Machineries and workers pave the new E18 road, with the forest visible in the background.

E18 Knapstad-Retvet

NCC is building a new section of the E18 expressway in the counties of Østfold and Akershus, between the Municipalities of Hobøl and Ski in Norway.

E18 Knapstad-Retvet is a sub-contract in the extension of the E18 Ørje-Vinterbro in Østfold county. The contract involves the construction of a new 6.3 km four-lane highway on the Knapstad-Retvet route in the Municipalities of Ski and Hobøl.

The contact is extensive and the ground conditions are complicated in places. The contract includes all associated construction on the section, which mainly comprises five bridges on the main road, one bridge on a side road, one ecoduct, one wildlife viaduct and one underpass. This work will involve the installation of about 5,000 tons of rebar and pouring about 28,000 m³ of concrete. Work will also take place on side roads, primarily the about 800 m expansion of the Fv120 country road at Elvestad. Furthermore, the contact includes establishing a water and wastewater facility for the Municipality of Hobøl, which is part of a separate road project and part of this project. About 1,700 m of guided boring has been carried out for water and wastewater pipes.

The expressway crosses three areas of quicksand which will be covered in about 70,000 m³ of lightweight/super-lightweight fill material. A six-lane bridge, the widest in Norway, will be built over the River Hobølelva and the largest quicksand area. The bridge is about 300 m long and 28 m wide. The foundation of the River Hobølelva Bridge comprises about 3,300 m of ø711 x 12 mm steel piles driven at an angle. This work was carried out by Hercules Fundamentering AS, NCC's foundation-specialist subsidiary. This was the first time that such a foundation made from drilled, large steel piles was conducted in Norway. The tallest pile was drilled to a depth of about 60 m. The River Hobølelva is a protected water system with strict discharge requirements. NCC established its own wastewater treatment plant to purify the water from drilling before it is pumped into the river. A county official inspected the treatment plant and reported no objections.

High volumes of earth are being moved at the site. A total of 735,000 m³ of rock will blasted and moved, and 815,000 m³ of earth will be removed. The contract also includes establishing facilities covering about 17,500 m for rainwater runoff, assembling 350 pylons with accompanying electrical fittings, establishing a 3,500 m water and wastewater facility, and laying about 80,000 tons of asphalt.