Examination of Witnesses (Questions 3140
- 3159)
3140. Thank you. We looked yesterday at table
4.1 in this document at page 65.[7]
Can you explain to the Committee what you see as the relevance
of this table to their deliberations as to which design criteria
ought to be adopted?
(Mr Thornely-Taylor) This table
is a frequently quoted table and it is a statement of guideline
values for the onset of the effect on the chart listed, they are
called Critical Health Effects. The meaning of "critical"
is that sometimes noise has more than one effect. It may disturb
sleep, it may disturb concentration, it may disturb speech, intelligibility
and, whichever one requires, the lowest noise level is the critical
one and it is therefore entitled—in international English
that we are dealing with—the Critical Health Effect. At
these levels the guidance is that this is the point below which
there really is not the noise effect. We heard yesterday about
the eight hour LAeq of 30 for sleep disturbance, night-time inside
bedrooms and LAmax fast of 45. One could place these numbers at
point A on Camden's exhibit LBC28.
3141. We will look at this screen. We are looking
at Camden's LBC28.[8]
(Mr Thornely-Taylor) This was
Mr Methold's graphical interpretation of a passage in the supplementary
environmental statement addressing the broad philosophical approach
to the choosing of the noise standards for policy purposes. Point
A is where you emerge from a region of no material noise effect
for anyone, and then progress up through a zone where there is
a progressively increasing threat until you reach point B above
which it is wholly unacceptable for almost everyone. Planner and
decision makers usually set their goals somewhere in the zone
between A and B according to the balance of advantage to the Treasury
and the public and all the other things one is asked to take into
account. Nearly always these targets are in that middle zone,
quite a long way above A. Airport developments, and public inquiries
into them, spend time deliberating the large numbers of people
predicted to be annoyed and significant numbers highly annoyed.
The same is true of highway schemes, the same is true of surface
railway schemes. A judgment has to be made by a decision maker
or politician where to pitch point C. The guidance that we have
been looking at in table 4.1 is what is meant by point A on that
boundary.
3142. If we put the 40 dB LAmax criteria in
the context of the values in table 4.1, whereabouts does that
lie on the line in LBC28?
(Mr Thornely-Taylor) We
need to make an allowance for the switch from LAmax fast to LAmax
slow, and I mentioned on Day Seven that it was accepted in the
CTRL proceedings in Parliament that they differ by only about
1 dB for a modern railway on continuous welded rail. If we call
40 LAmax slow and about 41 LAmax fast, it is well into the zone
labelled "no material effect for anyone".
3143. Yes. The point was taken that of course
it has to have regard to the effect continuing over a period of
time. Can you explain to the Committee how you have addressed
that in the context of the LAeq level of 30 for an eight-hour
night-time period?
(Mr Thornely-Taylor) There
are two ways of doing this. One is to look behind table 4.1 at
the reasoning that produces it. If you go back to page 46, we
find that the 45 in that is meant to be never exceeded. It says
in the second paragraph from the top that indoor sound pressure
levels should not exceed approximately 45 dB LAmax, more than
10-15 times a night. They do envisage some exceedances of 45dB
LAmax. The more formal way of taking into account duration of
number of events is to use LAeq. As Mr Methold said, we are not
advocating, either of us, that as a principal metric for assessing
this problem, but it is the only thing we have got to do a formal
calculation of the effect of a number of trains. We see from the
paper, that tab F—we looked at it briefly yesterday—in
any viewing terms, 40 of a train service concerned is 22 LAeq.
Very few locations, if you heard two trains together, have to
take them into account in the LAeq calculations. It would be 24,
but that is at the most, the minimum of six less than the figure
of 30, which, once again, one can regard as point A of the boundary
of the no material noise effect for any one point. We are so well
below the figure of 30 that even if it were right—and that
is something which is not straightforward and it might be seen
that allowance should be made for low frequency noise—we
are still into that no material noise effect zone.
3144. Mr Taylor: The point was also taken
yesterday that the 30 LAeq figure applied only to continuous noise.
Train noise would not be continuous. What comment have you to
make with regard to that?
(Mr Thornely-Taylor) That
is mistaken because it is made clear in text 6 of the WHO document,
the example on page 44, the second paragraph from the top. It
notes that most of the more recent field observances on disturbance
have been conducted for aircraft noise. Other concerns are in
terms of the effect of road traffic and railway noise. If you
plod through the document and check what all the references are,
they are virtually all about transportation noise, but that is
a source which is far from continuous.
3145. It is transportation noise sources and
research into the effects there which has given rise to the identification
of the 30 LAeq eight hour pressure to protect sleep.
(Mr Thornely-Taylor) Yes.
