This is the type of connection we love to make!


Over the last few weeks, we have been working on the connection for a new 450OD rising main in Bowen St, Wellington CBD on behalf of @Wellington Water. The connection is approximately 6m deep from a new 2.55m diameter shaft into Wellington’s main intercepting sewer – a hand tunneled structure from the 1930’s.

This job has been a long time in the making; part of an ECI with Stantec. Careful planning was required to work around 90-year-old critical infrastructure. Protecting the existing asset was at the heart of the design and construction methodology.


The existing tunnel was located remotely using sonde and survey. A small diameter hole was drilled from the surface to confirm the position. The shaft was sunk as a caisson using hydro-excavation. And the connection was drilled and excavated by hand. A core sample from the existing structure was crushed and returned a result of 44MPa – the structure looked like it was in good condition considering its age.


Thanks to Hydrotech, Admason Shaw, Prodrill, Hynds, JB Environmental, Allcutt and Matts for the assist on this one.


#caisson #undergroundinfrastructure