The tunnel was strengthened because a seismic assessment of the tunnel showed that the portal walls at the tunnel entrances and nearby slopes were likely to suffer significant damage in a major earthquake.
This work is part of the Council's ongoing programme to strengthen important transport routes and earthquake-prone structures.
Karori Tunnel was built in 1900 and is Wellington's oldest road tunnel. Linking Karori with Kelburn and the city centre, it is regularly used by motorists, pedestrians and buses. Around 114,000 vehicles pass through the tunnel each week.
The tunnel is 76m long, 7.71m wide and 5.8m high. The Wellington Fault lies within 20m of the eastern (Kelburn-side) tunnel entrance.