1990-01-09_REVISION - M1988112 ‎(6)‎

• Permit No: M1988112
• IBM Index Class Name: Revision
• Doc Date: 1/9/1990
• Doc Name: FAX COVER
• From: STEFFEN ROBERTSON & KIRSTEN
• To: MLRD
• Type & Sequence: AM1
• Media Type: D
• Archive: No

'90 01169 16:36 ~ $ 303 585 9947 BFK DENUE~
BATTLE MOUNTAIN RESOURCES, 5AN LUIS PROJECT
CMLRD ADEQUACY LETTER RESPONSES
page 18 of 28
31. The water balance calculations are referred to on pages D-73, D-74,
and 6-3 as being found 1n Appendix I. The apparent correct reference
is Appendix K.
RESPONSE: The correct reference for the water balance is Appendix K. Pages D-
73, D-74, and G-3 have been revised to show the correct reference.
32. The units for monthly shallow lake evaporation are referenced in
Appendix K as "miles". The apparent correct reference would be
inches.
RESPONSE: The first page of Appendix K has been corrected to read inches as
the unit for monthly shallow lake evaporation.
33. A pan evaporation coefficient of 0.70 was used in the water baiance
whereas 0.74 was given in Exhibit K of the original permit. Please
clarify,
RESPONSE: The pan evaporation coefficient of 0.74 was used in the water balance
calculations for treatment of ore in a heap leach facility. The
current ore treatment process involves closed cell leaching coupled
with deposition of spent ore in a tailings facility. Use of the lower
coefficient is more conservative than that of 0.T4.
34. The diversion ditches iocated upslope from the collection pond are
shown in cross-section on Detail 2 of Figure C-8 end in plan form
on Figures C-3 and C-4. No peak flow calculations are provided to
substantiate their design, however the size appears to be
conservative. Please provide the following information on each
diversion:
a. The upland drainage area;
b. The minimum slope to ensure drainage;
c. An estimate of the size of runoff event which would overtop
the berm; and
d. The erosion control measures to be utilized at the ditch outlet
downslope to the natural dralnageway.
a. The diversion ditches adJacent to the collection pond have
upland drainage areas of 23.5 and 17.g acres on the north and
south sides of the pond, respectively. An analysis of runoff
potential for the 100-yr, 24-hr storm was performed for the
northern diversion ditch. This area represents the worst case
with respect to total surface area and overland slope. Results
of this analysis are presented as Attachment 13.
The analysis was performed using the computer program WASHED.
A peak discharge of 17 cis can be expected to occur in the
northern diversion ditch.
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