New Zealand
Background
The upgraded Rangitahi Peninsula Bridge and Causeway will provide all tide access to the Rangitahi Peninsula development accross an arm of the Raglan Harbour via Opotoru Road and will replace the current causeway and bridge which are only usable by vehicular traffic for a few hours either side of low tide.
The new road will sit on a proposed causeway embankment, with a bridge crossing the mid-section to allow for Raglan Harbour tidal flows. The bridge and causeway will maintain two-way traffic via two lanes. The bridge is a five span structure with an overall length of approximately 93m.
Scope
- Site investigation including the drilling of machine boreholes, hand augers and cone penetrometer (CPT) testing;
- Development of a ground model, inluding cross sections and plans;
- Detailed geotechnical design and specification of the North and South causeway and bridge pier foundations. Working closely with the client to ensure a robust and cost-efficient design;
- Temporary works design for crane pad;
- Continued liaison with the client through construction methodology and temporary works design;
- Construction support and MQSA.
Findings/Challenges
The site is underlain by soft marine deposits of silts and clays which are highly compressible. Preloading of the causeway was recommended in our design to reduce post construction settlements, and geogrids adopted to provide stability. This was a much more cost effective solution for the client in comparison other options such as undercutting or piling beneath the causeway.
One of the key challenges for this project so far has been the constructability of the causeway in a tidal environment. During the initial stages of the southern causeway construction, working hours were governed by high-tide. CMW's rapid response to the Client/Contractor's needs was required under this limited working window.