Before the floods hit
On one particular project, prior rehabilitation works helped to protect the Brisbane Convention and Exhibition Centre (BCEC) – the venue for No-Dig Down Under 2011 – from significant flood damage.
The BCEC was affected by the floods, but fortunately, thanks to previous sewer rehabilitation works carried out in late 2010, the impact was significantly minimised.
In 2010, Insituform was contracted to reline a 700 mm sewer main running beneath Grey Street, adjacent to the BCEC. A contractor had accidentally piled through the sewer and as a result, a 1 m length of pipe was completely destroyed, causing the entire 55 m length of pipe to become half full of debris when the surrounding ground fell into the gaping hole in the side of the main.
Insituform installed its trusted tight-fit structural cured-in-place-pipe (CIPP) liner to renew the pipe and prevent further debris from falling into the pipe, which was resulting in significant ground subsidence.
The site set-up was challenging, as Grey Street is the main street in the bustling South Bank precinct. One of the maintenance holes was in the middle of the street, in front of the Queensland Performing Arts Centre, as well as the busy South Brisbane railway station, popular with city commuters.
A carefully thought-out flow bypass was established by Insituform, as it ran directly in front of the railway station. This required extensive pedestrian management, barricading and ramps around the main entrances to the train station. One of Insituform’s specialist crews then moved onsite to complete the difficult task of carefully cleaning the pipe without bringing more soil into the pipe in the process. This was assisted by winching a thin stainless steel “÷shield’ into the pipe to cover the hole, in order to protect against further ground collapse.
The new liner was then installed directly over the thin shield using Insituform’s efficient air inversion/steam curing process. Once completed, the shield was barely visible under-the-liner, and the pipe was returned to as new condition. The project was successfully completed, with the client extremely satisfied with the technical expertise, excellent community relations and team work between Insituform and other parties on a restricted site.
As expected, the liner was not affected during the January floods and may have helped to avoid a much more critical public health issue had the unlined pipe failed during the flooding.
Post-flood rehabilitation
Since the floods, Insituform has also completed a number of trunk sewer rehabilitation projects in Brisbane.
These included the lining of three above- ground sewer mains that were showing signs of leakage and cracking. The physical location of these major conduits presented environmental concerns due to the sewer pipes being positioned over natural creeks and waterways.
The scope of works included the relining of a 160 m stretch of 525 mm diameter concrete pipe located at Inala, and two 600 mm diameter clay pipes located at Oldfield Road, Seventeen Mile Rocks, which were 44 and 78 m in length. External visual inspection of the concrete pipe at Inala showed leaking joints and evidence of exfiltration. The two 600 mm diameter pipes at Oldfield Road were both cracked and deteriorated.
Such was the damage that Insituform’s project team was concerned about the pipes breaking during the installation of the CIPP liners. Using an innovative yet simple method to support the pipes during lining, Insituform executed the relining of these above-ground sewers using its air inversion/steam cure technology to minimise pressures inside the pipe during installation.
The results of Insituform’s CIPP installations saw no further damage to the existing pipes. These above-ground sewers in Brisbane now have a new,
joint-free pipe within a pipe with no risk of further leakage or exfiltration into the environment.
Insituform achieved another company milestone last June, by installing its thickest liners in Australia in severely deteriorated pipes running beneath Norman Creek in East Brisbane.
The client was concerned about two 150 m long sections of 600 and 675 mm diameter parallel concrete pipes that passed under the creek between an area of bush and a busy industrial area. The challenge was to reline these critical trunk sewer mains, deteriorated from hydrogen sulphide gas attack, without causing too much disruption to the natural environment or business owners and residents. The 675 mm pipe had snaking bends and dips and a hole in the top of the pipe from the gas attack, causing infiltration under the creek.
Norman Creek flows from South Brisbane to East Brisbane before entering the Brisbane River. A pipe collapse or failure could have resulted in an environmental disaster.
Insituform accepted the challenge and one of its specialist lining crews was deployed to implement the strategy. The inversion maintenance hole was in the middle of a busy road in an industrial and residential area of Brisbane, near the Brisbane Cricket Ground.
Insituform would normally invert this size CIPP liner with air and cure it with steam. However, to meet the client’s design requirements, 25.5 mm and 28.5 mm thick liners had to be installed in the 600 and 675 mm diameter pipes respectively. Also, to help counteract the effects of significant infiltration, it was decided to invert the liners using water pressure and cure using hot water.
These successful projects not only demonstrate the versatility of CIPP lining, but they also show the important role that pipeline rehabilitation plays in reducing public health risks by reducing sewer overflows and leaks into the environment.