2009-08-18_HYDROLOGY - M1977436 - Laserfiche WebLink

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Mr. Jeffrey Clark August 11, 2009 Page 2 Depletions This plan describes the maximum proposed water uses from August 2009 through July 2010 for this existing pit. The estimated gross evaporation from the 28 acres of exposed ground water surface area is 98 acre-feet. The gross evaporation is reduced by 53.3 acre-feet due to the phreatophyte credit for the 28 acres of pasture grass that occupied the site prior to mining. The total depletion that must therefore be replaced during the plan period is 44.7 acre-feet. The edge of this existing pit is located less than 100 feet from South Platte River, so the resulting evaporative depletions are considered to be instantaneous. Replacements The Applicant proposes to replace the depletions with 18 shares of Fulton Ditch (out of 70 shares total that the Applicant owns), which are delivered directly to the South Platte River or stored and released later, depending upon season. The Applicant will use the remaining 52 Fulton Ditch shares to replace depletions from the Bromley Pit and Ready Mixed Pit 1, two other gravel pits it owns and operates, managing the 70 shares in a joint operation to cover depletions for all three pits. All the shares are delivered down the lateral that historically served the Bromley Lakes site and will be measured prior to release to the river for replacement of depletions or to storage. The historical consumptive use credit of Fulton Ditch shares is based on 1.76 acre-feet per share as determined in the South Adams County Water and Sanitation District change case engineering report for Division 1 Water Court case no. 2001 CW258. The 18 shares would have a total consumptive use yield of 31.7 acre-feet. The distribution of these shares is shown as column 8 on the attached Table 1. The historic yield of these Fulton shares will exceed the depletions in the summer months and requires replacement of historic return flows in the winter months. However the excess yield from the Fulton shares will be placed into storage in Kenneth Mitchell Lake for later release to the river during the fall and winter months, as shown in Tables 1 and 2. Ready Mixed has obtained an agreement with the City of Brighton to store up to 200 acre-feet of water in the Kenneth Mitchell Lake. Additional replacement requirement will be provided by water that Ready Mixed already has in storage, which is projected to be 110 acre-feet at the beginning of June 2009. Releases from storage for North Tower Pit replacement are shown in Table 1, column 11. The total storage releases are shown in Table 2, column 6. Ready Mixed portion of the Kenneth Mitchell evaporation was estimated based upon conservative storage projection provided by the City Of Brighton. The balance of the replacement requirements of 9.2 acre-feet will be provided by a lease for augmentation credits with the City of Brighton ("Brighton"). Table 1, column 13 shows the distribution of their respective credits. A copy of the lease with Brighton was provided to this office with this SWSP request and is attached to this letter. The monthly evaporative depletions and proposed monthly replacement requirements can be found on the attached Table 1. Conditions of Approval I hereby approve the proposed substitute water supply plan in accordance with C.R.S. §37-90- 137(11), subject to the following conditions: This SWSP shall be valid for the period of August 1, 2009 through July 31, 2010, unless otherwise revoked, modified, or superseded by decree. If this plan will not be made absolute