Environmental Assessment
Volume C-3.7
Slurry Pipeline
Water Quality
Ambatovy Project
63
January 2006
3.7.5
Impact Assessment
The slurry pipeline route is about 195 km long and runs along a route from the
mine site at Ambatovy to the processing plant at Toamasina near the coast
(Volume A, Figure 7.2-2). The first 30 km of the route descends from the
highlands to the coastal plain. The remaining portion of the route runs from the
base of the escarpment, across the coastal plain and finally to the plant. The
route crosses numerous watercourses (streams, rivers and wetlands) that could be
potentially influenced by construction, operation and post-closure activities
related to the slurry pipeline.
During the construction phase, site preparation and clearing has the potential to
result in increases in suspended sediment concentrations in receiving
watercourses and water bodies. Suspended sediments may also be introduced
during installation of the pipeline at watercourse and water body crossings.
Changes in suspended sediment concentrations are addressed in the Hydrology
Section (Volume C, Section 3.7). The bed sediments disturbed during
installation of the pipeline may release water quality substances that are typically
associated with particulate material.
Water withdrawals for hydrostatic testing of the pipeline will be required during
the construction and operations phases. Water withdrawals and disposal of
hydrostatic waters have the potential to cause changes in flow and local hydraulic
characteristics of the watercourse or water body. The flow and hydraulic
characteristics changes could potentially cause mobilization of bed sediments and
sedimentary-bound contaminants to the water column.
If a pipeline failure occurs, releases of substances into receiving watercourses
and water bodies could potentially change surface water and bottom sediment
quality downstream of the pipeline crossing. Spills during construction or leaks
during operations also have the potential to affect water quality.
Finally, erosion during the decommissioning phase could potentially introduce
sediments and water quality substances associated with sediments into water
bodies. Changes in water quality, particularly for metals and nutrients that tend
to be adsorbed to sediment particles, may cause changes in sediment quality in
receiving watercourses and water bodies.
3.7.5.1 Assessment Methods
In general, effects on water quality associated with construction, operation and
decommissioning activities related to the slurry pipeline are expected to be low
