Environmental Assessment
Volume B-3.4
Mine
Climate and Air Quality
Ambatovy Project
43
January 2006
3.4.2
Assessment Boundaries
3.4.2.1 Temporal Scope
Temporal considerations for the EA are based on the Ambatovy Project
description and they vary among EA components because of the different ways
the project components interact with the environment. The air assessment is
based on consideration of the mine plan and the year in which the highest
emissions are expected to occur. This approach results in a conservative impact
assessment since the worst case emissions are expected for only one year. All
other years in the life of the mine are expected to result in lower air predictions
than those presented here.
3.4.2.2 Spatial Scope
The study area selected for the air quality assessment of the mine is 20 by 20 km
in size, centred on the mine site, as illustrated in (Volume A, Section 7,
Figure 7.2-1). Within the 400 km² study area is where the majority of the air
quality effects associated with the mine are expected to occur. The study area
has also been used when presenting the air quality predictions graphically.
One of the objectives of the air quality evaluation is to help address questions
from regional stakeholders regarding the possible effects of the mine on the air
quality in their communities. To facilitate this, air quality predictions were made
for each of the community receptors indicated in Table 3.4-1.
3.4.3
Assessment Methodology
The air quality assessment of the mine made extensive use of an air dispersion
model to evaluate potential air quality effects due to emissions from the mine.
The steady-state (2-D) version of the CALPUFF dispersion model was
determined to be the best model for assessing the air emissions from the mine.
This modelling system has been reviewed extensively and is recommended for
use by regulators in various jurisdictions. One advantage of CALPUFF is that it
can account for the chemical transformations of emitted SO
2
and NO
X
.
Furthermore it can model wet and dry deposition.
