Environmental Assessment
Volume E-3.3
Tailings Facility
Soils
Ambatovy Project
29
January 2006
3.3
SOILS
3.3.1
Introduction and Study Area
This section presents the Environmental Assessment for the effects of the tailings
facility on soils, as per the Ambatovy Project (the project) Terms of Reference.
The tailings study area for soils is the tailings project footprint study area
presented in Volume A, Section 7, Figure 7.2-3. It includes all the tailings
facility direct disturbance areas.
3.3.2
Baseline Summary
3.3.2.1 Regional Overview
Inland around the tailings facility, the geology consists of continental clayey-
sandy sandstone with migmatite (gneiss) at the surface. This is in contrast to the
geology near the plant site which consists of sandy marine sedimentary materials.
The migmatite formations near the tailings facility have convex relief (low
elevation hills and hilltops) separated by well-drained valleys
(Randriamboavonjy, J., 2005: pers. comm.).
The coastal area near Toamasina has a warm and humid climate with an average
annual rainfall of approximately 3,300 mm and an average temperature of 24°C
(Kilian 1968; see also Volume I, Appendix 4.1). These climatic conditions in
association with the area geology, have created podzolization in sandy soils near
the coast (plant site) and ferrallization on the migmatite rock further inland
(tailings area).
3.3.2.2 Tailings Soils
At the crest of convex slopes, ferrilitic soils (Oxisols) are typically found.
Ferrilitic soils have a sandy-clayey textured granular humus horizon with a
polyhedral structure, overlying a sandy-clayey to clayey-sandy textured B
horizon with a polyhedral structure. The entire soil profile is rich in quartz and
red or yellow in colour.
On upper slope positions, ferrilitic soils (Ultisols) are typically present. Ultisols
have an underlying clay rich B horizon with a polyhedric structure containing
mica flakes. Mid-slope positions usually are ferrilitic soils (Ultisols) with a
humus horizon directly overlying a loose eluvial horizon rich in primary minerals
such as mica. These soils are very susceptible to erosion.
