Examination of Witnesses (Questions 17820
- 17839)
17820. Ms Lieven: Sir, I was going to
call Mr Berryman first to deal with the settlement-related issues
in general terms and then Mr Thornely-Taylor to deal noise if
that is acceptable. Much of the material will be that the Committee
is quite familiar with in general terms but it would be useful,
I suspect, for Mr Jeffrey to hear it again. Mr Berryman?
Mr Keith Berryman, recalled
Further examined by Ms Lieven
17821. Ms Lieven: Mr Berryman, could
you start by explaining to Mr Jeffrey what your position is with
Crossrail, please?
(Mr Berryman) I am the Managing
Director of CLRL Limited which is the company set up by Government
and Transport for London to promote the scheme.
17822. Could you start by explaining what Crossrail
works will be undertaken in the immediate area of Ms Jeffery's
property?
(Mr Berryman) Yes. The main works, as you outlined
in opening, are the construction of the running tunnels between
the Pudding Mill Lane portal going down towards the junction at
Stepney Green, which are these lines here, the dotted lines running
east-west. The tunnels there have an internal dimension of about
six metres, external dimension about 6.7. At the point at which
they pass under Ms Jeffery's house they will be about 15 metres
off cover above the tunnels, that is to say about two and a half
tunnel diameters above the tunnels. There is another smaller tunnel
to be constructed some way away from Ms Jeffery's house which
is the sewer diversion, which you mentioned earlier. That is about
a two and a half metre diameter tunnel. All of the tunnels will
be constructed using what are known as "earth pressure balance
machines" which is a tunnel-boring machine which maintains
the pressure on the face of the tunnel all the time to reduce
settlement to the absolute minimum.
17823. So far as the settlement is concerned,
has Crossrail undertaken a settlement assessment in respect of
the Crossrail tunnels?
(Mr Berryman) Yes, we have
gone to stage two with the properties in this area. There was
some concern about the combined impact of the two tunnels crossing
each other; in fact when we did the analysis we found the effects
were actually very small. We went to Stage Two and I think the
study identified that the possible damage to this property would
be in the negligible to slight area. I feel bound to say that
in making our assessment we have used very pessimistic assumptions.
Not to go into too much detail, we assumed about one per cent
face loss which is what leads to settlement. In fact, on other
projects, Channel Tunnel in particular, they have been achieving
less than a third of that, so we are confident that the settlement
impact on this property would be absolutely minimal.
17824. It may seem a very long time ago to the
Committee, but in the distant past we had a session on settlement
with Professor Mayer where he explained the basis of our protections.
I would presume that applies here just as much in any other location.
(Mr Berryman) Indeed.
17825. Just to try to put Mr Jeffery's mind
at rest, assume that there is some damage. What steps would Crossrail
take to make good that damage?
(Mr Berryman) As set out the relevant Information
Paper, I think it is D12—
17826. It is.
(Mr Berryman)—which makes a commitment
that any damage caused by tunneling would be repaired and that
will be based on surveys before and after tunnelling is done.
It is a procedure that has been well tried on many tunnelling
projects and has worked quite well.
17827. Ms Lieven: I suppose really there
are two key points here. First of all on the basis of our assessment
how likely is it that there will be any settlement damage to this
property?
(Mr Berryman) It is very
unlikely that there will be any significant damage. There may
be hairline cracks or something of that sort, but it is extremely
unlikely that there will be anything beyond that and it is quite
unlikely that there will be hairline cracks.
17828. Chairman: Does that mean you surveyed
all the properties or are you just doing a general survey for
the area?
(Mr Berryman) Normally we
get surveyors to come around before tunnelling starts to check
the condition of the properties because obviously there are some
unscrupulous people who, after tunnelling is complete, will report
structural damage to their buildings, so we have to do a survey
before and after.
17829. Ms Lieven: Just to be absolutely
clear, the work that we have done so far to drawing up the assessment
does not involve going into individual properties, does it?
(Mr Berryman) No, indeed,
those assessments are done just by inspections from the outside
and obviously at the moment we are not particularly interested
in the present condition of the properties. It is only immediately
before we start tunnelling that becomes significant.
17830. The other key is point is if there is
any damage, am I right in understanding that Crossrail will make
it good?
(Mr Berryman) Yes, absolutely.
17831. Ms Lieven: Those are the only
points I need to ask you, Mr Berryman. I am going to ask Mr Thornely-Taylor
about the noise points.
17832. Chairman: Mr Jeffery, would you
like to ask any questions?
17833. Mr Jeffery: Yes, Chairman. Through
you, could I ask Mr Berryman whether he is saying that because
the assessment has already been done it will move on to a specific
survey of this property because it is almost over the line of
the tunnel?
(Mr Berryman) Yes, prior
to the tunneling commencing, it is intended a conditioned survey
of the property will be carried out so that we can ascertain if
there is any damage caused by tunneling activity.
17834. Chairman: Thank you very much
indeed, Mr Berryman.
The witness withdrew
17835. Ms Lieven: Could I then proceed
directly to calling Mr Rupert Thornely-Taylor.
Mr Rupert Thornely-Taylor, recalled
Further examined by Ms Lieven
17836. Ms Lieven: Mr Thornely-Taylor,
you and the Committee know each other well but it is for Mr Jeffery's
purposes if I could introduce you as somebody with extensive qualifications
in the assessment of noise and vibration and very extensive experience
particularly in the issues around noise and railways. Is that
accurate?
(Mr Thornely-Taylor) Yes,
I think it is.
17837. First of all, could we put up the noise
contour map, which might need a bit of expanding.[2]
Mr Thornely-Taylor, can you tell us what the criteria are for
a property such as Ms Jeffery's and what is the assessed noise
level?
(Mr Thornely-Taylor) The criterion
is a maximum noise level due to the passage of trains of 40 LAMax
slow, which is the maximum sound level using a sound level meter
set to a slow response and I think Mr Jeffery indicated that his
daughter would be quite content if she was sure that it would
not exceed 40. We can see from these contours, which have been
shown I think to the Committee before, and have been done from
portal to portal for the generic case of a residential building
with a single basement. It is probably true that Mr Jeffery's
house has no basement, certainly some of the other houses nearby
have no basements, in which case, this is a worse case because
it does assume a single basement. The outer contour that is up
on the screen represents 25 dBA LAMax slow, and that is slow and
they go up in one dB increments. The position of the next thick
contour up, which is 30, I think is about where No 48 is, if I
am correct in remembering which is the house. It is not specifically
identified.
17838. Yes, I have got two plans I can compare
with each other and it falls almost exactly on the blue line.
(Mr Thornely-Taylor) In that case, the prediction
is 30.
17839. The predicted level here is 30, is that
right?
(Mr Thornely-Taylor) That is right.
2 Crossrail Ref: P131, Noise Contour Map of Crossrail
tunnels at Wrexham Road (SCN-20070116-001). Back
| 
