SINGAPORE - A worksite on the Cross Island MRT Line (CRL) will be downsized and partially shifted into Singapore Island Country Club (SICC) so that indigenous monkeys that roam the area will not be endangered.

The A1W1 site will now be about 150m from a tree canopy link over Island Club Road where Raffles' banded langurs are known to roam, the Land Transport Authority (LTA) said on Monday (March 15).

This is five times further than the initially planned 30m distance. The size of the worksite, originally set at 15,000 sq m, has also been more than halved to 7,000 sq m. Part of it will occupy non-playing grounds in SICC.

LTA said the club will not be compensated as the area will be returned to it upon the project's completion at an unspecified date. The Rapid Transit Systems Act also allows for the authority to make use of the land.

The move comes amid consultations with nature groups concerned about the environmental impact of the CRL near the Central Catchment Nature Reserve.

This part of the line will run directly under the reserve instead of skirting round it - a decision made in 2019 - and there are fears that it could affect the surrounding flora and fauna.

In a written reply to MP Louis Ng (Nee Soon GRC) in March, Transport Minister Ong Ye Kung said that the key representatives of nature groups have reviewed the revised A1W1 worksite and are supportive of the changes.

Mr Ong said an engineering consultant had been engaged early last year to look into the problem of the worksite's proximity to the monkeys. It is now "significantly further away" from their habitat, he said.

"LTA will continue to work with them on further measures to mitigate any potential environmental impact at the A1W1 worksite when construction of the CRL begins, so as to strike a balance between preserving the environment and wildlife, and improving transport infrastructure for the benefit of Singaporeans," he added.

According to Wildlife Reserves Singapore, the Raffles' banded langur is one of only three non-human primates found locally, and was discovered by Sir Stamford Raffles almost 200 years ago.

Although they were once common across the island, urban development confined them to central Singapore. By the 1990s, they were on the verge of extinction, with only 15 to 20 left in the Central Catchment Nature Reserve.

There are now about 40 to 60 of them and they remain at high risk of being wiped out.

President of Nature Society Shawn Lum said he was relieved to hear of LTA's decision, adding that it bode well for the continued engagement of the authorities with nature groups on the environmental impact of the rest of the CRL.

He said the footprint of the revised worksite is much smaller, based on briefings by LTA.

"There will be a much reduced traffic load of lorries hauling out stones and soil during the shaft excavation process, as the amount of material is a fraction of the original amount envisaged," he said. "The effort has led to a more successful project outcome with reduced impacts on the forest and wildlife."

The A1W1 worksite is part of CRL's phase two, the rest of which is still undergoing advanced engineering study.

All the civil construction works tenders for phase one, which stretches from Aviation Park to Bright Hill, have been called and are progressively being awarded.

Works at the respective sites will commence when the contractors are on board, the LTA said.

Phase one of the line is set to be operational by 2030.