Twin 385 m long two lane motorway tunnels were
constructed beneath Johnson’s Hill near Puhoi, North
of Auckland. The tunnels facilitated a faster motorway
alignment (significantly reduced motorway gradients)
while maintaining a tract of bush over the tunnels.
The tunnels pass through an active slip scarp in
Pakiri formation sandstones and were designed and
constructed by the Northern Gateway Alliance of
which Tonkin & Taylor was a full member.
Watercare Services Ltd (Watercare) is the bulk
water and wastewater utility provider for the
Greater Auckland area.
A 50-year-old hand excavated tunnel at Cossey’s
Dam, a water storage dam in the Hunua Ranges
south of Auckland, was nearing the end of its
economic life.
Watercare was raising the height of the dam
and thus increasing the head on the tunnel. A
solution designed by Tonkin & Taylor that relined
the existing tunnel at a reasonable cost providing
structural integrity while maintaining sufficient
capacity for full volume delivery.
Feasibility study for twin underground rail lines to
complete the Auckland rail loop - back to Mt Eden
Station. This allows Britomart Station to become a
through station, thus increasing its capacity.
A number of route options and tunnel configurations
were considered before settling on twin 6.2 m
diameter tunnels beneath Albert Street.
One key issue was finding a route beneath the
downtown buildings while minimising the impact
of the tunnels on the building foundation piles
which project below the tunnel alignment.
A 90 m long tunnel was designed and constructed
to convey power cables from the Victoria Street
substation to the main road within the Auckland
CBD. The tunnel became an necessary solution
due to the density of existing services within the
city streets.
Project Hobson is Watercare’s project to replace
the aging sewer line crossing Auckland’s Hobson
Bay. The project involves the construction of a 3km
long 3.4m diameter tunnel running 35m below sea
level from Parnell under Hobson Bay to Orakei.
Wastewater flows are conveyed to the tunnel via
dropshafts, with a major highlift pumpstation at
the downstream end. The project will improve
Hobson Bay water quality and remove the old
sewer line from the sensitive coastal environment.
Discipline : Geotechnical investigations (onshore and offshore)
The North Shore Outfall project requires a tunnel 3 km long and approximately 2.4 m in diameter from the existing sewage treatment plant to Mairangi Bay Beach and then another 3 km of either tunnel or submarine pipeline to an ocean outfall. The tunnel will be constructed predominantly through the East Coast Bays Formation (sandstone).
The Vector Tunnel project involved the construction of a 9.2 km long tunnel in Auckland. The tunnel is 3m in diameter and runs at a depth of 20 metres to 100 metres below ground level, and almost entirely below sea level.
