Tuesday, 31 May 2011
Presentation of the NLE at the Tunnels and Tunnelling Conference 2010
This presentation by David MaCann from Halcrow, the engineer for the NLE, speaks for itself but it is worth noting that there will be a train every 2 minutes at peak time (32 trains per hour). (There is an interesting part more specifically about Kennington after 20 & 32minutes).
It is also mentioned that the updated Environmental Assessment should be available now. (it will be completed a few months after the talk which was in September 2010). Considering that detailed information is available, it is difficult not to be paranoid of the virtual absence of information that has been issued on noise to date; at all recent consultation events and on their website the NLE team only mention the 2008 Environmental Report.
On the positive note, they state that they are designing the tunnels to be big enough for the tunnels to "accommodate a floating track bed" as they "anticipate noise and vibrations is likely to be an issue along the route" and considering the recent experience on other projects of London Underground and Crossrail (after 17 minutes). They don't confirm where this measure will be used, or if it will be used either. I am not yet clear if "floating track bed" is the same as "floating slab track" ; the later is the one used at Crossrail in sensitive areas.
Also worth of note is that the reason for the tunnel route avoiding the Oval grounds is that it is feared that the vibration will impact the Cricket games (not an issue with piled foundations as has been previously presented). The route has been curved more and lengthened to achieve this re-routing - and therefore made costlier. If it impacts cricket games, shouldn't we be worried that it impacts our homes?
Thursday, 26 May 2011
Consultation meeting - Wednesday 25 May 2011
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.
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.
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