WORKERS are able to graft for only three hours a night on a major project to strengthen rail tunnels beneath a new £200 million development.
Because of rail timetables and safety fears, the amount of time contractors are able to spend underground working on the tunnel linking Haymarket and Waverley stations has been severely curtailed.
It means the painstaking underground work is due to last a year, instead of weeks for a similar sized above-ground project.
The work is needed to strengthen the foundations of one of the city’s most exciting new developments. One project worker said: “The project will take a long time but that’s an inevitable consequence of the challenge of working on this site.”
The subterranean reinforcement job – that sees metal bars buttressed to underground stonework – can only begin when sleeper trains are finally taken offline at around midnight and must stop sharply before dawn to ensure early-morning commuters face zero disruption.
Overhead power lines must be isolated and a safety briefing delivered by Network Rail and contractors before workers are allowed to continue their nightly job of shoring up the tunnels.
Contractors are only offered access to the tunnel between midnight and 5am each day and must be in possession of Network Rail permits.
To ensure trains can begin running again, workers face a race against time to “demobilise” and leave the tunnels safely.
Among other things, this involves stripping mobile scaffolding towers, packing away rigs and collecting loose tools and equipment before making their way to an exit point by 4.30am.
This leaves an actual hands-on working period of around three hours.
David Westwater, of Interserve, one of the developers behind the huge project, said: “We have worked closely with Network Rail through the design process over the last 12 months to agree the scope and methodology required for the works.
“We’re all agreed that it’s essential to carry out the works safely and minimise disruption to rail services. It may be a year or so before we can start work above ground but this project as a whole has been a long time in the making and we will soon be looking forward to getting the foundations in place for what is one of Edinburgh’s most exciting developments.”
Some earth above the tunnels will also have to be removed to allow the foundations for offices, homes and retail outlets to be laid in future.
Once the first phase is complete in 2016, the four-acre site – dubbed The Haymarket – will be transformed into a eye-catching complex boasting a hotel, offices and shops.
The site has lain dormant for years following a long-running planning battle and the economic downturn.
Original plans for a 17-storey hotel next to Haymarket Station were scaled down following protests but were revived after constructor Interserve came on board with land owner Tiger Developments.
The development already has full planning consent and has the potential to create 3500 jobs.
Actual work on the site will create around 250 jobs.