Contracts awarded to 2 firms for Cross Island Line's site investigation works

A volunteer speaking about how the Cross Island Line will affect the central catchment area during a nature tour in MacRitchie Nature Reserve on March 19. PHOTO: REUTERS

SINGAPORE - The authorities have appointed two companies to conduct site investigation works to see if a train tunnel can be built under the Central Catchment Nature Reserve (CCNR) for the upcoming Cross Island Line.

This comes after nature groups had expressed worries about the environmental harm that can be caused by the construction and operation of an underground MRT line through Singapore's largest nature reserve.

The Land Transport Authority (LTA) has appointed Tritech Engineering & Testing (TET) (Singapore) and Ryobi Geotechnique International (Ryobi G) to carry out investigation works for the the alignment that shows the upcoming Cross Island Line cutting under the Central Catchment Nature Reserve, it said in a press release on Tuesday (Oct 25).The tender to conduct these works was called in June 2016.

The site investigation works will start in December and are expected to be completed by the end of 2017.

The 50km Cross Island Line was first announced in 2013 as a link between Changi and Jurong. Preliminary plans showed it cutting through primary and secondary forests in the Central Catchment Nature Reserve near MacRitchie Reservoir.

Nature groups reacted by raising concerns and suggested that the line be built along Lornie Road instead, in an alternate route that skirts around the reserve.

The LTA started an environmental impact assessment (EIA) of both routes in July 2014.

The findings of first phase of this assessment, which looked at the soil works and how to reduce their impact, was announced in February 2016. Some mitigating measures announced then include reducing the number of boreholes required for soil testing from 72 to 16, and to gather the data needed through geophysical surveys instead.

Geophysical survey methods require contractors to go off-trail into the forest and do not call for drilling, unlike the boreholes of about 10cm in diameter, which will be drilled into an existing trail.

Site investigation works into the alternative option that skirts around the reserve started in May 2016 for the Government to analyse and determine soil conditions and engineering feasibility. Findings from the works into the direct and skirting options will provide input for the second phase of the EIA.

The longer 9km skirt around the CCNR will incur an extra travel time of six minutes, compared with the more direct 4km route running underneath the reserve, Transport Minister Khaw Boon Wan had said in March 2016.

The Government will decide on the alignment only after it takes into consideration the concerns from all stakeholders and the potential impact on the CCNR, and after the completion of the investigation works and Phase 2 of the EIA .

In the latest site investigation announced, TET will carry out the borehole drilling works. It has extensive experience in borehole drilling, including in environmentally-sensitive areas, the LTA said. It was involved in borehole drilling operations for slope stabilisation studies at the Bukit Timah Nature Reserve and Bukit Batok Nature Park.

Ryobi G, supported by its subcontractor Geophysical Services, will carry out geophysical survey works within the CCNR. It has carried out geophysical surveys on Government projects like the Thomson-East Coast Line and the Rail Corridor. To reduce the impact on the environment, it will be using wireless equipment for the works.

The appointed contractors have to put in place additional measures to reduce the impact on the forest environment during the soil works. These include engaging a certified arborist (tree expert) to ensure that trees are not damaged during the works and requiring contractors to conduct trial runs and rehearsals of borehole operations and off-trail surveys off-site, before they venture into the forest, to ensure equipment is fully functional and within the stringent requirements of working with the reserve.

A team of LTA officers and the contractors will work closely with the National Parks Board and nature groups to ensure that all mitigating measures are "rigorously implemented", said the LTA.

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