Environmental Assessment
Volume C-3.2
Slurry Pipeline
Soils
Ambatovy Project
23
January 2006
3.2
SOILS
3.2.1
Introduction and Study Area
This section presents the Environmental Assessment for the effects of the slurry
pipeline on soils, as per the Ambatovy Project (the project) Terms of Reference.
The slurry pipeline study area for soils is the pipeline project footprint study area
presented in Volume A, Section 7, Figure 7.2-2.
3.2.2
Baseline Summary
3.2.2.1 Pipeline Soils
Soils of the pipeline region have developed on old, geomorphically stable terrain
with almost no vestige of the original rock structure. Intense weathering in the
humid tropics from high temperatures, abundant moisture and time has resulted
in deep soil development.
The soils in the slurry pipeline region are generically known as laterites, which
are defined as highly weathered iron-rich tropical soils (Young 1976). The word
laterite has been widely used in the literature to describe soils of the tropical and
subtropical regions of the world. These general terms are often used to describe
various morphologic, physical and chemical properties.
In general, soils along the pipeline route followed a relatively predictable pattern.
On slope crests, Oxisols were found, at midslope positions soils were generally
Ultisols and at the toe of slopes and in depressions, the soils were either Histosols
or Oxisols, depending on drainage. Characteristics of these soils are summarized
in Table 3.2-1.
In the western part of the pipeline, the soils have developed on heavily weathered
cretacious rock (Delbos 1961) consisting mostly of gneiss, migmatite, granite and
migmatic granites. Deep soils have developed on the easily weathered gneiss,
while soils developed on granite tend to be thinner. At some locations, erosional
processes have occurred more recently and soils were classified as Entisols.
