Resurfacing the only major crossing of the Beauly Firth in Scotland provided several logistical challenges for Balfour Beatty.
The Kessock Bridge connects Inverness with the Black Isle, carrying the A9 dual carriageway trunk road north to the Highlands of Scotland. It is the only major crossing across the Beauly Firth and so plays a vital role in the road infrastructure of the Scottish Highlands.
The bridge is now in the process of undergoing the first major resurfacing since it was built more than 30 years ago in 1982. The project consists of a full surface removal and resurfacing, with safety barriers, lighting columns and cabling replaced as well.
Splitting work avoids tourist season
It is being carried out over two phases: phase one ran from February to June this year and saw the northbound carriageway resurfaced, with phase two covering the southbound carriageway to follow over the same period in 2014.
Martin Fraser, site agent for main contractor Balfour Beatty, explains that this was to minimise the disruption to traffic crossing the bridge.
“A lot of pre-planning and traffic modelling was done to predict flows”
Martin Fraser, Balfour Beatty
“By finishing in June, we made sure we avoided the main tourist season for the Scottish Highlands,” he says.
Balfour Beatty won the job from a “fairly small” pool of tenders, according to Mr Fraser, and was awarded the contract back in September 2012.
“We were on site in February 2013 so it was a pretty quick turnaround,” he says.
Keeping the bridge open
As a major artery connecting Inverness with the north, traffic management was very important.
“A lot of pre-planning and traffic modelling was done to predict flows, and we installed lights with variable controls on the roundabout leading into the south side of the bridge,” Mr Fraser says.
“Once on the bridge, there’s very little we can do. There was just a contraflow running on the opposite carriageway.”
Mr Fraser explains that there were occasional long delays when the resurfacing part of the project was actually taking place.
“The process looked quite unusual because we were using a relatively new product – there were lots of big American-style lorries so cars were slowing down to have a look,” he says.
This new product is Gussasphalt, developed by Swiss company Aeschlimann International. It contains a high-performance polymer-modified binder, and relies on the properties of the bitumen mixed with crushed stone and limestone fines to provide the required level of performance.
“It was used before on the Avonmouth Bridge, but various tests were still carried out before we chose the Gussasphalt,” Mr Fraser says. “It was chosen because it was particularly durable so could protect the steel deck below and it provides a good running surface.”
Communicating with road users
In addition to all of the other pre-planning, an extensive pre-project public advice and education campaign was carried out in partnership with Transport Scotland.
This warned drivers about the works and tried to reduce the number of individual car journeys while encouraging the use of public transport.
“There were lots of big American-style lorries so cars were slowing down to have a look”
Martin Fraser, Balfour Beatty
“Delay times were managed very well overall, with the only major problems arriving when strong winds and rain affected some of our timings,” Mr Fraser says.
“We did manage to complete all of the central reservation works during phase one, which will reduce the time needed for phase two.”
The final piece of the puzzle will be to check the tension of the steel cables holding up the bridge, with re-stressing to be carried out by a specialist contractor over six weeks if required.
Once complete, it is expected that another 30 years will be able to pass before any further major works are required on this crucial link road.