Examination of Witnesses (Questions 7160
- 7179)
7160. You then just go back to BS4142 and say,
"We are not going to measure at particular times, therefore
the background has not gone up." Is that it?
(Mr Thornely-Taylor) It is frightfully important,
because in other places you will see me supporting for all I am
worth if a local authority is concerned about creeping background
noise. It is a major problem in Central London, where there are
blocks of flats looking inwards to a light well, and one after
another people get planning permission for an air-conditioning
condenser and the noise level creeps and creeps and creeps until
it becomes quite a significant problem at night, and you cannot
pin the cause on any one owner or any one piece of equipment and
it is very, very difficult for local authorities to take enforcement
action I wholly support that. But, here, we are talking about
something completely different: we are talking about a facility
which is not normally used, which will occasionally run, which
has intense engineering problems associated with its design and
with the achievement of better than acceptable noise levels, and
it will not give rise to that problem of creeping background for
the reason I have explained: that assessment of the next piece
of plant from the developer and adjoining piece of land will be
done without the fan running, so it will have absolutely no consequence
at all. Just as I fully support the concern about creeping background,
so I fully assure the Committee that that will not be a consequence
of this policy in the cases where we need to use up all of the
policy.
7161. If we go back, please, to page 106 of
125 within the British Standard, paragraph 7, we are there concerned
with contemplating the next person who comes along.[84]
(Mr Thornely-Taylor) Yes.
7162. As far as the next person who comes along,
he has to measure the background noise level at the assessment
location.
(Mr Thornely-Taylor) Yes.
7163. He has to do that—see 7.3—"on
days and at times when the specific noise source would normally
be operating".
(Mr Thornely-Taylor) Yes.
7164. So the background noise to be measured
is going to depend upon the prospective further development which
is under assessment.
(Mr Thornely-Taylor) Yes.
7165. If there is coincidence between that and
the running of the equipment with which we are particularly concerned—the
vent shafts—the background noise is bound to be higher.
(Mr Thornely-Taylor) No. The normal state of
affairs will be nothing happening in these vent shafts. The injunction
in BS4142 to measure the background noise level which is typical
of the background noise, means that you measure without these
fans running because they are atypical.
7166. Do the transformers run part of the time?
(Mr Thornely-Taylor) The transformers, as I
was talking about a moment ago, will be capable of easy attenuation
to levels which will, I am sure, be found in accordance with local
authorities' requirements and will benefit from the provision
in the draft IP that the contractors will be required to use reasonable
endeavours to achieve a better noise level.
7167. Do transformers run all the time?
(Mr Thornely-Taylor) They are live all the
time. The load on them varies substantially throughout the day.
7168. The transformers, you say, can be dealt
with in a way which would accord with what the local authority
is seeking here.
(Mr Thornely-Taylor) Yes.
7169. All other equipment can accord with what
the local authority is seeking, save for the ventilation shafts.
Is that it?
(Mr Thornely-Taylor) Save for the provision
of reasonable endeavours in the draft IP.
7170. Is there anything likely to be covered
by that other than the ventilation shafts?
(Mr Thornely-Taylor) The ventilation shafts
are by far the most difficult case. When we come to the matter
of the depot, which I know we are not talking about in detail
today, the combination of a very large number of geographically
distributed noise sources at the depot make it very hard to do
any better than LA90+5.
7171. Can you go, please, to LBH44.[85]
There we see a reference to the Environmental Statement for Thameslink
2000, and Thameslink 2000, in terms of an infrastructure project,
is the closest in kind of recent date to that which this Committee
is considering.
(Mr Thornely-Taylor) No, the closest
in kind is the Channel Tunnel Rail Link and the Jubilee Line Extension.
There are major differences between Thameslink 2000 and Crossrail.
7172. The closest in time, in any event.
(Mr Thornely-Taylor) It is the most recent
railway project to have been to public inquiry.
7173. This was something which you were, I think,
involved with.
(Mr Thornely-Taylor) Yes.
7174. So we see in LBH44 that the evaluative
criteria that have been adopted have been "reviewed and updated
so as to allow for recent changes in legislation standards and
guidance on noise assessment. In particular, absolute levels of
noise have been assessed. This enables the assessment to accommodate
the greater emphasis that is now being given to environments already
exposed to high noise levels as well as the requirements of the
European Noise Directive." Pause there. That has not happened
here, has it?
