Norway's undersea island hopping takes another step

Norway was the first country to experiment with unlined undersea tunnels when Furuholmen drove the 2800m road tunnel to the island of Vardo in the north of the country in 1981. Now the sixth such tunnel is being built largely to aid the local tourist industry in an island area 120km from Oslo in the south-east of the country. It will extend the island-hopping road from Asmaloy to Kirkeoy which has a population of only about 150 permanent residents. The tunnel will be 3.7km long with a cross-section of 50m2. Tunneling is proceeding from both ends, one on the island and one on the mainland, by drill+blast through red gneiss. The plans allow for up to 270m of the total 3.7km length of the tunnel to be completely lined with poured concrete. The tunnel profile will decline at an angle of 10% at both ends for 1.2 and 1.3 km respectively and flatten off to a slope of 1.4% (for 1.2 km) in the middle.