Examination of Witnesses (Questions 11480
- 11499)
11480. CHAIRMAN: I will take your word
for it!
11481. MS LIEVEN: Which deals with possession
of the land. You will have to take Mr Mould's word for it as he
has pointed me to it. What I am not absolutely sure about is whether
or not Departures Road would fall within paragraph 2.2 or 2.3
of the policy, but I do not think it matters because they both
reach the same end result. That was the only issue I was going
to deal with in re-examination. Unless the Committee has anything
else for Mr Berryman, I will call Mr Thornely-Taylor.
11482. CHAIRMAN: Thank you, Mr Berryman,
yet again.
The witness withdrew
MR RUPERT
THORNELY-TAYLOR,
recalled Examined by MS LIEVEN
11483. MS LIEVEN: Mr Thornely-Taylor,
you are well-known to the Committee and, indeed, to PRACT, so
I will not reintroduce you. I just want to go back, briefly, over
the issues around groundborne noise, particularly at this location.
I should say to the Committee I apologise; I misled you in opening
when I said that there were no properties that qualified for floating
track slab here. First of all, Mr Taylor, can you just recap on
the design approach to providing an acceptable level of groundborne
noise?
(Mr Thornely-Taylor)
My Lords, as I explained on Day 1, the approach is set out in
Information Paper D10, and the important feature of that is that
the nominated undertaker and his contractor will be required to
select a standard track form that will meet the groundborne noise
target for as much of the alignment as possible, so that special
track form is restricted to those cases where the standard track
form cannot meet the objective set out in Information Paper D10.
That, of course, means that the track is selected for the difficult
locations. At the other locations where the tunnel is deeper or
the trains are slower or for some reason the groundborne noise
is less, they will be even better off than the targets in the
Information Paper. Indeed, as a consequence of that, in the area
between Paddington Station and Hyde Park the contours for standard
buildings with a normal basement do not, in any location, go above
29dBA Lmax, and, in fact, fall away to lower levels than that
as you move towards the boundary of Hyde Park.
11484. If we just put up the plan of the tunnels
coming out of Paddington Station, 003, first of all, this is the
station and the tracks coming out this way across the Hyde Park
Estate, and then going in Hyde Park around here.[23]
How confident can we be that the design we are proposing will
suffice in respect of the groundborne noise environment in those
residential areas?
(Mr Thornely-Taylor) The first thing I will
just point to is the location, which is just here, where, as a
consequence of the request by the House of Commons Select Committee
on the Bill that floating slab should be provided wherever there
was less than 15 metres of cover between the tunnel and the residential
building, there is a short section there which, although its predicted
noise level is actually only 25 without floating slab, as a consequence
of that Committee's request, there will be a short section of
floating slab. To answer the question in more detail, the process
which has been agreed with the London Borough of Camden, and is
in the revised Information Paper D10, is one where the design
of the track form to be installed in the tunnel takes account
of uncertainty, makes predictions for all the buildings taking
specific account of their foundations (we have heard that there
is a building in Sussex Square with pile foundations—that
will be taken into account) and the form of track support selected,
so that including the uncertainty allowance the predicted LAmax,S,
the prime objective, is below 35, as agreed with Camden, but certainly
will not exceed 40 LAmax,S.
11485. One of the points specifically raised
by Mr Zamit was that PRACT has made a request for out-turn reports
on the Jubilee Line Extension and the Channel Tunnel, and as we
saw in the correspondence that was shown this morning we said
there were no reports because, as far as we were aware, there
have been no complaints about groundborne noise. Mr Zamit wanted
to know whether or not there were any comparable locations in
terms of either of those schemes going under residential properties
at the kind of depths that we are talking about in the Paddington
area.
(Mr Thornely-Taylor) Yes, indeed, there
are, my Lord. The Jubilee Line Extension, as it passes through
Bermondsey—into and out of Bermondsey Station—and,
also, at Canada Water, is quite comparable. I do not know whether
your Lordships remember, but when we were coming back from the
visit to the vent shaft we made a little detour actually to look
at a vent shaft at the back of Bermondsey Station. You will have
seen the residential locations there—quiet, back streets
with a relatively shallow depth to the tunnel of the Jubilee Line
Extension. After the completion of the Jubilee Line Extension
project the previous Crossrail project, which I was also involved
with, did commission some work to do some validation exercises
on the Crossrail prediction model, and I did in fact attempt to
get some groundborne noise measurements from the Bermondsey area.
It was not actually possible to measure anything useful in the
residential areas either side of that station.
11486. CHAIRMAN: What sort of depth is
the Jubilee Line there?
(Mr Thornely-Taylor) It is approximately
20 metres, from memory, my Lord.
