COMHAIRLE CONTAE ÁTHA CLIATH THEAS
SOUTH DUBLIN COUNTY COUNCIL

MEETING OF LUCAN AREA COMMITTEE

Tuesday, February 22, 2011

MOTION NO. 7

MOTION: Councillor W. Lavelle

That this Committee, following on from the report on the Greater Dublin Noise Action Plan requested by me and presented to the September 2010 meeting, welcomes the subsequent noise monitoring carried-out in mid-January by Environmental Health Offices at residential areas fronting onto the Outer Ring Road and backing onto the N4 at Lucan and at Kennelsfort Road in Palmerstown and requests that a report be presented on the findings of this monitoring and any resultant noise mitigations measures which may now be considered.

REPORT:

Environmental Noise Survey January 2011 – Outer Ring Road and N4

On Friday 14^th January 2011 an environmental noise survey was conducted in order to quantify the existing noise environment at locations affected by traffic noise.

Three measurement locations were selected in total, taking into account location and proximity to roads. The locations were as follows.

Location Survey Reference	Description of Survey Location
S1	This location was in Moy Glas Road, an access road in a housing estate running parallel to the outer ring road. The location of the monitor was at the roadside, approximately 5m from the outer ring road. A masonry wall of approximately 2m high separates the two roads.
S2	This location was in Mt Bellew Crescent, an access road in a housing estate also running parallel to the outer ring road. The location of the monitor was at the roadside, approximately 5m from the outer ring road. A masonry wall of approx 1.2m, with a metal railing set above it, separates the two roads.
S3	This location was in a back garden of a house in Hillcrest Drive, backing onto the N4. The length of the garden was approximately 14m, with a masonry wall at the end, separating the garden from the N4. The location of the monitor was near the back wall of the house.

Measurements were conducted over a course of a single survey period as follows:

• 11:00hrs and 16:00 hrs on 14/01/11

The weather during the survey period was variable cloud, some heavy showers and very blustery conditions. Temperatures were below 10°C.

Measurements were conducted at all locations on a cyclical basis. Sample periods were 15 minutes. The results were noted onto a Survey Record Sheet immediately following each sample, and were also saved to the instrument memory for later analysis where appropriate.

Survey Results

The survey results are presented in terms of the following four parameters.

L_Aeq       is the A-weighted equivalent continuous steady sound level during the sample period and effectively represents an average value.

L_A90       is the A-weighted sound level that is exceeded for 90% of the sample period; generally used to quantify background noise.

L_A10       is the A-weighted sound level that is exceeded for 10% of the sample period; this parameter gives an indication of the upper limit of fluctuating noise such as that from road traffic.

L_den       is the day-evening-night composite noise indicator adopted by the EU for the purposed of assessing overall annoyance.

Noise Criteria for Specifying Mitigation Measures

a)      There are currently no Irish standards or limits governing the assessment of noise and/or vibration associated with either new or existing roads. 

b)      The Environmental Impact Statement for the Adamstown Roundabout to N4 Scheme published in November 2003 indicates that mitigation measures are required when all of the three categories are satisfied in a residential area:

·         the combined expected maximum traffic noise level, i.e. the relevant noise level, from the proposed road scheme, together with other traffic in the vicinity must not be less than 68dB L_{A10 (18 hour)};

·         the relevant noise level is at least 1dB(A) more than the expected traffic noise level without the proposed scheme in place;

_·          the contribution to the increase in the relevant noise level from the proposed road scheme must be at least 1dB(A). 

c)      The National Roads Authority Guidelines for the Treatment of Noise and Vibration in National Road Schemes Revision 1 dated 25^th October 2004 states the following:

“When defining the initial design criteria, the Authority originally intended to reduce the existing working standard of 68dB L _A10(18hour) by 3dB to 65dB L_A10(18hour), including façade effect. Based on a UK conversion methodology, this was anticipated to represent 60dBL_den free field. However, following completion of the validation studies for Irish road conditions, a 60dB L_den free field measurement translates to 60dB

L_{­A10(18hour) ­}free field; when the façade effect is included, this equates to 62.5dB L_A10(18hour). This demonstrates that the original working standard was reduced by 5.5dB rather than the 3dB was initially intended by the Authority. Therefore, the 60dB L_den design criteria proved to be much more onerous than originally anticipated and significantly different from the criterion which it has been intended to introduce for Irish conditions. 

Despite this, the NRA Authority still considers it appropriate to maintain the 60dB L_den design goal…for the development of new national road schemes.”

Following on from this, the NRA document indicates that mitigation measures are only deemed necessary when the following three conditions are satisfied at designated sensitive receptors:

a)      the combined expected maximum traffic noise level, i.e. the relevant noise level, from the proposed road scheme together with other traffic in the vicinity is greater than the design goal;

b)      the relevant noise level is at least 1dB more than the expected traffic noise level without the proposed road scheme in place;

c)      the contribution to the increase in the relevant noise level from the proposed road scheme is at least 1dB.

The results for all three locations, along with the derived L_A10(18hour) and L_den values, are as follows:

Survey Location	Measurement Noise Levels	Derived LA10(18hour)	Lden
LAeq	LA10	L­A90
S1	60	63	54	63	64
62	64	55
62	64	55
S2	63	66	57	65	66
64	65	58
65	68	57
S3	61	63	56	63	64
64	65	62
62	63	60

Conclusion

The findings of the survey are submitted for your attention and interpretation.

In arriving at an overall assessment of the 2 road schemes cognisance was given to all of following

§         the EIA Design goals,

§         the commencement dates of the projects,

§         the date of the NRA document of 24/10/04

§         The NRA commitment to stick with the lower level of 60dB L_den for all new roads even though it is going to be much more onerous for Irish road schemes.

From our interpretation and assessment of The National Roads Authority Guidelines for the Treatment of Noise and Vibration in National Road. Schemes Revision 1, condition (a) does not appear to have been satisfied as the original design goal of 68dB L_A10 has not been exceeded.  I am basing this assessment on the fact that both these schemes based on the EIS schemes had pre-dated the publication of the NRA document. 

However, it would be wise not to overlook and rule out an alternative viewpoint that might interpret the wording of the NRA document differently.