Jurong Island is the heart of Singapore’s chemicals industry, home to more than a hundred oil, petrochemical and manufacturing companies. Oil giant ExxonMobil is expanding its operations with the construction of the Chemical & Refining Integrated Singapore Project (Crisp) to increase production of cleaner fuels with lower sulphate content.
Keller was awarded the design-build contract, working with main contractor Técnicas Reunidas.
“The project had tanks and process plant structures such as pipe racks spread over an area of around 137,000m2 and precast concrete spun piling would traditionally have been the choice for the foundations to satisfy the performance criteria,” says Deepak Raj, managing director for Keller‘s ASEAN business unit. “However, having established a strong, trusted relationship between ourselves with ExxonMobil over many years, they had enough confidence in us to ask if we could find a better, more innovative way to do the job.”
Keller proposed an alternative hybrid foundation solution of deep vibro compaction to densify the top sandy layers, along with vibro stone columns to reinforce the soft clayey strata underneath. The company said that not only are these methods together around 35-40% faster and more cost-effective than the traditional piling solution, but they’re also more ecological.
“Piling contains rebar and concrete, so you need a lot of steel and cement – materials that use a lot of energy and produce high levels of CO2 emissions to manufacture,” said Raj. According to the International Energy Agency, the construction industry is responsible for around 40% of CO2 emissions, with about 8% coming from cement production.
“As a leading geotechnical contractor, it’s our moral responsibility to contribute towards a more sustainable future and look at reducing CO2 wherever possible,” he added.
Keller’s engineers used a universal carbon calculator devised by the European Federation of Foundation Contractors and the Deep Foundations Institute to compare the piling proposal with Keller’s vibro solutions.
The result included everything from the diesel used to power machines and material production, right through to worker transportation and waste disposal.
The piling option would have generated around 22,000 tonnes of carbon dioxide equivalent (tCO2e), while the vibro methods produced just 1,900 tCO2e – 92% lower. Keller said that the saving is the equivalent of driving the average car around the earth 2,000 times.
Notably, materials consumption accounted for only 96 tCO2e of the vibro carbon total as natural crushed stone is far less carbon intensive than manufactured materials, produces no waste and is lighter, reducing the number of trips needed to bring it to site.
Most of the emissions – 1,369 tCO2e – came from the diesel used to power Keller’s machines. But here too, Keller sought to minimise impact. The stone columns were installed with in-house designed and manufactured vibrocats, which are increasingly efficient and have lower fuel emissions compared to crane-hung rigs.
“For companies like ExxonMobil, sustainability is increasingly important,” said Raj. “So if we can show how techniques are not only quicker and more cost-effective, but also much more environmentally friendly, that’s great for them, for us and for the planet.”