A ‘first-class’ solution needed by engineering firm AECOM to inspect a critical section of a viaduct was provided by the modular pontoon company TPA Pontoons.

TPA supplied a 49m2 dual-layer Versadock pontoon complete with operatives, outboard motor and Spider MEWP for the first principal inspection of the viaduct, part of which encompasses the Bridgewater Canal on the north of England, by engineering and infrastructure specialists AECOM.

Mewp on 7m x 7m Outboard Pontoon 2

MEWP on 7m x 7m Outboard Pontoon 2

The viaduct had a general inspection from ground level (points of safety) in 2019, two years after the 0.6km long viaduct was opened by operator Merseylink, but this was its first principal inspection since commission. These inspections are tactile and carried out at close quarters every six years, using access equipment and plant.

AECOM had originally requested lane closures on the dual-carriageway viaduct to deploy an underbridge unit to carry out the inspections on the spans over the canal and undeveloped land. However, due to journey time measurement obligations, Merseylink asked for an alternative method of access.

Steve Wilson, senior engineer (bridges, inspections and surveys) with AECOM, investigated using a spider MEWP to inspect a few of the spans including the Bridgewater Canal span, which required getting a Spider MEWP down to tow path level.

He contacted Spider lift hire specialists Higher Access, a sister Vp plc company to TPA, and met on site with one of their representatives, together with one of the operatives from TPA Pontoons.

TPA carried out a stability calculation report to confirm the pontoon design and loadings and maximum MEWP reach capabilities. They then supplied the complete access package – operators, on-site crew, outboard motor, plastic pontoon and MEWP – for the four-day contract. The pontoon was required to be a dual layer design to carry the weight of the 3t MEWP and allow it full range of operations.

Direct access to the A533 bridge was restricted so the pontoon, complete with 28m2 of perimeter edge protection, was motored some 1km downstream from a launch and recovery site on the Astmoor Industrial Estate in Runcorn, passing under a pedestrian bridge and a dual carriageway slip road onto the A558 Daresbury Expressway, to the viaduct.

The outboard motor was set up on a 3m x 2m single layer section extension to the 7m x 7m moduled main pontoon, in addition to a 4.5m containment bund to prevent any potential spillages from the MEWP.

In addition to the equipment, TPA provided the Spider MEWP, which worked to heights over water of up to 12m, and the pontoon and outboard motor operators, including an on-site operative who acted as marshall/lookout for boat traffic on the canal and pedestrian traffic on the canal banks.

“TPA were first class from start to finish and I had no complaints,” said Steve Wilson.

TPA’s business development manager for pontoons, James Myatt, said: “It’s still relatively uncommon to use a Spider MEWP from a pontoon. However, working with our sister company Higher Access we were able to provide a cost-effective package to allow safe working at height over water and we are delighted AECOM were so pleased with how we delivered this project.”

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