Produced for Claylands Green Area NLE Action Group, 18 May 2011

NORTHERN LINE EXTENSION AND YOUR HOME

Groundborne noise and vibration

What is groundborne noise and vibration?As trains pass along the NLE, they will create vibrations that will be transmitted through the soil to houses close to the line. When they reach your house, they will set the fabric in motion. This motion will radiate from the building surfaces in the form of low frequency sound and vibration. You will feel and hear a rumble. Effectively, your house will have been turned into a giant loudspeaker.

The effects of groundborne vibration include Feelable movement of floors Rattling of windows Shaking of items on shelves or hanging on walls Rumbling sounds. In extreme cases, it can cause damage to buildings.

Among the factors that exacerbate groundborne vibration and noise, there are two that are particularly relevant to us

The nature of the soil - clay soils transmit vibration more efficiently Building design - structures with no or minimal foundations and solid

floors are more susceptible to vibration

1. The noise levels are in decibels (dB). Without getting too technical, the scale used for measuring noise is logarithmic. This means that 31dB is 10% louder than 30dB; 40dB is twice as loud; 50dB is four times as loud.2.

40 38 36 34

41.8 41.77

41.3 40.8 40 39.3

32 30 28

37.8

The numbers shown in bold above indicate the noise impacts on Nos 28-40 of a tunnel running beneath 40, Claylands Road.

There will be similar impacts on Nos 42-52 and on homes everywhere else on either side of the two tunnels that will run through our area.

We have extrapolated the figures from data taken from the 2008Environmental Impact Assessment (EIA)2 that was carried out in for the Battersea and Nine Elms Developers, who are behind the NLE. It is the only EIA they have published.

30m approx (Not to scale)

24m

http://www.northernlineextension.com/media/5548/urs_nle_prelim_env_assessment_final.pdf

Produced for Claylands Green Area NLE Action Group, 18 May 2011

What does this mean for you?The EIA uses a threshold of 40dB, and concedes that noise will exceed even this by up to 5dB along the whole of the NLE i.e. up to 45dB.

The developers are now claiming that they will be able to reduce noise and vibration to 30dB, i.e. to more than halve it. HOWEVER, these claims are not in writing anywhere, and they have not provided any technical information or scientific data to support them.

There are other features of groundborne noise you need to bear in mind when considering any noise and vibration threshold the developers might propose.

1. Groundborne noise sounds louder than ‘normal’ noise at the same dB level.

2. Annoyance from it often occurs when it exceeds the threshold of perception by only a small margin.

3. Ground-borne noise causes greater annoyance in areas with low levels of ambient noise, such as street traffic, than in areas where traffic noise is louder.

4. Annoyance increases with frequency. 28 trains an hour will run along the NLE in each direction – one every two minutes. If you live between the tunnels, or where tunnels run side-by-side, then 56 trains an hour will be passing by close to your house – one a minute.

5. Annoyance is greater at night times. The NLE is likely to be operating from 6 in the morning until after midnight, 364 days a year.

What can you do as an individual?Houses can be shielded to some extent against airborne noise by double-glazing, curtains etc. If there is street noise outside the front of your house, you can escape it by moving to the back.

It is virtually impossible to shield buildings from groundborne noise. There is no escape from it, except by leaving home. Your whole house is affected.

Groundborne noise has got to be stopped at source.

What can we do together?

We can Fight for noise and vibration thresholds that are acceptable to

us Fight for NLE to be designed, constructed and maintained to a

specification and standard that can be guaranteed to meet it Insist that the developers’ claims about noise and vibration

and their proposals for reducing it are subjected to scrutiny and validation by independent experts acting on our behalf.

Until this happens the present ‘consultation’ is meaningless.

Produced for Claylands Green Area NLE Action Group, 18 May 2011

NORTHERN LINE EXTENSION AND YOU

The Claylands Green Area ventilation and access shaft

Operating the NLE requires the construction of three shafts spaced at roughly kilometre intervals. Their main function is to discharge heat and dust from the lines below, but some will also allow access to the tunnel for routine inspection and maintenance or in the event of an emergency. While the NLE is under construction, a number of temporary access shafts will also be needed. The developers are proposing to place a combined ventilation and access shafts in our area. The purpose of this leaflet is to give you some information on what the shaft will involve. Data are taken from the developers’ 2008 Environmental Impact Assessment (EIA) – the only one they have published1.

