Examination of Witnesses (Questions 4200
- 4219)
4200. CHAIRMAN: That is structural?
(Professor Mair) That is structural, precisely,
my Lord, precisely. Down the left-hand side is the building sensitivity
which is the work done by Alan Baxter. The point has already been
made that they are, of course, working closely with each other,
Alan Baxter and Mott McDonald, but Alan Baxter have been, as experts
in their field, primarily responsible for the building sensitivity
scoring. What you see down the left-hand side is the total building
sensitivity score ranging from zero up to the maximum of four,
remembering that the building sensitivity is divided into two
parts, the structure sensitivity and the finishes. The colours
or the remaining numbers are simply the addition of the building
damage classification to the building sensitivity score, so you
can simply see that, for example, if the building damage classification
is zero, which is the case for all of the buildings in the Spitalfields
area, so if we run down the zero column, you will see that the
total scores are simply the same as the building sensitivity score.
In other words, if the building sensitivity total score was one,
then the total is also one because the building damage classification
is zero.
4201. CHAIRMAN: On the previous page,
Professor, 25, I now see to my joy there are II* buildings not
necessarily here but in the general approach and SAM is presumably
"Statutory Ancient Monuments"?
4202. MR MOULD: Scheduled Ancient Monuments.
4203. CHAIRMAN: And there is none of
the Grade II* or Scheduled Ancient Monuments that we are talking
about in this part of Spitalfields?
4204. MR MOULD: I think I said there
was one Grade II*.
4205. CHAIRMAN: You are going to check
up on this?
4206. MR MOULD: Yes, 19 Princelet Street
is a Grade II *.
(Professor Mair) If I can return to this table at the bottom
here there is colour-coding. You will see that if the total score
is two or less, that is shaded green and you will see the key
at the bottom of the table describes that impact because it is
the total score that is the impact. If it is green, then it is
determined to be low magnitude. If it is yellow, which scores
above two but below six, it is a moderate magnitude and the red
zones correspond to total scores in excess of six or greater.
These represent the magnitude of the impact. What I want to take
you to now is the following page as to what that means. If we
go to the bottom of page 27 there is a table there, table 4.5,
which is titled "The Evaluation Matrix".[36]
What you see on the left-hand side as the level of input, so there
you have the three levels of impact, the low magnitude impact,
the moderate magnitude impact or the high magnitude impact, corresponding
respectively to the green, yellow or red shaded zones from the
previous table we were looking at and the right-hand two columns
show the meaning of that impact depending on the kind of building
with one exception, which we have just heard of, we are dealing
here with Grade II buildings in the Spitalfields area. You can
see that if it is of low magnitude impact, in other words the
green shading with a total score of two or less, and if it is
a Grade II building it has the word "NSig" written there
which stands for "Non-Significant impact". If it is
in the yellow shading, which is the moderate magnitude impact,
then the Grade II buildings go into a slightly higher category
of either non-significant impact or significant impact. The last
page I would like to take you to is the meaning of "significant
impact", what that leads to in this process and that is on
page 29.[37]
The title of this section is "Buildings with Potentially
Significant Impacts (Sig.)", and we should always remember
that the word "potential" potentially is important here
because all of this assessment has been done assuming conservative
values of volume loss, in other words knowing that the actual
tunneling will produce significantly smaller movements than have
been assumed in this assessment process. The word "potentially"
is important, but it is acknowledging this is a conservative and
safe process. What it is saying is, if I take you to the second
sentence of this paragraph of the first paragraph: "Once
the details of the construction and the techniques and equipment
to be used have been fully determined, one or more of the following
will be carried, as appropriate", and then there are three
bullet points. The first bullet point: "a more detailed settlement
assessment, more closely modelling the likely behaviour of the
building and the ground". The second bullet point, I believe
this is particularly relevant to the questions that have been
asked: "an internal inspection of the building to reassess
the sensitivity of the finishes and other features [that have
been assumed] in order to establish if the scoring needs to be
revised up or down". The third bullet point is an "inspection
of the buildings to assess further the condition and structural
sensitivity". Those last two bullet points relate to the
two kinds of scoring that were done earlier in the assessment
process. What this all leads to is this is all part of the very
well thought-out and considered process nearer the time of the
project actually starting when much more detail is known about
the sequencing of the tunneling, of the actual tunneling techniques.
If a building had been in the yellow shading, in other words had
got into the position of being potentially of significant impact,
then this process would be followed which would entail definitely
an internal inspection to be absolutely checking out on all of
the assumptions that had been made prior to that point.
4207. CHAIRMAN: Professor Mair, there
is nothing special about this is there in relation to Crossrail
tunnels? This is the sort of process that always goes on with
subsidence engineering, is it not?
