PERMFILE46723

• Permit No: M1988112
• IBM Index Class Name: Permit File
• Doc Date: 11/8/1988
• Section_Exhibit Name: APPENDIX Q ADEQUACY REVIEW QUESTIONS AND RESPONSES
• Media Type: D
• Archive: No

not necessary.
' The solution storage ponds have been designed in accordance with
Colorado MLRD requirements to store the minimum volume of
solution to meet operational requirements plus anticipated
seasonal fluctuations due to average precipitation and
evaporation alus draindown from the ore under active leaching or
rinsing in the event of a power failure plus direct onfall to the
pad and ponds area equivalent to a 100 year 24 hour storm. This
storage does not impinge on the upper 2 feet of dry freeboard.
All upgradient runoff has been routed around the heap leach
facilities.
The top 2 feet of storage in the ponds, normally reserved for dry
freeboard, will be available for excess solution storage in the
event of a storm larger than the 100 year 24 hour design storm.
The extra storage of 7.7 acre feet gives the facility the ability
to store 235Ye of the 100 year 24 hour storm during year 1 of
operations. This is then progressively reduced, due to pad
' expansion, to storage of 160 Y of the 100 year 24 hour storm
during years 8 through 10 of operations.
If additional storage beyond that described above is anticipated
to be necessary, BMR will be onsite to either initiate or
continue leaching and/or rinsing operations on the heap t.o
minimize the potential for draindown of the ore using a diesel
powered generator which will be available on site. In this
manner, an additional 21 acre feet of storage capacity (equal to
the draindown volume) can be made available. During year 1 of
operations 21 acre feet is equivalent to 3.75 times the inflow
from a 100 year 24 hour storm. The extra storage is reduced
progressively due to pad expansion to 1.65 times the 100 year 24
hour storm inflow during year 8 of operations. In addition, BMR
personnel will also be onsite at all times to take whatever
measures are necessary to ensure embankment integrity.
In summary, BMR believes that the design is conservative and
appropriate. The incorporation of an overflow spillway would
actually increase the potential for discharge of solution to
nearby surface and groundwater ponds of similar size and is
therefore believed to be less effective then retaining the use
of dry freeboard.
No application change necessary. This response along with the pond stability
analyses provided on 2/22/89 and incorporated into the application as
described in Comment 41 were deemed adequate by the MLRD.
41. Considering that no emergency pond has been provided in the design, and
that the pond will be constructed as embanked structures with 20-foot
depth, further documentation on pond stability should be submitted. No
technical specifications on pond construction are provided in Appendix
N. Materials, construction techniques, compaction specifications and
compaction testing anticipated for use in pond construction should be
documented. Please provide all documentation used to support the