New $116m tunnel and outfall officially opens on Monday

History will be made for North Shore City’s on Monday, 16 August when a short ceremony will be held by North shore City Council to officially open the Rosedale Tunnel and Outfall.

The $116million development, North Shore’s largest ever capital project, replaces a pipeline built in 1958 which carries treated effluent from the Rosedale Wastewater Treatment Plant to a discharge point 600m offshore from Castor Bay.

The new tunnel and outfall carries the highly treated effluent much further out to sea – from the treatment plant to Mairangi Bay along a 3km underground tunnel, and then a further 2.1km offshore through an outfall pipeline where it is dispersed deep in the Rangitoto Channel.

The completed project is part of North Shore City Council’s ongoing commitment to protect and improve the quality of our beaches. The new tunnel and outfall has a life span of at least 100 years and will effectively cater for the city’s continued growth.

The project was completed by North Shore City Council in partnership with McConnell Dowell, AECOM, Aurecon, LOVAT and Wilson Precast Tunnelling.

North Shore City’s Council General Manager Infrastructure Services, Geoff Mason says that the strong partnering relationships established between North shore City Council and its contractors have resulted in the successful completion of a world class outfall.

“These strong partnerships have allowed all parties to play a proactive role in achieving innovative and effective solutions throughout the project.”

Mr Mason says that a significant achievement of this project was the mitigation of disruption for local residents. “There were times when residents were aware of the project, but on the whole, the underground tunnelling, from Atlas Place to Mairangi Bay, was a minimum of 25 metres below the surface, resulting in minimum disruptions for the community.

He says that the council would like to thank local residents, and the citizens of the wider North Shore, for their patience, and for their ongoing interest and support.

The Rosedale Tunnel and Outfall will be officially opened by His Worship the Mayor of North Shore City Council, Mr Andrew Williams. The ceremony will be held on Monday, 16 August from 2pm on the foreshore of Mairangi Bay (corner of Montrose Terrace and Sidmouth Street). All local residents are invited to attend.

Memorial seats will be installed in Mairangi Bay to mark the route of the tunnel. These seats were designed by North Shore artist Phil Bonham, and constructed using concrete segments similar to those used to line the tunnel.