SINGAPORE: The new Marina Coastal Expressway (MCE) has been described as arguably "the toughest tunnelling project" the Land Transport Authority (LTA) has undertaken.

Senior Minister of State for Transport Josephine Teo said this at the opening ceremony of the S$4.3-billion expressway on Saturday.

The MCE is set to open to vehicular traffic at 9am on Sunday.

It's almost five years in the making and now, Singapore's 10th expressway is ready for operations.

Mrs Teo, Emeritus Senior Minister Goh Chok Tong and other MPs officially opened the expressway.

Spanning five kilometres, the project has been described as a massive engineering feat.

One of the biggest challenges was building the 420-metre undersea section, which is just 130 metres from the Marina Barrage.

This is because during periods of heavy rain, the barrage discharges large amounts of water, making the current strong and sometimes unpredictable.

As such, even before constructing the tunnel box on the sea bed, the construction team had to build a temporary undersea wall about 270 metres into the sea, with a width of 100 metres - bigger than the size of three football fields combined.

Another challenge is building most of the tunnel through reclaimed land.

Mrs Teo said: "The LTA engineers have very imaginatively described it as being similar to "peanut butter". But I want to assure you this is quite firm peanut butter, you won't have to worry about sinking through this peanut butter.

“They had to do many things to strengthen and stabilise the soil before the tunnel was constructed. For instance, piles as long as 85 metres, or 25 storeys, had to be driven into the ground."

More than 4 million cubic metres of soil were also removed - enough to fill 1,700 swimming pools.

The MCE will connect the Kallang-Paya Lebar Expressway (KPE), the East Coast Parkway and the Ayer-Rajah Expressway.

And MPs said the expected improvements in connectivity will outweigh the inconveniences faced by residents during construction.

Mr Lim Biow Chuan, MP for Mountbatten SMC, said: "For the construction of the MCE, there are a lot of big earth trucks moving around and I think that caused some concern.

"But by-and-large, LTA's engagement with the residents has been quite good, there's been quite minimal complaints from residents about noise and dust."

The MCE is also expected to help improve accessibility to the Marina Bay area.

Mr Gan Thiam Poh, MP for Pasir Ris-Punggol GRC, said: "The load will be divided and spread out. MCE has five lanes, certainly it will improve the load on the existing highways to both city and western areas."

Authorities said the MCE will help realise the vision of a new downtown at Marina Bay.

With the MCE, part of the ECP that currently cuts through the city centre will be removed, and make the area a more attractive place to live, work and play.

Together with the KPE, the KPE-MCE is touted to be the longest underground expressway in Southeast Asia.