(Professor Mair) Yes, that is absolutely
correct. I think it is fair to say that is an evolving methodology.
This is pretty much the methodology that was followed for the
Jubilee Line Extension and the Channel Tunnel Rail Link. It has
been refined as we learn with experience from previous projects,
but it is pretty similar, yes.
4208. MR MOULD: Now, Professor Mair,
there is just one thing we ought to make clear to the Committee
in relation to this which, as you have pointed out, is setting
out in detail the scope and methodology for assessment in relation
to listed buildings and the potential impacts upon them of the
ground movement from the tunnelling works. It has been prepared
by Alan Baxter, as is apparent from the front sheet that the noble
Lords have in front of them, but there is this point also, that
this scope and methodology was shared with English Heritage prior
to being finalised. That is right, is it not?
(Professor
Mair) I believe that is correct, yes.
4209. My understanding is that English Heritage
expressed their approval of this approach.
(Professor Mair) That is also my understanding.
4210. That of course would include the page
that you have just been looking at which, amongst other things,
sets a stage at which internal inspections may be necessary. The
other point I would wish to draw to the attention of the Committee
while we have this in front of us, picking up on another concern
expressed by Mr Wheeler yesterday, is that, if one turns back
to page 27, Mr Wheeler, you will recall, expressed concern as
to whether the methodology that had been followed in terms of
assessing potential impacts on listed buildings has been guided
by the process set out and the considerations set out in national
planning policy guidance in relation to the historic environment,
that is to say, Planning Policy Guidance 15 or PPG15.[38]
As the Committee will see, it is quite clear that relevant guidance
in that document did indeed inform the development of this method
and of this assessment process, so I hope that gives some reassurance.
Now, Professor Mair, we have focused on explaining in some little
detail the nuts and bolts of the assessment method and the thinking
behind it in order to explain why the judgment was that the sources
of information that were available as regards the particularly
sensitive features of the buildings in Spitalfields, those 20-odd
buildings that live over the running tunnels, have been followed
in the way that they have and why that did not at this stage involve
internal inspection of those buildings. Having done that, the
Committee has the extracts of the reports in relation to those
buildings in front of them, but is there anything more you would
wish to add in evidence in relation to this point?
(Professor Mair) No, I do not think there is.
4211. MR MOULD: Then all I need to ask
you now, for my part, and you are completing your evidence today,
is just to turn to Mr Wheeler's second point which was his concern
that there were buildings, individual listed structures, within
the Spitalfields area which had not actually been identified for
assessment. Can you comment briefly on that?
4212. LORD BROOKE OF ALVERTHORPE: Before
we get to that and before we conclude on the first aspect, if
I may, you say this methodology has been used before and has now
been developed in the light of experience.
4213. MR MOULD: Yes.
4214. LORD BROOKE OF ALVERTHORPE: Has
it encountered the same opposition that we have had put to us
on this occasion?
(Professor
Mair) My recollection with the Jubilee Line Extension was that
there were a number of listed buildings that were to be tunnelled
under and there was some concern expressed by the residents. I
would hesitate to compare the reactions of the different residents,
but I think it was certainly an issue and it was dealt with and
their concerns were alleviated in very much a similar way that
I have described today, and the project was undertaken and there
was no damage of any consequence to any of those buildings.
4215. LORD BROOKE OF ALVERTHORPE: I was
just wondering whether in fact the residents who have been petitioning
us have had knowledge of this. Have they had knowledge of this,
that this has been used before and that, in the event, people
afterwards have been reasonably happy with the outcome?
4216. MR MOULD: Well, the information
that they have had provided to them both through correspondence
with Crossrail, but also, more particularly of course, the presentations
given by Professor Mair both in another place and to your Lordships
ought to have alerted them to the fact that the settlement assessment
processes that we have described to your Lordships have been applied
successfully in relation to the Jubilee Line Extension construction.
That is the best I can say in answer to that, I am afraid.
4217. LORD BROOKE OF ALVERTHORPE: And
presumably English Heritage have followed this through, have they,
because it seems to me that they can be seen as a trusted independent
observer that perhaps could have been utilised to some extent?
4218. MR MOULD: Yes, indeed.
4219. LORD BROOKE OF ALVERTHORPE: They
have not been so far.
36 Scope and Methodology, Table 4.5 Evaluation Matrix,
Alan Baxter Associates (SCN-20080312-021) Back
37
Scope and Methodology, Para 5.2.2 Table 4.5 Buildings with Potentially
Significant Impacts (Sig.), Alan Baxter Associates (SCN-20080312-021) Back
38
Scope and Methodology, p27, Alan Baxter Associates (SCN-20080312-021) Back
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