Environmental Assessment
Volume C-3.6
Slurry Pipeline
Hydrology
Ambatovy Project
58
January 2006
sectional shape, channel width, and design flows, etc. This information will be
gathered and applied during detailed design phase of the pipeline.
Pipeline Hydrostatic Testing
No effects on sediment levels are expected from the withdrawal of water for
hydrostatic testing. Effects associated with the disposal of test water will be
minimized by release to vegetated areas and the use of sediment control measures
at these locations. Any discharges directly to receiving water bodies will be
controlled to minimize flow disturbances and ensure water quality discharge
criteria are met.
3.6.5
Impact Analysis
3.6.5.1 Residual Impacts
During construction, the slurry pipeline right-of-way is expected to have
negligible effects on flow and water levels, and low to moderate effects on
sediment levels in receiving water bodies. Effects during operations and post-
closure are expected to be negligible to low due to the proposed mitigation,
erosion control measures, and revegetation of the right-of-way. The impacts will
be short-term and the environmental consequence is therefore considered
negligible to low. A summary of the residual impacts is provided in Table 3.6-6.
Construction of the buried pipeline watercourse crossings will result in high-
magnitude impacts on flows and water levels in the immediate vicinity of the
crossings, but low to negligible impacts downstream of the crossings. At
crossings where instream construction is required, the impact on the sediment
levels will be high but of very short duration (on the order of hours and days
rather than months or years). The extent of the effects will be local, therefore the
environmental consequence is considered moderate based on Table 3.6-4. No
effects are expected during operation and post-closure provided that erosion
control measures are implemented and the stream banks are stabilized.
The location for water withdrawal and discharge for hydrostatic testing will be
determined upon detailed design. The volumes involved for testing will be
limited and withdrawal and discharge impacts will be minimized based on stream
sizes (using larger streams and rivers), receiving locations, quality and quantity
of the water discharged. Any changes in flows, water levels and quality are
expected to be negligible to low in magnitude. The extent of impacts will be
local and of short-term duration. The environmental consequence associated
with these types of effects is considered negligible.
