Taupō sewer line to provide for growth in southern suburbs

Taupō District Council project manager Peter van Niekerk explains how the new sewer main will be inserted under Lake Terrace. Photo / Dan Hutchinson

For some people, everybody’s business is their business.

It may not be glamorous, but contractors and council staff are pushing hard to get the new sewer line underground along the length of Lake Terrace in Taupō and hope to have most of the work on the road done by the end of the month.

The new pipe is an addition to the existing sewerage network and would provide the infrastructure vital to future residential growth at the southern end of Taupō.

Taupō District Council project manager Peter van Niekerk took the time to explain how the massive project was being done, and why they don’t need to dig up the whole road to put the new pipe in place.

The new 400mm pipe is being installed from just north of Maunganamu Drive, along Lake Terrace to Kaimanawa Reserve where it connects to the rest of the sewerage network.

Van Niekerk said it might appear the project was taking some time to complete because the road had not been dug up yet, but in fact the pipe was being tunnelled under the road, with most of the work taking place out of sight.

Work is done on the new sewer line at the corner of Lake Terrace and Taharepa Rd in Taupō.

The route is mapped out in advance and the path of the drill is guided by a person with a unit that can detect the drill tip and provide directions to another person who guides the drill using two joysticks.

He said they could guide the drill for about 1km using this process.

“This guy places this unit and picks up the end of the drill tip and says go left or right or down a degree or up a degree and this just keeps the drill in line to where it needs to go to.”

Once a small tunnel has been drilled, a larger drill is then inserted until the required width is achieved - in this case 500mm, or 100mm larger than the pipe to be installed.

“We have hit one stormwater pipe but nobody knew about it. It was a small one, a 50mm, other than that we haven’t hit anything along this whole waterfront – yet.”

Sections of the pipe are high grade aquatherm pipe that can withstand the extra heat from geothermal activity, with hot water found at the corner of Mere St and Lake Terrace, at Tremaine Ave, and some near Shepherd Rd. That was expected.

Nadia Whyte of Fulton Hogan and Peter van Niekerk of Taupō District Council, with the new sewer line to be inserted under Lake Terrace.

“Sometimes in the morning when you drive down there you see steam coming out of the catchments.”

The pipes are pulled through along with a layer of “drill mud” which encases the pipe and sets as hard as concrete.

One of the advantages of drilling the hole, rather than excavating a trench, was the pumice soil did not have to be compacted afterwards, left to settle and then compacted again.

Old water mains were being replaced at the same time to prevent a repeat of the water main blowout on Lake Terrace in July 2019 which washed out a section of sewer main, sending 800,000 cubic metres of waste into Lake Taupō.

A council spokesperson said the new sewer line was being installed along Lake Terrace because it was the lowest point. Having it further uphill meant sewage would need to be pumped uphill, which was far more expensive and required more pump stations, which meant more risk of something going wrong.

Niekerk said most of the work along Lake Terrace would be completed by the end of the month, although the pump stations at either end of the new pipe would take longer to commission, but would be ready early next year.

The larger pump station at the end of Kara Place would be landscaped or painted with murals to hide the visible structures on the surface, which would be the top of a concrete bunker and the pump shed.

He said the road surface would look a little patchy once finished, but Lake Terrace was due to be resealed.

The council spokesperson said they wanted to ensure they catered for future growth before it happened, rather than waiting for thousands of new houses to be built.

“It is about future-proofing this place and then we have got all the services in, new road surface and that is basically our front yard done.”

Niekerk said the project was scheduled to finish in December but due to the discovery of unknown services, issues with drilling, design changes and other unforeseen things, the end date had shifted out to the end of January. However, the pipe would be installed and most of the machines off the road by the end of this month.