The NZ Transport Agency says demolition of the old one-lane bridge on SH10 at Taipā is going according to plan and should be finished next month.
A new two-lane bridge has been built next to the old one, and while half of the new structure was opened to pedestrians and vehicles in February, the other half is being used for machinery and equipment in the demolition process.
"Demolishing a bridge is complex work, and the need to protect the marine environment has added an additional layer of complexity," NZTA senior manager project delivery Andrew Thackwray said.
"Each of the concrete spans cut out of the bridge is 15 metres long and weighs up to 16 tonnes. Spans are cut into four sections, lifted out on to the new bridge and then cut into a further three sections before being transported off-site."
The old pier has been removed, but the piles were sitting just below the water line at low tide. They would be cut down further so they were below the level of the river bed.
"This is why we insist there be no diving from the bridge or boats passing under the bridge. We will advise when the piles have been made safe and the ban can be lifted," Mr Thackwray said.
Meanwhile motorists were reminded that during work hours, traffic movements across the bridge would be controlled by temporary traffic lights or manual stop/go traffic managers.
"We ask motorists to follow the directions of the traffic managers and take extra care. We thank people for their patience and understanding while we complete the bridge construction," he added.