2018-05-23_HYDROLOGY - M2004009 - Laserfiche WebLink

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Turnpike Mining Resources Page 3 of 7 May 23, 2018 Computation of evaporation under this SWSP was reduced during the ice covered period. You have assumed the ice covered period will occur during the months of December and January based on average monthly temperatures less than 32°F taken from the Longmont South (record 1995-2015) NCWCD weather station. However, for the purpose of this SWSP, the Applicant shall replace the net evaporation depletions from the exposed ground water surface area that may occur during the assumed ice covered period (the months of December and January) for any time that the pit is not completely covered by ice. Computation of the net evaporation during any time that the pit is not completely covered by ice shall be determined as the pro-rata amount of the monthly gross evaporation rate distribution amount identified in the State Engineer’s General Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro-rata amount of the effective precipitation for that period. In addition to the evaporation, water is lost with the mined product removed from the mine site. The Applicant projected that they will produce 150,000 tons of gravel for each year during the SWSP period. Gravel mined will be in a dewatered state and will be washed therefore the ground water lost with the mined product during this period is estimated at 4 percent by weight. The water lost with the mined product is projected to total 4.43 acre-feet for each year during the SWSP period, as shown in Table AI.2, column 3. The total consumptive use at this site is 23.65 acre-feet during 2018 and 22.28 acre-feet during 2019, which include 16.73 acre-feet of net evaporative loss (for 2018), 15.36 acre-feet of net evaporative loss (for 2019), 4.43 acre-feet/year of water lost with the mined product, and 2.49 acre-feet/year of water used for dust control. The IDS AWAS stream depletion model was used to determine the lagged depletions from dewatering, evaporation and operational losses, to Boulder Creek. The aquifer characteristics used in the model for Cell 2A and 2B are: transmissivity (T) = 44,883 gallons per day per foot, specific yield (SY) = 0.2, the distance from the centroid of the exposed ground water to the stream =2,400 feet and the location of the parallel impermeable boundary was estimated to be 3,400 feet from the stream. In addition the aquifer characteristics used in the model for Cell 3 are: transmissivity (T) = 44,883 gallons per day per foot, specific yield (SY) = 0.2, the distance from the centroid of the exposed ground water to the stream = 700 feet, and the location of the parallel impermeable boundary was estimated to be 3,400 feet from the stream. The total lagged depletions for 2018 equals to 19.88 acre-feet of which 6.69 acre-feet are associated with the mining operation and 13.19 acre-feet are associated with the evaporation losses from Cell 3, 2A and 2B. In addition, the total lagged depletions for 2019 equals to 24.72 acre-feet of which 9.07 acre-feet are associated with the mining operation and 15.65 acre-feet are associated with the evaporation losses from Cell 3, 2A and 2B (Table AI.3). 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 Louisville (“Louisville”). A copy of the lease with Louisville was provided to this office with the SWSP request and is attached to this letter. The current lease is valid for the period of November 1, 2017 through October 31, 2018 therefore the SWSP will expired on October 31, 2018. The SWSP will be extended through December 31, 2019 if a new lease with Louisville is submitted to this office prior to October 31,