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Rifle Gr�ive Ot # J, <br /> qthjary zOZs <br /> 8.6.4 Exposed Groundwater Lost Due to Evaporation <br /> Evaporation from exposed groundwater during active mining will occur as mining operations <br /> progress. Annual gross evaporation for the Rifle area is estimated at 45 inches based on the <br /> contours from National Oceanic and Atmospheric Administration Technical Report NWS 33 <br /> dated June 1982, Map No. 3. Annual evaporation was distributed annually using the DWR <br /> General Guidelines for Substitute Water Supply Plans for Sand and Gravel Pits (DWR <br /> Gravel Pit Guidelines) annual distribution for elevations below 6,500 feet. The evaporation <br /> was then reduced to account for periods when the pit is expected to be frozen over when <br /> the average temperature is below freezing, typically December and February for Rifle. <br /> Groundwater will be exposed to the surface during the wet mining operations. The final <br /> surface area of the pond is estimated to be 9.55 acres. It is conservatively estimated that the <br /> total surface area of the pond will be exposed within the first year of operation. The total <br /> annual evaporation of the pond was calculated at 44.28 AF/year, based on a previous <br /> version of the mining proposal that involved a larger pond surface of 12.56 acres. Given that <br /> the pond has been reduced in size, annual evaporation will be lower in fact, but IHC Scott <br /> has elected not to revise the loss calculation downwards since augmentation/supplementary <br /> supply plans have already been prepared. <br /> 8.6.5 Water Used Indoors (Domestic and Commercial) <br /> Scott does not anticipate using water from the site for indoor water demands. As such, there <br /> will be no groundwater demands or depletions associated with domestic or commercial <br /> water depletions. <br /> Potable water is not available from City of Rifle or Town of Silt and drilling a well for potable <br /> water on the property is not feasible given minimal domestic needs and short operating <br /> period. Instead, Scott will truck potable water onto the site to supply employees with potable <br /> water. As sewer services are unavailable from City of Rifle or Town of Silt, Scott will provide <br /> portable toilets for wastewater needs. <br /> 8.6.6 Water Requirements During Reclamation Phase (Post Mining) <br /> After mining is completed, water depletions from the site will be solely from evaporation of <br /> the exposed groundwater in the finished gravel pit pond. Annual gross evaporation for the <br /> Rifle area is estimated at 45 inches based on the contours from National Oceanic and <br /> Atmospheric Administration Technical Report NWS 33 dated June 1982, Map No. 3. Annual <br /> evaporation was distributed annually using the DWR General Guidelines for Substitute <br /> Water Supply Plans for Sand and Gravel Pits (DWR Gravel Pit Guidelines) annual <br /> distribution for elevations below 6,500 feet. The evaporation was then reduced to account <br /> for periods when the pit is expected to be frozen over when the average temperature is <br /> below freezing, typically December through February for Rifle. <br /> The final surface area of the pond was originally estimated to be 12.56 acres and is <br /> estimated to have 44.28 AF of depletions annually. Table 4 presents the post-mining phase <br /> water use demand based on this estimate, although subsequent design changes have <br /> reduced the surface area of the pond to 9.55 acres. <br /> 50 <br />