Select Committee on Crossrail Bill Minutes of Evidence


Examination of Witnesses (Questions 7160 - 7179)

  7160. You then just go back to BS4142 and say, "We are not going to measure at particular times, therefore the background has not gone up." Is that it?
  (Mr Thornely-Taylor) It is frightfully important, because in other places you will see me supporting for all I am worth if a local authority is concerned about creeping background noise. It is a major problem in Central London, where there are blocks of flats looking inwards to a light well, and one after another people get planning permission for an air-conditioning condenser and the noise level creeps and creeps and creeps until it becomes quite a significant problem at night, and you cannot pin the cause on any one owner or any one piece of equipment and it is very, very difficult for local authorities to take enforcement action I wholly support that. But, here, we are talking about something completely different: we are talking about a facility which is not normally used, which will occasionally run, which has intense engineering problems associated with its design and with the achievement of better than acceptable noise levels, and it will not give rise to that problem of creeping background for the reason I have explained: that assessment of the next piece of plant from the developer and adjoining piece of land will be done without the fan running, so it will have absolutely no consequence at all. Just as I fully support the concern about creeping background, so I fully assure the Committee that that will not be a consequence of this policy in the cases where we need to use up all of the policy.

  7161. If we go back, please, to page 106 of 125 within the British Standard, paragraph 7, we are there concerned with contemplating the next person who comes along.[84]

  (Mr Thornely-Taylor) Yes.

  7162. As far as the next person who comes along, he has to measure the background noise level at the assessment location.
  (Mr Thornely-Taylor) Yes.

  7163. He has to do that—see 7.3—"on days and at times when the specific noise source would normally be operating".
  (Mr Thornely-Taylor) Yes.

  7164. So the background noise to be measured is going to depend upon the prospective further development which is under assessment.
  (Mr Thornely-Taylor) Yes.

  7165. If there is coincidence between that and the running of the equipment with which we are particularly concerned—the vent shafts—the background noise is bound to be higher.
  (Mr Thornely-Taylor) No. The normal state of affairs will be nothing happening in these vent shafts. The injunction in BS4142 to measure the background noise level which is typical of the background noise, means that you measure without these fans running because they are atypical.

  7166. Do the transformers run part of the time?
  (Mr Thornely-Taylor) The transformers, as I was talking about a moment ago, will be capable of easy attenuation to levels which will, I am sure, be found in accordance with local authorities' requirements and will benefit from the provision in the draft IP that the contractors will be required to use reasonable endeavours to achieve a better noise level.

  7167. Do transformers run all the time?
  (Mr Thornely-Taylor) They are live all the time. The load on them varies substantially throughout the day.

  7168. The transformers, you say, can be dealt with in a way which would accord with what the local authority is seeking here.
  (Mr Thornely-Taylor) Yes.

  7169. All other equipment can accord with what the local authority is seeking, save for the ventilation shafts. Is that it?
  (Mr Thornely-Taylor) Save for the provision of reasonable endeavours in the draft IP.

  7170. Is there anything likely to be covered by that other than the ventilation shafts?
  (Mr Thornely-Taylor) The ventilation shafts are by far the most difficult case. When we come to the matter of the depot, which I know we are not talking about in detail today, the combination of a very large number of geographically distributed noise sources at the depot make it very hard to do any better than LA90+5.

  7171. Can you go, please, to LBH44.[85] There we see a reference to the Environmental Statement for Thameslink 2000, and Thameslink 2000, in terms of an infrastructure project, is the closest in kind of recent date to that which this Committee is considering.

  (Mr Thornely-Taylor) No, the closest in kind is the Channel Tunnel Rail Link and the Jubilee Line Extension. There are major differences between Thameslink 2000 and Crossrail.

  7172. The closest in time, in any event.
  (Mr Thornely-Taylor) It is the most recent railway project to have been to public inquiry.

