The Waterview Tunnel is one of the most ambitious construction projects undertaken in Auckland. Connecting Mt. Roskill with Point Chevalier, the 2.4m tunnel has revolutionised transport in Auckland, and is the longest tunnel in New Zealand.
Unsurprisingly, a tunnel of this size requires a customised and reliable drainage system. To achieve this, Fletcher Construction and McDonnell-Dowell turned to Humes, who came up with an innovative solution that added value and saved money.
In addition to the standard concrete pipes and custom box culverts supplied by Humes, there were some specialised requirements for the tunnel that required Humes to think outside the box. This included a customised, fireproof cesspit that would be constantly filled with water and could not leak to the rest of the tunnel’s sewage system due to the highly flammable run-off from cars using the tunnel. This complex requirement posed a challenge to the Humes team, who realised the initial design brief was unachievable. Working collaboratively with the contractors, Humes designed a new system that was not only simple and easy to install, but cut 70% from the initial anticipated costs. Humes also designed a concrete pipe Y-junction for the tunnel – an uncommon product that avoided the need for manholes, and met the unique requirements of the tunnel.
“Normally a cess pit is a one-piece unit so making a system with such a large capacity was a challenge” says Steffan Roberson, Humes Concrete Product Design Manager. In the end we designed a system with custom openings to meet catchment requirements that ran all the way under the tunnel.”
“Each section of the system had larger openings to handle larger capacity, so we also had to ensure that each section was structurally sound”.
Humes also had to work hard to ensure that the logistics of the project were effectively managed. The size of the tunnel meant that large amounts of pipe had to be delivered to the construction site every day, requiring careful management of manufacturing and lead times to meet deadline and ensure that the contractors had what they need, when they needed it.
Humes Toasts the Tunnel
The unique solutions provided by Humes mean that the Waterview Tunnel is equipped with a unique, fit for purpose drainage system that can handle adverse weather conditions and the heavy traffic passing through the tunnel each day. Being involved with such a defining project right from the start was a special experience for the Humes team, who are proud of helping to make a difference in Auckland. As a reward, the project team was present at the ‘Toast the Tunnel’ opening, where they were among the first to enter the completed tunnel, and witness the fruits of their hard work.