Environmental Assessment
Volume B-3.4
Mine
Climate and Air Quality
Ambatovy Project
46
January 2006
Table 3.4-3 Impact Description Criteria for Air Quality
Resource
Direction
Magnitude
Geographic
Extent
Duration
Reversibility
Frequency
Air Quality
positive:
a
decrease in
emissions
and/or
ambient
concentrations
negative:
an
increase in
emissions
and/or
ambient
concentrations
magnitude
varies with the
air
contaminant
being
evaluated;
specifics
provided in
Table 3.4.4.
local
: effect
restricted to
the LSA
regional:
effect extends
beyond the
LSA
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
high
: occurs
continuously
Direction of an impact may be positive or negative with respect to the key
question (e.g., a reduction in predicted air concentrations would be considered as
positive, whereas an increase in air concentrations would be considered
negative).
Magnitude is a measure of the degree of change in a measurement or analysis
endpoint, and is classified as negligible, low, moderate or high. The
categorization of the impact magnitude was based on a set of criteria, ecological
concepts and professional judgment.
The air quality resources evaluated and the magnitude criteria used to evaluate
the residual effects are outlined in Table 3.4-4. Generally, the magnitude would
be classified as “negligible” if there was no increase predicted to result from the
mine emissions. A “low” magnitude would be assigned when an increase was
predicted, however the maximum value remains below 5% of the criteria.
A “moderate” magnitude would be assigned when the maximum concentrations
are below the criteria but above 5% of the criteria. A “high” magnitude would be
assigned when the maximums are greater than the criteria. In some cases,
applicable World Bank guidelines were not available. In these cases, WHO
criteria were substituted.
Reversibility indicates the potential for recovery of the ecological end point. An
effect is defined as not reversible if the resource element cannot be restored to
pre-impact condition within the long-term (as defined under duration in
Volume A, Section 7). The impact on air quality is always reversible.
Frequency describes how often the effect occurs within a given time period and
is classified as low, medium or high in occurrence.