11487. MS LIEVEN: Finally, Mr Taylor,
construction phase groundborne noise. Can you explain what arrangements
we have agreed with the local authorities in respect of that type
of noise?
(Mr Thornely-Taylor)
Yes. There are two aspects of that: one is the passage of the
tunnel-boring machine, and I think it is generally accepted that
it will be clearly audible as it passes through at quite a rapid
rate of progress, and there will be short-term disturbance which
will quickly pass. Then there is the installation of the temporary
construction railway, and that is also subject to the provisions
of IPD10, although it will not be possible to have as sophisticated
a method of track support for a temporary railway of that kind,
and it is more likely that in that case the predicted levels of
groundborne noise will come closer to the figures in the table
in IPD10 for the alternative test of whether they are greater
than the existing groundborne noise from pre-existing underground
railways.
11488. MS LIEVEN: Thank you. Those are
all my questions.
Cross-examined by MR
WALTON
11489. MR WALTON: Mr Taylor, can I just
be clear that I think you said that standard track form would
be used even if the predictions are substantially less than 35
decibels?
(Mr Thornely-Taylor)
That is correct. The important feature of the way Information
Paper D10 is structured is that we will not have the case where
the contractor, to save money, will put in some cheaper, more
rigid, less well-performing track just because in some location
he is well improving upon the requirement. The standard track
form will be put in everywhere except where special track is needed,
as a result of which, where it is much better than the targets
in IPD10 it will be much better than the targets in IPD10.
11490. It is the case, is it not—I believe
the Committee know this but I just wanted to be clear—that
there are measures in force that whoever operates the railway
will be obliged to maintain the track in such as way that the
noise transmission is kept to whatever it starts with?
(Mr Thornely-Taylor) They will, and of
course that is a most important part of the whole process because,
should the track deteriorate and should there for any reason be
want of maintenance, groundborne noise levels would go up; and
that is therefore one of the important parts of the process of
achieving the required low noise levels.
11491. In the areas where floating slab track
is specified, either because of special needs or because of the
tunnels being less than 15 metres, there is a reference I think
to the use of floating slab track or similar technology with the
same effect. I have probably got the words wrong, but there is
certainly a caveat there?
(Mr Thornely-Taylor) There is indeed.
This is in the report of the House of Commons Select Committee
in asking for floating slab track where there is less than 15
metres. However, they do provide, quite reasonably of course,
for the possibility that an alternative better technology might
be available that is not called floating slab track and that would
meet their requirements just as well.
11492. MR WALTON: Is it not the case
that in the report of the Select Committee of the House of Commons
at the end of paragraph 6 the last sentence is: "We therefore
ask the Promoter only to consider implementing floating slab track
across the route if the track became cost-effective"? In
other words, they had said that they were minded to recommend
floating slab track across the entire route. Could I just ask
you what the additional cost of that would be?
11493. MS LIEVEN: My Lords, I think I
am the person to answer that because it is a project figure. I
do not know if it would be helpful if I read out the cost, because
it is not entirely straightforward. The last estimated marginal
cost, that is the additional cost to the project if floating slab
track was to be installed throughout the tunnels—given that
a standard resilient track form would have to be installed in
any case, and taking account of the floating slab track already
assumed to be provided for the purposes of the Environmental Statement,
which is 4.7 kilometres, as well as a further 2.8 kilometres of
floating slab track required under the House of Commons Select
Committee 15-metre rule, that is what Mr Taylor has just been
referring to, and the decisions around the Soho area—is
£220 million outturn cost. I read it because it has all been
very carefully set out so we give your Lordships an accurate figure.
11494. LORD YOUNG OF NORWOOD GREEN: That
is additional?
11495. MS LIEVEN: That is additional.
11496. CHAIRMAN: Is there an additional
cost for maintenance as well?
11497. MS LIEVEN: Yes, there is, my Lord,
but we have not quantified that.
11498. MR WALTON: I do not know who to
put the question to; it will have to be to Mr Thornely-Taylor.
I have the Government's response to the Crossrail Committee, page
25, paragraph 21, which says, "Consequently the true marginal
cost of providing floating slab track in all of the Crossrail
running tunnels would be between £53m and £62m".
11499. MS LIEVEN: My Lord, again I rise
because this is an issue that is really engineering rather than
Mr Taylor's area. The costs have gone up through a combination
of increased engineering costs, so real additional costs, but
also the fact that the costs we were using in the House of Commons
were all based on the first quarter 2002 costs, and we are now
using outturn costs. The real figure has gone up as we have done
more work on the subject, but there is also an increase simply
because the cost base has changed.
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