  7173. This was something which you were, I think, involved with.
  (Mr Thornely-Taylor) Yes.

  7174. So we see in LBH44 that the evaluative criteria that have been adopted have been "reviewed and updated so as to allow for recent changes in legislation standards and guidance on noise assessment. In particular, absolute levels of noise have been assessed. This enables the assessment to accommodate the greater emphasis that is now being given to environments already exposed to high noise levels as well as the requirements of the European Noise Directive." Pause there. That has not happened here, has it?
  (Mr Thornely-Taylor) There is nothing more we can do. I think it has probably escaped the notice of the Petitioners that the consequence in terms of changes in the LAeq level, which is how you measure environmental noise, of meeting the Crossrail policy is an increase which is only measurable using decimal fractions of a decibel. There is no need to go better because we are having no material effect on the environmental noise levels as measured in, for example, the European Noise Directive.

  7175. Pause for a moment, please, if I may. The approach there identified has not been followed in respect of Crossrail, has it?
  (Mr Thornely-Taylor) Because we are already well ahead of the European Noise Directive. We are well ahead of the continental Europe in its practice. The practice in continental Europe is to look at changes in the noise environment by comparing LAeq with LAeq. They would look at the vent fans and say the LAeq level should not go up by more than 5 at night, in the case of France, and by 3 in the case of Italy. We are way ahead of continental Europe practice in adopting what is this extremely stringent approach of comparing LAeq with L90. So once something is good you do not need to make it better.

  7176. I am sure I am gratified to hear that but just help on the question which has been asked, please, as to whether the approach which has there been identified has been followed as far as Crossrail is concerned.
  (Mr Thornely-Taylor) Crossrail is completely compatible with Thameslink 2000 in its approach. I think what is being referred to is the standard which applies to the minor plant—parts of the infrastructure, signalling equipment—as set out in the specialist technical report for Thameslink 2000. Crossrail will be achieving very similar results and there is no difference between what the outturn will be for Thameslink 2000 and for Crossrail.

  7177. I am going to take that as a negative answer and move on to LBH45.[86]

  (Mr Thornely-Taylor) For the record, it is actually a positive answer. I am saying that Thameslink 2000 has allowed for recent changes, and Crossrail is doing exactly the same for the sources that are mentioned. So it leads to a positive answer.

  7178. If we go over the page we can expect to see the same results for Thameslink 2000. LBH45. Do you have that?
  (Mr Thornely-Taylor) I do but it is incomplete. The paragraph before says: "Given the context of Thameslink 2000 where no major ventilation plant is required, noise from permanent fixed installations excluding public address noise, eg power supply infrastructure, signalling equipment and ventilation shafts (I interpolate that passage as ventilation shafts) has been assessed using the methodology of BS4142 and the following design has been agreed with the Inner London Local Planning Authorities." If the two paragraphs are read together then, as I said a moment ago, the outturn of the two projects will be very similar.

  7179. Let us have a look at this then, please. "The design and installation of new fixed items of plant shall be such that, when operating, the noise level LAeq, Tr arising solely from the new plant measured or predicted at 1 metre . . . shall be 5 dB(A) below the background noise level LAF90." You are asking for 5 dB above?
  (Mr Thornely-Taylor) No, you have misunderstood the paragraph you have just read. The noise level is not the same as the rating level. That is stated slightly ambiguously because the little "r" has been put after every LAeq T, but the Crossrail policy refers to the rating level, which is not actual noise. The rating level of fans, which have terminal characteristics, is the actual noise with five imaginary decibels added as a penalty to the noise level. So what happens in all circumstances where there is tonal character is that the noise level in the Crossrail case is actually equal to the background noise level. Bearing in mind that the background or the ambient LAeq will be, as we saw in Mr Methold's exhibit 9, 7-10 dB greater than LAeq T, that is what we are combining the new noise with. If you combine two noises that differ by 7 the increase is less than 1 dB and if you combine the two noises that differ by 10 the increase is less than half a dB.


84   Crossrail Ref: P75, British Standard 4142:1997 Method for rating industrial noise affecting mixed residential and industrial areas, Background Noise Level (HAVGLB-14704-106). Back

85   Committee Ref: A81, Thameslink 2000 Extract from Environmental Statement-Scoping and Methodology Report June 2004 (HAVGLB-14705-044). Back

86   Committee Ref: A81, Thameslink 2000 Extract from Environmental Statement-Scoping and Methodology Report June 2004 (HAVGLB-14705-045). Back


 
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