2019-07-30_PERMIT FILE - M1996052

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L.G. Everist Combined SWSP Page 10 of 16 March 14, 2018 In addition to the Lupton Bottom Ditch water, L.G. Everist has approximately 190 acre-feet stored under free river conditions in the Swingle-North Reservoir located on the Fort Lupton Sand and Gravel mine available to meet depletions from Saint Vrain sites. The Swingle North Reservoir is part of the Aurora-Everist Reservoir (WDID 0203087) decreed for storage in case no. 2002CW330. The Aurora- Everist Reservoir will consist of seven interconnected water storage cells surrounded by an impermeable bentonite-based slurry wall keyed into the shale bedrock of a reclaimed sand and gravel pit. The Swingle North Reservoir's slurry wall liner was approved by our office on March 27, 2013 as a provisional liner. By the liner approval letter, the Division of Water Resources ("DWR") recognized the liner for the remainder of mining operations, however prior to its use as a water storage reservoir, the operator must perform a final leak test once mining is complete and the site is at final grade. In an email dated December 15, 2017 the Division 1 Office allowed L.G. Everist to book-in free river water into the Swingle North Reservoir and book- out native groundwater trapped inside the reservoir slurry wall. In addition according to a letter dated April 15, 2013 this office approved to use the Swingle North Reservoir for water storage purposes during mining operations as it has reasonably determined that the slurry wall isolates and minimizes the interaction of unregulated alluvial ground water from waters within the Swingle North Reservoir. However, note that reservoir's operation is limited to use only within the gravel pit SWSP approved pursuant to 5 37-90-137(11), C.R.S. for uses associated with the mining operation. Once mining commences within the reservoir's perimeter, no further water storage will be allowed until the reservoir is at final grade and a final leak test is performed and accepted by our office. The estimated storage amount in the Swingle North Reservoir is based on the following: • the as-built area, determined to be 36.6 acres • the average depth to bedrock of 34.07 feet, measured along the 520 feet trench of the as-built slurry wall • the average water level measurement of 4860.11 feet in three monitoring wells (MW-38, MW039 and MW-40) that are located within the lined reservoir and the average bedrock level depth of 4837.03 feet based on the trench measurement • the storage coefficient value of 0.20 (typical for the alluvial of the South Platte River). You indicated that the results of a pump test taken in the vicinity of the Swingle North Reservoir (approximately 5 miles to the west of the site) reports a storage coefficient of 0.25, therefore this values was also used in the calculation of the storable volume The storable volume of Swingle North Reservoir was determined as follows: the built area multiplied by the saturated depth multiplied by the storativity [36.6 acres x (4860.11'-4837.03') x 0.20= 169 acre-feet or 36.6 acres x (4860.11'-4837.03') x 0.25 = 211 acre-feet]. For the purpose of this SWSP an average value of 190 acre-feet was assumed to be in storage that can be used for replacement purposes and other uses associated with the mining operation. The amounts of storage water in the Swingle North Reservoir available for use for replacement purposes during the period of this SWSP is presented in Table 5 below (taken from the SWSP report) Table 5 also shows the amount available for replacement from the Star Water Reservoir that is being used on the Cache La Poudre River. The use of the Swingle North Reservoir water is summarized in attached Tables 10, 12, and Table 14.