The shaft will be 15m (almost 50ft) wide and 30m (100ft) deep. Seven double-decker buses could be stood on top of each other inside the shaft and still not reach the top! Above the ground the shaft will finish in some form of ‘vent’ or chimney. There are no details yet of how big this will be, or how it will be constructed and finished. All we know is that it will be 6m (20ft) high – roughly the height of a two storey house.

1 http://www.northernlineextension.com/media/5548/urs_nle_prelim_env_assessment_final.pdf

30m

15m

While the shaft is under construction

The EIA does not say how exactly long it will take to complete the shaft, but the developers concede that it could be in excess of two years. Three main impacts are likely.1. Noise Government guidance is that construction noise in residential areas should not exceed 70dB at the façade of the nearest building. Even at this level you would have to shout to make yourself heard by someone standing next to you. The EIA states that noise could actually be up to 95dB at a building 10m (33 feet) away from the site. This is far above the level advised by the Government advises. 2. Site trafficWe calculate that constructing the shaft will involve excavating 6535m3 of spoil - enough to fill two Olympic-sized swimming pools. The EIA says that

Produced for Claylands Green Area NLE Action Group, 18 May 2011

this will be by road. Using 32-ton four-axle tipper lorries with 15m3 capacity, disposing of this volume of spoil will require 872 journeys along quiet residential streets and already congested main roads. Each one will give rise to noise, fumes, dust, damage to road surfaces and potential damage to buildings through vibration. Two of the temporary access shafts near Kennington will be used to remove the tunnel boring machine. On top of this, there will be all the lorries bringing equipment and materials to the sites…..

3. VibrationWe have no details on how the shaft will be constructed, but it will almost certainly involve sheet piling (driving steel sheets into the soil to prevent it collapsing while the shaft is being built). The EIA acknowledges that vibration from this can cause damage to buildings up to 20m away. Many homes will be much closer than this. Older houses are likely to be particularly susceptible. Once the shaft is finishedConstruction impacts are temporary, but even when completed, shafts will impose operational impacts on the neighbourhood. These will be permanent.

1. Visual impactThe developers’ acknowledge the sensitivity of locating a 6m high piece of industrial plant in the middle of a Conservation Area. In addition to this, there is a risk that mature trees will have to be felled or will be compromised by the building of the shaft.

2. Air pollutionThe exhaust air that is emitted from the shaft will carry dust in concentrations that are up to 30 times above current limits and more than 60 times the target set for 2012. Everyone within 30m of the shaft could be affected. In the event of an underground fire, the shaft will act as a chimney for the products of combustion – smoke, soot, gases, chemicals (e.g from burning plastics).

3. NoiseThe developers’ solution to the dust problem is simply to dilute the concentration of it by spreading it out. To do this they will install fans in the ventilation shaft to speed up the exhaust air so that the ‘plume’ of dust rises higher and so falls more widely. The EIA gives no information on their design, construction or operation of these fans. How noisy will they be? When will they operate? While trains are running (i.e. 0600-2400)? Or 24/7? Whichever it is, any noise from them will be emitted on a level with many people’s bedroom windows.

4. Access and security issuesAll of the shafts represent weak points for the security of NLE. It is likely therefore that they will need to be security hardened to prevent terrorist access. This has major implications for their appearance. In the event of an incident or accident underground access shafts will also need to be accessible not only by the emergency services but by the military. Access for the numbers and types of vehicles required is likely to be problematic along narrow residential streets with dense on-street parking. This issue is not even considered in the EIA.

SummaryAll of the information above has been taken from the 2008 EIA – the only source of ‘official’ information we have. Every time we have raised our concerns with the developers, they have told us that the 2008 EIA is ‘out of date.’

HOWEVER, they have been unwilling or unable to provide us with written details of the criteria and standards they are currently working to the techniques or technologies they intend to use in order to reduce the impacts

we have described

Produced for Claylands Green Area NLE Action Group, 18 May 2011

the precise benefits of those techniques and technologiesIn conversation we have received inconsistent and contradictory information from the developers’ spokesmen.

The verbal assurances of paid spokesmen are not acceptable. We insist on written responses backed by evidence and data that can be scrutinised by independent experts acting on our behalf.

Until this is provided, we believe that the current ‘consultation’ over the location of the shafts is invalid.