House of Commons - Crossrail Bill

Select Committee on Crossrail Bill Minutes of Evidence

Examination of Witnesses (Questions 6880 - 6899)

6880. If I could ask you to pause there, does that reference there to "likelihood of complaint" derive from BS 4142?

6881. (Mr Methold) It does indeed, yes, and the Committee will be well aware, I am sure from my previous appearance on groundborne noise, of my personal opinion about the use of a threshold of complaint for design purposes.

6882. That is the problem, and then the solution, please?
(Mr Methold) The solution is: "To design according to local circumstances and more contemporary guidance, where reasonably practicable to do so, recognising that many more people can be annoyed by noise than actually complain."

6883. Then we go to LBH 5, where you have simply produced diagrammatically the noise and pressure scale with some indication by the drawings of the sorts of things happening by reference to the decibel scale on the right hand side, which is logarithmic, and then the sound pressure scale on the left hand side, which is micro pascal, where one secures very large numbers as one goes up the scale.[4]

(Mr Methold) That is correct, yes. Excuse the phrasing. I was hoping not to subject the Committee to any more thermometers of noise, but this one is really just trying to demonstrate why we use a decibel scale. The ear responds to pressure fluctuations, which is on the left hand side of that thermometer and you can see that the range between 20 and 100,000,000 micro pascals is clearly unmanageable and that is why we use the logarithmic scale of the decibel, which is shown on the right hand side—a much more manageable scale. That is all I really wanted to show with that slide.

6884. Then on LBH 6 you have a recap of certain noise basics and perhaps you can take us through this, please?[5]

(Mr Methold) Certainly. The Promoter provided us with an introduction to noise basics, I believe at the beginning of February. Some of these are very pertinent to what we are talking about today, so I feel it is important that we have a quick recap on some of the basics, and I will go through these as quickly as I can. Firstly, as you know, noise is measured on a logarithmic scale. Doubling the number of sources will increase the noise level by 3dB; so, for example, if a noise source is generating a noise level of, say, 43 at a receiver position, if you double the number of noise sources the received noise level will be 46. Trebling the number of noise sources will increase the noise level by 5dB. A tenfold increase will increase the noise level by 10dB. In the Promoter's presentation the 3dB increase is described as "just noticeable change". That is certainly true for noise levels with very similar characteristics but it is very clear that smaller magnitudes of change can be noticeable where acoustic features are introduced, and this is very much the case with the fixed installations we are talking about today, where some very tonal features, or features such as clangs, bangs, clatters, clicks, hisses, screeches, et cetera, are quite common. So we should be aware that changes less than 3dB would certainly be noticeable in these types of noise sources. The final one at the bottom is showing that a 10dB increase corresponds to a perceived doubling of loudness.

6885. LBH 7, the noise metrics.[6]

(Mr Methold) Yes, these are the only two we will be talking about today. The top one is the Leq or the equivalent continuous noise level. This is often referred to as ambient noise, the all encompassing noise from sources both near and far, and it is a measure of the average noise level. The second one is the LA90 and this is defined as the noise level which is exceeded for 90per cent of the time and it gives us a measure of the background or underlying noise level. For example, if we were standing on a street corner the background noise level would be the noise without cars passing by close to us; it strips away the event noise, if you like, and gives us the underlying noise. So at night it tends to be from distant rumbling of road traffic noise. The list at the bottom there is just a summary. These are termed as sound pressure levels, they have been A-weighted—which I hope the Committee will recall that it has been weighted to respond to the human ear. We are going to be talking about outdoor noise levels and not internal noise levels today and the Petitioner does not seek to change or challenge the actual measures or the metrics that the Promoter has put forward in its designing. If we move on to LBH 8, this is one of the Promoter's slides from his presentation in early February, and it shows a cross-section of a walk through the Lake District, which is a way which is used to describe how noise levels may change over the day.[7] I have added a couple of lines in colour to that slide, but this is really showing that from left to right in a walk of some 35 kilometres you may expect to go up and down in altitude and the altitude is shown on the left hand side. The red line is analogous to the L90 so it is, if you like, the altitude that is exceeded in 90per cent of that walk, and in this case it is around about 100 metres. The other line I have added to the top there is the maximum level, which we will not be talking about today, which represents, if you like, the peak or the highest altitude you get to on your walk.