3146. The other point that was made with regard
to the relevance of the guideline values of table 4.1 was touched
on a moment ago about the low frequency levels. What do you have
to say about that, Mr Thornely-Taylor?
(Mr Thornely-Taylor) We heard yesterday about
low frequency noise. There was a slightly loose use of language.
Mr Methold showed an exhibit which I think all of us had to scratch
our heads over to follow. Again, I do not want to take too much
time on it. It was the multi-coloured chart with a frequency spectrum
on it; it is LBC 5.[9]
All I will do is point out that this spectrum with low frequency
at the left and very high frequency at the right has been subject
to a weighting, which I have described, which makes it approximately
a response to the human ear. We can see its highest is 125 Hz.
That is lowish, but that is not what is meant by low frequency
noise. What is meant by low frequency noise is the sort of thing
you get from very large combustion appliances, the flues of very
large boilers and the intake of a slow-speed reciprocating air
compressor. Its frequency is reckoned in the very few bands at
the left of LBC5. That is not what we get from underground railways.
If we do succeed in finding somewhere for the Committee to hear
underground railway noise during the trip on the 14th, you will
hear a low distant rumble, but it does not have the low frequency
content that is meant by the references to low frequency noise
in the report from the WHO that we have been looking at. They,
in fact, do not find that scale particularly inadequate, even
for low frequency noise. There was a passage which was mentioned
on page 28, in the top paragraph, around halfway down which says:
"A-weighted measures have been particularly criticised as
not being accurate indicators of the disturbing effects of noises
with strong low frequency components. However, these differences
in prediction accuracy are usually smaller than the variability
of responses among groups of people. Thus, in practical situations,
the limitations of A-weighted measures may not be so important".
Although they do in another passage point out that low-frequency
requires further consideration, I do not think it is a particularly
big issue by this group of authors.
3147. You have already explained that the guideline
values in this document of table 4.1 derive from research into
transportations. We have seen the frequency profile of a train
pass-by at 46 dB(A) in the LBC5. What other noise sources provide
similar frequency response ranges to those that we can see in
LBC 5?
(Mr Thornely-Taylor) Very
similar indeed to the sound of a lorry passing in the road as
heard through closed windows.
3148. While we are still on issues about frequency
and low frequency, you recall yesterday Mr Methold criticised
the measurements that had been undertaken in relation to the Social
Survey because the measuring equipment had been placed in the
corner of the room. He made the point that essentially if the
measurement is taken in the centre of room, it may be different.
What comment have you got to make about that point, Mr Thornely-Taylor?
(Mr Thornely-Taylor) The
general point is when we consider noise from a Crossrail train
is because of its resilience and support, will have most of its
noise energy around the 50 Hz point. With Crossrail trains there
would be a bit more frequency than the present day underground
train because of their track support. That is where most of the
sound will come through from a Crossrail train. It is above the
region I was talking about that could probably be described as
low frequency in the context of the references I pointed to. Nevertheless,
the essential thing is that most residential rooms are less than
a wavelength in dimension, which means you cannot have a normal
standing wave-path in the room, which is what gives rise to a
high noise level in the corner or placed by the wall and less
noise level in the middle. In fact, the whole room is just squashed
and expanded bodily to produce noise at that sort of frequency.
It does not make nearly as much difference, as we were invited
to believe yesterday, when you measure the noise.
3149. Another point that was raised yesterday
related to the extent to which you had taken into account the
combined effect of noise from trains passing in the two tunnels
at the same time. Can you explain to the Committee what your position
is on that matter?
(Mr Thornely-Taylor) I have
looked at what happens if we were to consider two trains heard
passing at the very same time with maximum noise level occurring
at precisely the same moment. It will happen occasionally in most
places because of the separation between the tunnels, where that
would raise the received noise level by the 3dB, which I have
explained we get from doubling the noise source. You are some
distance from both tunnels, so the actual noise level is well
below the 40 or even the 35. I did find in very restricted locations
some cases where the highest noise level would be increased slightly.
The largest increase I could find was 2 dB and I recall that was
towards the western portal, up past Paddington station, which
is not a residential location in those parts of the contours.
3150. Mr Methold also suggested yesterday that
the Environmental Impact Assessment carried out for the Crossrail
scheme in its environmental state adopted a different threshold
of significance in terms of groundborne noise, that it had being
adopted in relation to the CTRL scheme. What comments do you have
on that point, Mr Thornely-Taylor?
