Laserfiche WebLink
Consumptive Water Use <br /> The consumptive uses at the Lafarge Brown Mine will include evaporative losses, water used for <br /> dust control, and water consumed in the mined material removed from the site. The Lafarge Brown <br /> Mine consumptive use volumetric projections are described below. <br /> Evaporative Losses <br /> The NOAA Technical Report NWS 33, Evaporation Atlas for the Contiguous 48 United States <br /> (U.S. Department of Commerce) was used to determine gross evaporation. For this location, the <br /> annual evaporation is 45 inches or 3.8 feet. Monthly evaporation percentages established by the <br /> State Engineer's Office (SEO) for elevations below 6,500 feet were used to calculate the monthly <br /> evaporation. <br /> Annual precipitation at the site was estimated using the Colorado Decision Support Systems' <br /> precipitation isohyets map, located at http://cdss.state.co.usIDNNIMapViewerltabidl62 <br /> /Default.aspx. The monthly distribution of precipitation was adjusted based on the average monthly <br /> data from the Western Regional Climate Center's Colorado Climate Summaries website, <br /> http://www.wrcc.dri.edulcgi-binIcliMAIN.pl?cogree, for the Greeley UNC Station from 1967-2006. <br /> Effective precipitation is 70 percent of total precipitation. Net evaporation is the difference between <br /> gross evaporation and effective precipitation. Net evaporation at the site is 3.1 feet. <br /> Evaporative consumptive use at the Lafarge Brown Property will be from exposed groundwater <br /> within the dewatering trench. In order to facilitate dry mining at the site, Lafarge will excav4te a <br /> dewatering trench around the perimeter of the mining cell. The tot engt f the dewatering trench <br /> around the mining cell will be approximately 1,250 feet. Assuming a width of 5 feet, the trench will <br /> expose an area o approxima e y T2�acres. The total evaporative consumptive use during mining is <br /> 0.6 acre-feet for the exposed surface area of the dewatering trench. The exposed surface area will <br /> vary slightly throughout the course of the mine life; however, all evaporative consumptive use will <br /> be augmented during mining. <br /> Operational Losses <br /> The moisture content of the material removed from the site is four percent by weight as required in <br /> the State Engineer's Office (SEO) Guidelines. The production rate for the mining site is 500,000 <br /> tons of aggregate material per year. This results in an annual consumptive use of 14.7 acre-feet for <br /> water retained in product. <br /> Lafarge will apply water to haul roads and stockpiles for dust control. The estimated annual <br /> consumptive use for dust control is 2.0 acre-feet with a distribution throughout the year based on the <br /> same percentages as the production of the aggregate mined. The total annual operational <br /> consumptive use at the Lafarge Brown Mine is 16.7 acre-feet, which includes moisture in material <br /> removed and dust control. <br /> Total Consumptive Use <br /> Th otal calculated consumptive use from evaporation and operations for the Lafarge Brown Mine <br /> is 17.3 acr -feet per year during mining. After reclamation the planned long-term exposed surface <br /> area of the unlined lake is approximate 9 acre . The long-term evaporative consumptive use is <br /> 27_.5 acre-feet. <br /> Greeley 35`h Avenue Mine(M-1977-036) <br /> DRMS 112 Reclamation Permit Amendment Application <br /> P:\23511V33-23511-08005\Deliverables\DRMS4pplicationPackage\ExhibitG\ExhibitG06-05-09.doc Page G2 of G3 <br />