The brief
Traffic between two districts was squeezed onto a single ageing bridge, with pedestrians walking in the carriageway. The state roads agency, an example client, wanted a second crossing with room for people on foot.
Ground and water
Boreholes found soft clay over dense sand at 22 metres. We chose bored piles to the sand, cast inside temporary casings that also kept the creek water out.
The deck
Precast prestressed beams, made in a yard beside the site, let the deck go up quickly between floods. A continuous slab over the beams removed most of the joints that usually leak and wear.
People first
The 2.5 metre walkway sits behind a raised kerb and a steel barrier, with lighting on its own circuit and solar backup.
Checking
An independent check engineer reviewed the design. Load tests before opening matched our predicted deflections within a few millimetres.
