Environmental Assessment
Volume E-3.1
Tailings Facility
Topography and Geomorphology
Ambatovy Project
23
January 2006
The existing topography of the tailings facility LSA is hilly with relatively steep
slopes, except at the eastern end of the tailings facility access corridor, which
extends into level terrain. The areas affected by topographic change due to the
tailings facility include relatively steep-sided valleys and ridges, and flatter
valley bottom areas.
The tailings facility will have a direct impact on the landscape. Generally,
impacts will be long-term, because to maintain the integrity of the dam
structures, they will be left in place following closure. Construction will occur
continuously through the operations phase since embankments will be raised
periodically. The magnitude of the changes are considered moderate during
construction and operations, with the development of embankments and ponds
contained within them. The impact magnitude is moderate during the closure
phases, as the development of the flat-topped facility will be a large, locally
observable change in the shape of the landscape.
Slopes of tailings facility dam features, both during mining and after reclamation,
will fall within the natural range of variation of slopes existing in the area.
However, the orientation, regularity and diversity of slopes will change, and on a
local basis the topographic changes will be very noticeable, with the potential to
affect local biological systems and human use of the land in the long term.
An overall residual impact classification for topography and geomorphology for
each phase of the project is presented in Table 3.1-3.
Table 3.1-3 Residual Impact Classification for Topography and Geomorphology
Phase
Direction Magnitude Geographic
Extent
Duration Reversibility Frequency Environmental
Consequence
Key Question TG-1
What Effect Will the Tailings Facility Have on Topography and Geomorphology?
construction/
operations
negative
moderate
local
long-
term
no
medium
moderate
closure
negative
moderate
local
long-
term
no
low
moderate
Prediction Confidence
The baseline status of topography in the LSA is well understood. The eventual
form of the landscape following reclamation has also been established. Impact
ratings are dependent on the success of the mitigations proposed, including
erosion control and slope stability engineering. Overall, the prediction
confidence for this assessment is considered high.
