Newlands Cross Upgrade EIS - European Investment Bank

South Dublin County Council N7 Newlands Cross Upgrade
Environmental Impact Statement
8. NOISE & VIBRATION
8.1 Introduction & Methodology
Arup Consulting Engineers
8.1.1 Introduction
This chapter of the Environmental Impact Statement (EIS) assesses the impacts of noise and
vibration associated with both the construction and operational phases of the proposed
Newlands Cross overpass. The proposed Scheme will remove the existing Newlands Cross
junction and upgrade it to a free-flowing overpass system on the N7. A number of existing
residential properties are located to the north of the proposed scheme.
This noise assessment follows the standard practice of adopting the traffic noise design goal
contained within the NRA document Guidelines for the Treatment of Noise and Vibration in
National Road Schemes 1 .
8.1.2 Methodology
The first stage is to assess and quantify the noise environment in the vicinity of sensitive
receptors that may be affected by the proposed development. In the case of a road scheme, the
selected noise-sensitive locations are likely to be those in closest proximity to the proposed
road. Both the construction and operational phases of the scheme should be reviewed when
selecting appropriate measurement locations.
Where possible, the noise levels resulting from both the construction and operational phases
are then calculated using established prediction techniques. Refer to section 8.5 for further
discussion of construction noise.
The noise levels associated with the operational phase of the proposed development were
predicted in accordance with guidance set out in Calculation of Road Traffic Noise (CRTN)2,
giving results in the form of LA10(18hour) values. These are then converted to Lden values
in accordance with the procedures detailed in the NRA guidance. The derived values for Lden
should be rounded to the nearest whole number, with 0.5 being rounded up.
The predicted values are then assessed against the three conditions set out in section 8.1.3 in
order to assess the need for mitigation measures.
8.1.3 Standards and Guidelines
For new roads in Ireland, it is standard practice to the adopt traffic noise design goal contained
within the NRA guidelines.
This document specifies that the Authority (i.e. NRA) consider it appropriate to set the
following design goal for Ireland:
• day-evening-night 60dB Lden (free-field residential façade criterion)
This design goal represents a more onerous limit value than those that have typically been
employed in Ireland to date 3 . Note that this design goal applies only at residential dwellings.
The application of this criterion at any non-residential locations in the vicinity of the scheme
is at the discretion of South Dublin County Council and the NRA.
Noise mitigation measures are deemed necessary whenever all of the following three
conditions are satisfied:
December 2007 Page 117