Disused tunnel at Forth Road Bridge made safe

Amey, the Forth Bridges Operating Company, has completed an unusual project to infill a disused railway tunnel underneath the approach roads north of the Forth Road Bridge.
The structure originally formed part of the Dunfermline to North Queensferry railway line, providing a link to the ferry service until the opening of the Forth Bridge in 1890 and continuing in limited use for freight until 1954.
The tunnel runs underneath the A9000 and B981 on the northern approach to the Forth Road Bridge. It is 420 metres in length, 4.3 metres wide and 5.1 metres high, with a vaulted roof and brick lining. Both ends had been sealed off and the adjacent cuttings filled in, so the only remaining means of access was via a vertical shaft at each end.
Amey engineers carried out a structural inspection in February 2016, finding that parts of the tunnel were degrading and in need of preventative maintenance to ensure continuing structural integrity. Due to the limited depth of cover above the tunnel, a failure could potentially have had an impact on the roads overhead.
Two options were considered: an ongoing programme of inspection and maintenance, or a one-off project to infill the tunnel with a low cost material. The infill option was chosen as it would eliminate the need for future inspections or maintenance and so prove more cost-effective in the long term.
After considering workforce safety, overall cost and the need to avoid disruption to the local community, it was decided to fill the tunnel with expanded polystyrene (EPS) blocks manufactured to a specific compressive strength capable of resisting the weight of rock and tunnel lining in the event of a localised failure. Unlike with concrete or aggregate material, EPS blocks can also be easily removed if the tunnel ever needs to be reopened.
The EPS blocks were pre-cut to a size and weight that allowed easy manual handling on site. This allowed work to be carried out from the access shaft at the north end of the tunnel, keeping construction traffic out of North Queensferry for the majority of the works. Another advantage of the lightweight blocks was that they could be delivered in large lorry-loads, significantly reducing the number of vehicle movements required.
Once offloaded, the blocks were passed down the access shaft and transported along the tunnel to the work face hooked onto a specially designed sliding monorail system.
The tunnel was lined with a hydrocarbon resistant membrane, before a total of 21,342 EPS blocks were installed, built up gradually in steps to allow safe working at height.
Local primary school children from Burntisland and Lauriston were invited to fill two time capsules with items of their choice. These were then buried in the tunnel amongst the blocks.
Once the body of the tunnel was infilled the access shafts were filled with concrete to seal the tunnel and prevent damage to the blocks, with work reaching a conclusion in late March 2018.
Mark Arndt, Amey’s Operating Company Representative for the Forth Bridges Unit, said: “This has been an unusual and interesting project where we’ve learned something new about the history of the area as well as gaining the satisfaction of making a disused tunnel safe.
“The team deserves particular credit for developing innovative solutions that maximised workforce safety while minimising the cost to the public purse and the impact on local communities.
“It’s a real measure of success that most local residents were not even aware this work was taking place, despite the tunnel emerging within metres of homes in North Queensferry.”

[@and11rew09]

Yup . Yet again those in charge who’ve never lifted a shovel or built anything deciding on the outcome of these kinds places . Perhaps if they had the slightest idea of the hard work that would have gone into such a place , then their decision making would be slightly different .

[@UKWMO]

Hope everyone got out before being filled with concrete!

[@ElectronicPleasure]

Was looking at NLS Maps for something else and saw the tunnel then came straight to youtube to see if there was urban explorers :) Sadly not anymore. I think a lot of the old tunnels need preserved but this was clearly not needed and could be a land collapse issue for the access road to the forth road bridge if the tunnel collapsed

[@Bob.W.]

Its well insulated. :)

[@LewisRhymes]

Nae wonder we have so many sinkholes if this is how they are filled in..

[@MrWombatty]

Instead of using fresh polystyrene, could've easily collected waste polystyrene packaging (before going straight to landfill) & mixed it with concrete to fill the tunnel (without all those hrs of work)!

[@rekless1875]

My first thoughts as well

[@xenon53827]

Wasn't it in the text? "expanded polystyrene (EPS) blocks manufactured to a specific compressive strength capable of resisting the weight of rock and tunnel lining in the event of a localised failure." Not sure old Burger King boxes would have done it…

[@timballam3675]

And we are soon to have the lost wax method!

[@TheNigel55]

Ok ok I see the need to make things safe but its your choice to go through it ,think i would you need a bit of danger to make life fun

[@TigerN7]

What a waste... could of used it as a footpath or cycleway...

[@gavinblack4927]

No they cant. Both ends buried deep underground. North end buried by the Forth Road Bridge A90 and south end was buried back to ground level and is now a housing estate.

[@Eb3nez3r]

@@gavinblack4927 So what was the point then if deep underground and inaccessible? Nice we earner i suppose...

[@gavinblack4927]

@@Eb3nez3r the point of it was rail access to North Queensferry long before the road bridge (or rail bridge) came along and buried it. The south side came out Into a deep cutting in the hillside which then gave way to the harbour at sea level

[@gavinblack4927]

@@Eb3nez3r some info here m.facebook.com/LostRailways/?__tn__=C-R

[@joachimschreiber7835]

instead of renting it out to somone as a storage or garage or workshop? What a nonsensical waste of time and money...

[@TheForthBridges]

Hi Joachim, the option of carrying out ongoing inspections and maintenance rather than infilling the tunnel was considered, however it was decided to infill as this would eliminate the need for future inspections or maintenance and so prove more cost-effective in the long term. The structural condition of the tunnel was deteriorating and the only access was via a narrow vertical shaft, so it would definitely not have been safe or practical to rent out for storage or as a garage or workshop.