Examination of Witnesses (Questions 2940
- 2959)
2940. LBC34.
(Mr Methold) It is okay
for me to bang on about having better standards but it is very
important that we understand whether this is actually achievable
in engineering terms and also in cost terms.
2941. Before you go into that, have you seen
a cost analysis from the Promoter on the issue of a floating slab?
(Mr Methold) No, we have
not. I asked the very direct question last week in a meeting with
the Promoter and it is clear that they have not costed for meeting
40 dB, let alone 35, although we understand that some kind of
budget allocation is in place. I do not believe they have costed
it. I have set about in the best way I possibly could with the
information that I had to try and understand what the additional
costs might be for the project in trying to achieve 35 and in
doing so I have had to make some cautious worst case assumptions.
In particular I have tried to over-estimate the cost that a floating
slab track might incur, and I believe, looking through all the
information I had, that we are probably looking at a worst case
of 3.5 km of additional floating slab track, which I believe would
only introduce an eight per cent additional cost to the budget
on the track system. I have already alluded to the fact that I
do not think that in most of the locations they would need to
use floating slab track to achieve 35, so this is in my view an
absolute worst case.
2942. Can I ask you to explain to the Committee
how you got there on that conclusion of 3.6 km?
(Mr Methold) I analysed
all the individual calculations that the Promoter passed to me
last Friday, all 192 of them, and identified the address and where
those properties were and by how much they exceeded 35. If there
was an exceedance of 35 I assumed for the purpose of this exercise
that floating slab track would be applied and I have already said
that in most cases we are only talking about a two or three decibel
exceedance, so floating slab track might not be needed. A better
resilient base plate system might do the trick.
2943. Is that cheaper?
(Mr Methold) It would be
cheaper, yes.
2944. But you have worked to worst case, have
you?
(Mr Methold) I have. I have
also heeded Mr Thornley-Taylor 's advice that you can assume a
double cost for floating slab track compared to a resilient base
plate system.
2945. Kelvin Hopkins: When you say "worst
case", by "worst" do you mean absolutely awful?
(Mr Methold) I will stand
by "worst" in my opinion.
2946. Mr Clarkson: That is worst in cost
terms as well; is that what you are saying?
(Mr Methold) I believe so,
to the best of my ability, with the information that I have. I
do think this is a very cautious over-estimate but I would like
the Promoter to respond directly on this point when their witness
is called to give evidence. I will be the first to admit if I
have got any of this model wrong but I believe this to be a cautious
and prudent assessment. The other thing to remember is that the
local authority standard will not necessarily require an absolute
commitment to 35 if the project can demonstrate that there are
unreasonable financial implications, and then the best practicable
means test that we are advocating would kick in.
2947. Is the best practicable means an objective
test or is it a test that the undertakers in due course can decide
for themselves?
(Mr Methold) They can decide
for themselves. It really is an attempt to try and focus the Promoter
on looking at all available track systems and putting them through
the test to see whether they can be applied reasonably, whether
they achieve a cost effective performance essentially. They can
make that decision themselves but, remember that if we followed
the model of CTRL we would expect a project representative to
be involved who would be scrutinising any undertakings and compliance
with undertakings.
2948. If they are cavalier in deciding what
is best practicable means what sanction is there, what supervision?
(Mr Methold) Currently there
probably would not be any supervision other than themselves and
the project representative, which is another reason why we would
like the local authority to be involved in those discussions,
and again I will allude to the fact that this is regarded as a
very successful process that CTRL adopted.
2949. You have worked out 3.6 km of additional
floating slab track. Then you go on to eight per cent additional
cost. How do you arrive there?
(Mr Methold) That is really
looking at the total length of the tunnel and applying the cost
to the standard track form, the resilient base plate track form,
plus the 1,500 metres of floating slab track that the Promoter
does mention in the Environmental Statement to achieve essentially
what I regard as their base case costs. I have then looked at
the areas that I think a floating slab track might be needed in
and in a couple of the cases it is actually where the Promoter
is proposing to install floating slab track as well, so we cannot
double count those. My figure is arrived at when comparing the
total anticipated floating slab track in my study against the
Promoter's base case cost.
2950. Just so that we can get it clear for the
Committee—and I am going to lead on this simply to try and
see if we can understand it—is it a case of you identifying
the length of a tunnel—are you with me?
(Mr Methold) Yes.
2951. And identifying that which already has
floating slab track according to the Promoter's scheme and then
bringing in your provisional length of floating slab track, and
then working out the percentage?
(Mr Methold) That is correct.
2952. So you have not actually entered into
pounds, shillings and pence?
(Mr Methold) No.
2953. It is a linear approach, is it not?
(Mr Methold) It is. It is
a relative exercise.
2954. Would you go on to LBC35?
(Mr Methold) We have heard
about projects that have adopted 40 dB as their Design Aim. We
have to be very careful that when we talk about the effectiveness
of a Design Aim of 40 dB we have to bear in mind that some projects,
for their own risk management purposes, may well have designed
and operated a railway to levels below 40, so that any reported
annoyance or complaint from a railway designed to 40 has to be
very cautiously considered, and I am thinking in particular of
the Jubilee line extension, which Mr Thornley-Taylor referred
to when he said he walked down the route and he found it very
hard to find anywhere where he could hear groundborne noise. That
is not necessarily a function of a successful Design Aim. It could
have been well engineered such that the levels were well below
40. What is of much more importance for this debate is whether
we have a railway scheme designed to 40 dB that has produced an
adverse public reaction. As part of my studies for this petition
I wrote to all the local authorities along the Crossrail route
but also all of the local authorities along the route of the Channel
Tunnel Rail Link where tunnels had been built. The responses I
received drew my attention fairly rapidly to the North Downs tunnel
and Tonbridge and Malling Borough Council. There is an interesting
series of events evvolving there and I have visited the area.
I have spoken to some of the residents affected and I have had
direct formal correspondence with Tonbridge and Malling Borough
Council on the issues. What is fairly clear is that there has
been an adverse reaction to the railway groundborne noise in this
area with 90 properties reported to be affected by excessive groundborne
noise.
2955. Just by way of introduction, remind us,
would you? It was Kent County Council which was pressing this,
was it not, at the CTRL? What was it that the local authorities
were seeking first of all?
(Mr Methold) The local authorities
were seeking a design based upon 35.
2956. What were they given?
(Mr Methold) They were given
40 dB.
2957. Predicted or measured?
(Mr Methold) Predicted.
2958. So when we are looking at this, and the
Committee has this material on LBC35, what it has is the product
of the North Downs tunnel on a predicted 40 dB(A) approach. Is
that right?
(Mr Methold) That is correct.
2959. Go on.
(Mr Methold) In response
to the concerns that have been raised by the residents the borough
council have commissioned some noise and vibration surveys and
they have undertaken quite an extensive survey of nearly 500 train
pass-bys in a total of 27 residential properties above the tunnel.
The information I have been provided with by the council indicates
that the measured noise levels are below 40 dB at 81 per cent
of those properties surveyed. They also undertook vibration measurements
and these were below any threshold of adverse comment, and having
visited what is reported to be the worst affected property myself
I can confirm that I could not actually perceive any feelable
vibration.
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