7 Jun 2018

The big dig is under way as portside trenching work gears up for the construction of submarine pipelines to carry wastewater from Governors Bay and Diamond Harbour to Lyttelton.

The work is part of a four-stage $53 million scheme aimed at ending the routine discharge of treated wastewater into Lyttelton Harbour by 2021.

All treated wastewater discharges from the Lyttelton Harbour Basin will go to the Christrchurch Wastewater Treatment Plant in Bexley.

The five-kilometre-long Governors Bay pipeline is expected to be completed by the end of 2018, while the 1.8km-long Diamond Harbour pipeline is due to be finished in early 2019.

Work is under way in Lyttelton on the wastewater pipelines project.

Work is under way in Lyttelton on the wastewater submarine pipelines project.

Trenching along Norwich Quay and Godley Quay to lay the wastewater pipe will continue for the next month, eventually connecting the treatment plant at Cashin Quay to a new pump station at Simeon Quay in Lyttelton.

To date, 500 metres of pipe have been laid in Norwich Quay and 150m in Godley Quay.

In tandem with the project, there will be a series of one-lane Lyttelton Tunnel closures at night in June, July, August and September.

Christchurch City Council Head of Three Waters and Waste John Mackie says the work at the tunnel roundabout will allow for the laying of wastewater pipes at the tunnel mouth.

“The first single-lane tunnel closure will be on the evening of Sunday, 10 June,” Mr Mackie says.

“We ask motorists to allow for delays in their travel time if they are planning on using the tunnel during the one-way closures. A schedule of closure dates will be available on the Council website.”

The lane closures will be from 9pm to 5.30am in June.

Preparation work for the Governors Bay submarine pipeline will start this month at Naval Point.

The pipe will be buried a metre below the seabed. It will be weighed down with concrete ballast blocks that are secured every 5.75m, with each block weighing 180 kilograms.

“The new wastewater pipe is being welded into eight 625m strings along the foreshore at Naval Point,” Mr Mackie says.

“These strings will be connected as they enter the water via a launch way to be built on the Naval Point breakwater.

“The pipe will be pulled into place by a winch, with the anchor point installed near Jetty Road.

“Both areas will be fenced and signposted.”

A 200m exclusion zone will be enforced around a work barge.

The work is expected to take about six months.