Built from 1927-1932, the Afsluitdijk, which runs from Den Oever in North Holland province to the village of Kornwerderzand in Friesland province, has protected large parts of the Netherlands for generations against flooding from the Wadden Sea and the IJsselmeer freshwater lake.
But after more than 85 years in service, the 32km dam no longer meets current requirements for flood protection and water discharge and requires major reconstruction.
The ever-present danger which water poses to the Netherlands and the global increase in extreme weather means it is essential that the Afsluitdijk is upgraded to be able to withstand these twin problems.
As part of the project, Europe’s largest pumping station will be built within the dam to ensure it can disperse large volumes of water, with excess being drained from the IJsselmeer into the Wadden Sea.
The causeway on the Wadden Sea side will be raised and reinforced with new facing and 75,000 Levvel blocks, one of the most innovative elements of the Afsluitdijk project.
The blocks, globally known as Xbloc+, were developed specially for the project by BAM Infraconsult. Each weighing about 6,500 kg, they are extremely strong, have a wave retardant effect and are relatively easy to install.
A specially designed clamp makes placement fast, accurate and safe with no people required to grab and release them during the process.
Around 100 blocks will be produced each day in the port of Harlingen, transported by ship to the causeway and installed by pontoon crane.
Drainage sluices at Den Oever will be expanded with new sluices built on the island sections between the existing sluices. This will allow more of the water that enters the IJsselmeer from the River IJssel to be discharged into the Wadden Sea, without the use of energy.
Enhanced safety and sustainability
Improved safety and sustainability are key elements of the project. One of the main benefits will be that the total energy consumption of the Afsluitdijk, including the energy consumption of the pumping stations that can produce a flow rate of at least 235 m3 per second, will be compensated by solar power.
But there are additional benefits for the local ecology and wildlife. Two large pumping stations at Den Oever will operate with very low energy consumption, will be fish-friendly and powered sustainably by 2.7 hectares of solar panels.
A fish migration river is being created which will enable fish to reach their natural spawning grounds and habitats with a key innovation being the installation of a fibre-reinforced plastic floodgate in the river.
As well as enhancing the dam’s pivotal role as a protective barrier against the sea and as a road link between two provinces, the New Afsluitdijk project will also have important tourist spin-offs.
To improve visitor facilities, a new cycle path will be installed along the full length of the dam. In addition, the area around the striking monument designed by celebrated Dutch architect Willem Dudok will be upgraded and made more accessible to the public and the existing pedestrian bridge relocated to highlight the approach to the monument. At Kornwerderzand, there will also be a new walking trail which allows access to the fish migration river.
In addition, the safety of the A7 motorway which serves the area will be enhanced by widening the road’s emergency lanes with a new type of guard rail used for the first time on a Dutch project.
Construction of the original Afsluitdijk was extremely labour intensive with around 5,000 workers positioning the dam’s basalt blocks one by one. The new structure will also make a major contribution to the local economy, creating employment for approximately 600 people, around 100 of whom will be jobseekers with previously limited employment options.
Project Director Carlo Kuiper commented: "The Afsluitdijk project is an extremely significant project which will create a number of benefits for the area.
"It will further enhance the safety of a large part of the Netherlands which is clearly the number one priority. However, the innovative approach which the team is taking means that the spin-offs in terms of the local environment and the area’s tourist appeal are also considerable."