Citycare Property has recently completed the renovation of four slipways and reconstruction of one seawall in the Banks Peninsula area for Christchurch City Council.
Overview
Christchurch City Council had tasked Citycare Property with the reconstruction of several slipways at Wainui, Akaroa, Charteris Bay and Governors Bay on Banks Peninsula. Council also requested that Citycare Property reconstruct a 14-metre section of seawall at the intersection of Seafield Road and State Highway as part of the overall project.
The Citycare Property team mid-pour at the Wainui slipway.
Challenges
Working in the tidal zone poses significant challenges, particularly in relation to available working hours in a day, says Chris Pinion, Contract Manager – Structures.
"As any avid boatie will know, low tide shifts by 30 minutes to an hour every day, therefore, over the course of one week, the tidal peak/trough can move by up to 6 hours."
Additionally, with the work zone also being inundated at high tide, a daily clean-up was generally required, with the overnight weather determining how much sand, stones, driftwood and the like, ended up within the work zone.
With the seawall reconstruction, the added impetus of the potential for the affected roadway to collapse into the bay meant the team was focused on getting the job done efficiently and effectively.
Solutions
To ensure tidal shifts didn’t impact the project, the teams varied their work days to ensure the most efficient delivery of the works and to minimise the impact to locals and other residents eager to use the rebuilt infrastructure.
For the slipways, high-strength concrete and galvanised reinforcing were used to ensure the reconstruction works will stand up to the marine conditions.
The slipway at Sandy Bay was greatly deteriorated and a slip hazard before the Citycare Property team worked their restoration magic. The newly renovated Sandy Bay slipway features a proper non-slip surface and now runs right to the lake’s edge.
For the seawall, new 1.6m x 4.7m panels were pre-cast by Citycare Property at its Hornby depot, delivered to site and tied into a mass concrete foundation to ensure they remain in place.
New 1.6m x 4.7m panels were pre-cast by Citycare Property at its Hornby depot. The face of the panels was seeded with local stone and shells to help them blend into the existing wall and the surrounding environment.
To help aesthetically tie the reconstruction works into the existing seawall, Citycare Property Structures Supervisor Pete McKenzie suggested the ‘seeding’ of local stone and shells into the face of the new panels to help them more seamlessly blend into their environment.
One of Christchurch City Council's heritage advisors was so pleased with the result that they requested details of the methodology used so that council could re-create a similar product for an upcoming project in Akaroa.
The panels were tied into a mass concrete foundation to ensure they remain in place.
Outcome
“This was a very challenging package of works with a number of time-sensitive and product-specific components that required a complex set of solutions. The final result in each case looks fantastic and is built to a standard that will continue to perform and to stand the test of time,” says Chris.
The successful delivery of this slipways and seawall remediation project demonstrates the strong capability of Citycare Property to deliver Civil Structural works in the marine environment.
As part of the seawall project, the part of the roadway that had collapsed was also remediated.