Base Ohakea Water Infrastructure Upgrade

Opened in 1939, Base Ohakea is the home of the Royal New Zealand Air Force (RNZAF). To address increasing operational demands on the base, upgrades to the existing infrastructure became essential. This included replacing the existing wastewater system and connecting the base to the new Manawatu District Council’s Wastewater Treatment plant in Fielding, as well as replacing the base’s existing bore for drinking water by connecting to the Council’s new potable water scheme in Sanson.

Our responsibilities included the installation of two new wastewater pump stations, including storage tanks, wet well and other chambers and mechanical fitout, along with a 5.5km rising main, gravity mains and fibre optic utility ducts, and final connections to the new district wastewater scheme.

We also installed the new potable water supply line, designed and installed chlorine and fluoride dosing systems, and built and installed a new equipment chamber and chemical dosing building as well as all utility ducts.

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Challenges and innovation

The success of the project had a lot to do with Seipp’s proven experience and methodologies. Our ability to adapt and innovate was also critical. Examples include:

Switching deep excavation methodologies when unexpected ground conditions in some areas made the proposed sheet piling unfeasible. In these areas we used a combination of proprietary shields and trench boxes which also saved significant time.  

Proposing the use of horizontal directional drilling (HDD) for as much of the 5.5km rising main as possible, which reduced the cost to the client as well as the installation time and had less impact on base operations.  

Changing the design for gravity mains from PE pipe to PVC, improving constructability in terms of alignment control, ease of trenched install, and better CCTV visibility.

Re-using contaminated material on site. This was removed separately and re-used as in-situ backfill, mitigating the considerable expense of transporting contaminated material off-site.

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A modern, fit-for-purpose solution

The project was delivered ahead of time and on budget, helping ensure Base Ohakea can continue to play a critical and increasingly important role in New Zealand’s defence network. Not only that, it was completed with minimal disruption to both the operation of the Base and the surrounding community.

The project has been nominated for the 2024 Minister of Defence Awards for Excellence to Industry. Seipp’s contribution to that success is reflected in this comment by the New Zealand Defence Force Project Construction Manager: “In my opinion (40 years in the construction industry) SEIPP is one of the very best contractors I have ever worked with.”

This modern upgrade to Base Ohakea’s water infrastructure demonstrates our ability to deliver innovative, cost-effective solutions with precision. By adapting to challenges and implementing smarter methodologies, we ensured seamless delivery with minimal disruption. This project reinforces our commitment to supporting New Zealand’s critical infrastructure, now and into the future.

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