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Sheet piling repair to remote island

This project was to repair a failed section of sheet pile revetment on a remote island between two weirs on the upper River Lea in Hertfordshire at a place called Amwell Magna, the oldest fly fishery in the UK!

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Due to extremely poor access an innovative approach had to be sought to prevent major enabling works being required to the surrounding countryside in order to bring in conventional large items of plant to carry out the work. The only access was down a narrow track suitable for a transit sized vehicle.

A jetfloat modular plastic pontoon was mobilised to site and assembled in the river to form a floating access track to the island that was approximately 4 metres wide and 20 metres long, filling the river immediately upstream of the island with an access ramp down onto it from the bank.

An upper deck was then constructed above the jet floats using steel framework and heavy duty plastic mats in order to strengthen it and take the loading that would be produced from the crane.

A spider crane and compressed air driven piling hammer were then mobilised to site and set up on the pontoon.

The piles were driven to plug the gap and the void behind was then filled with imported crushed stone before a concrete slab was poured on top to match the existing.

The area behind was the dressed with imported topsoil and seeded with grass.

CLIENT DETAILS

The Environment Agency

Apollo Court, Hatfield

LOCATION

The River Lea, Hertford

MATERIALS USED
  • Interlocking steel sheet piles
  • Imported crushed stone