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 excavate a <br />dewatering trench around the perimeter of the mining cell. The total length of 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 of approximately 0.2 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 />The total calculated consumptive use from evaporation and operations for the Lafarge Brown Mine <br />is 17.3 acre-feet per year during mining. After reclamation, the planned long-term exposed surface <br />area of the unlined lake is approximately 9 acres. 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 />PA23511V33-23511-08005\Deliverables\DRMSWpplication Package\Exhibit 6%&hibit G 06-05-09.doc Page G2 of G3