Increasing construction costs, tighter regulatory expectations and the need to maintain essential public services mean asset owners can’t afford drawn-out programmes. Drawing on a decade working on major transport schemes in New Zealand - including the post-earthquake rebuild led by the Stronger Christchurch Infrastructure Rebuild Team (SCIRT), City Rail Link (CRL), and Ōtaki to North of Levin (O2NL) - Carwyn believes wastewater can borrow proven delivery discipline from large-scale transport.
Start sooner, finish sooner
“Infrastructure projects often have five years of construction but only one year of design,” he says. “If you can bring construction forward, you shorten the overall programme and reduce exposure to cost escalation.”
Traditionally, wastewater schemes have followed a largely sequential path involving business case, procurement of designers, concept and detailed design, tender, contractor appointment, then construction. That model works for smaller business-as-usual upgrades. On larger, more complex projects, however, it can waste valuable time.
Big transport projects take a different approach. Early works packages and quick wins are identified so construction teams can mobilise while other elements of detailed design continue in parallel. On O2NL and CRL, contractors were able to get boots on the ground before every drawing was complete, securing a construction season that would otherwise have been lost.
“The key is managing risk,” says Carwyn. “You leave yourself room to complete the design of later elements, but you don’t hold up the entire programme."
Strong design management
Accelerating delivery does not mean cutting corners. In fact, Carwyn argues that strong design management is what makes speed possible without compromising safety or quality.
“You can spend a lot of time chasing shadows in the design space,” he says. “You might feel like you’re making progress, but you’re heading towards a dead end.”
Good design management means identifying constraints, hazards, and contentious decisions early. It also means mapping stakeholders - operators, regulators, community groups - and bringing them into the conversation before designs are locked in. Overlooking a critical voice can lead to costly redesign and delay.
By making robust decisions early and aligning stakeholders around them, teams reduce rework and protect programme certainty.
“It’s about de-risking the design so construction can proceed with confidence,” he says.
Digital coordination and 4D thinking
Digital tools are central to this approach. Coordinated 3D models allow a diverse project team to understand instantly what is being proposed.
“A model advances the conversation quickly,” says Carwyn. “You can bring it up on screen, spin it around and explore options together."
Beyond visualisation, digital models support cost forecasting and carbon tracking as the design matures. They also provide a clearer route from design to construction, improving build accuracy and reducing waste.
Adding time as a fourth dimension further strengthens delivery. With 4D modelling, teams can visualise not just what will be built, but when. On live wastewater treatment sites, this is critical. Understanding how new assets interface with existing systems - and precisely where and when tie-ins occur - reduces the risk of service disruption.
“Imagine building a new system and discovering something critical is in the way. A well-developed digital model helps avoid those surprises.”
Applying transport discipline to water
Carwyn has already seen these principles applied in the water sector. Following the collapse of a major wastewater main in Auckland, WSP worked with construction teams to design and deliver repairs in parallel with on-site activity, significantly reducing the time required to restore service.
Alliance-style partnerships which are common in transport also play a role. When owner, designer and constructor operate as one team, focused on best-for-project outcomes, decision-making accelerates and temporary works can be integrated seamlessly into the overall plan.
Ultimately, speed is as much about people as process. High-performing teams with a shared vision and aligned goals are more likely to challenge inefficiencies and maintain momentum.
For wastewater treatment plants, the lesson is clear. By combining strong design management, digital coordination and disciplined programme control - hallmarks of major transport delivery - the sector can move faster, reduce risk and keep essential services running, without compromising on quality or safety.
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