The $40 million project, which got underway in earnest in 2021, includes a roundabout on the Kāeo side of the river to improve traffic flow.
Police were notified of the possible leak at around 9:50am Monday.
The single-vehicle collision happened on Wednesday night.
Two helicopters equipped with monsoon buckets are on their way to a large scrub fire near Doubtless Bay in the Far North.
Police were called to the beach this morning after a man got into difficulty in the water.
Wastewater from four different sites ends up in the Hokianga Harbour, which is considered a taonga.
The Northland Rescue Helicopter winched her out of the swimming hole.
The driver of the car died on the way to the hospital.
One person is currently in a critical condition and the second in a serious condition.