Examination of Witnesses (Questions 3060
- 3079)
3060. But without any scientific base?
(Mr Methold) Apart from
well used project experience.
3061. I have to put a point to you, Mr Methold,
so that you can respond. There is no evidence, is there, that
the adoption of a 35 dB LAmax criterion would produce any material
improvement to people's lives compared with the adoption of a
40 dB LAmax criterion?
(Mr Methold) There is no
published scientific evidence to suggest that but I draw your
attention to the summary data that I presented in terms of the
North Downs tunnel.
3062. And so when one is weighing up whether
or not additional cost is justified in terms of introducing additional
mitigation measures, for example, floating slab track, to meet
the 35 dB LAmax criterion that you have recorded, one needs to
bear that particular conclusion in mind?
(Mr Methold) One does, and
the magnitude of the costs would be a material consideration.
3063. Again, I am going to put to you, and Mr
Thornley-Taylor will explain this later on, that our calculations
are that to provide floating slab track throughout the central
section, which obviously is the worst case because it is the most
robust case, where the greatest amount of money would be spent,
would cost about £10.6 million.
3064. Mr Clarkson: Is that for the whole
of the central section?
3065. Mr Taylor: It is for the whole
of the central section, both parts of it.
(Mr Methold) So that is
a location where it is probably not needed as well; is that the
case?
3066. I do not know whether it is needed or
not. I am just a lawyer. I am sure Mr Thornley-Taylor will be
able to explain that. The point is simply this, is it not, that
what we have to do is weigh up the potential costs which may be
as high as £10.6 million against the potential benefit for
which there is no scientific data to support, which is if 35 was
adopted.
(Mr Methold) The cost is a consideration to
weigh up.
3067. I am just being told to give the document
numbers again. P43 is the table 4.1 and at P44 is the page 5 from
the documentation relating to the LAeq, a note that Mr Thornely-Taylor
has produced.[8]
Mr Methold, thank you very much.
Examined by The Committee
3068. Kelvin Hopkins: The CTRL, when
it goes from North Downs, there were complaints about noise when
it was way below 40 decibels. Is that on floating slab tracks
or is that on the standard embedded track or the standard concrete
track or what?
(Mr Methold) That is a ballasted
track system so it is a different kettle of fish and I understand
that the system that is in place there is based on a resilient
rail pad. That is one that we did not discuss this morning. The
resilience is placed directly underneath the rail. It is a bit
higher up as a system than the base plate system.
3069. How deep is the CTRL tunnel below ground
and is it clay or is it chalk and does it make a difference? How
would that tunnel compare with Crossrail?
(Mr Methold) It is very
different. I understand it is 80 metres cover at its deepest and
some of the residents are on a slight hill there, which means
that it is as low as 40 metres and it is predominantly chalk.
3070. Does chalk conduct noise more easily than
clay?
(Mr Methold) It will do
and also at higher frequencies.
3071. Would it be possible to use floating slab
track selectively for sections of Crossrail where it goes under
sensitive areas, such as residences, rather than for the whole
of the central section?
(Mr Methold) I believe that
is the case. That is clearly what Crossrail were putting forward
at this stage in any case. They are saying that they will apply
a standard track form throughout but in certain locations they
may need floating slab track, and it is not all just in one location.
I talked about theatreland and around Tottenham Court Road station
but there is also a section proposed for the Barbican and that
is some distance away. The project is acknowledging that it can
accommodate different sections along different parts of the route,
discrete sections.
3072. There is reference to Wigmore Hall, which
is very sensitive, is it not, where they have concerts of chamber
music? I travel every day on Thameslink and I am familiar with
wheel flats, as I mentioned in a previous session. Quite frankly,
Thameslink do not grind out their wheel flats very often. Almost
every train I go on has a wheel flat, sometimes several, and the
track, as you know, is not looked after in some areas as well
as it should be. Camden is seeking guarantees that the operator
will make certain that the track and the wheels are kept in good
order because it would make a significant difference.
