Floating Pontoon in Bintulu

These river structures are common in most of towns near the Rivers in Sarawak. The floating pontoons are made of thin reinforced concrete box structures with a overall density less than water density, and link to the land by rotatable steel truss bridge structures, so that the pontoons can be used  all time, whether high tide or low tide. Tide level difference can be more than 6m and any fixed wharf and jetty will not be workable unless multilevel staircases are built. Floating pontoon is still the cheapest and practical method, although maintenance is more. 
Leakage into the voided RC structures often causes the pontoons to sink and the bridges to fall into river. Regular inspection and pumping maintenance are required to prevent such failures. Nowadays, the empty spaces in the boxed structures are filled with polystyrene to prevent water occupying the empty space and cut down the maintenance.