2023-02-16_HYDROLOGY - M2000158 - Laserfiche WebLink

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David M. Heintz S &t H Mine SWSP February 16, 2023 Page 3 of 11 The total consumptive use at this site is 56.61 acre-feet during the period of this SWSP, as shown in Table 1, column 12. You have provided a monthly breakdown of the annual depletions, which include 36.60 acre-feet of net evaporative loss from the 13.39 acres exposed at the site, 10.02 acre-feet of water lost with the mined product, and 9.99 acre-feet 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 the South Platte River. The aquifer characteristics used in the model for the alluvial well are: transmissivity (T) = 156,000 gallons per day per foot, specific yield (SY) = 0.2, the distance from the centroid of the pond to the stream =1,000 feet and the location of the parallel impermeable boundary was estimated to be 16,100 feet from the stream. The total lagged depletions for the October 1, 2022 through September 30, 2023 period equal 53.33 acre-feet, as shown in Table 1, column 13. This SWSP accounts for actual depletions determined to accrue to the steam system during this plan period. The Applicant has provided a monthly schedule of lagged actual depletions to the river, together with a schedule of replacement requirements, as shown in the attached Table 2. The location of depletions from mining operations accrue to the river in the NW1/4 of the SW1/4 of Section 35, Township 4 North, Range 67 West of the 6th P.M. (UTMs E511423.02 and N4457283.25) Replacements Out-of-priority depletions associated with the mining operation at this site will be replaced using water previously stored during free river in Milliken Reservoir which has been leased by Scout Investments ("Scout") to MMM. MMM also requests the ability to use water stored in Heaton Reservoir pursuant to the storage right decreed in Case No. 2001CW193; water stored in MMM's 35th Avenue Reservoir under free river conditions; excess credits available from MMM's 35th Avenue Pit from a lease of effluent from the City of Greeley; excess credits available from MMM's South Platte Combined Plan from a lease of effluent from the City of Aurora; and excess Whitney Ditch consumptive use credits owned by MMM. Milliken Reservoir Leased Water (aka Gilcrest Reservoir WDID 0203388) Milliken Reservoir is a lined reservoir owned by United Water and Sanitation District ("United"). According to the lease agreement between United and Scout dated April 26, 2018, United agrees to lease to Scout up to 60 acre-feet of water every calendar year from Milliken Reservoir. MMM has entered into an agreement with Scout for up to 60 acre-feet/year of water stored in Milliken Reservoir to replace depletions at the S&tG Mine. The Milliken Reservoir is located in the center of the Platte SFIG Mine site as shown in Figure 1. As shown in Column 4 of Table 2 it is expected that 53.33 acre-feet for the October 1, 2022 through September 30, 2023 period will be pumped from Milliken Reservoir to replace depletions from the S&tG Mine during the SWSP period. The water will be pumped from the reservoir directly to the South Platte River near the same location as depletions from mining operations accrue