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

i,
the heap will be rinsed per each stage, and each rinsing stage is
estimated to take 12 months (1 year) it appears that a 10 year heap
rinsing schedule is required.
Response: The reader is referred to the response to Comment 46
Appendix G, Water Balance Table revised for heap neutralization and Exhibit
E, Section E.3.3 revised to include a discussion of final heap neutralization
2/15/89.
' 72. Hydrogen peroxide is recommended as a cyanide detoxicant due to its
oxidation potential and minima) impact upon the environment; the end
products of hydrogen peroxide decomposition are oxygen and water. Use
' of hypochlorite is not recommended as it is toxic to fish, requires a
high pH (approximately I1J thus requiring additional pH neutralization.
Sulfuric acid is not recommended for use, as it will solubilize heavy
metals in the heap and will also require pH neutralization prior to
final detoxification of the heap effluent. Please commit to use of
hydrogen peroxide as the cyanide detoxicant to be used at this site.
' Response: Hydrogen peroxide is expensive and difficult to use but BMR will
commit to using hydrogen peroxide if necessary during heap
detoxification.
Exhibit E, Section E.3.3.1 revised to show the use of hydrogen peroxide
4/20/89.
73. Recirculation of pond solutions through the heap for cyanide oxidation
and pond volume depletion is not recommended, as salt accumulation has
been observed in other processed heaps, believed to be caused by
continued evaporation of solution and resulting precipitation of the
f salt(s) component. Please consider spraying pond solutions over the
ponds, or onto an evaporation field, such that the salts may be
' collected and disposed of. fresh water, or an oxidizing solution made
by using fresh water, shou]d be added to the system to rinse the heap
of salts, metals and cyanide, Please discuss.
Response: Fresh water will be periodically added to the rinsing of the heap
as discussed under the response to Comment 46. The fresn water
will eventually replace the original solutions eight fold. Some
salt accumulation may occur but it will not be in sufficient
quantities to affect revegetation efforts.
No application change necessary.
74. The cycle of oxidizing the heap water followed by spraying to rinse the
]each pile should continue until the effluent draining from the leach
' pile reaches a pH between 6.0 and 9.0 and free cyanide concentration
of 0.2 ppm in consecutive sampling over a three to four week period.
The 0.2 free cyanide concentration is recommended as this is the
' Colorado ground water standard. We feel that the alluvial/colluvial
cover tributary to Culebra Creek would be the likely recipient of heap
effluent. Thus, the ground water standard would appear to be most
applicable.