Breakthrough was achieved on the 16th November 2000 on the 1.9km long Skatestraum undersea tunnel that will form an important part of the new road linking the Norwegian mainland with the island of Bremanger. The tunnel will be the first underwater tunnel in the county of Sogn og Fjordane.
The calculated cost of the tunnel is NOK 110M ($1.76M) at the 1999 price level. Construction work started in September 1999 and will be completed in the year 2001. The tunnel is being constructed by the Norwegian Public Roads Administration‘s production department.
The Skatestraum Tunnel will be approximately 40m below the seabed with the lowest point being some 80m below sea level. The cross-sectional area of the tunnel is 52m2, the gradient will be 1:10 from both tunnel ends and it will have two lanes.
Drill and blast was used for the construction of the tunnel. The importance of sealing the rock to control leakage has been emphasised during the construction phase. At the beginning very poor rock was encountered and a 300m long bore hole was drilled along the line of the tunnel to obtain advance knowledge of the rock. However, recently good rock has been met and leakage has been less than expected. The rock has been grouted to reduce the leakage to an acceptable level, but a controlled volume of water will still leak into the tunnel. This water will be collected in the bottom of the tunnel and pumped back into the sea.
There will be emergency stop zones containing fire-fighting equipment and emergency telephones throughout the tunnel. In the event of an accident, police, fire brigade and ambulance will use dedicated radio channels. The tunnel will be monitored at all times by the Emergency Surveillance Station in Florø and by the controlling stations of the Norwegian Public Roads Administration Sogn og Fjordane in Laerdal or Bergen. Extractor fans will start automatically to ensure premium air quality at all times.
