Examination of Witnesses (Questions 4260
- 4279)
4260. MR MOULD: I am very grateful. We
shall certainly deal with it and I should very much like to say
more about the Settlement Deed as well. In that case unless there
are any other questions I shall ask Professor Mair to leave.
4261. CHAIRMAN: I think the only thing
that we can do is to thank Professor Mair very much and if the
Petitioners of Petition 20 do not turn up to ask him questions
it may very well be that they will not get another chance.
4262. MR MOULD: That is certainly right.
4263. CHAIRMAN: And they had better read
the transcript.
4264. MR MOULD: I am grateful for that.
4265. CHAIRMAN: I have no intention of
calling you back unless it is an emergency. We will have to see
how things go, but I think you have told us everything that we
need to know. Thank you very much.
The witness withdrew
MR RUPERT
THORNELY-TAYLOR,
recalled Examined by MR
TAYLOR
4266. CHAIRMAN: Mr Thornely-Taylor, I
think everybody in the room is part of the Crossrail team except
us, the shorthand writers and our clerk, so I think you need not
be introduced again.
Spitalfields—Noise Issues
4267. MR TAYLOR: My Lords, it is the
first time I get to stand on my feet and address you. Good afternoon.
I am calling Mr Thornely-Taylor to address you on four issues
in relation to noise aspects of the Spitalfields Petitions.
4268. CHAIRMAN: Which Petition are we
dealing with at the moment?
4269. MR TAYLOR: We are dealing with
all of the noise aspects raised in all of the Spitalfields Petitions.
4270. CHAIRMAN: So there is nobody here
from any of them?
4271. MR TAYLOR: There is not. There
are four aspects on which we are going to address you: firstly,
ground borne noise; secondly construction noise from the Hanbury
Street worksite; thirdly, construction traffic noise; lastly,
noise issues relating to the operation of the vent shaft once
constructed. So, Mr Thornely-Taylor, perhaps we can begin by addressing
the question of groundborne noise issues. A number of Petitioners
from Spitalfields are asking for a noise limit to be imposed upon
the operation of the railway to provide them with 25 dB LAmax
within their residential properties. I wonder if we can start,
please, by looking at page 2 of the Information Paper D10, which
addresses groundborne noise.[42]
It is coming up on the screen now. Here we have Table 1 in the
Information Paper, headed "Construction and Operation of
groundborne noise criteria."[43]
Can you explain, please, to the Committee what is shown in this
table?
(Mr Thornely-Taylor) Yes. This table shows the
targets which are applied according to different types of building
along the route. The general objective from tunnel to tunnel is
that nowhere does the maximum noise level go above 40, and that
applies particularly to residential buildings. However, certain
types of building do have a need for lower levels, and we see
courts, lecture theatres, small auditoria, halls and places of
meeting for religious worship have a 35 target. Sound-recording
studios have an even lower target of 30 and large auditoria such
as the Barbican Hall have a target of 25. I think your Lordships
will appreciate that, in the light of the experience we had in
the Chancery Court Hotel, we are effectively talking about silence
when we get down to those levels.
4272. Thank you. Just to place the 25 dB LAmax
that has been requested by Petitioners into some context, we can
see that that is 5 decibels below the measures being proposed
for sound-recording studios.
(Mr Thornely-Taylor) Yes, it is. Indeed,
it is lower than probably the background noise in many of the
houses concerned.
4273. I was going to ask you about that, if
I may. What is the likelihood of noises being experienced above
25 dB LAmax in residential properties at night at present?
(Mr Thornely-Taylor) We discovered on
the site visit that merely raising an arm and rustling a jacket
disturbed our noise measurements. In fact, 20 people in the room
we found were actually contributing to the background noise level
just by standing there and breathing. Any event in a room which
is other than in a wilderness is significantly more than 25.
4274. So what do you say about the appropriateness
of adopting a noise criterion of 25 dB LAmax for residential properties
in Spitalfields?
(Mr Thornely-Taylor) It is not necessary.
