The subject of noise impact on the properties around the planned Northern Line Extension was approached by the team at yesterday's consultation meeting.
Their presentation lacked clarity in terms of noise impact, the slide only mentioned a "quiet library" description of the expected sound level inside properties. The measurement they first declared as maximum was the average, called Laeq, instead of the measurement that matters most to our community which is the strict maximum noise level created by each train, called Lamax, ie the one that we will hear inside our homes. It is surprising that they used the average, Laeq, as the maximum, Lamax, is the standard for punctual sounds such as the tube and the one refered to most in previosu similar projects such as Crossrail. The Laeq they are committing to at present is 30dB.
Once directly asked, they confirmed that the true maximum they are committing to at present is Lamax of 40dB. This is the level of a quiet normal human voice in your bedroom (20dB is a whisper, more information on sound can be found here).
They presented these parameters as those used by Crossrail, as does their environmental report of 2008. It is only once they were corrected that they accepted that crossrail is working towards a maximum of Lamax = 35dB for residential properties that will be strictly applied in large parts of central London. Crossrail is using a combination of resilient track support system AND floating slab technology to achieve this. (More information about crossrail can be found here).
Once asked further, they explained that the design team was working on an option following the "Crossrail" parametres and attenuation measures but they would not commit to these standards. They conceded that these parameters were achievable and might be used in the worse areas.
We asked them twice to release the new information that has been developped for their team to develop the design and costing ; they replied that it will be part of the overall application that will be completed in 9 months time.
Their reluctance at releasing now up to date and precise data on the noise impact showed clearly how fundamental it is to put pressure on them to use decent sound levels for all residential properties. We should also ask further for the release of the draft noise and other environmental impact documents that already exist and which ought to form part of a true consultation exercise. This will help everyone in the area to get a clear picture of how they will be affected, in particular those who are trying to sell their home and are faced with concerned buyers.
Thanks for your work on this to date. As a Methley Street resident I much appreciate all efforts on this big topic.
ReplyDeleteOne question: I had no advance information about last night's consultation. How was this publicised? The only thing I was aware of are the ongoing "exhibitions" included in the main colour consultation leaflet distributed to houses, for example last weekend's at the Oval which I attended.
Yesterday's meeting was publicised directly only to the owners of properties under which the line might be build.
ReplyDeleteWhich is quite shifty as noise doesn't stay within site boundaries ; it travels in all directions.
ReplyDeleteWhich follows a wider pattern: - a map of Methley Street and other surrounding streets was shown to us on Sunday with some properties marked as being directly affected. But suggesting that the temporary works might actually have some bearing on people more than a few feet away was greeted by some degree of astonishment.
ReplyDeleteIt would be great if your blog could advertise any meetings that you know of. Thanks.