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Holcim South Platte Combined SWSP April 14, 2025
<br /> Plan IDs 3614, 4773, 3624, 4772, 4616, 3437, 3376, 3650, 3668, 5475, 5829, Ft 6243 Page 10 of 37
<br /> 'Lagged Dewatering Depletions, as shown in the table, are from past dewatering operations
<br /> that have ceased but continue to impact the stream system.
<br /> So long as the pit is continuously dewatered, the water returned to the stream system is
<br /> considered to be adequate to offset depletions attributable to the dewatering.
<br /> A stream depletion model using either the Glover method, or Stream Depletion Factor (SDF)
<br /> method (for the Brighton Pit) was used to calculate the lagged depletions to the river. The
<br /> Glover method uses four aquifer input parameters for each site as follows: 1) X - distance
<br /> (ft) from centroid of exposed groundwater to river, 2) W - distance (ft) from the aquifer
<br /> boundary through the well (gravel pit) to the river channel, 3) T - transmissivity of the
<br /> alluvial aquifer (in gallons per day per foot) between the well (gravel pit) and the river, and
<br /> 4) S - specific yield (0.2 was used for all sites). The parameters used in the model for each
<br /> site are listed in Table D below.
<br /> Table D - Aquifer Characteristics
<br /> Site Name T (gal/day/ft) X (ft) W (ft) OF (days)
<br /> Jeronimus Pit 100,000 1,600 23,000 -
<br /> Hazeltine Pit 100,000 1,200 23,000 -
<br /> Brighton Pit - - - 10
<br /> Tucson South Pit 75,000 1,600 4,600 -
<br /> Wattenberg Pit 80,000 1,200 5,500 -
<br /> Platte Valley Pit 150,000 1,400 7,400 -
<br /> DPG Pit 180,000 1,300 -
<br /> Distel Pit 50,000 700 5,300 -
<br /> Tull Pit 50,000 4,900 9,300 -
<br /> Irwin-Thomas Pit 50,000 1,900 6,000 -
<br /> W.W. Farms Pit 120,000 900 8,750 -
<br /> F-Street Pit 120,000 2,600 5,000 -
<br /> The consumptive use and lagged stream depletions from each site are summarized in
<br /> the attached "South Platte Combined Substitute Supply Plan Accounting 2025" sheet.
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