SINGAPORE — The Cross Island Line will run directly under the Central Catchment Nature Reserve, with the authorities deciding that it is more beneficial to Singaporeans than the other option of having the line skirt around the reserve. The decision was made after six years of public engagement including with nature groups.

Advanced engineering studies on the direct alignment option will begin next year, before the Land Transport Authority (LTA) makes the next move, the Ministry of Transport (MOT) said. Advanced engineering studies typically take up to two years.

Announcing the Government’s decision on Wednesday (Dec 4), MOT said that it had considered various factors, including “concerns expressed by all stakeholders” and the findings of an assessment on the environmental impact of construction activities.

The direct option will benefit Singaporeans in reducing commutes by about six minutes compared with the skirting option, the ministry added.

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The public will also pay lower fares as the route is shorter, the ministry said, and the construction cost to taxpayers is reduced by about S$2 billion.

“In the longer term, it is a more environmentally friendly option as the direct alignment has a lower energy consumption,” MOT added.

This option of direct tunnelling means that 4km of the route will run beneath the Singapore Island Country Club’s Island Golf Course, Central Catchment Nature Reserve and Pan Island Expressway. Of this, 2km will be under the reserve.

Transport Minister Khaw Boon Wan said that the authorities have agonised over the alignment because the Central Catchment Nature Reserve is “a special part of Singapore”.

He also thanked the nature groups for their advice, suggestions and understanding, and pledged to continue working with them as the project moves into the next phase of advanced engineering study, design and construction.

Mr Khaw described the Cross Island Line as a critical transport infrastructure that “will vastly improve the quality of life” for commuters who need to cross the island regularly.

“It will interchange with almost all the other MRT lines and hence raise the network resilience,” Mr Khaw, who is also Coordinating Minister for Infrastructure, said on Facebook.

“The Cross Island Line will also support the development of new hubs such as the Jurong Lake District and the new Build-to-Order estates in Sengkang, Punggol and Hougang. The Cross Island Line will meet the needs of a million commuters.

“I know many will look forward to its completion.”

MITIGATING MEASURES

As part of measures to mitigate the environmental impact, the tunnel will be built about 70m below average ground level, or around the height of a 25-storey public housing block.

Bencoolen MRT Station on the Downtown Line is the deepest at 43m, followed by Promenade MRT Station on the Downtown Line at 42m.

On average, underground MRT tunnels are built at less than half that depth, at about 30m.

During the public engagement, several groups had raised concerns about the impact of construction activities on wildlife and the loss of vegetation and habitat resources if mitigating measures are not taken.

A report assessing the environmental impact released in September found that, before mitigating measures are taken, the impact on species at both worksites would be major owing to the loss of vegetation and habitat resources. This is because 1.5ha of forested land would have to be cleared, with 1.2ha to be replanted after construction.

Clearance and construction activities were also assessed to have a potentially major impact in breaking up habitats at the Island Club Road worksite.

MOT said on Wednesday that LTA is in talks with the Singapore Island Country Club to use a part of its “non-playing area” to reduce potential disturbance to flora and fauna near this worksite.

The authorities are exploring the possibility of adjusting the worksite, such that it is further from the crossings for the Raffles’ banded langur, a critically endangered monkey. They could not give details about the size of this area being explored, as advanced engineering studies have not been done.

On the other hand, building tunnels skirting the reserve would create a 9km route, and a government estimate in 2016 showed that it would cost about S$2 billion more.

With this option, commuters will face a longer travelling time of 11 minutes from Bright Hill to the next station in the second operational phase of the Cross Island Line.

Three above-ground worksites will have to be built. The first worksite will be near Lakeview estate and the other two are along Lornie Road as well as between Adam Drive and the Pan Island Expressway.

Experts had cautioned that the risk of incidents — tunnelling works could cause damage and cracks to buildings, for example — is higher for this option than for the direct option, because of the concentration of existing infrastructure and buildings.

The Cross Island Line, which will have about 30 stops, will be built in stages. When fully completed by about 2030, it will be Singapore’s longest underground train line at 50km to 60km long.

It is expected to carry more than 600,000 commuters daily in its initial years, with the number eventually hitting more than one million. REPORTING BY KENNETH CHENG