Environmental design: Infrastructure choices for sensitive areas of Aotearoa
April 03, 2025
From walking paths to water supply, the land can be an infrastructure project¡¯s biggest hurdle. Designing for sensitive environments is key.
How do you build crucial infrastructure in a sensitive location? In New Zealand, it¡¯s a special challenge. We are geographically unique, from our exposure to natural disasters to our treasured native ecology. From transport to water supply, getting major projects off the ground often means fitting complex designs into challenging sites.
Striking the right balance requires a sustainable approach to our infrastructure.
Wellington Water¡¯s new Kaitoke Network Arch Bridge is a great example. The 52-metre-long structure conveys around half of the region¡¯s raw water supply with the seismic resilience to withstand a major earthquake. Sitting on the meeting point of two tectonic plates, ; three major fault lines run through the region. But the complexity doesn¡¯t stop there. The bridge also stands among native kauri, a threatened tree species and one of the longest-living in the world. This dual focus guided the project¡¯s success.
The new Kaitoke Network Arch Bridge is nestled into the park as it conveys 140 million litres of the Wellington Region¡¯s drinking water every day.
Protecting the pristine Kaitoke Regional Park through environmental monitoring was as crucial as the new bridge¡¯s resilience. Water is a precious resource, especially in a state of emergency. Every day, the pipe under the bridge carries over 140 million litres of?water from the river. It helps support the peak of 280 million litres of drinking water consumed in the Wellington region daily.
Before replacement, the original flume bridge was more than 60 years old; and it lacked seismic resilience. Since the leaky concrete structure couldn¡¯t serve its community in case of a large earthquake, our job was to replace it with an design that worked with the environment.
Even smaller infrastructure projects can be in difficult places and present unique challenges. For example, consider the Stocking Stream Toilets in the Aoraki Mount Cook National Park. In January 2019, the number of visitors walking the Hooker Valley Track had increased by 20 percent from the previous year, for the first time. Finding an environmental design solution was critical for the track. Traditional long-drop toilets weren¡¯t appropriate as the terrain was too rocky and waste disposal into the ground wasn¡¯t culturally acceptable. Faced with a lack of road access, we helped the Department of Conservation to think beyond traditional approaches.?
The Stocking Stream Toilets in the Aoraki Mount Cook National Park. Waste is removed via helicopter. The structure¡¯s precast concrete panels match the surrounding alpine boulders.
The Stocking Stream Toilets are bespoke in function and form. Waste gets removed in drums via helicopter and treated offsite; with minimal effort, empty drums take their place. Visually, the structure¡¯s precast concrete panels match the surrounding alpine boulders, even allowing for the growth of lichen and moss to help them blend in further.
An environmental design approach should be carried through construction. At Kaitoke Regional Park, site access proved challenging via the narrow road. For construction, we had to navigate a 96-foot tower crane to the site. A 1,000-year-old kauri tree inhibited entry. And the original plan from the contractors was to cut it down. Instead, our team completed early assessments to show that traffic could get past the tree, allowing it to remain.
Saving this ancient tree represents a common engineering dilemma: the tension between preservation and new development. For Kaitoke, we had to put in the time to make our environmental design work. And we had to find a way around the issue when it didn¡¯t. Sensitive environments often require innovative solutions, not the easy way out.
Saving this ancient tree represents a common engineering dilemma: the tension between preservation and new development.
¡°Remote¡± work within the city
Another thriving project on difficult terrain is Auckland Transport¡¯s Te Ara Ki Uta Ki Tai¡ªThe Path of Land and Sea. This 7-kilometre shared path spans from Glen Innes to the Auckland waterfront, a previously missing link for cyclists. The project comprises three sections, each presenting environmental design challenges from space to topography. Not least was archaeology, with 10 sites significant to mana whenua along the path. Where we couldn¡¯t avoid these areas, the team used construction fencing and archaeological monitoring to help protect the land.
Mana whenua helped guide the project¡¯s environmental design framework. It¡¯s led by the principles of kaitiakitanga, meaning guardianship and a reciprocal relationship with the natural world.
Te Ara Ki Uta Ki Tai¡ªThe Path of Land and Sea takes walkers and cyclists to the Auckland waterfront.
Despite falling within Auckland city, the site was often remote with lots of vegetation; even access on foot proved difficult. Like the Stocking Stream Toilets, we used a helicopter to deliver equipment for the geotechnical investigation. The resulting shared path is an elegant solution that encourages active modes. Section 2 unveils views through the Purewa Valley to the city that were previously hidden.
Te Ara Ki Uta Ki Tai¡ªThe Path of Land and Sea¡¯s environmental design, like its name, celebrates the route¡¯s heritage. It respects the natural shape of the land, settling the pathway and its users into the surroundings.
Balancing the new and the natural
Aotearoa is filled with native plant life and cultural history. And many of our projects are built in remote locations with geological hazards.
Though the natural world can present a series of obstacles, there are solutions. Resilient pipe bridges. Innovative alpine toilets. Ecological cycleways. Each of them shows us why a sensitive approach is necessary. The power is in designing sustainable infrastructure that lives in harmony with the land for generations to come.
The goal of the Kaitoke Flume Bridge project is to future-proof Wellington¡¯s raw water supply. It is designed to withstand a major earthquake.