From the magazine

Trenchless in the sunshine state

The area of Cairns is often characterised by the slogan “÷adventurous by nature’, a fitting description for the area’s natural attributes and key attractions which include snorkelling in the Great Barrier Reef and white water rafting along the region’s rainforest creeks and rivers, just to name a few.

While the natural environment attracts thousands of tourists to the region every year, the use of Trenchless Technology to maintain the area’s underground infrastructure for tourists and residents alike is growing according to Cairns Regional Council’s (CRC) Senior Project Manager Peter Thoren.

“Currently, the Council’s Water and Waste Infrastructure branch is the primary user of trenchless technologies, which are being implemented to install new gravity and rising sewer mains as well as watermains,” Mr Thoren said.

In choosing to adopt Trenchless Technology, Mr Thoren said the CRC needed to look outside of Council walls for the specific expertise required when applying trenchless methods.

“It is a very specialised area and we work with sub-contractors who have the relevant experience and knowledge for each individual project,” he said.

“We use local contractors when we can, but given the specialised nature of the work, we do need to look outside the Cairns area at times.”

Mr Thoren has been the Senior Project Manager at the CRC for four years now, a position he says involves a daily co-ordination of multiple projects simultaneously within the bustling Council.

Mr Thoren said in a region as diverse as Cairns, and in respect to its growing population and delicate coastal environment. “A rapidly growing population combined with Cairns sensitive environmental conditions is currently the greatest challenge facing our region from a Council’s perspective,” Mr Thoren said.

“We all have things going on in the same place so co-ordination within the council and with our contractors is critical, and we also want to achieve “÷value for money’ outcomes for our residents, now and in the future,” he said.

Upgrading assets

The Cairns Region is made up of a diverse range of infrastructure assets that the CRC regularly maintains, including just over 580 km of stormwater pipes, 176 km of stormwater open drain pipes, 2,105 km of watermains and 1,083 km of wastewater mains.

Mr Thoren said major upgrades are currently underway to Cairns’ sewer infrastructure to meet present and future demands, which includes making way for an increased demand of drinking water supplies, options for which are currently being investigated and considered.

With any provision and maintenance of water and wastewater infrastructure there are often challenges.

Mr Thoren said the location of Cairns’ assets were primarily underground, posing the biggest obstacles for the organisation.

“When dealing with a predominantly underground group of assets, unlike, for example, a road where an issue can be visually and quickly identified, underground assets usually require engaging specialty consultants or equipment in order to view them and to determine if there may be a problem,” Mr Thoren said.

The Council currently has a Core Asset Management Plan in place that covers the long-term planning for the underground asset class.

It maps out the replacement requirements of assets based on their age and works identified in the Council’s capital works program.

As part of the plan the Council has a ten-year capital works program for installing, replacing and upgrading underground assets, which has been formulated from both external and internal investigations.

In addition, every five years Council undertakes a comprehensive inspection and revaluation of the drainage assets which involves physical inspections of the asset.

These programs allow for the CRC to generate plans for sewer relining, manhole refurbishment, customer meter replacement and watermain replacement programs annually.

Preferred technologies

The CRC’s application of trenchless methods across several major infrastructure projects has predominantly used pipe bursting as the primary trenchless technique.

The Council has also applied directional drilling techniques in order to use a steerable head to drive and align the pipe, in addition to pipe jacking and the application of earth pressure balance tunnelling machines.

CRC’s current water and wastewater infrastructure projects are all using at least one of these trenchless methods.

Mr Thoren said the CRC’s selection of specific trenchless techniques was dependent on each project and that an external consultant would provide advice on the technology selection.

“With input from our design consultant and access to a specialist technological consultant external of the Council, we’ve been able to move away from trenched solutions,” he said.

“We’re always open to new methods and ideas, and at present we are gearing up for delivery of long directional drill projects throughout the Cairns City area that will need to take into account traffic, businesses and pedestrian access and public safety, however, the impact is going to be minimal compared to what we would have been facing with a trenched project,” Mr Thoren said.

One thing’s for certain, the forecast in Cairns will continue to be bright as the region advances through the CRC’s adoption of trenchless techniques.

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