(Mr Thornely-Taylor) There is nothing more
we can do. I think it has probably escaped the notice of the Petitioners
that the consequence in terms of changes in the LAeq level, which
is how you measure environmental noise, of meeting the Crossrail
policy is an increase which is only measurable using decimal fractions
of a decibel. There is no need to go better because we are having
no material effect on the environmental noise levels as measured
in, for example, the European Noise Directive.
7175. Pause for a moment, please, if I may.
The approach there identified has not been followed in respect
of Crossrail, has it?
(Mr Thornely-Taylor) Because we are already
well ahead of the European Noise Directive. We are well ahead
of the continental Europe in its practice. The practice in continental
Europe is to look at changes in the noise environment by comparing
LAeq with LAeq. They would look at the vent fans and say the LAeq
level should not go up by more than 5 at night, in the case of
France, and by 3 in the case of Italy. We are way ahead of continental
Europe practice in adopting what is this extremely stringent approach
of comparing LAeq with L90. So once something is good you do not
need to make it better.
7176. I am sure I am gratified to hear that
but just help on the question which has been asked, please, as
to whether the approach which has there been identified has been
followed as far as Crossrail is concerned.
(Mr Thornely-Taylor) Crossrail is completely
compatible with Thameslink 2000 in its approach. I think what
is being referred to is the standard which applies to the minor
plant—parts of the infrastructure, signalling equipment—as
set out in the specialist technical report for Thameslink 2000.
Crossrail will be achieving very similar results and there is
no difference between what the outturn will be for Thameslink
2000 and for Crossrail.
7177. I am going to take that as a negative
answer and move on to LBH45.[86]
(Mr Thornely-Taylor) For the record,
it is actually a positive answer. I am saying that Thameslink
2000 has allowed for recent changes, and Crossrail is doing exactly
the same for the sources that are mentioned. So it leads to a
positive answer.
7178. If we go over the page we can expect to
see the same results for Thameslink 2000. LBH45. Do you have that?
(Mr Thornely-Taylor) I do but it is incomplete.
The paragraph before says: "Given the context of Thameslink
2000 where no major ventilation plant is required, noise from
permanent fixed installations excluding public address noise,
eg power supply infrastructure, signalling equipment and ventilation
shafts (I interpolate that passage as ventilation shafts) has
been assessed using the methodology of BS4142 and the following
design has been agreed with the Inner London Local Planning Authorities."
If the two paragraphs are read together then, as I said a moment
ago, the outturn of the two projects will be very similar.
7179. Let us have a look at this then, please.
"The design and installation of new fixed items of plant
shall be such that, when operating, the noise level LAeq, Tr arising
solely from the new plant measured or predicted at 1 metre . .
. shall be 5 dB(A) below the background noise level LAF90."
You are asking for 5 dB above?
(Mr Thornely-Taylor) No, you have misunderstood
the paragraph you have just read. The noise level is not the same
as the rating level. That is stated slightly ambiguously because
the little "r" has been put after every LAeq T, but
the Crossrail policy refers to the rating level, which is not
actual noise. The rating level of fans, which have terminal characteristics,
is the actual noise with five imaginary decibels added as a penalty
to the noise level. So what happens in all circumstances where
there is tonal character is that the noise level in the Crossrail
case is actually equal to the background noise level. Bearing
in mind that the background or the ambient LAeq will be, as we
saw in Mr Methold's exhibit 9, 7-10 dB greater than LAeq T, that
is what we are combining the new noise with. If you combine two
noises that differ by 7 the increase is less than 1 dB and if
you combine the two noises that differ by 10 the increase is less
than half a dB.
84 Crossrail Ref: P75, British Standard 4142:1997
Method for rating industrial noise affecting mixed residential
and industrial areas, Background Noise Level (HAVGLB-14704-106). Back
85
Committee Ref: A81, Thameslink 2000 Extract from Environmental
Statement-Scoping and Methodology Report June 2004 (HAVGLB-14705-044). Back
86
Committee Ref: A81, Thameslink 2000 Extract from Environmental
Statement-Scoping and Methodology Report June 2004 (HAVGLB-14705-045). Back
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