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

storm (varies from 29 to 41 ac-ftJ. In order to support the design
principal for containment, please submit either a revised pond capacity
volume or model documentation which indicates sufficient pond capacity
will be provided.
Response: The water balance table contained in Appendix G contains
cumulative storage requirements, i.e. normal storage plus
draindown or normal storage plus draindown plus 100 year storm
flows. The draindown estimate is fixed at 21 acre-ft, while the
100 year storm volume ranges from 5 to 13 acre-ft as the facility
is expanded. The range of total required storage volume to
contain all the variables is calculated to be 29 to 4l acre-ft
which is less than the 52 acre-ft capacity. A figure has been
added to Appendix G to show the pond storage fluctuation with
time. In addition, the water balance table shown in Appendix G
has been revised to explain each of the water balance components
in more detail.
Appendix G, Water Balance Table clarified 2/15(89.
39. The draindown volume of the heap leach pad was estimated to 6e 10
gallons per ton of ore (approximately 20 cubic ft. or .74 cubic yds.).
Appendix G, Heap Leach Water Balance indicates that although only
700,000 tons of ore will be processed at any one time, the heap )each
pad is planned to contain up to 6.5 million tons of ore. Therefore,
the vo]ume of the total draindown of the maximum amount of contained
ore should be 6.5 mi 11 ion tons x 10 gallons per ton = 65 mi 11 ion
gallons. Please clarify.
Response: The operating concept for the leach facility is based on a
maximum irrigation rate of 700 gpm distributed as 0.005 gpm/sq.
ft. This criteria provides the basis for the pond sizing and
water balance. Based on these numbers, only 140,000 sq. ft. of
the heap surface will be under leach at any one time. Assuming
that this area was the uppermost lift, 5 lifts of ore would
underlie the area and approximately 700,000 tons of ore would be
under active leach. 700,000 represents the maximum tonnage under
leach at any one time and thus the source for the design
draindown volume used in the water balance calculations and pond
sizing. Under no circumstances will all 6.5 million tons of ore
be under leach at one time.
No application change necessary.
40. The solution containment ponds should include spillway structures
allowing for controlled release of solutions, rather than possible
embankment erosion and resulting failure, in the event that a storm
which exceeds the design event occurs. Please provide design
specifications, including embankment erosion control measures and
locations of spillway structures.
Response: BMR believes that spillway structures for the purpose of
channeling excess solutions from the solution storage ponds into
the natural drainage channel are potentially undesirable and are