A major concrete pour began on 03 August for the south pylon foundation, pumping 1,400 cubic metres of concrete into the south cofferdam for approximately 24 hours.
The three pylon foundations will reside below the riverbed, measuring 4.5 metres high and up to 22 metres in diameter.
Development of the foundations involves creating a concrete base layer, or floor, inside the cofferdams.
Following this, a cage made of steel reinforcing bars will be assembled and encased in steel matting, with a working platform also installed to provide access for site workers.
Upright steel reinforcement bars will then be fixed into the centre of the cage to form the beginnings of the pylon shaft, a tall structure rising out of the river bed to support the bridge deck.
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Once the assembly work is finished the concrete pour can take place.
Approximately 127,000 cubic metres of concrete will be used across the project, the equivalent of around 20,000 truck mixer loads of concrete.
Merseylink's site agent, George Houston, said: "This is one of the biggest concrete pours that I've ever been involved with. We're using a massive amount of concrete – over 600 truckloads just for the three pylon foundations. It's an extremely technical part of the project and our teams will be working round the clock to get the job done."
As each pylon foundation is completed, work will begin on the pylon shafts.
A metal mould, known as formwork, will be lifted into place by a crane and attached to the pylon foundation for the concrete to be poured into.
The formwork will move up the pylon shaft, allowing the pylon to 'grow'. It is estimated each section of the shaft will take around five days to build.
The three pylons, which will rise out of the riverbed to support the bridge deck, should begin to be visible in the estuary from September 2015.
Hugh O'Connor, General Manager of Merseylink, said: "Starting work on the bridge pylons marks another significant step for this important infrastructure project. Work is progressing at pace now on all sections of the site and a huge amount of activity will be taking place over the next few months."
(LM)
