Medium term solution sought to replace Alma Bridge in Sidmouth
Posted on: 15 December 2016
Devon County Council is focusing attention on a medium term solution to replace the Alma footbridge in Sidmouth.
The temporary structure currently in place was only intended to have a very limited life expectancy and, due to ongoing cliff erosion, the bridge will be lost in the near future.
The authority is committed to ensuring this well used bridge is replaced if viable and has been exploring two options: one crossing 55 metres upstream of the existing bridge with ramps providing access to the bridge, and the other option using steps at each end of the bridge.
The ramp option includes a 30 metre long ramp on the west side from the pumping station, which would also form part of an upgraded coastal flood defence wall. The ramp was proposed to rise eight metres above the river to access a high level bridge and would require significant additional civil engineering work.
Flood modelling would be needed to design the west ramp to the correct standard of coastal flood defence. The modelling could be undertaken as part of East Devon District Council’s Beach Management Plan work, but it is anticipated this information would not be available for possibly up to 12 months. This would mean construction of a replacement bridge would be unlikely to commence for two or three years.
Extensive geotechnical investigation of the east cliff would also be required as there may also be considerable costs to stabilise the ground for a ramp structure on the east side. The scheme, which is anticipated to have a lifespan of more than 50 years, could cost up to £1.5 million.
The alternative option will provide a bridge with a flight of steps at either end of the bridge rather than extensive ramps. The original Hanger Path on the east side of Alma bridge was a series of steps close to the cliff edge before being abandoned for a very steep path realigned inland. As the cliffs erode it is likely that Hanger Path will have to be re-aligned again, possibly within the next five to 10 years. Due to very steep gradients the path may have to return to its original design using steps.
Councillor Stuart Hughes, Devon County Council Cabinet Member with responsibility for bridges and local member for Sidmouth, said: “Our teams have carried out a thorough examination of both options and at this time it makes sense to pursue a medium term solution until the preferred option from the Beach Management Plan is implemented. At that stage we could then look in more detail at longer term options with ramps to safeguard a crossing to the coast path which will also provide easier access.
“If the bridge option with ramps is pursued the coastal path could be diverted inland for up to three years until a new bridge is provided. It could also potentially be unviable for cost and engineering reasons. The second bridge option using steps could be considered more of a medium term solution but it’s a good compromise. It could be built sooner at a much lower cost, minimising the potential duration of the coastal path diversion. It will also keep the coast path in operation close to the sea front which will benefit both local residents and visitors alike.”
Martin Davies, Flood Risk Advisor from the Environment Agency said: “The River Sid defences currently provide a good standard of protection against flooding. We are aware that due to ongoing erosion of the cliffs to the east of the River Sid and the likely increase in storminess and sea level rise due to climate change these flood defences along the river upstream of Alma Bridge will need to be improved in the future. Although further improvements to manage flood risk along the river frontage are not justified at this time we are currently reviewing maintenance requirements along the River Sid wall and look forward to working with DCC to assist in developing their options for bridge access over the river.”
The County Council will target an opening for the new bridge during 2018.
Posted in: Environment