NZTA - SH1 PUHOI TO WARKWORTH:
CN8A CULVERT CONSTRUCTION, EARTHWORKS, STREAM DIVERSION
CLIENT: NX2 - Northern Express Group Contractor
COMPLETED: 2019
With a depth from pavement to invert of 45mtrs deep, this is most likely the deepest culvert ever to be installed on a NZTA Roading project. This project involved the construction of a Triple Barrel 3x large diameter Stormwater culvert, consisting of 1x 2500 dia. pipe & 2x 2000 dia. pipes, at a 220m length across the main SH1 Motorway alignment.
The project had significant challenges, outlined below:
Highly sensitive Clean stream diversion works with full electro-fishing for relocation of fish eels and freshwater crayfish.
Cutting through a large Rock Bluff, Rock Stabilisation work, and Shear Key works.
Placing of flowable fill (approx. 3,300m3) as backfill to keep the culvert safe from high overburden loads.
One million m3 of fill placed on top of Culvert pipes, filled to 45m height above invert of pipe to top of road pavement alignment.
Due to the complex challenges, P&I provided the client with a detailed pre-construction methodology using 3D modelling. P&I’s use of 3D modelling at the planning phase helped to reach planning consensus for a one of the most challenging areas of the P2Wk project critical path, and ensured effective & efficient completion of the works at the actual construction phase.
The works were carried out with high level implementation of health & safety procedures, quality assurance and strict environmental awareness, with none of the approx 3,300m3 of flowable fill concrete reaching the diverted stream.
Precision prior planning was required due to difficult access and rough terrain. The extra time spent planning and 3D modelling meant that only minor methodology adjustments were made during construction, allowing execution to go as planned.