Wairau Diversion – Campground Flood Damage Repair
Client: Marlborough District Council (MDC)
A series of storm events caused damage to the true left rock armoured wall at the exit of the Wairau Diversion into Cloudy Bay.
The works comprised:
Supply and import river protection rock – 11500 tonne of rock sourced from Taylor Contracting’s Lee Valley Quarry in Tasman. Import free issue materials from Pukaka Quarry – 20870 cubic metres of hard fill. Placement of all materials imported to site – Riprap length 400m (main wall) 440m completed made up of a 12m wide rock face (half of which was placed under the high tide line). Spot repairs of damaged bank.
Challenges:
Construction of a competent Riprap wall with the toe below the waterline in a tidal zone prone to high flows in rainfall events and ensuring toe location, lines, levels and batter angles were correct.
Achieving the correct rock density per lineal metre of wall.
The location of the site is on the coastal side of a freedom camping area that has high foot traffic with pedestrians wishing to walk through the work site to the coast.
Ensuring correct the grades of rock were delivered onsite to meet the specifications while maximising truck weights. and managing up to ten truck and trailer units on site at any one time delivering different products from different locations.
Health & Safety:
During 2024 there were two fatalities in the forest industry where excavators fell into deep water and the operators drowned. This led to Taylors undertaking a deep dive review into our task risk assessments for working beside water. An internal safe work permit system was updated for working beside deep water and this was implemented for the Campground job and continues to be used across the company work sites.
Environmental
Our planning included a response plan to weather events with triggers for action and response. With the operation occurring within the water column, we worked from the outside inward toward the land so as to contain sediment discharge as much as possible. We monitored the tides and adjusted our work to avoid working the deepest water on the spring tides.
In the early stages of the project one of our team identified the potential for there to be penguins on site, particularly around the rock storage area and with the onset of the nesting season. MDC were notified of the issue which had not been contemplated in the contract specification. Marlborough District Council authorised a bird survey and regular checks were put in place through the project so as we didn’t inadvertently hurt any birds.
Within three months the rock placed has already provided an anchor point for algae, providing fish habitat. It’s possible that our rock placement may well create penguin habitat for the future.
Photos:
Row 1: Before the work commenced (left and middle), placing Riprap (right)
Row 2: Wairau Campground sunrise (left) and complete work (middle and left)
