North Ring Stormwater Network
Eighteen kilometres of trunk drainage under established suburbs, sized for a storm the city had only seen twice.
The challenge
The alignment ran under settled residential districts with no as-built records worth trusting. Every metre of trench risked striking a live service that appeared on no drawing, and the design depth reached eleven metres in places.
Our approach
We surveyed the whole alignment with ground-penetrating radar and vacuum-excavated 340 trial holes before a single machine dug in anger. It added seven weeks at the front and saved considerably more than that in strikes that never happened.
Where cover allowed we used microtunnelling instead of open cut, which kept 4.2 kilometres of residential street open that would otherwise have been trenched, and removed the deepest sections from the confined-space risk register entirely.
The outcome
Completed with two recorded service strikes across eighteen kilometres, both on unmapped private connections. The network took its first hundred-year storm in November 2022 without surcharging.
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