Environmental Assessment
Volume C-4.3
Slurry Pipeline
Fish and Aquatic Resources
Ambatovy Project
129
January 2006
4.3.5
Key Question FA-1: What Effect Will the Project Have
on Aquatic Habitat?
4.3.5.1 Impact Pathways
Aquatic habitat can be affected by slurry pipeline activities during construction,
operation and closure phases. Habitats will also be affected by ancillary facilities
and services such as watercourse crossings by access roads, infrastructure such as
construction camps, and laydown areas. Changes in the availability, quality or
quantity of aquatic habitat may result from:
•
riparian disturbance at watercourse crossings;
•
instream habitat alteration; and
•
changes in water quality.
Riparian Disturbance
Clearing of forest canopy, riparian vegetation and disturbance of the stream
banks for the pipeline or service road approach to watercourses by grading or
other activities, and clearing or grading for camps and laydown areas, can result
in an indirect loss of aquatic habitat primarily due to the change in slope or
drainage pattern, with increased erosion potential. The resulting sediment
entrainment, increased levels of TSS and downstream transport can impact fish
habitat.
Instream Alteration
In-water activities from trench excavation, pipe laying and back filling will result
in sediment entrainment (increased TSS) and change in channel morphology,
affecting fish habitat. Associated activities such as hydrostatic testing of the
pipeline can result in similar changes. Construction of culvert, bridge or ford-
type crossings for access and service roads and placement of fill in water can
result in a disturbance or loss of instream aquatic habitat, or change to
watercourse hydraulics.
Changes in Water Quality
Changes to surface water quality (i.e., increased sediment loading) will occur as a
direct result of riparian disturbance and instream alterations at pipeline and road
approaches and crossings. Water quality may also be affected by accident or
spills during construction or operation, affecting the availability and quality of
aquatic habitat. The location of work camps, withdrawal of water from local