6886. You also represent that in the LAeq do you not?
(Mr Methold) Those are actually from the Promoter's original slide but the point that was being made with that slide is that the LAeq actually weights further towards the higher noise levels—it is an unusual average, it is a logarithmic average of the energy.

6887. LBH 9, please.[8]

(Mr Methold) That is a slide showing some noise measurements undertaken by the Promoter quite recently at a site in Havering. The slide shows the L90 the LAeq, and just for the record the LAmax also. These are measurements taken over a six-day period, the red line representing the background noise levels recorded every 15 minutes over that six-day period. So it shows that we actually see some quite regular patterns occurring on a daily basis, very much akin to doing the same walk, if you like, in the Lake District every day. The red line does show that the background noise levels drop off at around about two or three o'clock in the morning, and this is fairly common for most sites, both urban and rural. It also shows the difference between the L90 and the LAeq and this situation is anything between 10 and 15 decibels. That can vary according to the location and in urban situations you might expect the LAeq to be a lot closer to the L90 than you see here. The black line, the LAmax is here probably due to train noise pass by into a particular location. If we move on to LBH 10 I would like to introduce the Committee to British Standard 4142, which really is the crux of our disagreement with the Promoter.[9] The title of this British Standard is "Method for rating industrial noise affecting mixed residential and industrial areas." The scope of this British Standard makes it quite clear that the assessment of nuisance and annoyance falls outside the scope of the British Standard; it is solely concerned with an assessment method for looking at the likelihood of complaint. The process that the British Standard introduces for assessing industrial noise is as follows: firstly, to determine the background noise level, which you notice is the L90. Secondly, to determine the specific noise and this is the noise in terms of the LAeq from the new noise source or the industrial noise source. The third item, if the new source has acoustic features, and we mean internal components, screeches, hisses, clicks and clatters, then you add a 5dB penalty to that noise level to take them into account. You then produce what is called the rating level, and that is the specific noise level plus any of these acoustic features corrections. You then subtract the background noise level from the rating level to come up with the difference and the table at the bottom is telling us that the difference is around plus 10—that is, the rating level is above the background noise level by at least 10 and complaints are likely. If the difference is around five it is described as of marginal significance. If the rating level is below the background noise level by at least 10dB then it is a positive indication that complaints are unlikely. The next slide is an attempt to represent that graphic point, those three conditions.[10] The blue line represents our background noise level that we have measured, then for each of the red lines we are presenting the different conditions of the rating level. So the first one on the left hand side represents L90-10—and I will be referring to L90 plus zeros and L90 plus fives from hereon in. The rating level of L90-10, complaint unlikely. The second one, the rating of L90+5, marginal significance; and the third one, rating level of L90+10, complaint likely. The point to make here is that there is a 20dB difference between the condition for complaint unlikely and complaint likely, which you know is essentially a fourfold increase in perceived levels.