It goes far beyond reasonable requirements for the balance between
engineering design, cost and necessity and the design of an underground
railway.
4275. I am going to have put on the screen some
of the groundborne noise contour mapping that was produced in
the Noise Technical Report.[44]
We are zooming in here on the map for the Hanbury Street/Princelet
Street area in Spitalfields. Can you explain to the Committee,
please, what the contours show here?
(Mr Thornely-Taylor) Yes. The starting point
for the contours is an assumption made about the general system
of track support that is selected from tunnel to tunnel. It is
not going to be the case that the track will be chosen so that
we just bump along the 40 figure as we go along, putting in cheaper
track form because the noise levels are lower. The approach will
be to select a form of rail support which will, in nearly all
cases, achieve these targets from end to end, and the same basic
track form will be used for that purpose. We will need an enhanced
track form in special locations, which we will be hearing about
later in the proceedings, but it follows from that that, if a
rail support system is selected which achieves these criteria
in nearly all cases, there will be many locations when, for a
variety of reasons, particularly if the tunnel is particularly
low relative to the surface, if train speeds are low locally,
the predictions come out much better than the target. The Hanbury
Street area is no exception. Whereas the residential properties
there, strictly speaking, are subject to the 40 LAmax,S figure
we saw in the table we have just been looking at, these predictions,
which are an extract from a set of contours that run from tunnel
portal to tunnel portal, show actually what is likely to be the
groundborne noise level in this area. They are a little bit like
airport noise contours, except that aircraft are flying through
the ground, if you understand what I mean. The lowest contour
represents a groundborne noise level of 25 and each contour is
a 1 dB(A) increase. We do not, in fact, get above about 28. If
I say conservatively that we are below 30 in this area, we can
compare that with trains that are quieter than the quietest ones
we were hearing on the site visit.
4276. CHAIRMAN: Just on that, the ones
we heard on the site visit were going on jointed track, were they
not?
(Mr Thornely-Taylor)
Yes, they were running on the old-style track support system of
the Central Line and the quieter ones were probably on the Piccadilly
Line. As you rightly say, my Lord, that kind of track has many
things in it, including joints, which will not be present in Crossrail
track; it will be both continuously welded rail, aligned very
precisely and resiliently supported, and not directly fixed to
hardwood blocks, as is the traditional, old-fashioned method of
track support that the existing Tubes (apart from the Jubilee
Line Extension) have.
4277. LORD BROOKE OF ALVERTHORPE: Just
on the site visit, and I recognise you will not be able to answer
this, but we were accompanied by independent assessors who, when
prompted, decided to turn on their recording machines. They are
not here today and I just wonder if we anticipate they are going
to be coming back later.
4278. MR TAYLOR: My Lord, I think the
parties you are referring to were there representing the British
Board of Film Classification, who have a Petition coming up, I
think, in two weeks' time, and also Grand Central Recording Studios,
who also have a Petition coming up in the same week.
4279. LORD BROOKE OF ALVERTHORPE: Will
we have the pleasure of your company on that occasion?
(Mr Thornely-Taylor)
Of course, my Lord. Those Petitioners, of course, will enjoy the
much lower noise targets that we saw in that table because, in
the one case, they have a film theatre in the basement and in
the other they have a recording studio in the basement, and in
both cases there will be floating slab track and noise levels
will be much, much lower. In fact, their interest in our site
visit is a little unclear because there is no question of 40 dB(A)
LAmax or anything approaching that occurring in their properties.
42 Crossrail Information Paper D10-Groundborne Noise
and Vibration, http://billdocuments.crossrail.co.uk
(LINEWD-IPD10-002) Back
43
Crossrail Information Paper D10-Groundborne Noise and Vibration,
Table 1 Construction and Operation of groundborne noise criteria,
http://billdocuments.crossrail.co.uk
(LINEWD-IPD10-003) Back
44
Crossrail Ref: P23, Noise Technical Report, Hanbury Street/Princelet
Street area (SCN-20080312-023) Back
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