Tailings Management
State-of-the-Practice Waste Rock and Tailings Management
The Proposed Project is based on a state-of-the-practice strategy for the waste rock and the tailings that remains after the mineralized rock mined at Pebble is treated, which minimized both impacts and risks. The key elements include:
- When the mineralized rock is treated in the mill, the bulk and pyritic materials will be separated and sent to designed tailings storage facilities that use of different water management strategies suitable for their geochemical conditions
- The main embankment of the bulk facility is designed with flow-through construction and downstream seepage capture, minimizing the water in the facility during construction and operations and facilitating a drained closure condition, reducing the likelihood of water accumulation leading to failure
- The embankments around the facility is designed with 2.5:1 downstream slopes with high factor of safety – a 1.9:1 static factor of safety, versus normal of 1.5:1.
- The overburden below all embankments will be excavated to ensure weak layers are removed and then founded on rock - thus eliminating that potential source of failure
- The pyritic facility will be fully lined to reduce seepage and to ensure the pyritic tails do not react and produce acidic runoff
- Potentially acid generating waste rock will be stored with the pyritic tails to ensure the waste rock also does not produce acidic runoff
- The pyritic tails facility will be decommissioned at closure. Those tailings and the co-disposed waste rock will be returned to the open pit as a gravity well, ensuring no downstream contamination and eliminating the possibility of failure
Cross section diagrams of the TSF embankments and liners