6888. Then your slides come to reveal the evidence sub-sections, do they?
(Mr Methold) They do. Before we leave LBH 11, what we can see here is that the background noise level is very critical to defining where the red lines are placed on here, and if the background noise level has been measured incorrectly or derived incorrectly then it can mean that you can have a serious situation on your hands. For example, if it turns out that the background noise level is actually 5dB lower than we have on this chart, but you have designed it to the incorrect background noise level and all of a sudden for something that is designed for an L90+5 and you could actually find yourself in a situation of L90+10, we know that that means complaints are likely. The background noise level is a very, very important component for BS 4142 assessment. Moving on to LBH 12, my evidence today is really sub-divided into two sections.[11] It is looking at the design aim itself, the numerical target that the Promoter has put forward, that we disagree with; and secondly it is looking at these background noise levels which, as I have said previously, are a very important part of the assessment. LBH 13 presents the wording of the Promoter's design aim.[12] We have received recently a draft Information Paper which elaborates slightly on the wording in front of us now, but I think that the general theme is very much the same which is written in red at the bottom, namely that the Promoter is designing these fixed installations to a rating of no greater than L90+5, which is described as of marginal significance in terms of complaints. If we move on to LBH 14.[13] This is a very brief summary of what we believe the Promoter's approach is: that it is based solely on consideration of British Standard 4142 and therefore the likelihood of complaint; that a significant impact in the Environmental Statement has only been identified if the rating level is greater than L90+5 and we know that the design aim that the Promoter is putting forward is based upon the same criteria. LBH 15, I mentioned earlier about my personal views about the use of a complaint threshold for design purposes.[14] We discussed this at great length during the groundborne noise evidence earlier in the hearing, but I really just want to sum up my views on this with an extract from the Wilson Committee, chaired by Sir Alan Wilson, reported to government in 1963: "Although the information has enabled us to form a picture of the types of noise that caused complaint, we do not think that it always gives a reliable guide to the number of people who are annoyed nor to the degree of their annoyance. For instance, many people who are annoyed do not complain for one reason or another, although they may be disturbed as much as those who do complaint . . . returns of numbers of complaints [do not] necessarily give the correct impression of the relative importance of different noise sources as causes of noise nuisance." Many more people can be annoyed by noise than actually complain. LBH 16 presents what I believe is the appropriate way of assessing noise in fixed installations.[15] It is also the Petitioner's preferred approach. Firstly, obtaining information on local circumstances and policies from the local authorities. This is always the first step in these types of assessments; you have to understand the particular requirements of the local authorities, whether they have their own standards or policies. The second, third and fourth bullet points are introducing a combination of assessment techniques that together need to be used to understand the overall impact. It is the use of 4142 but not on its own. We also need to consider absolute noise levels—that is, how high the noise levels actually reach. Also, the magnitude of change in noise levels—"creeping" noise levels, which is something I would like to talk about next, on LBH 17.[16] This is commonly referred to as "creeping background" or "creeping ambient". I have there a quotation from the London Mayors' Ambient Noise Strategy: "A new noise source, or an increase in the noise intensity of an existing activity, might typically be considered not to make a readily perceptible contribution to noise levels in areas which are already, at least to some extent, `noisy'—where one noise would tend to be masked by another. However, an accumulation of such additional noise may, over time, lead to a deterioration." This is an important description because it is actually saying that perceptibility of a noise change is not necessarily the main issue here, it is the gradual deterioration of noise levels in already noisy areas that is the consideration. This is not a new concept; this was first introduced in the Wilson Committee Report in 1963. It then became planning policy on the part of the government in 1973 with the issue of Circular 10/73. All of a sudden in 1994 PPG 24, Planning Policy Guidance Note 24, had disappeared, so currently national policy does not include any guidance on creeping noise levels. In 1996 the review of PPG 24 revealed certain recommendations, one of which being that creeping noise levels should be considered, and the net effect that that has on absolute noise levels. Just for the record, that review was undertaken by the Promoter's specialist. LBH 18, Strategic Trends and Guidance, we have here a list of documentation which I believe shapes the way that Environmental Noise Impact Assessment should be undertaken for fixed installation in industrial noise.[17] I want to go through each of these very quickly, just pulling out some key pointers and hopefully showing a theme that emerges. Moving straight on to LBH 19.[18] The British Government Panel on Sustainability 1999 had the remit of considering a number of environmental topics but on the issue of noise it concluded that: "An area where UK noise policy is particularly weak is a failure to tackle a gradual deterioration in noise climate." LBH 20, in 1999 the World Health Organisation revised its guidelines for community noise.