2021-10-29_HYDROLOGY - M2014043 - Laserfiche WebLink

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October 29, 2021 Page 3 of 3 The total consumptive use at this site is 17.89 acre-feet for the period of April 2021 through March 2022, 18.77 acre-feet for the period of April 2022 through March 2023 and 1.76 acre-feet for April 2023. A revised Table 2, which shows the monthly breakdown of the annual depletions for this SWSP amendment has been provided with the SWSP amendment request and is attached to this letter. There are several lined gravel pits located between the Frey Hatchery Pit and the South Platte River. No drains were constructed between or around the pits to facilitate the passage of groundwater that may mound up gradient of the lined pits. According to the information provided, the Frei Hatchery pit depletions will affect the Bull Seep because the water will not make it to the South Platte River due to the existing gravel pit liner between the river and the pit. The Bull Seep, is a natural spring -fed tributary to the South Platte River that runs along the west side of the Frei Hatchery Pit permitted area. The seep is up gradient of the lined gravel pits below and travels approximately 1.75 miles north before discharging into the South Platte River. Dewatering from Phase 2 of this operation ceased in September 2020 and no dewatering is approved under this SWSR This SWSP will account for lagged depletions from past dewatering operations. This SWSP also accounts for lagged depletions from prior evaporation at the site located outside of the pre-81 areas. A Glover analysis was used to determine the lagged depletions from dewatering, evaporation and operational losses to the Bull Seep. The aquifer characteristics used in the model for the exposed surface area, dewatering and the water lost with the mined product are: transmissivity (T) _ 87,000 gallons per day per foot, specific yield (SY) = 0.2, the distance from the centroid of the exposed ground water to the stream = 350 feet, and the location of the parallel impermeable boundary was estimated to be 12,900 feet from the stream. The total lagged depletions from evaporation, water lost with the mined product, dust control and dewatering is 18.68 acre-feet for the period of April 2021 through March 2022, 19.23 acre-feet for the period of April 2022 through March 2023 and 3.61 acre-feet for the period of April 2023 through November 2023, as shown on the attached revised Table 2, column 9. Replacements Out -of -priority depletions associated with the mining operation at this site will be replaced using fully consumable municipal return flows leased from the City of Aurora ("Aurora"). The current lease with Aurora dated June 4, 2021 covers depletions through November 30, 2023. Under the lease, water will be delivered to the outfall of the Robert W. Hite Treatment Facility (aka Metro Sewer, WDID 0200700) located on the South Platte River. Aurora may alternatively deliver water at other points along a reach of the South Platte River beginning at or below the Hite Treatment Facility and continuing downstream to a point at or above the location where the South Platte River crosses the East 104th Avenue. The Applicant must notify the water commissioner at least 48 hours prior to making replacement deliveries at a location other than the Hite Treatment Facility. The Hite Treatment Facility is located approximately 6.8 miles upstream of the Frei Hatchery Pit site. The delivery schedule includes a transit loss of 0.5% per mile (3.4 % for 6.8 miles) during the months of April through October and 0.25% per mile (1.7% for 6.8 miles) during the months of November through March. Conveyance loss for delivery of augmentation water to the South Platte River is subject to assessment and modification as determined by the division engineer. Any