Laserfiche WebLink
Calculation Brief <br />Estimation of Percolation Through Development Rock Areas Using UNSAT-h <br />U <br />Lakewood, Colorado. These data are included in Attachment 3. Capillary moisture <br />data were fit to the van Genuchten model using the program SWCC Fit (Seki 2007). <br />The van Genutchen-Burdine model was used for estimation of the unsaturated <br />hydraulic conductivity. The SWCC Fit output files for the West Sunday and Topaz <br />Mines are included in Attachment 1. Vapor flow was simulated using a tortuosity <br />of 0.66 and a vapor diffusivity of 0.27 centimeter squared per second. The average <br />soil temperature was assumed to be 283 degrees Kelvin. <br />¦ The model simulated percolation occurring during an average precipitation year <br />(assumed to be 1968) and the wettest year on record (1997) for both the West <br />Sunday and Topaz Mines. <br />The climate data used in the model includes precipitation data from Uravan, <br />Colorado, which is similar in magnitude to precipitation at the site based on <br />regional evaluations presented by Weir et al. (1983). Because wind speed, wind <br />direction and relative humidity data are not available for the Uravan site, these <br />data were compiled from a nearby weather station located in Montrose Colorado. <br />Average percent cloud cover data were compiled from Grand Junction, Colorado. <br />Solar radiation data for the site were compiled from the National Solar Radiation <br />Database. Other meteorological parameters included in the model include an <br />albedo of 0.4, altitude of 1,737 meters, and average annual atmospheric pressure of <br />852 millibars. Climate data and solar radiation data (with appropriate unit • <br />conversions) are provided in Attachment 1. <br />¦ A variable flux atmospheric boundary was applied at the surface and a unit <br />gradient boundary was applied at the bottom of the 3 meter profile. Vapor pressure <br />at the surface was computed based on the daily atmospheric humidity specified in <br />the climate input files. The daily temporal distribution of potential evaporation was <br />assumed to be sinusoidal. A matric suction. of 1X 10-7 centimeters was used for the <br />initial conditions at all nodes. <br />The model was run using a 39 year initialization period followed by either an <br />average precipitation year (assumed to be 1968) and the wettest year on record <br />(1997). The initialization period is based on sequential average precipitation years <br />to reduce the potential effect of initial conditions regarding the soil moisture at each <br />node on the estimated percolation resulting from either the average precipitation <br />year or the wettest year on record. <br />Table 1 summarizes the results of the modeling effort for the West Sunday and Topaz <br />Mines. The corresponding UNSAT-h output files are included in Attachment 1. <br />cm 4 <br />T164986-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.12 - Soil, Ore. Rock Data Assessment Report\Unsat_h models\final modelsTinal Report\calc bdef.doc