[19] We have already heard about these guideline levels, both during the groundborne noise evidence and also in subsequent Petitions. This document represents some of the most recent research in critical health effects from noise, and the noise levels we have presented here are described as guideline levels really avoiding the onset of critical health effect in the majority of the population. These are external noise levels. At the bottom there I am making reference to British Standard 8233, Sound Insulation and Noise Reduction for Buildings—Code of Practice 1999. This is a British Standard that is widely used for determining a suitable internal noise climate for buildings and is very consistent with the external noise levels that we have provided in front of us from the WHO. These are widely used as absolute guideline noise levels in many assessments. LBH 21, Pollution Prevention and Control Regulations.[20] These were updated in the year 2000 for the first time to include noise, and they apply to major industrial installations. The regulations require permits to be sought to operate from the Environment Agency, and they also require consultation with the local authorities to determine what noise standards should be used. The principal requirement of any permitting requires that the installation can demonstrate that it has adopted best available techniques, which is essentially a cost benefit exercise. The last three bullets there on the PPC Regulations, as you can see, are very common with the previous documentation, from both absolute noise levels and creeping noise levels in conjunction with it being a BS 4142 type assessment. LBH 22, in the year 2000 the government announced that it was consulting on a National Ambient Noise Strategy and in 2001 issued a consultation document.[21] The theme on this document was quite clearly to establish techniques to take action to improve the situation where ambient noise is bad or preserve it where it is good. LBH 23, the Institute of Environmental Management and Assessment set up a joint working party with the Institute of Acoustics and drafted some guidelines for noise impact assessment.[22] This document has been nearly 10 years in the making and is intended to provide guidance to both those undertaking impact assessments and those criticising impact assessments. Importantly in this document it indicates that consideration of noise changes should not just be limited to LAeq it is quite clear that L90 is to be taken into account and it is consistent with our understanding of background creep. It refers to the use of absolute and creeping noise levels again and there is a quotation from that document. "A proposal which would cause an increase on an existing level which is already well above the existing guideline should probably be regarded as worse than if the existing level were below the guideline. If the existing noise environment is regarded as so unsatisfactory that ideally every effort should be made to reduce it, then almost any increase regardless how small is an impact which should be considered." LBH 24, in 2002 the European Parliament agreed to what we call the Environmental Noise Directive—END—which had a stated aim: "To define a common approach across the EU with the intention of avoiding, preventing or reducing on a prioritised basis the harmful effects, including annoyance, of exposure to environmental noise."[23] LBH 25, the London Mayors' Ambient Noise Strategy, again we introduced this during the groundborne noise evidence.[24] This document has a stated aim: "To minimise the adverse impacts of noise on people living and working in, and visiting London using best available practices and technology within a sustainable development framework." Rather importantly it makes specific reference to the relationship between background noise level and industrial rating noise level by stating: "Avoiding creep could require new sources to be 10dB below background L90 though judgment needs to be exercised in relation to local circumstances. Sustainable development requires a pragmatic approach taking into account all of these in the local context." That, in my mind, indicates that consultation with local authorities on such issues is essential. Last year a Draft British Standard was introduced—I think somebody is trying to confuse us by introducing the number 9142 on this one as opposed to 4142—Assessment Methods for Environmental Noise.[25] This document is aimed again at those charged with providing recommendations to the decision-maker and also those contesting whether an assessment has been undertaken correctly. The table below is produced for the situation where a new noise source is introduced and, as you can see again, we have this three-pronged approach recommended, looking at an absolute noise level—and the example would be the WHO criteria we talked about earlier—and the context criteria, which is essentially a BS 4142 approach, comparing one noise metric with another; then the actual change in each of those from the noise increase that would occur from an LAeq to an L90. LBH 27 is another quote from the British Standard referring to creeping noise levels: "However, small increases might not be significant in terms of public perception. Increases which do not cause the benchmark or context criteria to be exceeded are less significant than those that do."[26] Again, the emphasis is on where we have high noise levels, to keep those controlled and not allow any further creep. LBH 28 is really just that list again, but the point to be made here is that all of these publications are subsequent to the CTR and the JLE Select Committee hearings, so this in my mind shapes the way that noise impact assessment should be done.[27] I think the tide has changed very much since the times that CTR were considering their particular designs which are similar to Crossrail's.

