Silvertown Tunnel worksite
Piling work is taking place underneath the Thames Cable Car, from where this photo was taken yesterday

Levels of air quality monitoring for the Silvertown Tunnel have not been decided – even though work is already well under way on the £2billion new toll road under the Thames.

London mayor Sadiq Khan took four months to answer an assembly member’s question on how Transport for London will watch levels of pollution after the tunnel opens. At present, just one form of pollution, nitrogen dioxide, is due to be monitored.

Khan also took three months to answer a question about pollution monitoring around schools.

The Liberal Democrat candidate for mayor, Luisa Porritt, said it showed that the tunnel was Khan’s “dirty little secret”.

Piling work is already taking place on the north side of the Thames to make room for the tunnelling machine that will dig the new road from the Royal Docks to the Greenwich Peninsula, where it will join the Blackwall Tunnel approach road. A large area of trees has also been cleared in preparation for work on the tunnel’s northern entrance.

Both Khan and TfL have insisted that the tunnel, which is due to open in spring 2025, will not lead to an overall rise in pollution levels. TfL will only concede that a housing development close to the north exit – the Hoola towers – risks seeing a specific increase, and that mitigation measures are planned as part of the permission for the scheme.

Silvertown Tunnel worksite
The piling work is to create a launch chamber for the tunnelling machine which will head under the Thames to Greenwich. The Crystal – the new City Hall – is to the left of the tower

But while they plan to monitor for nitrogen dioxide – associated with burning petrol and diesel – after opening, there are no plans to monitor for PM10 and PM2.5, microscopic particles which can come from tyres and brake linings and pose a threat even from electric vehicles.

Research carried out in 2016 showed that all of Greater London failed to meet World Health Organisation guidelines on PM2.5 levels, with the areas around the Blackwall Tunnel’s approaches being among the worst hit in the capital outside central London.

While Khan and TfL have insisted the tunnel will “eliminate” persistent queueing at neighbouring Blackwall Tunnel, and that the twin crossings would be able to cope with more traffic. Opponents say that the crossings – which would be tolled – and neighbouring roads will simply become more congested.

Silvertown Tunnel worksite
Construction crews have taken over a large area of riverside. The tunnel would emerge at Tidal Basin Roundabout, to the top of the picture. The twin Hoola towers are the other side of the viaduct

In October, the Liberal Democrat London Assembly member Caroline Pidgeon, an opponent of the tunnel, challenged Khan on the issue, and was told that “my air quality team is considering options for further PM 2.5 monitoring in support of the work already under way”.

She asked for an update at November’s mayor’s question time, but one did not arrive until last Thursday – four months late, and just before City Hall wound down for elections. Khan said his team was still deciding whether not to monitor PM2.5 pollution.

“TfL does not anticipate that Silvertown [Tunnel] will have a significant impact on particulate matter, however, given the significance of this pollutant my air quality team is considering options for further PM2.5 monitoring in support of the work already underway on NO2,” he said in a written response.

Khan also took three months to answer a question on air quality monitoring around schools from Conservative assembly member Andrew Boff, another opponent of the tunnel. Of 38 air quality monitoring sites across east and southeast London, 18 are within 400 metres of schools. “TfL does not expect there to be any significant air quality impacts at any schools as a result of the scheme,” Khan said last Friday in response to the question submitted in December.

TfL’s main forum for engaging with boroughs about the project is a body called the Silvertown Tunnel Implementation Group, which includes council officers from most east and southeast London boroughs – including Greenwich, Lewisham and Bexley – as well as Highways England. It is next due to meet at the end of May, when it will hear more about the monitoring of the scheme.

However, elected councillors play no role in the group – the job is delegated to council officers, and the meetings are not held in public.

Silvertown Tunnel worksite
A Google Streetview image from September 2020 showing Tidal Basin Roundabout before the crews moved in
Silvertown Tunnel worksite
Trees have been cut down to make way for the area where the tunnel will emerge

Pidgeon told 853: “It is quite staggering that the mayor has taken four months to answer such a basic question about the monitoring of air pollution from the Silvertown Tunnel. It says everything about the wrong priorities in place and also the lack of transparency of the Silvertown Tunnel Implementation Group that we are in the incredible situation that work has already started on the Silvertown Tunnel, but the actual level of air monitoring is still being considered.

“It is self evident that any new road building project, which will inevitably generate further road traffic, should have extensive air monitoring in place on all approach roads covering both Nitrogen Dioxide and harmful particulate matter. To only monitor one type of air pollution would be indefensible.

“If the advocates of the Silvertown Tunnel hope that their record on air pollution will be overlooked they are seriously mistaken.”

The answers came just before City Hall wound down for elections on 6 May. Both Khan and his Conservative opponent Shaun Bailey support the tunnel, while Lib Dem Luisa Porritt and Green candidate Sian Berry have pledged to cancel the scheme.

Silvertown Tunnel worksite
This stump is all that remains of an area of vegetation and trees next to the busy Lower Lea Crossing dual carriageway

Porritt told 853: “The Silvertown Tunnel project is the Mayor’s dirty little secret, so it’s no wonder he’s also trying to hide the true extent of the new road’s impact on air pollution.

“No matter how Khan tries to spin it, the fact is a new road in the city will cause more air pollution and make meeting our climate change targets much harder. The only responsible thing to do is to abandon the project and invest in greener forms of transport instead.”

Last week the officials in charge of the tunnel project were told by a member of a TfL committee that they needed to “rebuild trust” with local people. Lewisham, Hackney and Southwark councils all submitted formal objections to the scheme at planning hearings in 2016, while Newham council later changed its mind to oppose it.

Greenwich & Woolwich MP Matt Pennycook – the shadow climate change minister – also opposes the scheme, as does West Ham MP Lyn Brown, whose constituency’s entire riverfront is now taken up by the tunnel worksite.

Greenwich’s Labour councillors asked for a rethink in 2019 but leader Danny Thorpe rejected a proposal to join a cross-borough campaign against the scheme.

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