2015-07-22_REPORT - M1980244

• Permit No: M1980244
• IBM Index Class Name: REPORT
• Doc Date: 7/22/2015
• Doc Name: Response
• From: CC&V
• To: DRMS
• Email Name: TC1
• Media Type: D
• Archive: No

In 2012 and 2013 there were buried pipe header failures involving two barren lines and
one pregnant solution line that serviced the Phase IV PSSA area. These lines are now out
of commission and construction of replacement lines on the surface were close to being
finished, but have met with construction delays. Mr. Winterton noted that these
replacement lines are all on the surface except where they cross haul roads.
The inability to apply barren solution to the Phase IV pad area results in a significantly
reduced area available for solution application, especially considering the reduced surface
area of the Phase V pad as it nears its ultimate height, resulting in a smaller surface area
than at lower lifts.
Overflow resulting from Phase V PSSA 100% exceedance drains to the Phase I PSSA.
Overflow resulting from both Phases I and IV PSSA 100% exceedances drains to the
Phase II PSSA. The Phase II PSSA solution is the most down -gradient of the four PSSAs
and solution in this "pond" must be pumped to the External Storage Pond to avoid
exceedance levels. (Note: PSSAs are triple lined, all other portions of the VLF is double
lined.)
The mine was focusing on keeping the Phase II PSSA well below the 80% operating
level by applying solution to the Phase I and V pads.
The AGVLF leaching circuit is a closed system and the only practical short-term method
of reducing the amount solution is through evaporation.
Mr. Winterton agreed to provide an additional written summary report to the Division within 60
days of the inspection. The report should:
1. Summarize the water balance problem,
2. Discuss critical timelines such as the 20 -day filling of the Phase II PSSA, and
3. Describe the actions being and/or may be taken to remedy the AGVLF water balance
problem.
CC&V Response
Summary
In May 2015 the level in the Phase 1 drainage PSSA exceeded the 80% and, subsequently, 100%
capacity marks. The situation resulted from an unexpected increase in the amount of flow
crossing over from areas in the (up gradient) Phase 5 drainage leading to an overall inflow in
excess of the Phase 1 pump capacity. Actions were undertaken immediately to mitigate the
excess inflow by redistributing application areas and the (down gradient) Phase 2 PSSA was
carefully managed to maintain levels well below critical — less than 20% of maximum by volume
— to eliminate any chance of possible solution discharge off liner to Arequa Gulch.
Effects of course changes on the VLF require several days to fully propagate because of the great
depth and, hence, high solution levels in the Phase 1 persisted for several days as drainage
continued to reported to the PSSA. Inflows are again in line with pump capacities and the PSSA
level is below the 80% mark. Adjusted application strategies are presently, and will remain, in
effect to manage the Phase 1 and Phase 5 PSSAs according to current understanding of expected
crossover volumes. The discussion below provides an expanded background of the conditions
contributing to the incident along with figures illustrating timing and relative exigency of events.