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GMs. Brent Kerr <br />April 16, 2007 <br />Page 2 <br />hatching, 0.14 acre-feet of water used for asphalt production, 0.28 acre-feet of water for <br />sanitary purposes at the facility, and 6.70 acre-feet of water loss associated with the 227,250 <br />tons of aggregate mined below the water table. <br />This mining operation will rely on dewatering to allow for removal of aggregate by rubber <br />tired vehicles. Only Phase 1 of this operation will be mined during the period of approval for <br />this SWSP. Should the operator discontinue mining for any reason, the maximum surface area <br />of groundwater exposure in Phase 1 will be 10.44 acres. Annual evaporative losses from this <br />pit area will total 32.6 acre-feet. Additionally, the Division Engineer has estimated transit losses <br />of 2.8 acre-feet per year for the delivery of water from Blue Mesa Reservoir to the point of <br />depletion. <br />Even though the operator of this aggregate mining operation anticipates dry mining of the <br />Anderson Pit by dewatering, the proposed plan accounts for lagged evaporative depletions from <br />10.44 acres of exposed groundwater as if the excavation were not dewatered. Comparison to a <br />more rigorous analysis for all lagged operational depletions shows this approach to be more than <br />adequate to replace the 13.58 acre-feet of depletions. <br />Replacements <br />The operator proposes to provide replacement for the maximum depletion, plus transit <br />losses, that might occur during the period of time that this approval is in place (i.e., 35.40 acre- <br />feet per year or 70.80 acre-feet for the two-year period) from a lease agreement with the <br />Bureau of Reclamation for stored water in Blue Mesa Reservoir. The monthly lagged <br />evaporative depletions and proposed monthly replacement requirements for this operation can <br />be found on the attached table. <br />The SWSP estimates that in the event that the operator were to cease mining and <br />dewatering at the site, there would be a maximum of 10.44 acres of exposed water surface at <br />the site. Based on Map 1 (copy attached) and Map 2, the bottom of the lake would be at 4920 <br />FSL and a water surface elevation of 4948 FSL. Therefore it would require 292 acre-feet to fill <br />the pit. To provide the security of a permanent, renewable source of replacement water, 34 <br />shares of the Bona Fide Ditch have been dedicated to this plan and will be made appurtenant to <br />the tract of land where the gravel pit is located, until a permanent augmentation plan for the <br />gravel pit has been adjudicated or all consumptive use at the site has ceased and all lagged <br />depletions have been replaced. The depletions resulting from the evaporation off of the 10.44 <br />acre pond are estimated to be 32.6 acre-feet per year, and filling the pit would require 292 acre- <br />feet. The 34 shares represent a 6.8% interest in the Bona Fide Ditch which averaged 21,434 <br />acre-feet of annual diversion between 1970 and 2004. The 34 shares, which equate to 4.43 cfs <br />of the 65 cfs decreed to the ditch, were used to irrigate 148 acres of the landowner's property. <br />Based on a full water supply, the consumptive use of 34 shares is approximately 364 acre-feet, <br />which is greater than the annual depletions anticipated for this SWSP plus the amount needed <br />to fill the pit, and are therefore considered to be adequate. Please note that a detailed analysis <br />of the consumptive use of the Bona Fide Ditch will be required prior to the use of this <br />replacement source in any future new or renewed SWSP. <br />