. You have also performed a depletion analysis based upon the net replacement <br />obligation and the, aquifer characteristics to show the lagged depletion schedule to the Arkansas <br />River, as presented in your Table 3. The total lagged depletions for this plan year are estimated <br />to be 56.56 acre-feet (54.83 from the Active Pit and 1.73 from the Unused Wash Pond). During <br />the April 1, 2009 through March 31, 2010 plan year, the site excavations will not expose any <br />additional ground water. You have submitted an analysis that shows the calculated <br />evaporation, effective precipitation, and resultant net replacement obligation in the same tables <br />above. You have also performed a depletion analysis based upon the net replacement <br />obligation and the aquifer characteristics to show the lagged depletion schedule to the Arkansas <br />River, as presented in your above referenced Table 3. The total lagged depletions for this plan <br />year are estimated to be 56.56 acre-feet, and there is an additional 1 acre-foot depletion from <br />Well Permit No. 66042-F (1405128). No mining or dewatering will take place during these plan <br />years unless an amendment to this plan is approved. <br />Your analysis shows that 17.30 acre-feet of depletions from the Active Pit will accrue to <br />the river after the expiration date of this plan. The analysis for the unused wash pond from prior <br />years' submittals shows that about 0.95 acre-feet. of post plan depletions will accrue to the river <br />from this pond. Therefore, the total combined post plan depletions are approximately 18.25 <br />acre-feet. <br />Stream depletion analyses for both the Active Pit area and the Unused Wash Pond <br />(attached) used the Stream Depletion Factors of 7.3 days for the Active Pit and 120 days for the <br />Unused Wash Pond, obtained from the USGS Publication 72-192 "Stream Depletion Factors, <br />Arkansas River Valley, Southeastern Colorado". <br />REPLACEMENTS <br />The source of replacement water is the Lower Arkansas Valley Water Conservancy <br />District, and a 5-year lease agreement has been submitted as verification to this office. The <br />terms of the lease are 99 shares of Twin Lakes water per year, commencing April 1, 2005. You <br />have considered transit losses of 10% from Twin Lakes Reservoir to Pueblo Reservoir and 0.25 <br />percent per mile for 18 miles to the Rich Pit. The total transit loss is 9.5 acre-feet. You estimate <br />that 93 of these shares will provide in excess of 70.68 acre-feet per year of replacement water <br />and will therefore be sufficient to replace depletions associated with the Rich Pit and transit <br />losses, which total 65.91 acre-feet. A new lease agreement must be provided for any renewal <br />of this SWSP in the coming years. <br />The source of renewable long-term replacement water sufficient to cover evaporative <br />depletions has not been secured for this plan. Lafarge West, Inc. is negotiating with the City of <br />Aurora and Aurora has filed amendments to Case Nos. 99CW169 and 99CW170 to include the <br />Rich Pit for water storage. Aurora has also included the Rich Pit in Case No. 05CW105 as an <br />upstream point of exchange. You state that if Aurora purchases this site, then Aurora will <br />provide the long-term commitment of water supply from its Arkansas Basin water rights. Aurora <br />intends to construct a slurry wall liner and use the pit as a reservoir.