Working with the tides to remove a redundant pipe from Bideford bridge


Bideford Old Bridge in North Devon is a Grade 1 listed structure which spans the River Torridge near its estuary. It connects the old part of the town of Bideford on the left bank with East-the-Water on the right bank. It is one of the longest mediaeval bridges in England, being 203m long with 24 arches and is a Grade 1 Listed Structure.

The client, Wales & West Utilities Ltd, had installed a new gas main across the River Torridge further downstream of the site. The two old gas mains which crossed the river via the bridge structure were therefore redundant, and the client wished to remove them from the bridge structure.

The gas pipes were accessed from both sides of the structure using floating plant consisting of a sectional steel pontoon barge and a NATO tug.

The pontoon sections were delivered to an adjacent wharf by road transport, and then lowered into the water for assembly into a 20m x 5m barge, complete with 2 x 10m long spud legs operated by air winches. The Nato tug was also road transportable and lowered in by crane.

 A MEWP on the barge deck was used to gain access to flame cut the pipes from the North side, and from the South side a scaffold tower was used mounted on a barge of jet-float modular pontoons.

The pipes were to be cut into 3m lengths using Oxy-Propane flame cutting methods. Flame cutting was chosen to the cut pipe sections due to the limited access beneath the bridge and adjacent services, and the precaution of shielding other services and the bridge structure was carried out prior to cutting using flame proof fire blankets.

As the pipes were covered with a bitumastic coating, it was necessary to remove sections of the coating by mechanical means prior to flame cutting

Once each section of pipe had been cut, it was lowered down on to the deck of the barge using a 4.2m material lift. The lengths of cut pipe were moved onto and temporarily stored on the deck of the steel pontoon barge for later off loading at the wharf at high water using a small crane.

The pipe sections were then transferred to a specialist scrap metal recycling contractor to remove and dispose of the bitumastic coating prior to recycling the steel.

 


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