Environmental Assessment
Volume C-3.4
Slurry Pipeline
Noise
Ambatovy Project
40
January 2006
3.4.4.6 Residual Impact Analysis
Based on the proposed construction schedule, clearing will occur one or two
seasons in advance of grading and pipe laying operations. Noise from clearing
activity will include chain saws and rough terrain vehicles pulling salvageable
lumber from the pipeline route. Noise from this type pf equipment is expected to
attenuate to the World Bank nighttime criteria of 45 dBA within 500 m of the
activity. During the normal operation of the pipeline, no noise will be emitted.
The loudest activity is expected to be pipe laying due to the number of trucks and
heavy equipment to be used. Pipe laying will also occur for the longest period in
any area along the pipeline route, as it is the activity with the slowest advance.
Pipe construction activity will occur sequentially along a 1 to 2 km section
(based on standard pipeline practices). Along this area will be various
excavators, welders, trucks and people.
This type of construction activity will typically have three or more large diesel
engines active. Attenuation calculated based on four, 1,500 HP diesel engine
machines. will result in noise levels of 45 dBA within 500 to 700 m of the
activity. These noise levels may be sustained at any point along the pipeline for a
period of several days up to a week, based on a 700 m daily progression along
the route.
Due to the localized effects for noise and expected short duration of construction,
impacts are not considered significant.
Traffic on public and access roads during construction is discussed in Section 5.5
of this volume.
3.4.4.7 Prediction Confidence
The calculation of outdoor noise attenuation is conducted using standard
algorithms and assumptions that tend to simplify the acoustic environment.
Noise, whether natural or man-made, is normally variable over time. The
algorithms and the L
eq
indicator account for that variability, but do not predict it.
The variation of noise sources over time can be addressed in the CadnaA model
in many ways, depending on the noise source being assessed and the level of
detail required.
The quality and relevance of noise predictions from the noise model is dependant
on the data inputs. For the assessment, noise sources were established with
