The end result has led to significant cost savings as well as allowing footpaths to reopen ahead of schedule. Furthermore, the units have performed well against the increased water levels associated with the worst tidal surge to hit the East Coast for sixty years in December last year.
The 1.2km length of northern floodbank along the River Yare from Breydon Bridge to Railway Marsh provides important flood defences for the Norwich to Great Yarmouth rail line and the A47, as well as being a popular footpath with walkers and a significant conservation area. This section of bank is vulnerable to erosion and had not received any major improvement works for decades, leaving parts of it relatively low and with a narrow crest width.
As part of the wider 20 year Broadland Flood Alleviation Project, BAM Nuttall was appointed as main contractor specifically to carry out floodbank strengthening and footpath resurfacing along this stretch of the River Yare.
While another soil reinforced mesh product was originally specified, BAM Nuttall consulted specialist supplier Burdens who advised that a significant time and cost saving could be achieved with a specially designed Enviromesh slope system. Enviromesh visited the site and designed an all-in-one steel mesh facing unit that would create, retain and support the flood bunds, as well as providing the grass protection mesh which needed to be installed on the new floodbank crest to reduce erosion caused by walkers and ensure the footpath could be reopened as soon as possible.
Neil Holmes at Enviromesh, explained: “We visited the site and were able to design an all encompassing mesh system specifically for the needs of this project, which was much more cost effective than the original specification. We created an all-in-one unit design, with more efficient use of materials to get 710 metres long and two metres high embankment stabilisation using green plastic coated welded mesh with a 120 year design life.
“Our Enviromesh system has a steel mesh base unit to create and stabilise the slope for the flood bank, along with horizontal tails that provide the soil reinforcement. The fact it is an all-in-one unit saves the time and cost that would have been taken in onsite assembly. We carried out full trials in our factory before training the site team to install the product.”
The Enviromesh system was approved for use by both the EA and Network Rail and is now being sold by the manufacturers as a solution for other geotechnical solutions requiring soil reinforced structures. Keith Dorling, md at Burdens, said: “BAM Nuttall asked us if we could provide any alternative products to the one specified and as specialists in this area, we were able to work with one of our suppliers, Enviromesh, to design a bespoke pre-assembled system that saved time and cost on the project.”