Tarmac is well underway in a £7.7M project to protect 10,500 people from Humber estuary floods.
Led by the Environment Agency, the Humber Estuary Flood Risk Management Study has identified an initial package of five schemes with a total value of £45M, to deliver long-term protection for up to 400,000 people across the estuary.
Stallingborough is the first of the five schemes and will see the replacement of 1.6km of aging flood wall protection on the shoreline between Grimsby and Immingham Docks, North East Yorkshire.
Main contractor Birse Coastal has secured Tarmac to supply around 3,000 m3 of its Topforce concrete and 2,000 m3 of conventional concrete for the construction of the new sea defence at Stallingborough.
Birse Coastal and Tarmac previously worked together on sea defence schemes in Blackpool. For the Stallingborough scheme, Birse has specified Topforce, a high strength, fibre-reinforced concrete, ideally suited to coastal defence work.
According to Birse Coastal’s site agent, Alan Smith, “Typically, mesh fabric is used on sea wall defence schemes, but the macro-synthetic fibres within Topforce have allowed us to reduce the use of steel mesh fabric on the overall scheme by around 35%. Mesh can easily get exposed and can quickly corrode, so using a material with added fibre is beneficial.”
“Every day we are working against nature’s clock and only have a six hour tidal window in which to operate. Using Topforce has delivered both cost and time savings, because using mesh fabric typically requires significant onsite preparation time. I believe we are saving around a week compared with the time we would have had to set aside for mesh-based material. We have also found that the concrete delivers an even distribution when discharged,” he said.
Tarmac’s national special products manager James Freeman said: “We are currently delivering between 30m to 60m of concrete a day to site and our technical team will conduct regular slump tests as well as taking cube samples of cured concrete to check the product strength
“Long-term durability of the sea wall is critical and the concrete has to deliver a strength of over 50 Newtons. Because of chlorides in the sea water we have to ensure that the concrete can meet an exposure class of XS3,” he says..
The Stallingborough project is set to be completed by October 2009. The next project in the Humber package of works is the replacement of the flood wall at Swinefleet, near Goole. The project team will then move to Halton Marshes, near East Halton, Donna Hook, near North Somercotes and onto a location on the north bank of the Humber.
It is estimated that the five projects within the Humber Estuary Flood Risk Management Strategy will be completed by July 2011.