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Cross Island Line site investigations will have moderate impact on nature reserve

SINGAPORE — Sixteen holes as deep as 70m will be drilled in the Central Catchment Nature Reserve from the third quarter of this year to determine ground conditions for one of two possible alignments for the Cross Island MRT line.

Cross Island Line site investigations will have moderate impact on nature reserve

A look at the Cross-Island Line. Photo: LTA

SINGAPORE — Sixteen holes as deep as 70m will be drilled in the Central Catchment Nature Reserve from the third quarter of this year to determine ground conditions for one of two possible alignments for the Cross Island MRT line.

The holes will be drilled only on public trails and areas without vegetation, as part of measures to manage their impact on the nature reserve, said the Land Transport Authority(LTA)  today (Feb 5) as it gazetted the first phase of the Environmental Impact Assessment (EIA) of the Cross Island Line on the nature reserve.

Phase One of the EIA report concluded that with mitigating measures and controlled access, the proposed site investigation works would have moderate impact on areas of the nature reserve where the works will take place.

The site investigation is to gain knowledge of soil and rock conditions, as the Government decides how to align the future 50km MRT line that will link Jurong and Changi.

Two alignment options are on the table and site investigations will be done for both. One alignment cuts through the biodiverse Central Catchment Nature Reserve for about 2km, while the other skirts around it near Adam Road for about 9km. The latter alignment entails less ecological impact and the LTA said about 250 boreholes will be drilled to study its ground conditions.

For the alignment that affects the nature reserve, the number of holes, 16, was determined with input from nature groups and the environmental consultancy conducting the EIA. The number of holes was reduced from 72; the LTA will do non-intrusive geo-physical surveys to complement findings from the 16 boreholes.

Besides drilling along public trails and vegetation-free areas, there will be 30m buffer zones around streams, wetlands and marshes, as well as fluid containment tanks, to ensure no spillage of drilling fluid and to minimise erosion and siltation.

To reduce intermittent noise from the drilling, machines will have enclosures added. This will cut noise levels of around 80 to 85 decibels by 5 to 10 decibels.

The boreholes in the nature reserve will be up to 400m apart and two holes will be drilled at any one time, in general. The diameter of each hole is about 10cm and each workspace will measure about 2m by 11m. Drilling of each hole takes about two weeks and the work will take six to nine months, said LTA.

Personnel doing the non-intrusive geophysical surveys, using gadgets such as gravity meters, will work with the National Parks Board to ensure minimal disruption to the environment, said LTA.

The boreholes do not mean the Cross Island Line’s alignment has been decided; site investigations are to gain understanding of soil and rock profiles and structural geology, so that risks can be managed for any tunnel construction in future.

The consultancy conducting the EIA, Environmental Resources Management, will also assess the impact of the proposed MRT line cutting through the nature reserve during the construction and operation phase – this will make up the second part of the EIA report and will completed by the end of the year.

The EIA will be one of the factors determining the Cross Island Line’s alignment, said LTA. Other factors include travel times, cost and impact on home and land owners. When the MRT line, scheduled to complete around 2030, was first announced in 2013, nature groups had expressed serious concerns that it would cut directly under primary and regrowth forests that were over a century old, and over the potential impact of surface works.

Their input was incorporated when LTA called the EIA tender, and a report setting out about 400 tree species, 200 bird species, 400 insect species and 150 species of mammals and amphibians has also aided the EIA consultants.

Senior Minister of State for Transport Josephine Teo thanked the nature groups for their efforts, and LTA chief executive Chew Men Leong said: “The findings from the engineering feasibility study and the site investigation will provide critical information to help the Government make a considered decision on the CRL alignment that best serves the public interest.”

The EIA (Phase One) report will be available for public viewing, by appointment, for four weeks.

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