drainage

Effective drainage is essential for the longevity and safety of any civil works – and it’s something we do exceptionally well. TWC combines technical expertise with practical experience to deliver compliant, high-performance drainage solutions, from stormwater and wastewater networks to complex multi-staged installs. Our crews understand the importance of getting levels, falls, and flow right the first time – saving time, reducing risk, and keeping programmes on track.

drainage

Effective drainage is essential for the longevity and safety of any civil works – and it’s something we do exceptionally well. TWC combines technical expertise with practical experience to deliver compliant, high-performance drainage solutions, from stormwater and wastewater networks to complex multi-staged installs. Our crews understand the importance of getting levels, falls, and flow right the first time – saving time, reducing risk, and keeping programmes on track.

Construction worker standing inside a deep excavation, with trench shield walls around.
Construction worker standing inside a deep excavation, with trench shield walls around.
Construction worker standing inside a deep excavation next to a large concrete drainage structure, with trench shield walls around.
Construction worker standing inside a deep excavation next to a large concrete drainage structure, with trench shield walls around.
Construction site featuring a yellow CAT excavator and a large concrete sumps in the foreground, with workers in orange safety vests and helmets, around a deep excavation. Residential houses, trees, and a car are visible in the background under a clo
Construction workers operating an orange excavator on a hillside, clearing dirt on a rural road, with a traffic cone in the foreground and green hills in the background.
Construction workers operating excavation equipment near a body of water, with orange cones and safety barriers, as they work on laying or repairing underground utilities.
Construction workers installing a large concrete culvert pipe in a hillside on a construction site.
Construction site with deep excavation, an orange excavator, temporary concrete barriers, and safety fencing near a busy road.
Official logo of NZ Transport Agency featuring a stylized green and blue emblem and blue text.

“I am really happy to say that the final product that we anticipated was perfectly achieved.”

— Stormwater Delivery Manager, New Zealand Transport Agency

Gross pollutant traps (GPTs)

Construction worker in orange safety jacket and white helmet shoveling dirt at a construction site with deep excavated walls and marked measurements on the ground - the initial works for a Gross Pollutant Trap.

TWC has developed specialist capability in the design, modification, and installation of gross pollutant traps (GPTs) across Auckland’s transport and stormwater networks. Our team works with leading suppliers like Hynds and Stormwater360 to deliver custom-built solutions that remove sediment, debris, and pollutants from stormwater flows before they reach sensitive waterways. From large bespoke chambers installed in constrained urban environments to retrofitted systems that enhance existing infrastructure, we bring hands-on experience and technical know-how to every project.

Construction worker in safety gear working on a Gross Pollutant Trap installation, including large concrete panels and reinforcing steel bars.

Our work in this space is backed by practical innovation, tight construction management, and a collaborative design approach. We’ve successfully delivered GPT installations under live traffic conditions, around critical services, and in highly space-constrained locations – all while meeting council expectations around maintainability, environmental compliance, and safety. As a result, TWC has become a trusted delivery partner for councils and consultants seeking effective stormwater treatment at scale.

Construction worker in safety gear working on a Gross Pollutant Trap installation, including large concrete panels, deep excavated walls, reinforcing steel bars and wooden formwork around.