GREENWICH: What goes on in the Blackwall Tunnel during overnight closures?

IT’S 9pm on a weeknight and at the Blackwall operation centre, roads leading to the tunnel are gradually being closed off.

This process, watched over on a bank of CCTV screens, has been going on since night time closures began in February.

Once that is complete, machinery and workers can roll into the northbound tunnel, a process leaving a five hour window to make progress before they move out again and the road reopens.

Tonight I’m taking a look inside, where the sides of the structure have been scoured by trucks which ignore the 4m height restrictions. Drivers have been known to lower their suspensions and let pressure out of their tyres in a bid to make it through.

Tunnels manager Joe Figueiredo explains the need for work was underlined when a people carrier caught fire there in November.

He says: “This money is being spent on safety systems. During that fire people were actually walking towards it and we had no way of warning them.”

Part of the funds will be spent on PA systems which can cut into car radios and new lighting systems.

A large part of the refit involves installing new six-tonne fans held in four vent shafts.

That noisy work has to be done during the daytime, explaining the occasional weekend closures, as one shaft lies beneath an expensive Tower Hamlets estate while another is beneath the O2 complex.

Walking through the 1897 tunnel you are hit by just how narrow it is - a product of its time which makes it difficult to refit.

Project manager Shaun Pidcock says: “It’s a bit like refurbishing your house. It would be an awful lot cheaper to knock it all down and start again.”

During the closures, the southbound tunnel has been diverted northbound, leaving many drivers this side of the river having to take a mammoth detour.

But Mr Pidcock insists there is no choice. Overnight more traffic goes north than south, especially on busy nights at the O2, while contraflow has also been ruled out for safety reasons.

Mr Figueiredo says: “If you look at two HGVs driving in opposite directions, if there’s an incident you wouldn’t be able to open your door. If there was a fire you’d pretty much be fried.

“Police were the first to call for contraflow to be stopped. There were quite a few near misses.”

Work is now six months ahead of schedule meaning it swill be completed in time for the 2012 Olympics.

Mr Pidcock says: “A six-month closure would have been by far the best thing to do. But we’ve always tried to do the best for the public.” The next weekend closures begin on October 15

BLACKWALL TUNNEL BY NUMBERS

The northbound Blackwall Tunnel was opened in 1897 and is 1,350 metres long.

Around 100,000 vehicles travel use both tunnels every day.

The road level in the tunnel is approximately 20 metres below high watermark.

1,400m of new lighting is being added.

Fifty CCTV cameras and 80 public address system speakers are being installed.

Workers are using 800 tonnes of structural steel and 22,400 metres of new cabling.