2016-01-14_HYDROLOGY - M1981022 - Laserfiche WebLink

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Mr. Todd Williams G.L. SWSP January 14, 2016 Page 2 be instantaneous and have been lagged back to the Cache La Poudre River. The lagged depletions 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) = 1,900 ft • Alluvial aquifer width (W) = 5,800 ft • Specific Yield (S) = 0.2 • Transmissivity (T) = 160,000 (gpd/ft) You have provided a monthly breakdown of the annual lagged depletions totaling 2.41 acre-feet of evaporative loss (Table 2). This value includes lagged depletions due to consumptive use from prior approved SWSPs. Replacement The proposed source of replacement water for this pit is a lease of fully consumable water from the Lake Canal Reservoir Company ("LCRC"). The lease is for the period of June 2014 through May 2015. A copy of the LCRC lease, dated April 15, 2015 is attached to this letter. The replacement water will come from a system of reservoirs owned by LCRC known as the Gray Lakes, which can deliver water to Boxelder Creek and from there to the Poudre River downstream of the GL Pit. The LCRC recently obtained a decree to change the use of water stored in North Gray Reservoir and South Gray Reservoir in case 2006CW276. The decree adds augmentation and replacement as a changed use for water stored in the Gray Lakes. The total lease is for 5.44 acre-feet of water of which 2.41 acre-feet represents the consumptive use portion to be used as replacement water, 2.95 acre-feet represents the return flow, and 0.08 acre-feet will be used to cover transit losses assessed at 0.25% per mile along Boxelder Creek. The use of this water must be in accordance with the decree in case no. 2006CW276. The SWSP could not be approved until the accounting for case no. 2006CW276 was approved, which occurred on January 14, 2016. Providing replacement at the confluence of Boxelder Creek and the Poudre River is sufficient for the irrigation season. This replacement location may not be sufficient for the non -irrigation season if the Timnath Inlet Canal (WDID 0300924) is drying the river. At times when the Timnath Inlet canal is drying the river, the Applicant shall insure that the LCRC water is instead delivered to the canal. Long Term Augmentation In accordance with the letter dated April 30, 2010 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 requires 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. The DRMS letter identifies four approaches to satisfy this requirement. In accordance with approach no. 1 and 3, you have obtained a bond for $116,700 through DRMS which may be used for backfilling the exposed ground water in the unlikely event that the mining operator abandons the site. Please note that the approval of this SWSP does not relieve the Applicant and/or the landowner of the requirement to obtain a water court decree approving a permanent plan for augmentation or mitigation to ensure the permanent replacement of all depletions, including long-term evaporation losses and lagged depletions after gravel mining has ceased. The Applicant has demonstrated that the backfilling of the site will continue, thus an augmentation