Where is soil excavated in Singapore dumped?

Minister Khaw Boon Wan explained the soil is reused in land reclamation, in a recent post on his blog.

Photo from Minister Khaw's blog post.

But there is no mention of how much of this soil continues to be dumped at sea.


In his post NEWater and New Earth? on 10 Aug, Minister Khaw shared that "Last year, 8.5mil m3 of materials were excavated to build basement carparks and shops, underground expressways, and MRT tunnels – this is equivalent to about 3,400 Olympic-sized swimming pools."

This humungous quantity of earth has led to complaints in June in the Straits Times that "Lorries [carrying excavated earth] now line up for as long as five hours to discharge their loads of earth when just six months ago, there was no wait." Indeed, I came across this very long queue of lorries in April, at the Changi stanging ground during my field trips in the area.

Minister Khaw added that "When properly treated, both soft clay and good earth can be used for land reclamation. Lorries transport these excavated materials from construction sites to staging grounds at our coast. There, they are loaded onto barges, which move them to our various land reclamation sites for use as fill material." He goes on to explain the environmental measures taken during dumping of earth at the reclamation site.

Image from Minister Khaw's blog post.

However, Minister Khaw did not mention how much of this excavated soil continues to be dumped at sea. A Straits Times article about Minister Khaw's blog post says that "A National Development Ministry spokesman said almost 50 per cent of the debris collected - or 3.9 million cu m - was sent to Pulau Tekong for land reclamation."

The June Straits Times article mentioned there were four 'staging grounds' or offloading points for lorries to transport excavated soil for disposal:

Currently, most lorries go to the one in Changi, which is managed by the Housing Board, and takes in earth from all construction projects. There are three others. Two, in Marina Coastal Drive and Fort Road, are run by the Land Transport Authority, and open only to lorries from transport-related developments, owing to the extensive excavation from projects like the new MRT lines.

The third, at Tuas, accepts only a certain high-quality grade of earth that can be used immediately for land reclamation. It is costly and difficult for sites to identify and sort the types of earth beforehand, so few lorries go to Tuas, said construction bosses.

Where does the excavated soil go after the staging grounds? 
From the June Straits Times article I got the sense that most of the soil is dumped at sea!

The earth from all four points is then loaded onto barges and moved to various offshore dumping sites, like one near St John's Island.

Why is dumping at sea an issue for marine life?
When soil is dumped at sea, this buries whatever is directly under the dumping site. And our seabed is not dead! See the amazing marine life found in June on Singapore's sea bed during the Mega Marine Survey!

Photo by Sam Yeo

More seriously, dumping at sea results in sedimentation, a 'haze' of suspended particles that make the water murky. Not just in the dumping area but also beyond, as currents carry suspended particles away. Very much like haze in the air, which can result from burning very far away from Singapore.

Murky waters at Kusu Island.

Just as humans suffer during hazy days, suspended particles in the water affect the health of hard corals which rely on sunlight for healthy growth. Sedimentation can also affect many other marine animals, clogging up delicate gills, tentacles, filter-feeding body parts, and smothering animals that are stuck to the sea bottom in a thick blanket of soft icky stuff. Sediments may also interfere with the dispersal of tiny larvae of marine life and their effort to settle down on our reefs, such as during the spectacular mass coral spawning that takes place in Singapore every year. More in what is sedimentation and why does it matter.

So how much is being dumped at sea and how is this controlled?
I raised this question of dumping at sea with the Maritime Port Authority (MPA), who replied recently by email that

MPA has controlled measures in place, with regard to the dumping of dredged and land-based excavated materials at offshore dumping grounds managed by MPA, land reclamation sites and Offshore Disposal Sites (ODS).

All applicants need to submit information such as the sampling size, method of dredging, characteristics of dredged or excavated material etc, to MPA’s Committee for Marine Projects. Please see attached document for reference [online here as a DOC for download www.mpa.gov.sg/sites/doc/chemical17oct07.doc]

MPA also monitors the actual dumping that takes place, in terms of the time, route and amount that is being dumped. 

Unfortunately, I'm unable to find in the public domain, a list of these Offshore Disposal Sites and their exact locations. When large scale dumping does take place, though, there is usually an MPA circular about it.

Related links

• NEWater and New Earth? on Minister Khaw's blog - Housing Matters
• Khaw Boon Wan on recycling excavated materials Julia Ng Channel NewsAsia 10 Aug 12;
• Builders facing long wait to dump earth Too few sites to cope with spike in construction projects, they say, Rachel Chang Straits Times 16 Jun 12;
• What is sedimentation and why does it matter on the wild shores of singapore blog.