The impact of tests needed to see how a train tunnel can be built under Singapore's largest nature reserve will be reduced to a level that is "as low as reasonably practicable", Senior Minister of State for National Development Desmond Lee told Parliament yesterday.
This will be done through adopting mitigating measures to reduce damage and disturbance, he said.
An environmental impact assessment had determined that site investigation works for the Cross Island Line will have a "moderate" overall impact on the Central Catchment Nature Reserve. Non-Constituency MP Leon Perera had asked how the consultants arrived at the conclusion.
Mr Lee said consultancy Environmental Resources Management had considered the sensitivity of the nature reserve and magnitude of the impact the work will have.
Referring to a table he distributed to MPs, he told the House that the reserve comprising primary rainforests with ecologically sensitive habitats is considered highly sensitive.
But the magnitude of impact of the investigation works will be "small", he said, as the Government will put in place mitigating measures.
Soil works are slated to start later this year to investigate the area's geological properties. Phase one of the environmental impact assessment had focused on the potential impact of this. Phase two will study the impact arising from the construction and operation of the MRT line that will link Changi to Jurong by 2030.
Mr Lee said the site investigation works will involve drilling boreholes about 10cm wide to extract soil samples, and geophysical surveys. Surveyors will go off-trail into the forest to collect data using hand-held equipment. Though it is less intrusive than the drilling, said Mr Lee, there are still concerns that surveyors may trample on plants.
He said stringent mitigating measures have been developed in consultation with nature groups and the National Parks Board. Among them:
• Geophysical surveys will be limited to a 100m-wide corridor and not be conducted in streams, swamps and dense vegetation
• NParks officers will be deployed to supervise surveyors
• 16 boreholes will be drilled instead of an earlier estimated 72
• Drilling will be confined to existing trails
• Drilling machines to be modified to reduce the noise level and prevent spillage of slurry and fuel
• Works will be done in the day to not disturb nocturnal animals
Studies on the total impact of the project may take more than two years to complete, and a decision on the route will only be made after.
Mr Louis Ng (Nee Soon GRC), who also raised questions on the issue, said he was glad options are being kept open. Nature groups have raised concerns that an MRT line running under the reserve would cause environmental harm.