2006-09-21_REVISION - M1980149 - Laserfiche WebLink

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annual mean precipitation is 12.95 inches or 1,08 feet. The precipitation at the mine site is estimated to be the same as found at the nearest weather station, which is located in Longmont. The effective precipitation is computed to determine the net evaporation from the exposed groundwater. Effective precipitation is calculated as 70% of the average annual precipitation and is 0.76 feet for the Hokestra Pit. The net evaporation is then determined by subtracting the effective precipitation from the gross evaporation. The net annual evaporation is approximately 2.58 feet, thus the resulting net annual evaporation consumptive use during the mining operation is 161.38 acre-feet. The pit will be lined concurrent with mining and reclamation and will not require augmentation of evaporative losses. The water retained in the mined material is considered a consumptive use. The anticipated amount of material that will be mined each year is 150,000 tons. Assuming 4% moisture content by weight as suggested by the SEO, the total annual depletion is 4.4 acre-feet. There will be approximately 13,8 acre-feet of water used for dust control. The total annual consumptive use associated with mining aze as follows: • Evaporative Losses = 161.38 acre-feet • Moisture Retained in Product = 4.42 acre-feet • Dust Control = 13.8 acre-feet Total = 179.59 acre-feet Water Riehts Replacement water will be provided under the Hokestra Pit Substitute Water Supply Plan approved by the SEO. The following sources will be used in combination to more than adequately replace the depletions associated with the permit area shown on Exhibit G-1: • 3.75 shares of Rural Ditch (approximate consumptive use ~ 149.5 acre-feet) • A year by yeaz lease with St. Vrain and Left Hand Water Conservancy District Weld County will maintain a SWSP until the liner is constructed and approved by the SEO. After completion of the lined reservoirs at Hokestra, there will be no long-term evaporative depletions associated with the 62.6 acres of reservoir requiring augmentation. Sunoundine Water Ri¢lrts Groundwater will be pumped and dischazged directly to the St. Vrain River. Exhibit G shows all the water rights and permitted wells within one-half mile of the site. The SEO tabulation database was used to locate all the surrounding wells and water rights as shown in Exhibit G. AIthough there may be other wells in the area, they aze not registered or permitted with the SEO. Exhibit G-2 lists the 9 decreed water rights that are within the half mile radius. Exhibit G-3 lists the all the permitted wells that are within the half mile boundary as well As required by the SEO, gravel pit Well Permit No. 63693-F was issued on December 13, 2005 for uses of groundwater at the site. If the use of groundwater at Hokestra Pit results in material Weld Caunry Hokestra Pit DMG 112 Permit Amendment Page 10