JACOBSON'S TUNNEL REFURBISHMENT
Client Watercare Services Ltd
Project Value $1.3 Million
Description : Jacobson’s Tunnel is located in the Waitekere Ranges and was constructed in the 1960’s. The existing precast lining system was deteriorating and partially collapsing in places. March Cato won the design and build tender to refurbish the tunnel using semi-circular precast concrete segments.
The conventional approach to refurbish this tunnel was to shotcrete the existing precast segments, but it was considered that a more robust liner was required:
• The precast liners were constructed using fibre reinforced concrete. They were transported into the tunnel on a 600mm gauge railway track, rotated 90 degrees and lifted into place using a purpose built hydraulic machine mounted on a railway bogey.
• The tunnel had deteriorated to such an extent in places that a timber ‘heading’ had to be constructed prior to installation of the liner segments.
• Confined space tunnelling and robust health and safety systems were required.
• The existing watermain in the tunnel was live and had to be protected at all times.
• The remote location in the Waitakere Ranges provided difficulty of access.