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Calculation Brief
<br />Evaluation of the Sensitivity of Percolation Estimates through
<br />Mine Rock Stockpiles on the Simulated Precipitation Rate
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<br />Additional UNSAT-H simulations were completed to address this DRMS comment by
<br />evaluating the sensitivity of the UNSAT-H model to various rates of precipitation.
<br />The simulated rate of precipitation in the UNSAT-h model is governed by a variable
<br />called HPR, which is the simulated hourly rate of precipitation. This calculation sheet
<br />describes a sensitivity evaluation of the UNSAT-H model completed for the Sunday
<br />Mines Group to the hourly rate of precipitation. This calculation evaluated simulated
<br />precipitation rates (HPR values) ranging from 0.1 centimeter (cm) per hour to 4 cm
<br />per hour.
<br />2.0 Procedure
<br />¦ Estimate physical and hydrological characteristics of development) rock using site
<br />specific sampling and laboratory analyses.
<br />¦ Compile climate data from locations as close as possible to the site.
<br />¦ Estimate percolation through development rock areas using UNSAT-H.
<br />¦ Conduct a series of model runs using varying values for HPR to evaluate the effect
<br />that the precipitation rate has on estimated annual percolation.
<br />• 3.0 References/Data Sources
<br />Advanced Terra Testing (ATT), 2009, Laboratory data for soil water characteristic curve,
<br />saturated hydraulic conductivity, grain size analyses, and moisture content. These data were
<br />developed from samples collected at the Topaz Mine in August, 2009.1
<br />Benson, C., 2006, An Introduction to Water Balance Modeling, in: Benson, C., Albright, B.,
<br />Rock, S., Valceschini, R., Waugh, J., Alternative Covers for Landfills, Waste
<br />Repositories, and Mine Wastes Workshop, November.
<br />CDM, 2009, Environmental Geochemistnj Investigation of Soil and Rock Materials, Sunday
<br />Group Mines, prepared for Denison Mines (USA) Corp, April
<br />Colorado Division of Reclamation and Mine Safety (DRMS), 2009, Comments received
<br />from the Colorado Division of Reclamation and Mine Safehj on the Environmental Protection
<br />Plan for the Denison USA Corp. Sunday Mines Group, May 29, 2009.
<br />Fayer, M.J., 2000, UNSAT-H Version 3.0: Unsaturated Soil Water and Heat F107V Model
<br />Theory, User Manual, and Examples.
<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.
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<br />C:Wetson_worRV)enisonlUNSAT_HtHPR sensitidty\Sunday HPR Sensitivity talc brief doc
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