2013-03-28_HYDROLOGY - M1999050 - Laserfiche WebLink

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Mr. Todd Williams Timnath - Connell SWSP March 27, 2013 Page 3 diversions for the Box Elder Ditch for the years 1950 to 2004 assuming 10% ditch Toss and 55% field efficiency. The pro -rata historical consumptive use credit for the 2.5 shares is 105.75 acre -feet and the pro -rata return flow obligation for the 2.5 shares for October through April is 51.39 acre -feet. The expected volume of water available for diversion into the recharge pond for 2.5 shares is 225.51 acre -feet per year. This figure represents the pro -rata average headgate diversion less'a 10% ditch loss. Pursuant to previously submitted accounting, 286.54 acre -feet were diverted into the recharge site during the 2012 irrigation season. The lagged accretions from the Timnath - Connell recharge pond were estimated by the Applicant's consultant using the Alluvial Water Accounting System (AWAS) stream depletion model developed by the Integrated Decision Support Group with the following assumptions: • Distance from the gravel pit centroid to the river (X) = 3,500 ft • Alluvial aquifer width (W) = 5,300 ft • Specific yield (S) = 0.2 • Transmissivity (T) = 50,000 (gpd /ft) The lagged accretions to the Cache la Poudre River are estimated to total 224.39 acre -feet for April 2013 through March 2014 (includes carry over from recharge in previous years). The summer and winter return flow obligations from the 2.5 Box Elder Ditch shares will be maintained by this substitute water supply plan. A monthly breakdown of the stream depletions from the mining operation as well as the replacements made by the recharge accretion credits of the Box Elder Ditch shares are shown in the attached Table 8. Long Term Augmentation The final reclamation plan for this site includes both a lined reservoir and unlined lakes. The successful completion of a Tined reservoir will eliminate long term depletions that would require a long term augmentation plan. After completion and approval of the reservoir liner this area must continue to be covered by a valid SWSP until the lagged depletions from mining operations are no longer impacting the river. The creation of permanent unlined lakes will result in long term evaporation of ground water which requires a long term augmentation plan. The Applicant is required to obtain a water court augmentation plan to cover the long term depletions associated with such ground water lakes. In accordance with the letter dated April 30, 2010 (see attached) from the Colorado Division of Reclamation, Mining, and Safety ( "DRMS "), all sand and gravel mining operators must comply with the requirements of the Colorado Reclamation Act and the Mineral Rules and Regulations for the protection of water resources. The April 30, 2010 letter from DRMS required that you provide information to DRMS to demonstrate you can replace long term injurious stream depletions that result from mining related exposure of ground water. In accordance with approach nos. 1 and 3 identified in that letter, the applicant holds a bond through DRMS in the amount of $510,198. A site inspection on August 31, 2012 by DRMS confirmed the bond remains sufficient to complete the reclamation plan. 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 plan is approved with an effective date of April 1, 2013 and shall be valid through March 31, 2014 unless otherwise revoked or modified. If this plan will not be made absolute by a