Client: Waka Kotahi NZTA

Contractor: Fletcher Construction Limited

Status: Completed

The Whirokino Trestle and Manawatu River bridges are located between Foxton and Levin in the Horowhenua region of the lower North Island. The site is approximately 6km inland from the Tasman Sea.

The project includes 2 bridges, the Moutoa Floodway and the new Manawatu River Bridge, and an Agricultural Underpass. The construction replaced the existing SH1.

The Moutoa Floodway is an overflow floodplain of the Manawatu River and is confined by 4-5m high stop banks constructed on each side. The new Moutoa Floodway Bridge spans the floodway west of the old Whirokino Trestle Bridge. The total bridge length is 609.4m between the centre lines of the abutment piers. The bridge structure consists of 17 spans, divided into 3 sections. The first and third sections consist of 6 spans (end spans of 33.6m and 33.8m and 4 intermediate spans of 37m). The total section length is 215.4m. The second section is 178.6m long and consists of 5 spans (2 end spans of 33.8m each and 3 intermediate spans of 37m). The spans are made up of five precast prestressed supertee girders.

The Manawatu River bridge runs over the Manawatu River which is confined by stop banks constructed on each side. The new Manawatu River Bridge spans beyond these stop banks and is approximately 10m longer than the old bridge. It is located downstream and to the west of the old bridge. The total bridge length is 192.3m between the centre lines of the abutment piers. The bridge structure consists of 6 spans, with three 36m spans, two spans of 34m made up of five precast prestressed supertee girders, and one span of 16.3 (DHC span).

The underpass structure is situated within the fill embankment between the two new bridges. It is a concrete box structure with internal dimensions of 16m x 4.5m x 4.5m excluding wingwalls. The underpass was constructed perpendicular to the road centreline alignment designed to maintain access under the new section of the state highway for the existing agricultural track. Embankment retaining beyond the underpass is provided by a combination of concrete wingwalls parallel to the road alignment and MSE wingwalls perpendicular and splayed. The underpass structure consists of mirrored precast C-shaped units connected by in-situ slabs top and bottom. The base and roof sections between the walls will be cast in-situ from starter bars projecting from the cantilever section of the roof to provide an integral box structure..