Preventing Major Underground Gas Leaks

Er Dr Lee Bee Wah asked the Minister for Trade and Industry (a) what measures are in place to maintain all underground gas and water pipes in good working order; (b) what is the lifespan of these pipes before they are replaced; (c) how are underground pipes inspected; and (d) what are the safeguards to prevent leaks that can cause a serious explosion.

Ensuring the safety of our utilities infrastructure is a key priority. EMA has put in place robust regulatory requirements and conducts regular inspections to ensure the reliability and safety of Singapore's gas pipelines.

Careful attention is paid to the planning and design of our gas network. SP Power Grid (SPPG), which manages Singapore's gas network, must conduct a risk assessment exercise and meet the requirements set by SCDF and other authorities, before constructing a pipeline.

All high-pressure gas pipelines are constructed using high-strength steel with anti-corrosion coating. Pipelines on the mainland are buried at a depth of 1.5 metres on average

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and further protected by concrete slabs to ensure pipeline integrity. Gas that is distributed to consumers is also odorised to facilitate detection in the event of any leak.

To ensure that the pipeline network remains in good working condition, SPPG carries out various surveillance and maintenance measures, as required by the Gas Transporter Licence and relevant codes of practice such as the Gas Safety Code and Gas Supply Code. SPPG continuously monitors pipeline pressure and flow for any anomalies. It also surveys the pipeline network regularly for leaks using gas detectors. Such surveys are conducted more frequently in crowded and residential areas. For example, SPPG inspects the pipelines in the vicinity of MRT stations on a monthly basis, while non-residential areas are surveyed on an annual basis.

In addition, SPPG conducts annual mechanical inspections of critical pipeline components and inspects high-pressure pipelines using pipeline inspection gauges every five years to ensure that the pipelines remain in good working conditions. EMA conducts annual audits and enforcement checks to ensure that SPPG carries out the pipeline surveillance and maintenance processes as scheduled.

The service life of gas pipelines is about 50 years. SPPG systematically replaces pipelines before the end of their service lives, or earlier if the condition of these pipelines is found to have deteriorated. Our high-pressure pipelines are less than 20 years old, so they are well within the estimated service lifespan.

As for water pipes, PUB's water mains are relatively new, with an average age of 24 years. Since the 1980s, older pipes have been systematically replaced with cement-lined ductile iron and steel mains, which are more durable and have an expected lifespan of 70 years. A strict maintenance regime is in place to ensure that our water pipes remain in good working condition. There is a dynamic leak detection programme in which all water pipes are checked for leaks at least once a year. Our leak rate is six leaks per 100 km of pipes each year, which is among the lowest in the world.

Mdm Speaker, I would like to thank the Senior Minister of State for the reply. I would like to ask the Senior Minister of State what lessons can be learnt from the Taiwanese experience, as well as what is the possibility of such an incident happening in Singapore. I would also like to ask, for example, about water pipes. There are ground movements and as Members of Parliament, we do receive complaints from residents about water pipe leakages as well as bursting of pipes. Water pipes may not be as dangerous as gas pipes. So, I am just wondering what other measures are taken to make sure that such instances do not happen, and in the past, how many of such cases have happened in

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Singapore.

Madam, in the Taiwanese case, the recent explosion is due to a pipeline supplying petrochemicals to a chemical plant. The gas carried there is propene (C3H6), which is different from the natural gas that our SPPG is distributing. Propene is a heavier gas than air. So, when it leaks, it tends to stay underground until it gathers a bigger mass, which makes it more dangerous. Whereas natural gas, in our case, is lighter. So, if it leaks, it tends to dissipate into the air quickly, therefore, reducing a volume build-up and explosion.

Having said that, they are all inflammable. The results of the investigation in Taiwan have not been released, so, we probably can take some lessons from that incident at a later stage. In the case of Singapore, I mentioned SPPG being the one that manages our natural gas distribution pipelines on the mainland mostly, whereas our petrochemical pipelines are mostly concentrated on Jurong Island. And therefore, they are supervised by SCDF which imposes in them another and more stringent set of construction, operation and maintenance regime. We have confidence that the two sets of pipelines are separately managed, and there is sufficient rigour and robustness in the way that they are maintained and operated.

The Member also asked about the frequency of leaks. For high-pressure gas pipelines, there was one case that took place in 2012 on Jurong Island. The leak was detected early, so there was no casualty or fatality. It was rectified in a relatively short time, as the gas supply was resumed after a short while.

Over the last five years, there were 500 minor gas leaks – 300 were detected by SPPG and 200 were reported. These represent a frequency of 0.1 incident per 1 km of pipeline. This makes us very comparable to Hong Kong, and well ahead of other cities like New York, Melbourne and London.