Gladiatorial games, part 17

(… continued from Gladiatorial games, part 16, posted on 22 Feb 2016).

In the light of the barrenness of the exploration, both in evidence before the HS2 Select Committee and in HS2 Ltd documentation, of the point at which noise becomes “intrusive”, the debate that took place in Committee Room 5 about the correct value for the daytime LOAEL threshold was, inevitably, reduced to the more practical approach of looking at sources that recommended values, rather than concepts (see footnote 1).

You will recall that the Promoter found himself having to defend his choice of 50dB LpAeq,16hr as the value for the daytime LOAEL (lowest observed adverse effect level) threshold on the basis that the World Health Organisation (WHO) advises that levels of daytime noise below this level “cause little or no serious annoyance in the community” (see footnote 2). The expert acoustics witness called by Chiltern District Council, Rick Methold, accused the Promoter of “misusing the World Health Organisation guidance levels” in that the WHO intended its guidance to apply to total noise from all sources, whereas the Promoter was interpreting it as applying to the noise impact from HS2 alone (see footnote 3).

It is also not an insignificant factor that the WHO guidance does not associate 50dB with LOAEL, having been published before the concept was in general use within the acoustics community.

It was Mr Methold’s stated view that the daytime LOAEL threshold for noise from HS2 sources alone should be set lower than 50dB, and he offered the alternative of 45dB LpAeq,16hr (see footnote 4). His justification for lowering the threshold was primarily to compensate for its use against HS2 noise only, rather than total noise (see footnote 5), but he was also able to point to some authoritative support for this lower value.

Perhaps the most significant citation that Mr Methold was able to present to the Committee is the Department for Transport’s own transport modelling and appraisal guidance WebTAG. He showed the Committee an extract from this guidance, which refers to 45dB LAeq,18hr as the level that “should be used as the lower threshold for both annoyance and monetary value calculations” (see footnote 6). Putting aside the very minor difference in the eighteen and sixteen hour periods over which LAeq is specified, and the failure of the WebTAG documentation to refer to LOAEL, this does appear to align with Mr Methold’s interpretation of LOAEL as “the point at which annoyance starts to occur” (see footnote 7). So it is, perhaps, not stretching credulity too far to claim this as an endorsement for setting the daytime LOAEL threshold to 45dB.

It appears that convincing support for a lower value for the daytime LOAEL threshold may also be found from the European Environment Agency (EEA) of the European Union. Mr Methold referred the Committee to a table extracted from the EEA’s 2010 publication Good practice guide on noise exposure and potential health effects (see footnote 8). The first row of this table refers to an “annoyance disturbance” effect of noise, having a “psychosocial, quality of life” dimension starting to occur at 42db Lden, which Mr Methold converted to 44dB LpAeq,16hr and added that this was a façade level. Again there is no mention of LOAEL, but it appears to be a clear indication that “observed adverse effects” can occur at below a level of 45dB level (see footnote 9).

Further support for Mr Methold’s proposition was provided, he claimed, by “a very recent report” that is intended to contribute to a review of the requirements of the EU Environmental Noise Directive. This report opines that “for annoyance the threshold is less than 40dB Lden”. Again, LOAEL is not specifically mentioned, but the inference that it should be pitched at a level somewhat lower than 50dB is clear (see footnote 10).

In the next posting I will report what the Promoter had to say in response.

(To be continued …)

Footnotes:

  1. The debate spanned both the morning (video) and the afternoon (video) sessions of the HS2 Select Committee that were held on Wednesday 4thNovember 2015 to hear the petition of the Chiltern District Council, acting as lead for the HS2 Local Authority Noise Consortium.
  2. See paragraph 14 and footnote 8 of Appendix A to High Speed Two Information Paper E20.
  3. I reported on Mr Methold’s objections regarding this point in part 6 of this blog series. In part 7 I covered the Promoter’s defence, and added my own views in part 8.
  4. See paragraph 75 of the transcript of the morning session of the HS2 Select Committee that was held on Wednesday 4thNovember 2015.
  5. See paragraph 403 of the transcript of the morning session of the HS2 Select Committee that was held on Wednesday 4thNovember 2015.
  6. See exhibit A1571(63) in CDC’s evidence pack. I have been unable to find the source for the text quoted on this slide within the WebTAG documentation.
  7. See paragraph 96 of the transcript of the morning session of the HS2 Select Committee that was held on Wednesday 4thNovember 2015.
  8. See exhibit A1571(61) in CDC’s evidence pack. The source is Table 2.1 on page 8 of the publication Good practice guide on noise exposure and potential health effects, EEA Technical report No 11/2010. Mr Methold’s commentary on this slide may be found in paragraphs 375 and 376 of the transcript of the morning session of the HS2 Select Committee that was held on Wednesday 4thNovember 2015.
  9. If LpAeq,16hr=Lden – 1.5 is used for the parameter conversion, rather than Mr Methold’s version of LpAeq16hr=Lden + 1.5 (refer to the explanation in footnote 6 to part 14 of this blog series), then the equivalent of 42dB Lden is 40.5dB LpAeq,16hr. If this is then converted from façade to free-field it becomes 38dB LpAeq,16hr. Confirmation that the levels given in the EEA publication are façade levels may be found in the first note under Table 1.1 in the document.
  10. See exhibit A1571(62) in CDC’s evidence pack. Mr Methold’s commentary on this slide may be found in paragraph 376 of the transcript of the morning session of the HS2 Select Committee that was held on Wednesday 4thNovember 2015. The source document is Evaluation of Directive 2002/49/RC relating to the assessment and management of environmental noise, Workshop working paper 3: Cost-benefit analysis, Centre for Strategy & Evaluation Services, 23rd September 2015, p 10.

Acknowledgement: I wish to thank Michael Woodhouse for his suggestions and comments, which I have found invaluable in preparing this series of blogs.

Important Note: The record of the proceedings of the HS2 Select Committee from which the quote reproduced in this blog has been taken is an uncorrected transcript of evidence, which is not yet an approved formal record. Neither witnesses nor Members have had the opportunity to correct the record in such instances, and it may therefore be subject to changes being made in the light of any such corrections being requested.

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