A BRIDGE TOO FAR? – Not for CVD

As Scotland’s leading diamond drilling company, Clyde Valley Drilling (CVD) Ltd, is well used to undertaking large, and at times, technically challenging projects.

Headquartered at Eurocentral, Lanarkshire, the company specialises in controlled and robotic demolition, and uses some of the most technical and expensive machinery in the drilling industry, and it was for this reason that Morrison Construction called on its expertise earlier this year.

Glencoe Bridge Demolition for Morrison Construction pictures: enabling / removal

As part of its ongoing investment in the trunk road network, Transport Scotland awarded Morrisons a £2.5 million contract to demolish and replace the Achnambeithach Bridge, located on the A82 near Glencoe.

Constructed in the 1930s, the two-lane bridge was part of the main route to Fort William but had fallen into a serious state of disrepair and was no longer suitable for modern traffic loadings. The bridge was deemed to be unsuitable for strengthening so the only option was to demolish and replace it.

Having previously worked with CVD on similar projects, Morrisons invited the company to assess the best way in which to safely dismantle and remove the bridge. Headed by contracts manager Garry Downie, the CVD team conducted an extensive site survey to establish the best way to remove the existing bridge deck. It was then agreed that the only way was to cut the deck into slices, then lift them out with a large mobile crane.

Garry Downie said: “The bridge was in a very poor state and the concrete was extremely weathered to the extent that it was actually disintegrating, with some of the reinforcement exposed in places. Morrisons considered a number of options but after consulting with CVD they decided that controlled demolition was the safest way to carry out the job.

Glencoe Bridge Demolition for Morrison Construction pictures: enabling / removal

“We worked in conjunction with Morrisons to devise a methodology and the most cost-effective cutting pattern to suit the maximum safe lifting capacity of the crane, therefore minimizing the overall cutting program.

“There were also a number of environmental concerns as the bridge site lies within a Site of Special Scientific Interest (SSSI), a Special Area of Conservation (SAC) and at the heart of the Ben Nevis and Glen Coe National Scenic Area, it is within a designated Area of Great Landscape Value (AGLV). On top of this, the bridge crosses the River Coe which is a salmon river.

“Due to the location of the site and the environmental constraints no debris of any kind was allowed to fall into the river. To prevent this, a filtration system was placed beneath the old bridge which would catch any falling concrete or excess water, and as soon as this was in place, we were allowed on site on 29th April 2008 to begin the demolition process.”

A series of 50mm diameter enabling holes were drilled through the piers to allow access for the diamond wire. This allowed the use of a wire saw to detach the deck from the piers.

Using a quanta road saw with a 1,200 diameter blade, CVD’s team of skilled operatives then began the job of cutting the bridge into 25 tonne sections. A series of 200mm diameter holes were drilled into the support beams to allow CVD to burst the bridge deck into sections, and these concrete blocks were lifted away by a 300 tonne crane before being transported offsite. Work was then able to start on the support structures.

Jim Cassidy of Morrisons, added: “We had worked with CVD on a number of occasions and it was clearly the most qualified to carry out a job of this nature. The CVD team was very methodical in its approach and they did exactly what they said they were going to do. What was most impressive was that CVD’s team completed the bridge demolition in just nine days, allowing us to get on with the job of replacing the bridge.”

For more information contact Gary Downie at CVD on 0845 450 1701.

Pictures by Richard Scott