In 2020 we were approached by Westland District Council (WDC) to scope and repair the Jackson Bay wharf. To make accurate assessment possible, our team went to site and set up a timber identification system and inspected every piece of timber beam and piles.
To make this project financially viable, we had to develop unique repair processes to minimise costs while still achieving a long term successful fix. This work was carried out with the end goal of enabling access for ‘stage two’ - refurbishment work to the main wharf.
Scope of works
Given the location of the site, and harsh coastal conditions, all materials had to be selected to withstand the corrosive environment and continual exposure to these elements. It was essential to build a structure within WDC’s budget, but one which would also have an optimum life span. For this reason, quality and whole-of-life consideration for components were a high priority and included:
- Ensuring rescue steel and denso tape were applied to galvanised fastenings to extend life.
- Sourcing hardwood timbers to replace the beams.
- Blasting and arc spraying of all components for corrosion protection.
- Deflections of the jetty were monitored to gauge structural integrity.
- All new bolts are tightened to specified torque.
- The project engineer carried out site visits fortnightly and checked all completed work.
Innovation was essential to being able to deliver this work as site access was extremely limited with only some of our smaller, more lightweight cranes and machinery able to get into the area or go on the wharf. The answer was the bespoke development of plant:
- 12M barge with crane
- Tractor-mounted crane
- Purpose-built pile rig that was lightweight and mobile
We also needed to devise a budget-friendly methodology; this put the skills and out of the box thinking of our in-house designer and engineers to the test.
Reading tide timetables and planning the work around these was essential to success. Our crew worked varied hours onsite to best maximise windows of opportunity. This meant kit, such as lighting, needed to be available, in portable form, and on items of machinery.
Other challenges and solutions
This project necessitated closure of causeway access from Monday to Friday Initial plans were to do this work in a 10-day window, but as this would cause disruption to domestic fishing operations we worked with local vessels to ensure they could still get goods through as needed when closed, with the assistance of our crews and a platform we set up that we could slide full fish crates over to a vehicle waiting on the other side.
During this project we were extremely careful to ensure our work did not create any detrimental impacts to the amazing environment and natural beauty of this area. Mobilisation activities included setting up a marine split kit on site (although this was never actively required throughout the project), and ensuring machinery was checked thoroughly for leaking hoses, and all bolts and timber removed from the wharf were disposed of off-site. We also sealed grout pours to eliminate spillage.
Once works were complete, the object was to leave the site pristine. This included removing timber material from site and transporting back to Greymouth for recycling or reuse. To support this, our site set-up included establishing a laydown area where materials could be sorted and stored, ready for re-use on the wharf, or removal from site.