Horizontal directional drilling, Pipelines, Sewer, Trenchless technology

Townsville turns to trenchless for sewer upgrade

Townsville Council is employing innovative technology to undertake a major upgrade on underground sewer pipes in the suburbs of North Ward and Belgian Gardens.

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Tracking the drill head through a newly built roundabout, which would have to have been excavated using a trenching construction method.

The sewer infrastructure in Townsville is being upgraded to support existing and future population growth in North Ward and Belgian Gardens.

The installation of approximately two kilometres of sewer pipeline from the pump station at Howitt Street will provide an additional link that will connect the Belgian Gardens and North Ward sewer network with upgraded facilities in Leichhardt Street (part of the CBD Utilities Upgrade Project).

The $1.5 million project is using trenchless construction technologies to lay lengths of pipe to minimise the impact on residents and motorists in the busy suburb.

The pipe will be laid along Isley and Mitchell Streets, connecting the Belgian Gardens and North Ward sewer network with upgraded facilities in Leichhardt Street.

Townsville Water and Waste Committee Chairman Cr Paul Jacob said the use of trenchless technology would ensure minimal disruption to the road network, which was especially important given the area’s popularity as a thoroughfare for The Strand.

“By using an advanced drilling process to tunnel an underground passage for the pipe, we won’t need to excavate large sections of the road, verge or footpath,” Cr Jacob said.

“Instead, the pipe is fed through entry and exit pits spaced 100-300 metres apart, meaning the surface stays intact. It also means we can install the pipe below other existing services without any disruption to those services.”

A bentonite mix recycling plant, used to recapture the large volume of fluid injected while drilling through rock material.

A bentonite mix recycling plant, used to recapture the large volume of fluid injected while drilling through rock material.

The benefits of trenchless

Currently, approximately 50 per cent of the 2km pipeline installation has been completed. Drilling through variable ground conditions (sand, mixed ground and sandstone) in a single bore length has proved to be challenging, and has slowed down the speed of the pipe installation somewhat.

According to a Townsville Council spokesperson, drilling in the tight space between service crossings worked well, highlighting the benefits of utilising a trenchless technology.

By using trenchless technology, the council has also been able to install some sections of the pipeline approximately five metres below the surface, avoiding existing buried assets.

There were a number of reasons why trenchless appealed to Townsville Council. Given that the installation needed to take place in a built-up suburb with a number of busy road intersections and roundabouts, and with a number of underground services crossings, a trenchless methodology quickly emerged as the only feasible solution.

When these factors were combined with the high impact on traffic and the environment, and the restoration costs associated with a conventional trenching method, the case for a trenchless solution was further enhanced.

The potentially shorter construction duration that comes with trenchless technology was another factor that appealed to council.

Directional drilling in progress

Directional drilling in progress

Infrastructure for a growing population

Divisional Councillor Ann-Maree Greaney said the new 315mm diameter pipe would substantially increase the capacity of the sewerage system to meet the demands of a growing population.

“The duplication of the sewer network in Belgian Gardens and North Ward will increase its capacity, which is important in suburbs with medium density buildings,” Cr Greaney said.

“The new sewer pipeline will also reduce the risk of failures and environmental issues that can be associated with older infrastructure.”

Construction started in early March this year, and is anticipated to take six months. Works will be staged with installation of the pipeline currently underway in Mitchell Street, between Howitt and Landsborough Street.

Safety fencing, signage and traffic control will be in place during construction to keep residents and motorists safe.

Several temporary laydown areas for storing pipe will be created in the work area.

With the project expected to be completed by early September, council is now considering other projects on which they can utilise trenchless technologies.

According to a council spokesperson, on projects in heavily built-up areas, and which feature a number of road, rail or waterway crossings, trenchless technologies will be the obvious choice moving forward.

 

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