(Mr Methold) In so far as
it can at this stage. One of the problems is that I do not think
the Promoter can tell us how often they need to maintain the railway
and we have to acknowledge that. We do know that the Docklands
Light Railway, for example, has quite a strict noise vibration
policy which actually requires them to regrind their rails or
have their vehicles maintained if certain noise levels, on an
annual survey basis, exceed certain trigger thresholds. That is
something that we are looking to the project to mimic almost and
give assurance on. That is why our undertaking at this stage is
merely couched in, "Please involve us in those discussions.
We understand your problem that you cannot tell us now but we
do want reassurance on this because we do not think your commitments
in D10 go far enough for us. We want to understand what `adequate
control' means".
3073. This is for my interest, to get some feel
for what different track sounds like. I travel, as I said, on
Thameslink between the new MT box station under St Pancras, which
I think is in Camden and the Kings Cross Thameslink, which I think
is probably in Islington, or is it in Camden?
3074. Mr Clarkson: In Camden.
3075. Kelvin Hopkins: You go through
the box station, which has a very smooth sound, very modern, with
continuously welded track, and you go from there into a tight
curve with a jointed track and squealing wheels which make an
enormous noise. Presumably that kind of noise would transmit to
buildings above a lot easier.
(Mr Methold) High frequency
noise, if we are talking about a wheel squeal on cornering, probably
would not. It is more of an issue for passenger comfort when you
are sitting in the train. Airborne noise generated by wheel squeal
would normally be expected to be attenuated by the time it has
got through the tunnel and through the soil and come out.
3076. And the banging of the jointed track?
(Mr Methold) Banging of
jointed track definitely is a factor for groundborne noise and
vibration.
3077. Do you know what kind of base the track
through the box station is laid on?
(Mr Methold) I am not familiar
with the Thameslink section through there.
3078. I am very familiar with the noise. Thank
you.
(Mr Methold) One of the
interesting points that counsel raised there was that 40 dB is
applied to Thameslink 2000 and we must remember that that project
is more or less an upgrade of an existing alignment and, as you
are quite rightly pointing out, is already fairly bad in terms
of groundborne noise. I think I would be fair in saying that the
local authority has probably regarded 40 dB as an improvement
on what is there already but we have also to bear in mind that
an intensification of an existing railway corridor in terms of
legal terms sides very much on the side of the operator and the
Promoter. It is guarded by the Railways Act and so any attempt
to try and change the Groundborne noise criteria for a project
which is merely an upgrade or relaying of track is nigh on impossible.
This is a new railway.
3079. Chairman: Earlier in your evidence
you talked about floating slabs and the cost and so on. As I recall
in the Environmental Statement there was a commitment to have
systems incorporated in all sensitive areas and now that seems
to have been lost a little bit. Can you elaborate a little bit
more on your costings because you said you were very cautious
about the maximum of eight per cent added to the cost? It seems
to be being implied that it is significantly higher than that?
(Mr Methold) This is the
point I probably made inappropriately earlier, but if you compare,
and you will hear from Mr Thornley-Taylor , that with this section
of floating slab track they based their costs on is over the entire
central section. If you look at the individual buildings which
have been looked at, and this is exactly what I did, I do not
think you need to apply floating slab track the whole way across
the central section. I alluded earlier in my evidence to the fact
that you can probably squeeze a few extra decibels out by using
a softer base plate system. The other point I should make is that
the modelling so far has been done for the purposes of the Environmental
Statement and has used worst case assumptions, and the Promoter
is reserving its right to go back and do more detailed modelling
at the detailed design stage. We can perfectly expect the levels
to come down as a result. Therefore, it could be the fact that
the end predicted levels will already be performing well below
35 and below what we have already seen in the Environmental Statement.
8 Crossrail Ref: P43, World Health Organisation, Guidelines
for Community Noise, p65, Table 4.1 Guideline values for community
noise in specific environments. Crossrail Ref: P44, Crossrail
groundborne noise LAmax and LAeq, 2 February 2006. Back
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