To minimise disruption, the tunnel will be two-way as usual when traffic flows are heaviest (7.00am-9.30am and 3.00pm-7.00pmpm) but during the day (9.30am-3.00pm) and after 7.00pm, it will be down to one lane.
The temporary traffic signals that have been installed at either end of the tunnel will be used Monday to Saturday to allow traffic through in one direction at a time. Some Sunday work is possible but normally the tunnel will be two-way all day.
The Council's Transport Portfolio Leader, Councillor Andy Foster, says the project is part of the Council's ongoing programme to strengthen and protect important city transport routes.
"We've already done major strengthening work in Ngaio Gorge Road to secure a viable alternative route out of the city and future work is planned on Churchill Drive, the Hataitai bus tunnel and Seatoun and Northland tunnels."
The Karori work is being done because the tunnel is near the city's main fault line and assessments show that while the tunnel itself is likely to withstand a reasonably large earthquake, the portals are vulnerable. The hillside on the city side is also prone to slips.
To make things safer the Council is:
- rebuilding both tunnel entrances (portals) and anchoring them to the hillside
- constructing a new sprayed-concrete retaining wall along Glenmore Street on the Kelburn approach to the tunnel.
Contractors have been working above the tunnel in Raroa Road and will need to operate the traffic signals at times next week as further preliminary work is carried out. From Monday 27 February, the work is expected to be in full swing six days a week. All going well, it should be finished by early November.
Council Infrastructure Director Stavros Michael says the work will be noisy at times and people will need to be patient particularly when the tunnel is down to one lane.
"We'll be closely monitoring traffic flows and making adjustments if necessary to help minimise disruption but there will be delays. Depending on when people are travelling, they might want to leave 10 minutes earlier or consider taking an alternative route to avoid congestion."
The trolley bus wires are being disconnected soon for safety reasons and Go Wellington will operate diesel buses to Karori until the work is finished.
Pedestrians and cyclists will be able to use the tunnel, though there may be short delays at times. The Birdwood Street car park is closed while it is used as a site office and for storing equipment but pedestrians can use the steps.
At times, the tunnel may close overnight after the last bus, and for up to five minutes during the day. Mobile electronic signs will provide traffic updates, advance warning of closures and detour information.