2014-06-30_HYDROLOGY - M1981022 - Laserfiche WebLink

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Mr. Todd Williams Page 2 G.L. SWSP June 27, 2014 The centroid of the remaining ground water exposed at the G. L. Pit site is located approximately 1,900 feet from the Cache La Poudre River, thus depletions were not assumed to 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) The distance to the no-flow boundary was changed from the previous SWSP to better reflect the actual conditions and it was determined using the USGS — Geohydrology of the Shallow Aquifers in the Fort Collins — Loveland Area, Colorado (as seen on the attached map and a close-up of the of the area near the G-L Pit). You have provided a monthly breakdown of the annual lagged depletions totaling 3.03 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 and corresponds with this SWSP approval period. A copy of the LCRC lease, dated April 29, 2014 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's pending change case 2006CW276 lists augmentation and replacement as a changed use for water stored in the Gray Lakes. The total lease is for 6.84 acre-feet of water of which 3.03 acre- feet represents the consumptive use portion to be used as replacement water, 3.70 acre-feet represents the return flow, and 0.11 acre-feet will be used to cover transit losses assessed at 0.25% per mile along Boxelder Creek. 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. Note that this replacement water source is accepted for the purpose of this SWSP, however for any SWSP renewals this replacement water source will not be accepted unless case no. 2006CW276 is decreed by the water court. In addition, the applicant is advised that a historical consumptive use analysis of the Gray Lakes water must be submitted with the next plan renewal request if case no. 2006CW276 was not decreed by the water court. 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