Waka Kotahi NZ Transport Agency had planned to add the top coating of the low noise asphalt to the motorway later this month, but ongoing supply chain disruptions have delayed some of the materials.
James Caygill, NZTA's director regional relationships, said the delay is due to a hold-up in getting one of the key ingredients for the top coat - epoxy resin - from the United States.
"We have recently become aware that Covid-related shipping problems have delayed us getting the epoxy here as planned," Caygill said.
"We are sorry about this delay, given the concerns of nearby residents."
He said the shipping delay is part of the Covid-19 supply chain disruptions being experienced world-wide.
The epoxy gives the low noise asphalt a significantly longer life and maintains its noise reducing powers for longer.
"We did have the option to use a low noise asphalt without epoxy, but this coating would only last for up to eight years instead of 30-plus years with epoxy," Caygill said.
"We know Redwood residents living closest to the motorway will be disappointed about this delay, but we hope they can see a short delay now will reap benefits longer term."
The remaining chip sealing work on the CNC has been postponed until the epoxy arrives.
At this stage, Caygill says the delay is likely to be a "month or two, into the New Year".
He said NZTA still hoped to complete all the low noise surfacing work for the entire motorway, from Cranford St to the Waimakariri Bridge, and along QEII Drive, between Main North Rd and the Innes Rd roundabout, by April next year.
