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Cheryl Signs, P.E. Page 2 <br />Kurtz Pit, DRMS-1999-006 <br />The IDS AWAS stream depletion model was used to determine the lagged depletions to the <br />Saint Vrain Creek. The aquifer characteristics used in the model are: transmissivity (T)= 30,000 <br />gallons per day per foot and specific yield (SY)= 0.2 (which is typical for an alluvial aquifer). The <br />nearest stream is a natural drainage ditch that originates uphill from the site and flows continuously <br />through the west side of the property to Saint Vrain Creek. The distance of the exposed ground water <br />to the stream=520 feet, and the location of the parallel impermeable boundary was estimated to be <br />3,950 feet from the stream. <br />Replacement <br />The proposed source of replacement for this pit is the historical consumptive use from the land <br />historically irrigated with 1.9627 shares of Last Chance Ditch diverted from the Saint Vrain Creek and <br />previously used for irrigation of the mined property. Irrigation has ceased on the Kurtz Pit site due to the <br />mining operation and groundwater lakes. The Applicant owns 3 shares of the outstanding 20 shares of <br />the Last Chance Ditch. The 3 shares 'of the Last Chance Ditch were historically used for irrigation on the <br />Kurtz Pit mining site (264.7 acres). The historical use of the irrigation supply was quantified using the <br />average monthly diversion from 1949 through 1974. The ditch loss used the consumptive use analysis <br />was 28.5 percent based on the ditch location, its length and previous experience. Water in excess of the <br />irrigation requirement was added to the soil moisture bank, which was assumed to be three feet deep <br />with a water holding capacity of 20 percent. The consumptive use analysis for the three shares <br />averaged 465.40 acre-feet per year. The historical accretions/depletions for the 1.9627 shares were <br />prorated from the 3 shares of the Last Chance Ditch that originally irrigated the property. The dry-year <br />historical consumptive use credit from the 1.9627 shares of the Last Chance Ditch is 304.48 acre-feet <br />with a non-irrigation season return flow obligation of 15.45 acre-feet (Table 1). After applying the 1.9627 <br />shares of Last Chance Ditch water, there will be 97.21 acre-feet of uncompensated depletions. <br />Additional replacements for depletions during the non-irrigation season and during months <br />with insufficient credits will be made by releases of irrigation season excess credits from the Last <br />Chance Ditch water that is stored in the 112 and Dakolios lined pits and a portion of four shares in the <br />Rural Ditch Company. A decree for a storage water rights of the Last Chance Ditch water and the <br />Rural Ditch water in the 112 and Dakolios lined ponds was approved by the Division 1 Water Court in <br />Case No. 2001CW274. The Rural Ditch Company,four shares were historically used to irrigate 158.9 <br />acres on the 112-parcel site and these shares were used in the previous plans. Consumptive use <br />credits from the 4 shares of the Rural Ditch that are not used to replace depletions during the <br />irrigation season will be stored in the 112 Reservoir and subsequently released to replace non- <br />irrigation season depletions. An application for a change of water right (to allow the applicant's Rural <br />Ditch shares to be used in addition to irrigation for augmentation, replacement, exchange, <br />commercial, industrial, recreational, piscatorial, wildlife propagation and storage) and approval of a <br />plan for augmentation was filed with the Water Court in Case No. 2003CW306. The historical <br />consumptive of the four shares of the Rural Ditch water averages 265.50 acre-feet per year. The <br />Durham Pit M 78-056 plan requires 48.83 acre-feet per year to replace depletions from this pit leaving <br />216.67 acre-feet per year available for this plan. The historical return flow obligation of the four Rural <br />Ditch shares of 101.5 acre-feet will also be maintained by the Durham Pit plan. The monthly <br />depletions and replacement requirements are found on the attached Table 1. <br />Conditions of Approval <br />I hereby approve the proposed substitute water supply plan in accordance with §37-90- <br />137(11), C.R.S. subject to the following conditions: