USP Conversations: Questioning the Cross-Island Line Alignment

By Oh Kai En Rachel and Movin Nyanasengeran.

Pictures from Imran Shah and graphic from The Straits Times


The Cross Island Line is a 50 km-long MRT line first proposed in the 2013 White Paper. Planned to stretch from Changi to the Jurong Industrial Estate, it’s targeted completion date was 2030. Controversially, a segment of the line was planned to cut under part of the Central Catchment Nature Reserve (CCNR) and Macritchie Reservoir (‘Option 1’).

This option has raised concerns due to its potential environmental impact. An alternate route, proposed by Nature Society Singapore (NSS), skirts around the CCNR instead (‘Option 2’). Discussion on this issue has been rife, with attention focused on the potential environmental, economic and social impact of the line.


One such discussion took place at USP Chatterbox during an edition of The Sessions on 7 March 2016.

There to answer pertinent questions were Prof Leung Chun Fai, a tunnelling expert from the Department of Civil Engineering at NUS and Mr. N. Sivasothi, a biodiversity expert from the Department of Biological Sciences at NUS. Of attendance as well were USP faculty, students, alumni, and even other NUS nature enthusiasts who had heard of the event.

The discussion first touched on the engineering and ecological difficulties taken into account when tunnelling through areas such as the nature reserve. Prof Leung shared about the various strategies that a civil engineer can and will undertake to minimise the impact of construction, and mitigate the potential risks which may arise, including water seepage and problems in the soil layers, amongst others. Prof Leung also emphasised the importance of building a sufficient number of emergency exits, which makes LTA’s current reluctance to construct on the surface of the line (in CCNR itself) problematic.

The caveat was that such mitigation was only possible if all the necessary geological information, on the type of soil, rock formation, level of the water table etc. were known. The Environmental Impact Assessment (EIA) hence seeks to obtain this information through borehole drilling. This endeavour is being undertaken by Environmental Resource Management (ERM), the company engaged to conduct the EIA.

Mr. Siva also responded that while engineering efforts can mitigate and minimise the environmental impact on the construction, even the assessments to understand the geology of CCNR already has a high impact on the nature reserve. Mr. Siva emphasised that the total land area of the CCNR is much smaller compared to national parks found in other countries. Hence, the environmental repercussions would be more emphasised within a relatively small area in CCNR

Equipment and materials such as drilling fluid will have to be transported into the reserve. Access to areas beyond walking trails and the use of vehicles within the reserve are strictly prohibited, necessitating the manual transport of materials which increases the risks of spills and other forms of contamination. Noise created by drilling equipment is likely to adversely affect foraging behaviour of many of the animals in the areas surrounding the site. This risk would be multiplied by the number of boreholes that were to be made. In recognition of this, the number has since then been reduced from 72 to 16, and drilling activities will not take place in the vicinity of primary forest. These revisions were made following consultations between LTA, ERM and a volunteer group Mr. Siva works with.

However, such a solution leads to further problems itself. Less boreholes means less ecological data. Reliability of the ecological and geological measures would hence be affected and civil engineers would face difficulty in planning should the data be insufficient or incorrect.

CCNR also presented unique challenges for ERM, otherwise highly trained in accessing environmental impacts in more conventional nature areas. Singapore’s green landscapes are significantly smaller, thus presenting a scenario the company was not entirely equipped to handle – perturbations are far more damaging in small areas of habitat than in vaster areas – the severity of potential risks had to be raised to higher categories to accommodate this fact. Indeed the EIA undertaken in locally is perhaps one of the first in the world to deal with micro-fragments of rainforest.

Prof Leung explained that most civil engineers may not be aware of the ecological risks present when undertaking construction projects in proximity to nature areas. As Singapore continues with her developmental progress it appears that there is a very real need for more discourse between experts of previously disparate disciplines to truly inform policy. The present scenario with a heavy reliance on volunteers and nature groups to provide ecological perspectives led to some of the audience members questioning if such a case can be justified. There were suggestions for a team to be put together formally to gather opinions from the authorities and experts in biodiversity, geology, engineering and other related fields. In response to this, some civil engineering students stated that there is a need for greater emphasis on environmental issues and concerns in their syllabus.

Questions still remain regarding the lack of information regarding the make-up of the monetary costs of either option, and which option LTA is leaning towards.


Nonetheless, The Session closed off on a positive note; LTA’s present efforts to involve nature groups and to publicly release the EIA report online was a step in the right direction. The fact that this issue was generating much impassioned debate was also heartening to note. Mr. Siva encouraged students to be even more involved in the CRL debate by raising their concerns to policy-makers. The debate on the CRL has generated interest in the area of environmental protection and this interest hopefully will sustain in the minds of policy-makers in time to come. Perhaps, the first step towards making our voices heard is knowing what to say and what has been said. To this end, the Sessions is a useful platform.

If you wish to hold a discussion in an area which interests you, have interesting guests who might be able to engage our community, or both, contact The Sessions personnel Imran, Wei Leong or Peng Le.


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