Markets, Sliplining, Wastewater

Sliplining rescue in regional VIC

Several options were considered when it came to renewing a 9.9 m deep sewer manhole in the Victorian town of Echuca.

Alternatives evaluated by Coliban Water included coating with calcium aluminate cement or epoxy, internally rebuilding with new reinforcements, or installation of of structural liner. The condition of the manhole meant that some of these were rejected as being structurally risky, while others presented unacceptable dangers to the installers.

Initial inspection showed that while the lower half of the manhole was in reasonable condition, the top half was severely deteriorated, with the acid attacked concrete being in a “÷crumbling’ condition. The internal dropper that originally connected to a rising main at 1.5 m from the top of the manhole had corroded away, which meant raw sewage was now splashing onto the manhole wall and was accelerating the deterioration.

Interflow’s proposal to slip line the manhole with a length of steel-reinforced polyethylene liner grouted in position was considered as the best solution. Though this type of pipe is typically used to structurally line large diameter sewers, its properties made it adaptable for this application.

  • The steel reinforcement encased in the ribbed polyethylene provided sufficient strength for the liner to be considered as structural renewal.
  • Polyethylene is inert in sewer conditions and has high abrasion resistance.
  • Polyethylene has the strain capability to handle any ground movement.
  • The liner could be installed with minimal man-entry.
  • The liner could be installed in a single length, without joints.

Installation of the liner meant that no surface preparation was required inside the manhole. The only man-entry required was to take measurements at 1 m intervals inside the shaft to confirm the diameter of liner that could suitably fit.

Following the initial preparation, installation of the liner and filling of the annulus took no more than three days – a small fraction of the time that other options would have taken and with far greater safety.

The top of the manhole was then replaced, with the top slab poured and the lid re-fitted. A strong, corrosion and abrasion resistant manhole, with the flexibility to handle ground movement had been provided by a safe, minimally disruptive process.

Coliban Water’s Manager Infrastructure Delivery Corey Bourne said that working with Interflow on solutions for this project allowed for the delivery of a less intrusive process, which also reduced the overall project timeline.

“This method was not only less intrusive to our asset infrastructure but saved time to conventional methods, allowing the project to be delivered in a shorter overall timeframe than first anticipated.

“There was also a reduction in risk to staff, with no confined space entry required for construction. We are always looking to improve the way we do things when it comes to safety,” Mr Bourne said.

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