The Kerse Lift Bridge is being constructed just 5 m from an existing bridge that crosses the River Carron. Helix Photography
A compact site in the United Kingdom in the Scottish town of Falkirk presents myriad challenges in constructing a lift bridge across a new extension of the Forth & Clyde Canal.
June 11, 2013—Erecting a lift bridge across a new extension of Britain’s Forth & Clyde Canal in Falkirk, Scotland, requires a great deal of coordination. Engineers and builders must take care not to disturb an adjacent bridge or interfere with the intricate network of utility lines and chemical pipelines that pass through the site.
The Kerse Lift Bridge is being built as part of a 1 km extension of the Forth & Clyde Canal that will carry the channel through a new sea lock on the river Carron to the Firth of Forth, an estuary of the river Forth. The project will create a significant eastern gateway into Scotland's inland waterways by alleviating existing access challenges; the goal is to increase boat traffic along the canal and into the country’s wider inland waterway network. The extension is part of an even larger project known as the Helix, which will transform 350 ha of land between the towns of Falkirk and Grangemouth into a sprawling parkland filled with attractions, including two massive equine sculptures known as The Kelpies. (See “Massive Equine Statues Require Engineering Finesse,” on Civil Engineering online.)
At approximately 15 m long and 7 m wide, the single-leaf lift bridge won’t be a particularly large structure, but it will be one of several pieces of infrastructure that will play a significant role in the canal extension. Others include a new canal hub with improved marina facilities, the sea lock, and a 55 m long tunnel beneath a major highway. The bridge will make it possible for even large vessels with masts to sail beyond Kerse Road, a busy thoroughfare that will pass over the midpoint of the canal extension. “The lift bridge, specifically as part of the canal, will increase the opportunity for masted craft to pass through . . . because it has unlimited headroom coupled with demast facilities,” says Mike King, the program director for the Helix.
Other types of structures were considered for the site, including drop locks and a bascule bridge, but the lift bridge was selected for its efficiency and compatibility with the restricted site, King says. Approximately 5 m north of the site is an existing bridge that carries Kerse Road over the river Carron, near the new canal extension. This existing bridge must be preserved throughout the construction of the new bridge. To that end, engineers conducted vibration monitoring to ensure that installation of the new bridge’s pile foundations would not disturb the existing structure. Each of the bridge’s reinforced-concrete abutments is founded on 36 piles that are 350 mm in diameter and reach depths of approximately 40 m. “We’ve obviously done significant amounts of design on the piles themselves and the methodology of installation,” King says. “And we were completely confident that the vibration levels and impact of the activity would not adversely impact either on the historical bridge that’s there or indeed the local residential area.”
The single-leaf lift bridge will allow vessels to pass through a new
1 km long extension of the Forth & Clyde Canal. Mayflower
Scottish Canals, a public corporation of the Scottish government that is responsible for managing the Scotland’s inland waterways, will own and operate the canal extension, including the lift bridge. Powered by hydraulic rams, the bridge will rise at specified times during the day, so those wishing to pass through will need to be ready. “We have planned when the bridge can operate around the peak travel times” for Kerse Road, King says. “That will be under the full control of the Scottish Canals operators [who] will be working on the bridge.” A full cycle of the bridge from the moment it starts to rise to the moment it closes will take five minutes. Multiple vessels are expected to be able to pass through during that time.
Constructing the bridge and, in fact, the entire canal extension has required diverting and relocating utility lines and various other facets of infrastructure. “We have major, major chemical pipelines running through here from BP and INEOS as well as some of the largest—36-inch—water mains, which supply entire towns,” King says. “So having to work around all of these constraints without impacting on anybody’s business and still maintaining what was a very challenging program has been the key factor in this job.”
Balfour Beatty, a construction and engineering services firm headquartered in London, is the construction contractor on the canal extension and associated infrastructure. The extension, which will reach a depth of approximately 1.6 m and have a maximum width of 24 m, is being constructed by means of conventional steel sheetpiling methods.
The lift bridge is now under construction and is expected to be completed by the middle of September. The entire canal extension is scheduled for completion by the end of the year and is expected to be open next April for the tourist season. With improved access, boat traffic along the Forth & Clyde Canal is expected to increase from 200 vessels per year to 700 over the next five years, many of the vessels coming from Scandinavian countries. The Helix, The Kelpies, and the canal extension will join the Falkirk Wheel, a rotating boat lift connecting the Forth & Clyde Canal with the Union Canal that opened in 2002, as tourist attractions in the Falkirk area. “We’re confident we will see increased long-term boating traffic come into the waterways network,” King says. “And we would hope long term that we would see more people spending more time in the Falkirk area and using our fabulous hotels and staying here for a weekend.”