Azura-Edo Independent Power Plant Environmental Impact ... - IFC

Country Averaging period Recommended NO to NO 2
conversion ratio
United Kingdom
Short term (1 hour) 50%
Annual 100%
Hong Kong
24 hour 20%
Annual 20%
Ontario, Canada
24 hour 52%
Annual 68%
On the basis of the recommended ratios, adopting a pragmatic approach and
assuming that the suggested ratios are equally valid, it is recommended that
for long term a conversion ratio of 100 percent is appropriate, and for short
term a conversion ratio of 50 percent is appropriate. These conversion factors
have been applied in the results interpretation.
Assumptions
The modelling adopted a conservative approach and the following
conservative assumptions have been made in relation to the air dispersion
modelling undertaken as part of this assessment:
• Modelling has only been undertaken for emissions relating to the power
plant gas turbines ie not potential emissions relating to the back up diesel
generator, vehicles movements and construction activities.
• No assessment of changes in emissions during start-up and shut-down
have been made, as the plant is designed to supply base load.
• The proposed plant will operate at 100 percent capacity on a continuous
basis (24 hours per day).
7.3.2 Methodology for the Assessment of Dust
Emissions of dust will arise from the site during construction activities,
primarily as a result of earth moving activities and the passage of vehicles
over open ground. Dust emissions are primarily associated with nuisance
issues at nearby sensitive receptors, due to the deposition of dust on surfaces,
such as window sills, washing and vehicles.
Dust emissions related to construction activities are considered qualitatively,
on the basis of the potential for these emissions to primarily result in nuisance
issues. This approach is used as modelling of these emissions is not
appropriate due to uncertainties in the model source term. In considering the
location of possible receptors, the United States Environmental Protection
Agency (USEPA) states, in relation to dust emissions (EPA, 1995):
“… [dust particles 10-30µm in diameter] are likely to settle within a few
hundred feet [30-90m]… from the edge of the road or other point of emission.”
Ameliorating weather conditions such as rainfall and wind speed should also
be considered, as dust emissions are negligible during wet and calm periods.
AZURA EDO IPP
7-17
DRAFT EIA REPORT