When completed, in May 2020, the Transmission
Gully Project (TGP) will provide a new, 27 km long, four-lane motorway
north of Wellington, New Zealand. This modern and safe main highway will
bypass the coastal communities and space-limited choke points which resulted
in ever increasing traffic congestion on the existing SH1 highway.
The project is highly complex, with the alignment in places crossing steep,
difficult, terrain and in other places crossing flood plains with deep,
soft foundation soils. For much of its length the alignment is close to
the active Ohariu fault. Twenty-five new bridges and large culverts, are
required over the length of the alignment. Many of the bridges are single
span structures, with spans ranging from 22 m to 38 m.
The Wellington Gateway Partnership (WGP) and the New Zealand Government
formed a Public Private Partnership (PPP) to deliver the Project. The WGP
subcontracted the Design and Construction of the Project to a Joint Venture
between CPB Contractors Pty Ltd and HEB Construction Ltd (a VINCI subsidiary),
known as CPB HEB JV.
CPB HEB JV contracted Reinforced Earth Ltd New Zealand for the design and
supply of materials for 10 bridge abutments.
Reinforced Earth considered in the design the proximity to the active Ohariu
Fault with an effective magnitude of 7.
After the contract was signed, Reinforced Earth Ltd was awarded two further
structures: abutments for a further single span bridge and a TechSpan®
concrete arch system with extensive, associated RE Walls.
The abutments for the eleven single span bridges required a total of about
8,500 square meters of TerraClass® precast concrete facing panels, with
the height of the walls varying between 1.6 m and 10.7 m.
The TechSpan® arch has a nominal span of 14 m with a height of 6.8 m. Associated
Reinforced Earth® portal walls comprised 2,100 square meters of TerraPlus®
precast concrete facing panels up to a maximum height of 16.8 m.
Construction of the first set of Reinforced Earth® Abutments commenced
in July 2017, with all Reinforced Earth® structures substantially complete
in October 2019.