Sustainability Case Study #7

Combating Coastal Erosion Block by Concrete Block

Case Study 7: Westcoast Concrete Block Seawall
Westlock Concrete Solutions Ltd (WCS), based in Northern Buller on the West Coast of the South Island has designed a seawall of interlocking hexagonal, precast concrete blocks to battle rising sea levels.

WCS partnered Busck Prestressed Concrete Ltd, one of New Zealand’s largest manufacturers of precast concrete products, to engineer interlocking hexagonal blocks.

When appropriately arranged, the blocks create a versatile and durable structure that offers over 50 years of protection against the unrelenting ocean.

MANUFACTURING AND INSTALLATION
Extensive R&D was undertaken by WCS, with Busck manufacturing the blocks after its trials.

The concrete blocks have a low water/cement ratio and contains microsilica to ensure compliance with the marine requirements of class C in NZS 3101 Concrete Structures Standard for a 50-year life.

The blocks also have a concrete strength of 45 MPa, a F4/U3 surface finish, a minimum reinforcing cover of 60 mm, and returns as specified in NZS 3109 Concrete Construction.

Located near the West Coast town of Hector, the seawall was built in one week using a single 12-tonne excavator. Consisting of three different block types (base, standard and top), the seawall is five blocks high and 40 blocks long, totaling around 200, 2-tonne concrete blocks.

NEXT STEPS
The local community’s interest has been matched further afield, with inquiries received from along the West Coast and around New Zealand.

WSC is currently raising awareness of the interlocking block system with territorial authorities and central government as well as amongst civil engineers, with the objective to ensure every New Zealander affected by coastal erosion has the option of a long-term solution.