Environmental Assessment
Volume E-2
Tailings Facility
Project Description
Ambatovy Project
17
January 2006
2.8.2
Tailings Deposition Plan
The tailings deposition plan will be based on the following general objectives:
•
Rotate discharge of tailings around the perimeter of each basin on a
regular basis. This will deposit tailings in relatively thin layers and will
promote drainage of supernatant and air drying as much as possible to
maximize density and strengths.
•
Discharge tailings from the embankments and perimeter to locate the
supernatant pond towards the discharge side of the facility to maintain
gravity drainage and minimize seepage through the walls.
•
Discharge tailings such that the base of the basin is covered within the
initial operating period to minimize seepage through the foundation.
Phase 1
Tailings will initially be deposited into the Phase 1 tailings basin from the east
and north sides to push the initial return water pond to the southwest and move it
away from the tailings embankment and towards the spillway to the water basin.
This will require that the north service road is constructed for year 1 operations.
Following year 1, the south service road will be constructed so that additional
tailings can be deposited from the west. This will centralize the supernatant pond
with ongoing tailings deposition from the east and north to maintain gravity
drainage to the spillway location. Approximately 117 Mt of tailings will be
placed within the Phase 1 tailings basin with tailings elevations as high as 80 m
by year 14 of operations.
Phase 2
The Phase 2 tailings basin will be commissioned in year 15 by initially
discharging tailings from the east and south. This will push the supernatant pond
towards the spillway location along the north side where water will be decanted
to the water basin. Ongoing tailings deposition will then be cycled around the
west, south and east portions of the Phase 2 tailings basin. This will maintain the
supernatant pond against the north central part of the basin for decanting into the
water basin. It is anticipated that the Phase 2 tailings basin will be constructed to
an elevation of 65 m for storage of 50 Mt of tailings.
Phase 3
The Phase 1 and 2 water basin will be used for tailings storage starting in
year 21. This will require a new (final) water basin to be constructed to the east
within the TA-10 watershed. Initially, tailings will be discharged into the Phase 3
tailings basin from the west and north. This will push the pond to the southwest
