Examination of Witnesses (Questions 12280
12280. LORD BROOKE OF ALVERTHORPE: How
Four metres. The reason is that the stresses in a wall like this
go as to the square of the height, so if you double the height
you increase the stresses by fourfold. During the giving of evidence
by Sir Keith Bright he suggested that a wall of 1.5 metres would
be satisfactory and I did a bit of structural engineering (I am
actually a structural engineer) and came to the conclusion that
that would, roughly speaking, overload the existing wall by a
factor of two. The point I am getting to is that just sticking
something on top of this existing wall does not work even if it
is only 1.5 metres tall; the wall is simply not strong enough
to take that additional load. Whatever height we did, we would
have to independently find such a screen or a noise barrier and
that would either mean doing something on the street side, which
would be possibleit would need to be piled and it would
need substantial steel workor something on the railway
side, which is what we have drawn on this sketch. Obviously there
has not been detailed designed but it has been looked at by our
structural engineers Messrs Scott Wilson and we are reasonably
confident that some structure of this sort would be needed. We
estimate that for a four metre high wall the total cost of building
this structure on the whole length of that wall would be about
£5 million. For a 1.5 metre wall it would be much less, but
I do not know how much less it would be. Although the barrier
itself only costs something like £600,000, the structure
which would be needed to hold it up would cost very much more
than the barrier would.
12281. LORD SNAPE: Are you saying you
do not approve of Sir Keith's £90,000 somehow or other?
12282. I saw you wince a bit!
(Mr Berryman) In civil engineering terms
£90,000 does not go very far.
12283. CHAIRMAN: It is not your wall
It is not our wall anyway, it is Network Rail's wall. I have to
say, we have not run this past Network Rail at all so we have
no idea what their reaction would be.
12284. CHAIRMAN: Is it within the limits
of deviation? I suspect it is not. You cannot do any work on this
under the Bill, can you?
12285. MS LIEVEN: Where we got when we
investigated was that some of it was and some of it was not. I
do not think the entirety of it is. To some degree we are not
relying on that technicality because we could ultimately promote
a separate order or something. It just does not work quite apart
12286. LORD JAMES OF BLACKHEATH: Ms Lieven,
if some of it is and some of it is not, could you define that
between horizontal and perpendicular, please?
12287. MS LIEVEN: Not straightaway, my
Lord, but I can try and find somebody behind me who can work it
The limits of deviation are set in plan. It is a question of where
the lines on the plan are drawn which shows where it is.
12288. LORD BROOKE OF ALVERTHORPE: Did
Ms Lieven not say that there is a possibility there could be some
acoustic work done in the flats at a later stage if in fact the
noise levels were found to be high?
I think Mr Thornely-Taylor is better qualified than I to talk
to that, my Lord, but certainly that would be an alternative approach.
Mr Thornely-Taylor will cover it in due course. The point that
we would make is that the noise levels at the time when the railway
opens are not known. There has been a recent significant change
in noise levels in this area and there are likely to be more significant
noise changes before we build the railway; after all, it is ten
years in the future.
12289. What is the maximum height at which a
barrier could be put on top of the wall without the need for all
this very substantial additional expenditure?
(Mr Berryman) The current factor of safety
is roughly 1.4. The factor of safety with a 1.5 metre wall is
about 0.5. We could start drawing a graph and establish what is
the maximum that we could put up but it will not be very much.
12290. MS LIEVEN: If you were to build
the retaining part of it, the steel columns on the pavement side
and then stick a noise barrier up aboveI know you are not
a planning witness but I will use you, if I may, to answer this
questionis that likely to raise issues with the council
about the impact on the Conservation Area?
As you will know, the wall does add significantly to the Conservation
Area; it is rather an attractive wall in fact. I think the local
authority would have concerns about the impact of such a barrier
or wall on the Conservation Area, in particular on this wall.
12291. What about the impact on trees of putting
the barrier up there?
(Mr Berryman) This is for a four meter
barrier. If you put a shorter 1.5 metre barrier up you probably
would not need to do what is shown on this cross-section to the
trees. You might get away with it without too much difficulty.
12292. Let us move to the possibility of putting
the steel retaining structure on the side shown in this drawing,
that is the railway side. Can we just put up a photograph taken
from the railway side?
Can you just explain what difficulty, if any, there would be in
supporting an acoustic barrier on top of the wall from the railway
(Mr Berryman) The difficulties would be exactly
the same. It is a mirror image whether you put it on one side
or the other. The stresses induced in the wall will be identical.
To take the load down to an adequate load bearing position you
would need to put the columns down to roughly the level of this
track bed (indicating). There would be major issues with this.
I think Network Rail would be unhappy about this. As you can see
from the photograph, the wall actually supports a number of their
communications cables and they would need to be rerouted and so
on. On the railway this tends to be a very expensive and complex
operation. So I think there would be difficulties with that. There
is also a track here which I think is the empty carriage road
which is used to bringI had better not say that, my Lords,
because I am not absolutely sure, but I think this track is in
12293. CHAIRMAN: It does look very used.
(Mr Berryman) This one is certainly used,
my Lord. That one may or may not be; I am not sure you can tell
from this photograph.
12294. MS LIEVEN: Assuming that the track
next to the wall is not used very much at all but the one closest
to the photograph is used, if one was going to put the retaining
structure on this sideon the tracksidewould that
involve possessions of the railway?
You would certainly need to take possession of the adjacent track;
you probably would not need the whole width. You certainly would
not need the whole width but you would need to take possession
of this track.
12295. LORD BROOKE OF ALVERTHORPE: Could
I just interject with another question?
12296. MS LIEVEN: I think I am not going
to be able to answer the question about whether the wall is within
the limits of deviation straight off, so those are all my questions,
12297. LORD JAMES OF BLACKHEATH: Mr Berryman,
we are concerned about the number of leaves on the line. Can you
tell us: are these the right sorts of leaves or the wrong sorts
As you may know, Network Rail have been making strenuous efforts
to chop down all the trees which give off the wrong sorts of leaves.
I really do not know, I am sorry.
12298. LORD JAMES OF BLACKHEATH: We have
not got a third rail there either, have we?
There is no third rail at all on the north side of London, my
12299. Has anybody given any thought or any
costings, or would it be feasible to simply put bricks on top?
(Mr Berryman) That would give us exactly
the same problem as putting a steel structure on the top, my Lord.
The thing which governs this kind of wall is the wind-load. Whatever
kind of structure you put up it will still attract the same wind-load.
16 Crossrail Ref: P79, View of retaining wall from
trackside (SCN-20080507-015) Back