Environmental Assessment
Volume E-3.8
Tailings Facility
Hydrology
Ambatovy Project
71
January 2006
Table 3.8-5 Description of Development Phases and Potential Changes in Runoff Characteristics
Basin Disturbance and Potential Change in Downstream Runoff
Scenario
Tailings
Discharge
Location
Water Pond Location
Basin A
(Valley TA-11)
Basin B
(Valley TA-10)
Basin C
(South Valley)
operations
year 14 -
end of phase 1
A(tailings)
B(tailings1) –
upper northwest area of
Basin B
•
100% disturbance in upper basin due to tailings deposition
•
runoff from upper basin directed to water pond resulting in
reduced flows in downstream reaches
•
tailings groundwater seepage collected by interceptor wells
and pumped back to water pond
•
B(tailings1) used as water pond resulting in 65% disturbance
of the upper basin watershed area
•
runoff from this area collected in the pond
•
pond water discharged to ocean and a portion reused at the
plant
•
no land disturbance or diversion of water
•
no change in streamflows
operations
year 20 -
end of phase 2
C(tailings)
B(tailings1) –
upper northwest area of
Basin B
•
100% reclaimed
•
runoff from the upper basin returned to natural receiving
water body (small sedimentation pond remains)
•
tailings groundwater seepage collected by interceptor wells
and pumped back to water pond
•
B(tailings1) used as water pond resulting in 65% disturbance
of the upper basin
•
runoff from this area collected in the pond
•
pond water discharged to ocean and a portion reused at the
plant
•
100% disturbance in upper basin due to tailings deposition
•
runoff from upper basin directed to water pond resulting in
reduced flows in downstream reaches
•
tailings groundwater seepage collected by interceptor wells
and pumped back to water pond
operations
year 27 -
end of phase 3
B(tailings)
B(tailings2) – southeast of
Water Pond for Phases 1
and 2
•
100% reclaimed
•
runoff from the upper basin returned to natural receiving
water body (small sedimentation pond remains)
•
tailings groundwater seepage collected by interceptor wells
and pumped back to water pond
•
100% disturbance in upper basin (65% for tailings disposal;
35% for water pond)
•
runoff from upper basin directed to water pond resulting in
reduced flows in downstream reaches
•
tailings groundwater seepage collected by interceptor wells
and pumped back to water pond Pond water discharged to
ocean and a portion reused at the plant
•
100% reclaimed
•
runoff from the upper basin returned to natural receiving
water body (small sedimentation pond remains)
•
tailings groundwater seepage collected by interceptor wells
and pumped back to water pond
closure
year 42 -end of
interceptor well
pumping
not applicable
not applicable
•
100% reclaimed
•
runoff from the upper basin returned to natural receiving
water body (small sedimentation pond remains)
•
pumping of interceptor wells ends; groundwater levels near
wells begin to recover
•
100% reclaimed
•
runoff from the upper basin returned to natural receiving
water body (small sedimentation pond remains)
•
pumping of interceptor wells ends; groundwater levels near
wells begin to recover
•
100% reclaimed
•
runoff from the upper basin returned to natural receiving
water body (small sedimentation pond remains)
•
pumping of interceptor wells ends; groundwater levels near
wells begin to recover
–closure
year 100 - long term
not applicable
not applicable
•
•
as above (year 42)
•
groundwater levels near wells have recovered
•
As above (year 42)
•
groundwater levels near wells have recovered
•
as above (year 42)
•
groundwater levels near wells have recovered
Note: Basins A, B, and C are associated with Ambolona Tributaries 1, 2 and 3, respectively. They are also referred to as Valley TA-11, Valley TA-10, and the South Valley.
