Environmental Assessment
Volume A-7
Introduction
EA Methods and Study Area
•
identification of project activities that could contribute to environmental
change;
•
evaluation of the potential effects;
•
description of mitigations for potential effects;
•
analysis and characterization of residual effects; and
•
identification of monitoring to evaluate and track performance.
For the purpose of this EA, mitigation applies to the construction, operation and
closure design principles to minimize or eliminate potential adverse impacts and,
where possible, enhance environmental quality.
Quantitative methods of assessment are used where possible. The predictive
modelling is used as a tool in the air, hydrogeology, hydrology and water quality
assessments. Geographic information systems (GIS) will be used to assess
impacts on terrestrial resources and land use.
7.4.1
Impact Description Criteria
The impacts that remain following mitigation or residual impacts, for the
environmental components will be classified using criteria to determine the
overall effect, termed the environmental or social consequence. Each impact will
first be described using the following criteria: direction, magnitude, geographic
extent, duration, reversibility and frequency (including seasonal effects):
Direction
: this may be positive, neutral or negative with respect to the key
question (e.g., a habitat gain for a key species would be classed as positive,
whereas a habitat loss would be considered negative).
Magnitude:
is the degree of change in a measurement or analysis, and is
classified as negligible, low, moderate or high. The categorization of the impact
magnitude is based on a set of criteria, ecological concepts and/or professional
judgment pertinent to each of the discipline areas and key questions analyzed.
Much ecological literature points to changes in measurement endpoints of over
20% as compared to baseline as having a high magnitude impact on biological
systems. Suter et al. (1995) have identified that the 20% rule for the severity of
effects from contamination is applicable by analogy to areal scales of ecological
effects. Lande’s (1997) demographic model predicted that species with low
demographic potential cannot persist if suitable habitat is reduced by more than
20%. These impacts are variable; species are predicted to exhibit a diverse array
Ambatovy Project
61
January 2006
