2009-05-19_REVISION - M1977416 ‎(29)‎

• Permit No: M1977416
• IBM Index Class Name: REVISION
• Doc Date: 5/19/2009
• Doc Name: EPP‎(AM-01)‎ Att 4: Bioavailability; Att 5: Water Bal; Att 6: Percolation; Att 7: Lab Rpts. ‎(part 4)‎
• From: Denison Mines
• To: DRMS
• Type & Sequence: AM1
• Email Name: RCO
• Media Type: D
• Archive: No

Calculation Brief
Estimation of Percolation Through Development Rock Areas Using UNSAT-h
•
Table 2. Sensitivity analysis of selected input parameters
Simulation Site Precipitation (cm) Time Step
Control
Parameter
(DMAXBA) Initial Soil
Matric
Potential
(cm) Number of
Nodes Estimated
Percolation (cm)
1 Topaz 32.41 0.001 1.00E-07 28 0.027463
2 West Sunday 32.41 0.001 1.00E-07 28 0.032824
3 Topaz 50.47 0.001 1.00E-07 28 0.028401
4 West Sunday 50.47 0.001 1.00E-07 28 0.033676
5 Topaz 32.41 0.0001 1.00E-07 28 0.027463
6 West Sunday 32.41 0.0001 1.00E-07 28 0.032825
7 Topaz 50.47 0.0001 1.00E-07 28 0.028402
8 West Sunday 50.47 0.0001 1.00E-07 28 0.033676
9 West Sunday 50.47 0.0001 1.00E-05 28 0.033792
10 West Sunday 50.47 0.0001 1.00E-03 28 0.033765
11 West Sunday 50.47 0.0001 1.00E-05 111 0.026953
12 West Sunday 50.47 0.0001 1.00E-07 111 0.026868
6.0 Conclusions •
The UNSAT-h simulations suggest that significant percolation from the base of the
development rock stockpiles is unlikely. However, a small amount of percolation is
estimated for all simulations. The simulations further suggest that infiltration of
precipitation followed by upward evaporative flux of water stored within the
development rock areas are dominant mechanisms controlling the volume of
percolation through the development rock areas. Minor differences in the physical
characteristics of the development rock from West Sunday and Topaz mines as well
as the magnitude of annual precipitation are less important controls on the expected
volume of percolation.
The results of this simulation correspond to the input parameters including the
development rock physical and hydrologic parameters, and the available climate
data. Site-specific climate data are not available for the West Sunday and Topaz
mines, and differences between actual climate conditions at the site and the data
compiled from the Uravan and Montrose weather stations could result in variations in
percolation through the piles. In addition, inclusion of cobbles and boulders in
laboratory analyses of samples from West Sunday and Topaz mines may affect the
predicted percolation rates. However, available laboratory instruments do not
facilitate inclusion of these larger particle sizes. Unsaturated flow through mine waste
piles is controlled by the finer grained particles (Swanson et al. 2000). Therefore,
estimation of physical and hydrological characteristics of the development rock based
cm 6 •
TA64986-Denison Mines\Task Order 3 - DMO Sampling and Analysis Plan\Task 3.12 - Soil, Ore, Rock Data Assessment Repod\Unsat_h models\fnal models\Final Repor6calc bnef.doc