The Roma to Brisbane Pipeline (RBP) was the first natural gas pipeline to be commissioned in Australia in 1969. The 440 km pipeline transports gas from the regional gas hub near Roma to markets in Brisbane and regional centres along the pipeline route. It consists of two looped pipelines, DN250 and DN400 and has an average daily throughput of 190 TJ of gas. The pipeline is both owned and operated by APA Group.

The cause

The period from July to December 2010 was the wettest on record for Queensland. By mid-December 2010, many rivers in Queensland were already at, or near, flood level as a result of the rains in the preceding weeks. Heavy rain in late December 2010, on top of the pre-existing wet conditions, resulted in exceptional flooding in many parts of central and southern Queensland.

The most destructive floods occurred during the second week of January 2011 in the southeast corner of Queensland. On 10 January 2011, a violent ‘inland tsunami’ struck Toowoomba causing landslides and washouts. The RBP, which runs down the Toowoomba escarpment at an acute angle, suffered exposure and damage at several sites.

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In particular, there was a significant washout of the DN400 pipeline approximately 200 m from the top of the Toowoomba range where the pipeline crosses under a dual railway line. Approximately 20 m further down the slope there was also a loss of containment on the DN250 pipeline caused by an excessive amount of stress placed on the pipeline during a landslide.

The response

Upon identifying the loss of containment, the mainline valves of the DN250 pipeline were immediately closed and alternative gas lines were put in place for the Toowoomba city delivery station. Temporary pipework and compressor modifications were completed to provide continuity of supply to meet contracted customer demand.

The repair

The first crew was then immediately mobilised to begin the process of stabilising the pipelines and locating the site of the defect. A gas detector provided the crew with a general location of the defect. The first challenge was to stabilise the DN400 pipeline, which was situated above the defect and was now the only functioning pipeline delivering gas to Brisbane. This involved placing concrete bags to build a support under the exposed pipeline.

Once the DN400 was stabilised, attention could turn to removing the land mass over the DN250 defect site. This area was extremely unstable and required continuous geotechnical assessment and particular work methods to avoid a further landslip. Once the land mass was removed the defect was located and inspected. It was determined that the defect and areas immediately upstream and downstream from the defect needed to be removed to ensure both damaged and weakened pipe was removed.

On 26 January 2011, the DN250 pipeline was blown down between Oakey and Withcott to enable a cold cut of the defect. Cold cutting is where the gas is excavated from the pipe before the cut is performed. A field bend was constructed for the new pipeline section, the section was aligned and welded. Once the weld’s integrity had been certified, the pipeline was purged and re-pressurised incrementally, and gas leak surveys were conducted down the escarpment each time the pressure was increased.

The pipe was then coated with double-sided wrap and trenches were remediated for both pipelines. The repair effort from cold cutting to re-pressurisation was completed in two days. Once repairs were complete, a restricted gas flow with a maximum operating pressure of 6,000 kPa was returned to the pipeline until further integrity tests were performed.

Operations personnel from Western Australia, Victoria and NSW all assisted Queensland teams in the response.

In February 2011, intelligent pigging was conducted and confirmed there were no further issues with the pipeline, and it was able to return to full pressure and service.

Challenges and successes

According to APA Operations Manager – Control Centre and Gas Contracts, Elizabeth Livingstone, ensuring sufficient resourcing and delivering enough gas to APA’s customers were significant challenges of the emergency response effort.

“It was the first time since I’ve worked with APA that we’ve had to curtail deliveries on the RBP so that was a new challenge,” said Ms Livingstone. Luckily the impact on customers was minimal.

Despite operating pressures in both the DN400 and DN250 pipelines being reduced while damage was being assessed, sufficient supply to meet customer demand was maintained during this time by reconfiguring a compressor and swapping some pipe-work over.

The widespread devastation made access to the site difficult, particularly in the initial stages of the response. The unstable landslip over the leak site meant the APA crew couldn’t get any machinery on the site because it risked causing further landslides. In addition, the exposed DN400 pipeline needed to be taken care of first, which required some time and effort to fix due to inaccessibility and landslide issues.

Another big challenge was making sure all staff were kept safe throughout the whole response effort, but due to thorough emergency preparation and training, the APA crew achieved its objective of zero lost time injuries.

“I am proud of how APA’s people responded to this and other similar situations,” said APA Managing Director and Chief Executive Officer, Mick McCormack.

“Their skills, ingenuity and attitude contributed to the safety of the community, as well as the timely repair of affected assets such that there was minimal disruption to gas supply.”