(Mr Thornely-Taylor) I cannot see that there
is any difference. I have looked carefully at the Camden exhibits
that were produced. For the Channel Tunnel Rail Link it was exhibit
LBC 15 and Crossrail is LBC 14. Crossrail has low impact between
35 and 39 and medium/high and very high impact between 40 and
44. The two bands up identify that there is significant impact
which becomes a significant effect in the context of the law relating
to the preparation of environmental statements. The next page,
LBC 15 is the same save for the fact that it does not have quite
a considerable and significant impact.[10]
If you look in the CTRL Environmental Statement they explain that
between 35 to 39, not unless it is audible, is not high enough
to be significant and significant impact occurs at 40. It may
be that the difference Mr Methold was referring to was an accounting
of properties within the 35 band of CTRL and there is not in Crossrail.
That is largely to be clear, given the current climate in which
we work, about legal requirements for an Environmental Statement
what one has to report is significant effects. It would be obfuscatory
to report a lot of the effects that were not significant. On the
other hand, compared with CTRL, we do, in fact, show this in contours,
not in the Environmental Statement, but in the Specialist Technical
Report, under 25. I really cannot discern any material that is
between the two approaches.
3151. Mr Methold also criticised the Environmental
Statement for not identifying the properties that suffered significant
effects as a result of groundborne noise. Can you explain your
position on that please, Mr Thornely-Taylor?
(Mr Thornely-Taylor) It does identify a number
of significant effects, it is zero. It explains that all the groundborne
noise effects are mitigatable by measures which are certain to
have enough effect to eliminate them, and the answer is none.
CTRL had many properties in property count, but Crossrail does
not.
3152. Thank you very much indeed, Mr Thornely-Taylor.
Further examined by Mr
Clarkson.
3153. Mr Clarkson: May I deal with a
preliminary point, Sir, just to explain where we are on this calculation.
The Committee had it at 10 and we had it at a quarter to ten.
May I ask some questions of elucidation so that Mr Methold can
hear them and then, in due course, briefly or when appropriate,
I shall recall him to deal with this so that you are informed.
I can then go on to the points I want to put in cross-examination.
Mr Thornely-Taylor, firstly, we had evidence yesterday from you
that the figure was some £10.6 million, correct?
(Mr Thornely-Taylor) Yes, I referred
to that again this morning.
3154. Do you recall I asked specifically that
we have the detail of the 11.36 kilometres that were subject to
that 10. 6 million expenditure?
(Mr Thornely-Taylor) It was not asked of me
because I was not cross-examined yesterday.
3155. It was asked earlier by me and we were
told that we would be given it. Do you recall?
(Mr Thornely-Taylor) I have to say, I do not.
3156. I will show you it in a minute, if you
like, Mr Thornely-Taylor. I ask the simple question, where is
it?
(Mr Thornely-Taylor) I have explained in my
evidence this morning where the £10.6 million, which is £17
million when others matters are taken into account, came from.
It is the costing which has been allowed for, in the global costing
of the whole Crossrail scheme, making an engineering judgment
about what should be allowed for when we take into account the
things we do know at the present and will come to light during
the detail in the process.
3157. Mr Thornely-Taylor, where is the calculation
that enables you to say that? I presume you have the calculation
that says, in fact, it is going to be £7 million. Where is
the other calculation?
(Mr Thornely-Taylor) The calculation was based,
as I have said, on an engineering judgment and what I believe
the costing people do—the one quantity surveying and cost
accounting was not mine—was to look at what we know, make
a judgment about what we do not know and make the assumption that
excluding the Thames Tunnel and the section east of that, about
70 per cent would be resilient trackform, 30 per within the floating
slab and the corresponding rules applied to the remainder. It
is not a precise calculation by any case this morning.
3158. Is it finger in the wind or is it science?
If it is science it is documented, surely.
(Mr Thornely-Taylor) As I have explained it,
I understand by the costing people it was an engineering judgment.
3159. The only material the Committee is to
have is the document A 39 this morning that says the cost of the
FST is £7 million, correct?
(Mr Thornely-Taylor) That is what is said in
this document, yes.
7 Crossrail Ref: P43, World Health Organisation, Guidelines
for Community Noise, p65, Table 4.1 Guideline values for community
noise in specific environments (CAMDLB-31904-014). Back
8
Committee Ref: A37, Petition on Groundborne Noise, London Borough
of Camden, Interpretation of Promoter's Design Aim Philosophy
(CAMDLB-31905-029). Back
9
Committee Ref: A37, Petition on Groundborne Noise, London Borough
of Camden, Groundborne noise spectra train pass by at 46 dB Amax,
S (CAMDLB-31905-006). Back
10
Committee Ref: A37, Petition on Groundborne Noise, London Borough
of Camden, Channel Tunnel Rail Link-Groundborne Noise (CAMDLB-31905-016). Back
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