1998-01-10_REVISION - M1988112

• Permit No: M1988112
• IBM Index Class Name: Revision
• Doc Date: 1/10/1998
• Doc Name: SAN LUIS PROJECT PERMIT AMENDMENT ADEQUACY RESPONSES M-88-112
• From: STEFFEN ROBERTSON & KIRSTEN
• To: MLRD
• Type & Sequence: AM1
• Media Type: D
• Archive: No

' BATTLE MOUNTAIN RESOURCES, SAN LUIS PROJECT
CMLRD ADEQUACY LETTER RESPONSES
Page 13 of 28
22. Section N-H' on Figure C-10 shows the 48-inch culvert downdrain to
' be buried. What wit] be the minimum and maximum fill depths placed
on the pipe? Are anti-seep collars considered necessary for this
culvert?
RESPONSE: The pipeline will be below grade at the inlet structure and will be
sealed into the concrete head wall. The pipeline will be maintained
at a relatively constant grade from the inlet to the outlet and will
require some regarding of the natural topography along its alignment.
' The pipeline will, therefore, be daylighted downstream of the inlet
and subject to the regrading will either be on surface or be in cut.
' No seepage collars are considered necessary for the pipeline.
23. The text on page D-42 states that Figure D.6-2 shows the freeboard
required to contain PMF inflows as a function of the elevation of
the tailings. Figure D.6-2 is tit)ed "Borrow Map". Please provide
the missing reference on PMf elevations.
' RESPONSE: The incorrect figure was referenced on page D-42. The correct figure,
providing freeboard required to contain PMF flows as a function of
elevation, is included here as Figure D.6-15. The text will be
changed to cite the correct reference.
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' RESPONSE: Hydrologic data will be reported to the Division as required in the
approved permit.
' 25. Pseudostatic factors of safety of Less than 1.25 are unacceptable
for embankment slopes. Please provide further design specifications
which would provide for a minimum factor of safety of 1.25 under
pseudostatic conditions. The minimum acceptable factor of safety of
1.25 for embankment slopes is recommended because this would help
ensure a more stable condition during the life of the facility. The
U.S. Bureau of Mines and Canmet guidelines for tailings disposal
facility designs both indicate that 1.25 is a prudent design criteria
for pseudostatic conditions.
RESPONSE: In order to select suitable seismic design criteria for the tailings
embankment and provide stable conditions during and after operation
of the facility, SRK adopted the following approach.

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