"But ongoing maintenance is really important to keep the tunnel operating safely and efficiently."
The maintenance will involve checking and testing electronic equipment - such as smoke detectors, fire hydrants and deluge systems - and is required as part of the manufacturer's guarantees and the building code, Gliddon said.
Similar maintenance closures happen in the Victoria Park Tunnel and the Johnstones Hill Tunnels on the Orewa to Puhoi toll road north of Auckland.
