2024-03-25_HYDROLOGY - M2023033 - Laserfiche WebLink

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Ewing Gravel Mine Substitute Water Supply Plan Page 3 of 7 March 25, 2024 Lagged Depletions The Alluvial Water Accounting System ("AWAS") model was used with the alluvial aquifer boundary condition option to lag depletions to the South Platte River. The parameters used in the model are shown in Table A below. The location of the stream depletion is assumed to be perpendicular to the river. Table A. AWAS Parameters. Distance from the Distance from the aquifer Transmissivity Specific centroid of the surface of boundary through the Area (gpd/ft) Yield the exposed GW to the exposed groundwater to river (X, feet) the river channel (W, feet) Freshwater / Silt Pond 140,000 0.20 1,947 6,705 Lower Bench Mining Area 140,000 0.20 1,583 8,296 Upper Bench Mining Area 140,000 0.20 3,168 6,000 Dewate ri ng 140,000 1 0.20 1 1,948 6,000 *For both depletions and the recharge rate. The total modeled evaporative and operational lagged depletions are approximately 45.8 acre-feet for this SWSP as summarized on attached Table 3. Total lagged dewatering depletions during the SWSP period are 1,964.8 acre-feet. Direct discharge of dewatering water is 89 acre-feet and lagged recharge accretion of dewatering recharge is 1,877.5 acre-feet. It is assumed that the recharge pond will be 0.5 - 1 acre with evaporative losses of 5.1 acre-feet for this SWSP period which is subtracted from the dewatering credit. The net effect on the river from dewatering is 3.4 acre-feet of depletions. Therefore, the total replacement obligation is 49.2 acre-feet for this SWSP period. Replacements Out-of-priority depletions will be replaced using fully consumable municipal return flows leased from the City of Aurora. The replacement is provided through the attached renewable lease dated March 21, 2024. The lease can be renewed annually for one-year periods through December 31, 2030. If actual depletions are greater than projected depletions in any month, the amount of replacement water required from the City of Aurora may exceed the agreed upon volume. The Applicant is responsible for assuring that adequate replacement volume is provided. Under the lease, water will be delivered to the outfall of the Robert W. Hite Treatment Facility (aka Metro Sewer, WDID 0200700) located in Denver, CO on the South Platte River. According to the lease, Aurora may alternatively deliver water at other points along a reach of the South Platte River beginning at or below the Hite Treatment Facility extending downstream. 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. In the instance of an intervening call, the Applicant will not be allowed to make replacements downstream of the calling right.