Laserfiche WebLink
2025 Speer Mining Resources SWSP Page 3 of 9 <br /> January 23, 2025 <br /> exposure of groundwater. The DRMS letter identified four approaches to satisfy this <br /> requirement. In accordance with approach nos. 1 and 3, a bond has been obtained for <br /> $678,169 that can cover the cost of lining or backfilling the Speer Mining Resources Pit to <br /> prevent the exposure of groundwater. <br /> Depletions <br /> The depletions at the site consist of evaporation from exposed groundwater. There are no <br /> operational losses at the site since backfill is completed and the site is in reclamation. The <br /> current total exposed groundwater surface area at this site is 1.8 acres. For the purposes of <br /> this SWSP, it is assumed that the exposed groundwater at the site will remain at 1.8 acres. <br /> Net evaporative depletions were calculated using a gross annual evaporation of 44.5 inches <br /> from the exposed water surface (based on the NOAA Technical Report NWS 33) with a credit <br /> of 9.65 inches for 70% effective precipitation (based on the Brighton 1 NE Station period of <br /> record 1974-2023). The net depletion of groundwater due to evaporation from the <br /> groundwater exposed at the site is calculated to be 5.23 acre-feet for 2025 as shown on <br /> attached Table 2. <br /> The Alluvial Water Accounting System (AWAS) model was used with the alluvial aquifer <br /> boundary condition option to lag depletions to the South Platte River. The following <br /> parameters were used in the model: transmissivity (T) = 96,043.2 gallons per day per foot, <br /> distance (X) from the centroid of the surface of the exposed groundwater to the river = 578 <br /> feet, distance (W) from the aquifer boundary through the exposed groundwater to the river <br /> channel = 4,752 feet', and specific yield (SY) = 0.2. The location of the stream depletion is <br /> 1 The distance from the aquifer boundary through the exposed groundwater to the river channel used <br /> in the previous SWSP was 6,800 feet; however, the Applicant determined that this distance is 4,752 <br /> feet. Therefore, calculations of lagged depletions starting in January 2020 used a distance from the <br /> aquifer boundary through the exposed groundwater to the river channel of 4,752 feet. <br />