Good neighbours in narrow straits
Excavating 500,000 tonnes of seabed and safely replacing a 6,000-tonne section of oil pipeline in the busy Port of Singapore requires precision planning. It also demands careful environmental impact management and intensive consultation to limit disruption to neighbours and port users, including two fish farm owners whose sea bass swim in the Singapore Strait.
On the small island of Semakau lies the only fish farm in southern Singapore. Dutchmen Joep Kleine Staarman and Erik Vis – whose surname means “fish” – set up the firm four years ago. Today their team rears hundreds of thousands of Australian sea bass, barramundi, for shipment to Australia and Singapore.
Located less than a kilometre south of the country’s industrial islands, the quieter waters are ideal for nourishing fish. When the farmers heard about plans to dredge the seabed and lay a new oil pipeline section they feared churned-up silt could upset the natural balance.
“We were pleased to be informed of plans so early on,” said Joep. “But dredging poses a threat, especially to the young fish in our hatcheries.”
The ripple effect
Joep and Erik received a visit from Ramon Martinez, Shell Project Manager. His team was planning to clean and replace a 2.5 km section of pipeline which carries crude oil from tankers to the refinery on nearby Bukom Island, part of the Shell Eastern Petrochemicals Complex.
The Singapore Strait is the world’s busiest shipping channel, with heavy traffic including oil tankers on tight deadlines. The project team prepared with the Marine Port Authority, agreeing a way to let ships pass more closely than usual thanks to extra safety measures such as more tugs to help tankers dock at neighbouring facilities.
“It was also vital to build solid relationships with local businesses, divers and environmental organisations,” said Ramon. “These groups could be affected by our planned operations.”
During his visit to the fish farm, Ramon explained that specialist contractors would first run plug-like devices back and forth along the pipeline, flushing out any oily water onto a vessel for shipment to cleaning facilities.
Then a dredging tool, about the size of a minibus, would excavate the seabed using metal “teeth” and suck up any debris, creating a trench for new section. The old section, half-buried close by, was cut up with a diamond wire cutter and removed.
The dredging tool drags along the seabed, creating clouds of sediment in its wake. Joep and Erik saw this as a possible threat to nearby sea life – including their sea bass.
Pure and simple
The area is species-rich, home to corals and sea grass. Before starting any work, project teams carried out environment impact assessments including biodiversity surveys. The results and samples were shared with the team from Singapore’s National Marine Biodiversity programme - opens on Shell Singapore.
The project included several steps to protect the delicate environment, as part of Shell’s approach to limiting the impact of projects. One approach was to install sensors feeding live information on water quality to a team on board the dredger. If sediment reached high levels, the team would stop and wait for the tide to turn.
For the fish farm, Ramon proposed an economic but effective solution: the installation of two filters on the pipes which draw up seawater for the hatcheries. These were included as part of the overall poject, which was successfully completed in late 2013.
“The new system delivers water that is even purer than before,” says Joep. “We are very happy.”
The 150cm diameter pipeline being laid in the Singapore Strait.
5 pipeline challenges in the Singapore Strait
- The new pipeline section had to be buried 3-4 metres below the seabed.
- A rock layer was required to prevent damage from ships dropping emergency anchors.
- Strong sea currents prevented the use of remotely controlled robots which usually capture underwater images to guide operations; divers only had several hours each day to work in their underwater construction site.
- The pipeline is around 150 cm (around 60 inches) in diameter and the 2,500m section weighs 6,000 tonnes. Eight anchors exerted the necessary tension of the pipeline-laying barge firm, creating a wide web of anchor lines.
- Singapore is one of the world’s busiest ports: Bukom Island alone has more than 10 wharfs with tankers on tight schedules.
Project fast facts
- Around 1 million hours worked
- More than 1,400 dives
- No time lost due to injury
- More than 30 vessels used
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