The 1350mm diameter reinforced concrete pipeline left a hole some 6 metres deep. The collapse was in the footpath forming part of a popular riverside walk in the Geelong suburb of Belmont.

Quick work by Barwon Water prevented further catastrophe, and alleviated the danger of the pipeline overflowing and pouring raw sewage into the Barwon River.

Within weeks, Interflow had installed a structural Rotaloc liner in the deteriorated section of pipe. It was possible to wind the liner through the collapsed section of pipe, but only after the delicate process of debris removal, and close co-ordination with Barwon Water in relation to flow control.

CCTV inspection revealed that structural rehabilitation of other sections of this sewer was advisable. So in 2003, an additional 2,128 metres of 1350mm nominal diameter main was lined with Rotaloc.

The project involved all the difficulties typically associated with rehabilitation of a critical, large diameter sewer main in a built up environment.

While the invert of the pipeline was in reasonable condition, there was severe gas attack above the springline. Aggregate in the concrete pipeline was fully exposed and in some places, steel reinforcement had been lost.

The silt level in the pipeline was typically between 20% and 30%. Cleaning was made more difficult and dangerous as the silt contained needle sharp slivers of steel from the deteriorated reinforcement.

As with the previously completed emergency works, flow control needed to be co-ordinated with Barwon Water. Work in the pipeline could only be carried out during the low flow period of 10pm to 6am. A system of drop boards was used, and flow was stored and released at intervals during this working period. Despite the flow control measures, nothing that could be done about incoming flows from sewers connecting laterally. Thus lining was always carried out with some flow in the pipeline.

As the Rotaloc process can alter the diameter of the liner during installation, the installed liner was given the maximum diameter that the size and shape of the deteriorated pipeline would allow. The diameter altered to allow the liner to contact the wall of the host pipe, as far as was possible given
its shape.

After installation of the liner, cementitious grout was injected behind the liner to fill substantial voids in the deteriorated host pipe.

The project demonstrated that these difficulties could be overcome and a structural, circular line could be installed in a severely deteriorated, irregularly shaped pipeline.

Back to ROTALOC CASE STUDIES