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Calculation Brief
<br />Estimation of Percolation Through Development Rock Areas Using UNSAT-h
<br />•
<br />Ford, R.C., Pierce, S.A., Ankeny, M.D., Kelsey, J., 2000, Evaluation and Management of
<br />Acid Drainage Risk from Spent Ore, El Abra Mine, Chile, in Semi-Arid Mine Waste Issues,
<br />ICARD 2000-Proceedings from the 5th International Conference on Acid Mine
<br />Drainage.
<br />CLIMATEDATA, 2008, Climate data from Uravan, Montrose, and Grand function Colorado
<br />weather stations, Volume 19.0, NCDC Summary of the Day-West 1, Hydrosphere Data
<br />Products, 2008
<br />Seki, K., 2007, SWRC Fit- A Nonlinear Fitting Program with a Water Retention Curve for
<br />Soils Having Unimodal and Bimodal Pore Structure, Hydrology and Earth System
<br />Sciences Discussions, Vol 4.
<br />Swanson, D.A., Savci, G., Danziger, G., Williamson, A., Barnes, C., 2000, Unsaturated
<br />Hydrologic Assessment of Waste Rock Stockpiles in Semi-Arid Climates, in Semi-Arid Mine
<br />Waste Issues, ICARD 2000-Proceedings from the 5th International Conference on Acid
<br />Mine Drainage.
<br />Weir, James E.; Maxfield, E. Blair; Zimmerman; Everett A. 1983. Regional Hydrology of
<br />the Dolores River Basin, Eastern Paradox Basin, Colorado and Utah. USGS Water-
<br />Resources Investigations Report 83-4217.
<br />4.0 Assumptions •
<br />¦ This estimate assumes that the samples and associated laboratory data are
<br />representative of the development rock piles. An inherent uncertainty in this
<br />assumption relates to the presence of cobbles and boulders in the piles, which will
<br />not fit in the laboratory capillary moisture test apparatus. However, infiltration and
<br />percolation under unsaturated conditons occurs preferentially through the fine-
<br />grained materials (Swanson et al 2000). Therefore, this assumption is considered
<br />adequate for the purposes of this estimate.
<br />¦ This estimate includes development rock extending to a depth of 3 meters. Any
<br />water flux passing through the 3 meter depth is assumed to percolate to the base of
<br />the pile.
<br />¦ The estimate assumes that there is no zone of saturation within the development
<br />rock piles (i.e., no groundwater is present within the pile). This assumption is
<br />supported by the fact that there are no observed springs or seeps emanating from
<br />the development rock piles.
<br />5.0 Calculations
<br />The UNSAT-H model was chosen for this evaluation because it simulates both
<br />downward movement of water into the development rock piles during infiltration
<br />and upward movement of water from the rock piles caused by evaporation. •
<br />C? 2
<br />T:\64986-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.12 - Soil, Ore, Rock Data Assessment Report\Unsat_h models\fnal modelsTinal Report\calc bnef.doc
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