Select Committee on Crossrail Bill Minutes of Evidence


Examination of Witnesses (Questions 17820 - 17839)

  17820. Ms Lieven: Sir, I was going to call Mr Berryman first to deal with the settlement-related issues in general terms and then Mr Thornely-Taylor to deal noise if that is acceptable. Much of the material will be that the Committee is quite familiar with in general terms but it would be useful, I suspect, for Mr Jeffrey to hear it again. Mr Berryman?

  Mr Keith Berryman, recalled

  Further examined by Ms Lieven

  17821. Ms Lieven: Mr Berryman, could you start by explaining to Mr Jeffrey what your position is with Crossrail, please?

   (Mr Berryman) I am the Managing Director of CLRL Limited which is the company set up by Government and Transport for London to promote the scheme.

  17822. Could you start by explaining what Crossrail works will be undertaken in the immediate area of Ms Jeffery's property?
  (Mr Berryman) Yes. The main works, as you outlined in opening, are the construction of the running tunnels between the Pudding Mill Lane portal going down towards the junction at Stepney Green, which are these lines here, the dotted lines running east-west. The tunnels there have an internal dimension of about six metres, external dimension about 6.7. At the point at which they pass under Ms Jeffery's house they will be about 15 metres off cover above the tunnels, that is to say about two and a half tunnel diameters above the tunnels. There is another smaller tunnel to be constructed some way away from Ms Jeffery's house which is the sewer diversion, which you mentioned earlier. That is about a two and a half metre diameter tunnel. All of the tunnels will be constructed using what are known as "earth pressure balance machines" which is a tunnel-boring machine which maintains the pressure on the face of the tunnel all the time to reduce settlement to the absolute minimum.

  17823. So far as the settlement is concerned, has Crossrail undertaken a settlement assessment in respect of the Crossrail tunnels?

   (Mr Berryman) Yes, we have gone to stage two with the properties in this area. There was some concern about the combined impact of the two tunnels crossing each other; in fact when we did the analysis we found the effects were actually very small. We went to Stage Two and I think the study identified that the possible damage to this property would be in the negligible to slight area. I feel bound to say that in making our assessment we have used very pessimistic assumptions. Not to go into too much detail, we assumed about one per cent face loss which is what leads to settlement. In fact, on other projects, Channel Tunnel in particular, they have been achieving less than a third of that, so we are confident that the settlement impact on this property would be absolutely minimal.

  17824. It may seem a very long time ago to the Committee, but in the distant past we had a session on settlement with Professor Mayer where he explained the basis of our protections. I would presume that applies here just as much in any other location.
  (Mr Berryman) Indeed.

  17825. Just to try to put Mr Jeffery's mind at rest, assume that there is some damage. What steps would Crossrail take to make good that damage?
  (Mr Berryman) As set out the relevant Information Paper, I think it is D12—

  17826. It is.
  (Mr Berryman)—which makes a commitment that any damage caused by tunneling would be repaired and that will be based on surveys before and after tunnelling is done. It is a procedure that has been well tried on many tunnelling projects and has worked quite well.

  17827. Ms Lieven: I suppose really there are two key points here. First of all on the basis of our assessment how likely is it that there will be any settlement damage to this property?

   (Mr Berryman) It is very unlikely that there will be any significant damage. There may be hairline cracks or something of that sort, but it is extremely unlikely that there will be anything beyond that and it is quite unlikely that there will be hairline cracks.

  17828. Chairman: Does that mean you surveyed all the properties or are you just doing a general survey for the area?

   (Mr Berryman) Normally we get surveyors to come around before tunnelling starts to check the condition of the properties because obviously there are some unscrupulous people who, after tunnelling is complete, will report structural damage to their buildings, so we have to do a survey before and after.

  17829. Ms Lieven: Just to be absolutely clear, the work that we have done so far to drawing up the assessment does not involve going into individual properties, does it?

   (Mr Berryman) No, indeed, those assessments are done just by inspections from the outside and obviously at the moment we are not particularly interested in the present condition of the properties. It is only immediately before we start tunnelling that becomes significant.

  17830. The other key is point is if there is any damage, am I right in understanding that Crossrail will make it good?

   (Mr Berryman) Yes, absolutely.

  17831. Ms Lieven: Those are the only points I need to ask you, Mr Berryman. I am going to ask Mr Thornely-Taylor about the noise points.

  17832. Chairman: Mr Jeffery, would you like to ask any questions?

  17833. Mr Jeffery: Yes, Chairman. Through you, could I ask Mr Berryman whether he is saying that because the assessment has already been done it will move on to a specific survey of this property because it is almost over the line of the tunnel?

   (Mr Berryman) Yes, prior to the tunneling commencing, it is intended a conditioned survey of the property will be carried out so that we can ascertain if there is any damage caused by tunneling activity.

  17834. Chairman: Thank you very much indeed, Mr Berryman.

  The witness withdrew

  17835. Ms Lieven: Could I then proceed directly to calling Mr Rupert Thornely-Taylor.

  Mr Rupert Thornely-Taylor, recalled

  Further examined by Ms Lieven

  17836. Ms Lieven: Mr Thornely-Taylor, you and the Committee know each other well but it is for Mr Jeffery's purposes if I could introduce you as somebody with extensive qualifications in the assessment of noise and vibration and very extensive experience particularly in the issues around noise and railways. Is that accurate?

    (Mr Thornely-Taylor) Yes, I think it is.

  17837. First of all, could we put up the noise contour map, which might need a bit of expanding.[2] Mr Thornely-Taylor, can you tell us what the criteria are for a property such as Ms Jeffery's and what is the assessed noise level?

  (Mr Thornely-Taylor) The criterion is a maximum noise level due to the passage of trains of 40 LAMax slow, which is the maximum sound level using a sound level meter set to a slow response and I think Mr Jeffery indicated that his daughter would be quite content if she was sure that it would not exceed 40. We can see from these contours, which have been shown I think to the Committee before, and have been done from portal to portal for the generic case of a residential building with a single basement. It is probably true that Mr Jeffery's house has no basement, certainly some of the other houses nearby have no basements, in which case, this is a worse case because it does assume a single basement. The outer contour that is up on the screen represents 25 dBA LAMax slow, and that is slow and they go up in one dB increments. The position of the next thick contour up, which is 30, I think is about where No 48 is, if I am correct in remembering which is the house. It is not specifically identified.

  17838. Yes, I have got two plans I can compare with each other and it falls almost exactly on the blue line.
  (Mr Thornely-Taylor) In that case, the prediction is 30.

  17839. The predicted level here is 30, is that right?
  (Mr Thornely-Taylor) That is right.


2   Crossrail Ref: P131, Noise Contour Map of Crossrail tunnels at Wrexham Road (SCN-20070116-001). Back


 
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