6889. LBH 29 and 30, you have Local Authority Standards and Guidance and here you record in the left hand column the relevant local authority, the planning criteria in the next column, the status in the third and whether or not it is more stringent than the Promoter's design aim.[28] Perhaps you can help us on the first one, Brentwood, as illustrative of the design criteria, to explain what that signifies and then, I suspect, we will not need to read through the list under Planning Design Criteria in each case.

(Mr Methold) Certainly. The LAr.T is the symbol that we use for the rating noise levels. Essentially, that is saying that the rating level must be below the background by at least 5 dB. We have a list here that spreads across two pages. We do not need to go through all these, but the local authorities are pretty consistent on this. They are either L90-5 or L90-10.

6890. We can see in each of those items a minus preceding the figure, so as to make your point about it being minus 5 or minus 10
(Mr Methold) That is correct. There are some slight variations, but certainly there is a very consistent theme in terms of the relationship between the LT level and the L90 rating specified.

6891. The status for Brentwood, for example, has been adopted as part of the local plan, so it is part of the Development Plan Framework, and you have recorded the position in relation to each of the other authorities.
(Mr Methold) I have, yes. Rather interestingly, each of the responses we did get back had a fair amount of detail on this particular issue, which is actually symbolic of how important this issue is to local authorities. I think it would be fair to say that the majority of nuisance cases that local authorities deal with are related to fixed noise installations of some sort, which is why they have quite specific guidance and specific experience on how to deal with these types of noise source.

6892. In each case it is more stringent than the Promoter's design aim.
(Mr Methold) Yes, quite significantly. If we could move to LBH31 now, a summary of the local authority concerns.[29] The local authorities consider they have limited powers to control nuisance once operational. Although they have powers under the Environmental Protection Act, we are more than aware that under the Railways Act 1993, in particular Section 122, a statutory authority can claim that it cannot be subjected to an abatement notice. As we have seen from the previous two tables, there is an overwhelming conflict with the local authorities' planning guidance compared to Crossrail's design aim and this is a major concern for the local authorities. There is certainly a general feeling from the local authorities that Crossrail should not be treated any differently. One of the main reasons is that it undermines their attempts to try to control creeping noise levels—and remember these are stipulations put on all other developers, big and small—so I think that the local authorities feel that there should not be any special circumstances for Crossrail in this regard. It also damages the local authorities' credibility for non-Crossrail development, in that other developers will obviously ask the question why another project is allowed to have more lenient standards than the policy of the local authorities will allow. I have put in a quote from the Pollution Prevention and Control Regulations which is guidance to the Environment Agency: "The [Environment] Agency shall justify the occasions when it does not follow any local authority noise proposals"—and remember these are from major industrial installations, power stations, et cetera—so there is clearly an emphasis on consulting with the local authorities on these matters. The local authorities consider that a design aim based around L90-5 is appropriate for Crossrail, and we have arrived at this from a balanced and reasonable judgment about what the local authorities' collective policies are but also considering precedent on other major railway infrastructure projects. You will see that some of the local authorities do advocate L90-10, but we have had to take a balanced and reasonable judgment on our recommendation to our local authorities. On LBH32 I would like to run through a couple of examples on a 4142 situation.[30] In the first example, if we have a measured background noise level of, say, 60 dB LA90 in a nearby house and we have calculated that a noise level from, say, a new ventilation system will generate 49 dB LAeq, and for whatever reason we have deemed that that particular noise source does not warrant a features correction and therefore our features correction is zero, our rating level therefore becomes 49 + 0, so it remains at 49, and the difference between the rating level and the background noise level is 49 -60, which becomes -11 dB. According to 4142, that would indicate that the likelihood of complaint is "unlikely". In the second example, we have a background noise level of 44 dB LA90 and a specific noise level of 45 dB LAeq.[31] Let us say, in this particular example, that we think it does warrant a features correction because it has a tonal component. That would add 5 to that specific noise level, to come up with a rating of 50 dB. The difference would therefore be

50-4, which would be +6, and according to 4142 the likelihood of complaint would be around "marginal significance".

6893. Those are two examples taking those particular figures as to how matters might proceed. Then you LBH 34, dealing with the effect of designing to a Promoter's design aim. Do you utilise those examples?[32]

(Mr Methold) I do. The examples are background noise levels that the Promoter is using at two vent shaft sites in London. In the second column we have the measured L90 levels for those two particular examples of 60 and 44. Columns 3 and 4 are showing what would happen if the Promoter designed up to its design aim—and we have no assurance at the moment that they will not do that. We have an increase in the LA90 of plus 3 for both situations, and an increase in the LAeq of plus 2 for the first example and plus 3 for the second example.

6894. If we have the additional numbers, plus 3 in the LA90 column, that is the plus to the background noise which that area then enjoys, or suffers, as the case may be.
(Mr Methold) That is correct. This presumes that we have a continuous noise source, which of course a ventilation fan or a transformer would be. So this is essentially the creep that would occur to the LA90 and the LAeq as a result of designing to the Promoter's design aim, and these are two real examples.

