2010-03-18_REVISION - M1977285 ‎(6)‎

• Permit No: M1977285
• IBM Index Class Name: REVISION
• Doc Date: 3/18/2010
• Doc Name: Response to technical adequacy comments
• From: Denison Mines
• To: DRMS
• Type & Sequence: AM3
• Email Name: RCO
• Media Type: D
• Archive: No

•
Response to DRMS Comments
EnvironmentatProtection Plan
DEniSOn SundayMhes Group
2- Please provide a figure depicting the 3-dimensional nodal discretization of
the UNSAT-H model.
Response Agreed. This figure is included in the revised attached calculation brief
for the UNSAT-H simulations.
3 The textstates that the initial head was specified to he IE 07cm at all nodes,
but the inputfileshows IE+07cm. Please explain.
Response The text has a typographic error. The initial head used in the model is
1E+07 centimeters (cm). A revised calculation brief is attached.
It should be noted that the UNSAT-H models use a "warm-up" period of
39 years of average precipitation prior to running the actual model of
interest in the 40th year. In single year simulations, the UNSAT-H model
is sensitive to the initial head, which is unknown. The warm-up period of
39 years addresses this issue resulting in a model that is not sensitive to
the initial head of 1E+07 cm. The initial conditions at the beginning of the
40th year are shown at the beginning of the output file for the model run
for the model run, and range from approximately 1E+06 cm to 6E+04 cm
at the specific nodes within the model. This information is provided in
the calculation brief included with the Addendum to the Environmental
Geochemistry Investigation of Soil and Rock Material.
•
,l- fl decrease inpercolation with increasingprecipitation is counte>=intuitive,
because ofthe increasing head that should occur in thepile with increasing
precipitation. Please describe thephysicalprocesses that occzrr m the waste
rock to causepercolation through the waste rack to decrease asprecipitatiorr
increases, as depicted on Figure I ofthe "Addendum to the Environmental
Geochemistrylnvestigation ofSoil andRockflaterials, SundayMnes
Group."
Response It is important to note that the HPR sensitivity evaluation was based on
varying the rate of precipitation to address the August 28, 2009 DRMS
request to evaluate potential "high-intensity, short-duration precipitation
events such as thunderstorms". Each of the simulations in the HPR
sensitivity evaluation used the same daily precipitation data, which is
based on an actual year in the precipitation record that has total annual
precipitation as close as possible to the long-term average (the 1968 water
year). Therefore, the HPR sensitivity analysis shows that a higher hourly
rate of precipitation results in more runoff and less percolation. The
evaluation does not consider the effect of increasing total precipitation,
only increasing the rate at which this precipitation falls (expressed as
cm/hr).
The physical processes that occur with vertical infiltration of precipitation
into initially dry soil can be conceptualized by considering Darcy's law:
Final Sunday Mines RTC_v2.doc