Environmental Assessment
Volume E-3.3
Tailings Facility
Soils
Ambatovy Project
35
January 2006
Sustainability of soil nutrients in disturbed soil has been identified as a potential
issue in the tropics and will be a major issue in reclaiming the tailings area. It is
important to ensure that organic matter is reincorporated during reclamation since
the organic matter has an important controlling function on soil fertility
(see Volume E, Section 6).
Compaction
Soil compaction is most severe under moist conditions, high loads and areas of
repeated traffic use. The effects of soil compaction were discussed in Volume B,
Section 3.3.
Mitigation that will be implemented to prevent and alleviate compaction includes
the following:
•
cultivate compacted soil before revegetation; and
•
use deep-rooted vegetation to loosen the compaction.
As discussed in Volume E (Section 6), reclamation of the tailings facility also
includes a main challenge of the time required for the material to harden.
Soil Contamination
General mitigations to prevent soil contamination will include the following:
•
tailings equipment will be designed with collection systems to minimize
loss of containment; and
•
cleaning up all spills and leaks promptly.
3.3.3.4 Results
A total of 1,268 ha of soils will be disturbed by the tailings over the life of the
project (Table 3.3-3). The majority of disturbed soils will have an existing
moderate to high erosion risk (1,185 ha, 93 % of total) as they are under Tavy
land use. The remaining soils will have a low existing erosion risk as they have a
land use of agroforestry, rice paddies, disturbance and wetlands (83 ha, 7% of
total). Before constructing the tailings dikes and basin, sufficient topsoil and
subsoil will be salvaged to allow reclamation of the dyke slopes. Therefore,
there will be a loss of 1,268 ha of soils during tailings operation (Table 3.3-3).
When reclamation is completed following closure, there will a net deficit of soils,
due to burial of much existing soil under tailings, which will be mitigated
through reclamation of soil material at the surface of the tailings pond areas. A
