Visit us on Facebook

Akaroa Pole Retaining Walls


New Horizontal Civil Infrastructure: Akaroa Water Supply Stage 3, Reticulation Upgrade.

Client: Hawkins Infrastructure

Principal Stakeholder: Christchurch City Council

Duration: (Current)

Project Engineer (Hawkins): Ben Whitham

Project Supervisor (Tru-Line): James Robinson

Consultant Engineer: David Carshalton of Beca (Beca Carter Hollings & Ferner)

HDD Operator (Tru-Line): Grant Senior



Excavating pole retaining wall foundations with augurThere are two retaining walls in this project. One is for a pumping station the other one for a reservoir. Because the nature of the terrain at Akaroa is very hilly with very few flat sites available for structures as were required this necessitated selection of siting for these structures on sloping sites adjacent to the road, being Old Coach Road and adjacent to the newly installed main water pipelines laid by TruLine Civil, using the HDD method, that serviced these new water reticulation system structures. The structures were the pump station, called the Takimatua Pump Station, and the reservoir at the top of Old Coach Road which is an intermediate reservoir for the greater new water supply project for Akaroa.

Excavating pole retaining wall foundations with augurNow the work involved, first the geotechnical investigations to determine the strength of the existing ground and soils was carried out and an engineer’s design for suitable retaining walls for the terrain were provided. Truline set about constructing the walls which involved auger excavations for the poles to between 3 m and 6 m in depth. The poles were set to the correct alignment and angle and then concreted into place. Followed by the balance of construction of the whalers and the horizontal components of the retaining wall. All done to an aesthetically pleasing finish in compliance with the engineer’s design.

Checking the depth of the foundation excavationTwo walls were constructed, one was significantly larger than the other. One was to construct a retaining infill and the other was to retain an existing slope. We had to cut away a flat area into the existing slope and then had to retain the slope to prevent it from slipping into the new structure. This involved subsoil drainage, so we had to place a subsoil draining pipe at the base of the retaining wall and behind it. The pipe was placed within geotechnical filter cloth and drainage aggregate to prevent any surcharge of the wall due to groundwater migration. 

Akaroa Reticulation project retaining wall slideshow

>> Click to view the retaining wall  slideshow >>

Slideshow controls: [1] Double-click to "pause" any slide, [2] Double click to "play"/continue the show. [3] Jump to any slide in the show by clicking on the relevant thumbnail. [4] To escape at any time click "x" top right.

Contact us

TruLine Civil is determined to incrementally improve the service we deliver our clients, and the quality and range of civil engineering services that we offer to owners and stakeholders who expect excellence.

Excellence in Infrastructure.

TruLine Civil.

Interested in our services? You can contact us +64 (21) 228-5090 and ask for Geoff Powell or e-mail me at 

Christchurch Address 

Greywacke Road extension,
New Zealand 

Credits: Photos and case study documentation by Shaun G. Waugh



Click thumbnail for larger image

Akaroa Pole Retaining Walls

Our Difference

  • Award Winning
  • ISO 9001 Certification
  • NZTA Prequalified
  • ACC Tertiary Level
  • Family Company

Learn more ...