Temporary cofferdam in River Sid as replacement Alma Bridge work progresses

Work is progressing well on the scheme to develop a new footbridge to replace Alma Bridge in Sidmouth, says Devon County Council.

Contractor Mac Plant Construction Ltd has installed a temporary cofferdam in the River Sid. This has enabled work to get under way to stabilise and re-profile the cliff face to the eastern side of the river, ahead of the construction of the bridge abutment and wall.

The re-profiling is being undertaken in stages, with each section stabilised using nine-metre long rock anchors. While work is carried out, netting is being secured to the rock face to prevent any rock fragments falling onto the workforce. This work will eventually be concealed by the new bridge abutment.

Councillor Stuart Hughes, Devon County Council Cabinet Member with responsibility for bridges and County Councillor for Sidmouth, said: “I am sure people who have walked near this end of the seafront in the past month will have viewed the progress being made on site.

“The stabilisation work to the cliff face is all important and it has started well. It makes sense to keep the material from the re-profiling of the cliff on site by depositing it at the base of cliffs at Pennington Point. This will mimic the natural erosion process and it will be washed out to sea in the same way as material from cliff falls.”

Supports for replacement Alma Bridge

Once the cliff face stabilisation work has been completed, 44 piles will be installed at the base to support the new east side structure.

A temporary bridge is currently in place to provide unrestricted access between the contractor’s compound and the working area on the east side of the river. A section of The Ham’s perimeter stone wall has been temporarily taken down to accommodate this bridge. Following completion of work on the east side of the river, the temporary cofferdam and bridge will be removed and the stone wall rebuilt.

The temporary bridge reduces the risk of delay from adverse weather that could otherwise be experienced if a crane was used instead.

Test piles have been installed on the Ham to confirm the load capacity of the proposed piles that will be supporting the new bridge. These test piles will be cut-off below ground level. On the west side of the river, groups of piles will be installed on the lower river walk-way to support the new elevated steel ramp structure.

It is expected that cliff re-profiling, rock anchoring and piling activities will be completed by Christmas, allowing the construction of the concrete abutments and foundations to commence in the new year.

The new structure will be around 40 metres upstream from the existing Alma Bridge. Weather permitting, the scheme is expected to be completed in Spring 2020.

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