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Section 13 <br />Geochemical Data and Analysis <br />• ¦ A water balance approach; and <br />¦ Unsaturated flow modeling. <br />This evaluation is based on development rock samples collected from Denison 's West <br />Sunday and Topaz mines, which are located 10 miles south of the Van 4 Mine. These <br />development rock piles are composed of similar geological materials as the Van 4 <br />Mine, the physical characteristics of the piles are expected to be similar (e.g. particle <br />size distribution, moisture holding capacity etc.), and the mines are located in similar <br />climates. Therefore, the following evaluation of potential leachate production from <br />the West Sunday and Topaz Mines is thought to be generally representative of <br />potential leachate production at the Van 4 Mine development rock pile. <br />Water Balance Estimation of Percolation: This calculation estimates percolation through <br />the development rock areas using a water balance approach (adapted from Guymon <br />1994). To clarify water balance terms, percolation is the volume of water that <br />discharges from the base of the rock pile measured as cubic inches percolation per <br />square inches of rock pile footprint (i.e., inches). Infiltration is the volume of water <br />that infiltrates the surface of the rock pile measured as cubic inches percolation per <br />square inches of rock pile footprint (i.e., inches). Water that infiltrates into the pile <br />may be subsequently removed from the pile by evaporation or transpiration or the <br />water may move downward in the pile and become percolation. <br />Empirical information such as temperature and precipitation data and development <br />rock characteristics are used for the water balance evaluation. The procedure included <br />the following activities: <br />¦ Compile temperature and precipitation data from a location as close as possible to <br />the site; <br />¦ Estimate runoff and evapotranspiration (ET) for the rock pile; <br />¦ Estimate moisture holding capacity of development rock based on site specific <br />capillary moisture data obtained from soil water characteristic curve (SWCC) <br />testing; and <br />¦ Estimate percolation through the development rock pile using a water balance <br />approach. <br />Details of the estimation method are included in Attachment H of this report. <br />Development rock samples were collected for physical property analyses including <br />SWCC testing. Geotechnical laboratory data for the development rock samples, <br />including SWCC testing data, are also provided in Attachment H. Exhibit 13-1 <br />presents the results of monthly percolation estimates for an average precipitation <br />year. <br />• <br />13-5 <br />T:t64986-Denison Mines\Task Order 4 - EPP Sunday Mines Group-Van41Van4\FlNAL Report\FINAL - Environmental Protection Plan Van4.doc