Mine Water Management & Stability Control

Situation: Norwest consulted with a mining company that had been experiencing two separate instances of localized instability within a mining area. The first area was characterized as a creep type dump failure caused by placing waste material on what proved to be a weak foundation layer. The second area was characterized as a block type wall failure, which occurred along a weak “aqua putty” layer within the coal seam. Norwest quickly engineered a creative modification to the mine plan to allow for continued mining within the pit.

Solution: Norwest developed long-term remediation plans to mitigate the pit wall instability, which included detailed mining and water management plans and permit application submittals. The wall failure remediation plan required mining through two large sediment ponds located in series near the edge of the mine pit backfill, allowing for the pit wall angle to meet the stability requirements. After removing the weak aqua putty layer, a buttress of overburden material was placed to allow the replacement ponds to be reconstructed on a stable backfill surface. An interim water management plan allowed the ponds to be temporarily removed from service during the seasonal dry period.

Result: Norwest developed the detailed permitting and construction plans within a compressed schedule. Approvals were quickly obtained from State and Federal agencies so that implementation of the plan began on time with the exception of the mining and buttress construction which took a little longer than expected. Nevertheless, the interim water management functioned effectively to keep operations going smoothly despite near record rainfalls. Norwest’s efforts were pivotal in maintaining safe mining conditions and meeting coal extraction schedules.