COMHAIRLE CONTAE ÁTHA CLIATH THEAS
SOUTH DUBLIN COUNTY COUNCIL
MEETING OF LUCAN AREA COMMITTEE
Tuesday, June 28, 2011
HEADED ITEM NO. 17
Greater Dublin Noise Action Plan
REPORT:
Re Noise from the N4 and Outer Ring Road
1. There is no reference in the report to N4 EIS and Bord Pleanala decision and modifications
Cognisance was given to both the N4 EIS and the Outer Ring Road EIS when planning the noise survey. The attended measurement procedure used for the noise survey carried out by the Environmental Health Department was the procedure used in both Environmental Impact Statements. The An Bord Pleanala decision and modifications did not have any impact on the methodology out of the survey.
Modification 1(a) of the An Bord Pleanala report refers to mitigation of the road traffic noise levels to be achieved by the design year (2023).
Modification 1(b) of the report: This refers to additional mitigation measures to be undertaken by the provision of noise barriers at a number of locations as specified in the An Bord Pleanala report. We will need confirmation from the Roads Department as to whether these works have been carried out.
2. Re: Outer ring Road the report refers to the EIS but not the final Bord Pleanala decision and modification 1a re: noise:
Modification 1a refers to a requirement for the design year (2019).
3. The report suggest the time period selected was 10am to 4pm missing both morning and evening rush hours – Does this not make the finding incomplete?
The noise survey was carried out according to a method specified in the NRA Draft Guidelines for the Treatment for Noise and Vibration in National Road Schemes 2004. Directive 2002/49/EC relating to the assessment and management of environmental noise designates Lden as the selected common noise indicator to assess annoyance. Lden is defined as the sound level averaged over day, evening and night i.e. 24 hours. The method used for the noise report as approved by the NRA involves taking a number of 15 minute noise ‘snapshots’ between the hours of 10:00 to 17:00. The L10 is noted at each reading. The L10 is the noise level exceeded for just 10% of the sample period. These figures are then extrapolated by use of a mathematical formula to give the L10(18hour) value, which is the average noise level exceeded for 10% of the time between 06:00 and 24:00. A further calculation is then applied to determine the Lden. Thus it is considered that the methodology used gives a true representation of noise nuisance over day, evening and night.
4. The report doesn't indicate the height of the monitor given that An Bord Pleanala ORR ruling refer to measurements be at upper floor level of a two storey house
The An Bord Pleanala requirement referred to measurements to be taken in the design year, 2019.
Given the constraints of the noise survey it was not possible to monitor at the upper storey level i.e. four metres above ground level, as noise measurements must be taken at least 1.5m from the façade of the building to ensure accurate measurement.
Ultimately, the key goal of the noise survey was to take measurements at appropriate locations, for the appropriate time period and from the appropriate source, giving a robust representation of the sound level of concern. We feel this was achieved with the noise report as presented.