Acoustics Bulletin Jul-Aug 2011 - Institute of Acoustics

INSTITUTE
AFFAIRS
Meeting report: London branch
Construction noise on a large infrastructure project
On Wednesday 19 January 2011, Steve Summers of RPS Planning
and development gave a presentation to the London branch
of the Institute of Acoustics on ‘Assessing construction noise and
vibration for a large-scale infrastructure project’, based on the
Crossrail project. It was obviously a hot topic for discussion, as the
evening drew in a record crowd in excess of 75 attendees.
Crossrail is a major project that will link existing railways either
side of London and complement the existing London Underground
services. When complete, Crossrail will provide services through
central London, linking Maidenhead and Heathrow to the west of
the city with Shenfield and Abbey Wood in the east. It is currently
the largest rail project in Europe.
RPS provided noise and vibration consultancy advice direct to
Crossrail Ltd from 2003. The appointment started with work on
route selection, continued with extensive baseline noise surveys,
noise and vibration aspects of the Environmental Impact
Assessment (EIA) and subsequently providing support for the
Crossrail Bill through the Parliamentary process, where noise and
vibration effects were key issues. The Crossrail Bill gained Royal
Assent in 2008.
Steve provided an overview of the history of assessing construction
noise, from the Wilson Report to the ABC method, developed for
use on the Channel Tunnel Rail Link. Crossrail adopted a criterion
based on a significant effect being predicted where the total noise
(pre-existing ambient plus airborne construction noise) exceeds
the pre-existing ambient noise by 5dB or more. This applies to day,
evening and night-time periods but with a lower cut-off tailored to
each period. The assessment methodology adopted has since been
published as one of the example methods in Annex E of British
Standard 5228-1:2009. The assessment criteria were also designed
to work in tandem with the Crossrail noise and vibration mitigation
scheme. The scheme enables residential properties to receive noise
insulation or temporary re-housing, if certain noise levels will be
exceeded for a given duration.
As part of the EIA for Crossrail, baseline noise monitoring was
undertaken at over 300 locations along the proposed route. Many
of the surveys were over a seven-day period, with additional 24-
hour and three-hour surveys. Such extensive monitoring was
necessary primarily to provide the baseline levels needed for the
construction noise assessment.
Modelling was carried out using the SiteNoise module of Noisemap
in to predict construction noise from every Crossrail work site. The
construction sites modelled ranged from simple platform
extensions at existing surface stations to the major civil engineering
works for the central London sub-surface stations and tunnel
portals. Many of the assessments considered several phases of work
and needed to consider night-time effects of 24-hour activity at
Central London worksites, or possession working on the surface
railway sections. Steve highlighted the point that obtaining realistic
construction planning information became a key issue, and RPS had
to work closely with Crossrail engineers to obtain it.
Steve explained that standard mitigation measures were classified
into tiers to provide a simple indication of the level of construction
noise mitigation required for each work site. He also set out the
estimated numbers of properties qualifying for noise insulation and
temporary re-housing and those expected to receive significant
residual construction noise impacts.
For vibration from construction activity, levels were predicted in
terms of peak particle velocity (PPV). However, the Crossrail
assessment methodology assessed human effects in terms of
vibration dose value (VDV). There was no simple way to convert
PPV to VDV, so an approximate conversion method was used at the
time. Since then, the 2009 edition of BS.5228 Part 2 has been
published including a scale relating human impacts to levels of
vibration in terms of PPV. This makes the task of assessing
construction noise effects much simpler for similar projects. Steve
summarised the findings of the construction vibration assessment
which indicated that significant effects were predicted at the
majority of the central London worksites.
The presentation concluded that the assessment of construction
noise and vibration for Crossrail had been one of the most
extensive ever carried out. The assessment methodology for noise
is now reproduced in the guidance published in the 2009 issue of
BS.5228 and relevant developments on the assessment of vibration
are also covered by the Standard’s update.
For further information please contact Steve Summers on
summerss@rpsgroup.com.
The London branch would like to extend thanks to Steve for giving
his valuable time to join us for the evening to give a very interesting
presentation, which proved to be one of the most popular topics
on the London branch programme. The committee would also like
to extend thanks to WSP for providing the venue.
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22 Acoustics Bulletin July/August 2011