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• <br />Job #: 68838.64986.03.3.14 Calc By: N. Anton; M. Nelson <br />Client: Denison Mines CHK By: G. Hazen Date: 1/27/2009 <br />Project: Hydrogeology Report Date: 2/3/2009 Calc #: 1 <br />Detail: Water Balance Estimation of Percolation <br />Estimation of Percolation through Sunday Mines <br />Group Development Rock Stockpiles using a Water <br />Balance Approach <br />1.0 Purpose/Objective <br />To estimate percolation through the Sunday Mine Group development rock areas using a water <br />balance approach (method from Guymon 1994). Empirical information such as temperature and <br />precipitation data and development rock characteristics are used for the water balance evaluation. <br />2.0 Procedure <br />a) Compile temperature and precipitation data from a location as close as possible to the site. <br />b) Estimate runoff and evapotranspiration for site. <br />c) Estimate moisture holding capacity of development rock based on site specific capillary <br />moisture data obtained from soil water characteristic curve (SWCC) testing. <br />d) Estimate percolation through the development rock pile using a water balance approach. <br />• <br />3.0 References/Data Sources <br />-Benson, C., 2006, Introduction to Water Balance Covers, in: Benson, C., Albright, B., Rock, S., <br />Valceschini, R., Waugh, J., Alternative Covers for Landfills, Waste Repositories, and Mine Wastes <br />Workshop, November. <br />-Guymon, G.L., 1994, Unsaturated Zone Hydrology, PTR Prentice Hall, Englewood Cliffs, New <br />Jersey 07632, p. 81-83. <br />-Subramanya, K., 1994, Engineering Hydrology, 2nd Edition, p. 76-79. <br />-Precipitation and temperature data from Uravan, Colorado weather station (National Oceanic <br />and Atmospheric Administration [NOAA] weather station ID 8560). Data ranges from 1962 <br />through 2007. <br />-Laboratory data for SWCC testing, grain size analyses, and moisture content (Attachment 1). <br />These data were developed from samples collected at the Topaz Mine and West Sunday Mine in <br />August, 2009. <br />4.0 Assumptions <br />a) The wilting point and field capacity can be estimated from site specific SWCC testing, which <br />was conducted on development rock at a range of soil matric potential pressures. The wilting <br />point is assumed to be equal to the volumetric water content derived from the test at a soil matric <br />potential pressure of 1500 kilopascals (kPa), while the field capacity is assumed to be equal to the <br />MathCAD V14 Saved 2/17/20095:15 PM Page 1 <br />N:\64986-Denison Mines\Task Order 3 - DMO