6895. What bearing does that have on future development which may come forward which may itself include a source of noise?
(Mr Methold) Of course, you have modified the background noise level, increased the background noise level, and, therefore, for anyone coming along with a new development, the goalposts have moved essentially—arguably, in their favour. That clearly would undermine the whole premise of sustainable development, that we need to keep creeping noise levels down, particularly high background noise levels, of which example 1 is a very good example. These are night-time background noise levels, by the way.

6896. Those are those illustrations. Then you come to LBH35, where you ask the question why is the Promoter proceeding on L90+5.[33]

(Mr Methold) That is correct. The Promoter is saying that their design aim is based on precedent, namely the Jubilee Line Extension and Channel Tunnel Rail Link. They are also saying that they believe it constitutes best practice. The third point is an interesting one. The Promoter is asserting that L90+5 for an entire installation (that is, a collection of noise sources) provides better protection than L90-5 applied for numerous individual plant items. Could we go back through each of those points in terms of the Petitioner's position. In terms of JLE, I have not seen any commissioning surveys that would suggest that they have designed right up to their design aim in any case I know they are available and we did ask for them, but I think there are confidentiality issues about seeing all those commissioning reports. Channel Tunnel Rail Link, section 2—which is of course where the ventilation shafts are—is not yet operational, so we do not know the outcome of that particular project. Interestingly, in the Promoter's technical reports they make no reference to Thameslink 2000 in their review of criteria and we will come on to talk about that a little bit later on.

6897. To anticipate, if I may: what approach has Thameslink 2000 followed in connection with this debate?
(Mr Methold) It has firstly taken the approach of discussing fixed noise source criteria with the local authority up front and has agreed a set of criteria up front. Their criterion is L90-5 for fixed installations.

6898. Thank you. Could you go to your next bullet point, please.
(Mr Methold) Yes. I think we can probably tell by now that I do not believe the approach that the Promoter is taking does constitute best practice. In dealing with their third bullet point, their assertion that L90+5 provides better protection, we would have to remember that the local authority policies and guidance are aimed at being applied to combined noise from each individual development. If a developer comes along, I think it highly unusual that he would be trying to seek planning permission for an individual noise source. The idea in the final bullet point is that one development operated to the Crossrail standard is equivalent to 10 developments operated to the local authority preferred standard. That is assuming a steady noise source—again which we know is the case with ventilation shafts and transformers

6899. That is because of the additive effect, is it, of noise sources coming along? The local authority preferred standard producing less of an additive effect than the development from the Crossrail standard.
(Mr Methold) That is correct, yes. Slide LBH 36 shows us graphically what could happen in situations where we have consecutive developments designed to the different criteria.[34] The red is representing Crossrail's design of L90+5 and shows that after five developments we could have an increase in our background noise level of around 15 dB. The green shows a much smaller increase associated with consecutive developments for the Petitioner's preferred design aim.

4 Committee Ref: A81, Noise and Pressure Scale (HAVGLB-14705-005). Back

5 Committee Ref: A81, Noise Basics-Re cap (HAVGLB-14705-006). Back

6 Committee Ref: A81, Noise Metrics-Fixed Installations (HAVGLB-14705-007). Back

7 Committee Ref: A81, Modified Extract from Promoter's presentation on Noise Basics (HAVGLB-14705-008). Back

8 Committee Ref: A81, Example of Diurnal Variations in Noise Levels, Promoter's Measurement-HA 15 in London Borough of Havering (HAVGLB-14705-009). Back

9 Committee Ref: A81, British Standard 4142:1997 Method for rating industrial noise affecting mixed residential and industrial areas (HAVGLB-14705-010). Back

10 Committee Ref: A81, British Standard 4142-Graphical Representation (HAVGLB-14705-011). Back

11 Committee Ref: A81, Evidence Sub-sections (HAVGLB-14705-012). Back

12 Committee Ref: A81, Promoter's Design Aim (HAVGLB-14705-013). Back

13 Committee Ref: A81, Summary of Promoter's Approach (HAVGLB-14705-014). Back

14 Committee Ref: A81, Design Aim Philosophy (HAVGLB-14705-015). Back

15 Committee Ref: A81, Contemporary approach to assessment of noise from new fixed installations (Petitioners' preferred approach) (HAVGLB-14705-016). Back