Environmental Assessment
Volume C-3.6
Slurry Pipeline
Hydrology
Ambatovy Project
54
January 2006
Table 3.6-4 Impact Description Criteria and Numerical Scores for the Ambatovy
Project – Surface Water Hydrology
Resource
Direction
(a)
Magnitude
(b)
Geographic
Extent
(c)
Duration
(d)
Reversibility
(e)
Frequency
(f)
Surface Water
Hydrology
positive
,
negative
or
neutral
for the
measurement
endpoints
negligible
:
<5% change
low
: 5 to 10%
change
moderate
: 10
to 30% change
high
: >30%
change
local
: effect
restricted to the
LSA
regional
: effect
extends beyond
the LSA into the
RSA
beyond
regional
:
effect extends
beyond the RSA
short-term
:
<3 years
medium-
term
: 3 to
30 years
long-term
:
>30 years
reversible
or
irreversible
low
: occurs
once
medium
:
occurs
intermittently
(1 to 10 times
per year)
high
: occurs
frequently
(>10 times per
year)
(a)
Direction: positive or negative effect for measurement endpoints, as defined for the specific component.
(b)
Magnitude: degree of change to analysis endpoint.
(c)
Geographic Extent: area affected by the impact.
(d)
Duration: length of time over which the environmental effect occurs. Considers a three-year construction period and a
27-year operations period.
(e)
Reversibility: effect on the resource (or resource capability) can or cannot be reversed.
(f)
Frequency: how often the environmental effect occurs.
3.6.4.4 Mitigation
To mitigate the effects on flows, water levels and sediment levels, the Ambatovy
Project will implement the following measures:
•
selection of construction season, timing and method to minimize
sediment generation at stream crossing locations;
•
use of erosion control measures, revegetation and best management
practices to control sediment runoff along the pipeline right-of-way
during and after construction;
•
routine inspection of the disturbed areas and watercourse crossing
locations; and
•
selection of water withdrawal/discharge locations and rates to minimize
changes in water levels and sediment concentrations associated with
pipeline hydrostatic testing.
