Environmental Assessment
Volume C-3.6
Slurry Pipeline
Hydrology
Ambatovy Project
56
January 2006
however, the duration will be short, i.e., on the order of hours for small streams
and up to a few days for very large streams.
No effects on flows or water levels are expected in the streams during operation
or post-closure provided revegetation and erosion control is established and
stream banks are stabilized. Design and construction specifications, e.g.,
minimum burial depths, size of armour material, and sag-bend setbacks, will also
minimize the possibility of channel instability and geomorphic change.
Pipeline Hydrostatic Testing
Hydrostatic testing of the pipeline will require water withdrawal from rivers
and/or streams. The pipeline will be tested in sections and may require multiple
water withdrawals along the pipeline length. Withdrawal volumes and rates will
be specified at later stages in the project. Withdrawal locations will also be
selected with the aim of minimizing changes in affected water bodies. Water will
typically be disposed of to designated vegetated areas. Any water disposed
directly to receiving water bodies will be controlled to minimize flow impacts
and ensure there are no quality related issues. .
3.6.4.6 Results for Key Question H-2: What Effect Will the Slurry
Pipeline Have on Sediment Levels in Water Bodies?
Pipeline Right-of-Way
The clearing and excavation activities associated with the pipeline right-of-way
will expose large volumes of sediment and may result in increased sediment
transport from the disturbed areas. To reduce the exposure of sediments,
construction activities and active work areas will be phased. Erosion and
sediment control measures will also be implemented to limit the amount of
sediment transported away from the construction area. Typical examples of
erosion and sediment control practices are provided in Table 3.6-5. Throughout
pipeline construction and operation, performance of the control measures will be
monitored and maintenance and repairs performed as necessary. Any increases
in sediment yield that occurs during construction will decrease once the disturbed
areas are reclaimed and as vegetation is re-established through the operations and
closure phases.
