Arborists concerned over soil tests in MacRitchie
The Environmental Impact Assessment on the construction of the Cross Island Line has drawn varied responses from members of the public. Plant expert Lahiru Wijedasa tells SHAMIR OSMAN (email@example.com) about the impact of soil testing on vegetation
After going through the recently-released Environment Impact Assessment on soil investigations at the Central Catchment Nature Reserve (CCNR) at MacRitchie, plant expert Lahiru Wijedasa is concerned.
"The disturbance that might be caused by soil investigation is significant and if damage is caused, it will be irreparable," the former senior arborist at the Singapore Botanic Gardens told The New Paper.
"The most damage from the soil investigations will be on the rare plants and old trees in MacRitchie, from the weight of the machines that will go into the area."
Studying the various tables and schedules in the assessment, Mr Wijedasa explained that a boring machine weighing 2.5 tonnes will be moved into CCNR.
And with each borehole requiring 1,000 litres of water, an ancillary machine weighing 2.4 tonnes will have to transport the water to the various sites. (See graphics at right.)
He stressed the immense damage the tree roots and other plants will suffer even if the 16 boreholes within the CCNR are on existing footpaths.
From 2007 to 2014, Mr Wijedasa oversaw, among other projects, the development of the 5-hectare healing garden and boardwalk in the Botanic Gardens rainforest.
"In those projects at the Botanic Gardens, we put in place mitigating factors like a boardwalk or even temporary boardwalks to prevent putting weight on tree roots," he said.
"This is crucial because the clay soil in Singapore makes most trees grow their roots wide, not deep. If heavy weights are placed on them, they will die and not grow back.
"And it is almost certain that there are tree roots growing under the footpaths in MacRitchie."
Mr Wijedasa studied the map of boreholes in the assessment.
The map revealed that in addition to the 16 boreholes, there are 21 others in the forested area on the fringes of the CCNR, which will have an impact on the area.
"These additional boreholes, while not within the gazetted boundary, are still close enough to have an effect on the gazetted CCNR.
"You can't look at things in isolation," he said, pointing to hydrology - the circulation of water below the earth's surface - as another major cause of concern.
Mr Wijedasa presented his findings at a Green Drinks event at the Sing Jazz Club on Feb 25.
Mr Tony O'Dempsey from Nature Society Singapore, who was at the event, expressed concern.
"The impact of the soil survey shouldn't be played down or ignored," he said.
"The public can give their feedback on the assessment and I strongly recommend that Mr Wijedasa writes in to present his findings. This is an issue of grave concern."
Singapore Arboriculture Society president Rick Thomas, who was not at the event, concurred with Mr Wijedasa about root damage.
He said: "When it comes to works on the surface (during the soil investigation), you don't need heavy machinery to do damage.
"Any machinery going over the top will see damage sustained by the trees."
Member of Parliament for Nee Soon GRC Louis Ng believes it is not too late for robust discussions on the matter before damage is done.
Mr Ng, who was at the event, said: "The second phase (including soil investigations) is a gamble and if we fail with mitigation factors, the impact could be irreversible. It is a primary forest.
"I don't think the final chapter (on the soil investigation) is written yet. There is avenue for discussion, so let's start the debate."
MINISTER: KEEP AN OPEN MIND
Transport Minister Khaw Boon Wan urged Singaporeans to keep an open mind as the studies for the Cross Island Line (CRL) are being carried out.
In his address in Parliament on Monday, he also urged the public to "go with the facts... (and) look for the evidence."
- The CRL will stretch over 50km, with most of its stations serving as interchanges. Preliminary estimates show that 600,000 trips will be made on the CRL every day. Estimates indicate that the CRL will be higher in terms of capacity and usage compared to the existing North East Line and will provide more routing options for commuters.
- Option 2, the skirting alignment that runs along Lornie and Upper Thomson roads, will cost an estimated $2 billion due to required land acquisitions. No estimate for the total cost of the CRL was made available.
- Land acquisitions will force some Singaporeans out of their homes. The number has yet to be determined.
- Travel time on the CRL will be shortened by six minutes if it passes through the CCNR.
The CRL is a massive project and the Government will decide on its entire alignment only after making a total assessment… As the alignments can have a different impact on the environment, commuters, taxpayers, businesses and home owners, the Government has a responsibility to study both options thoroughly.
- Transport Minister Khaw Boon Wan
The Cross Island Line (CRL) will undergo a four-stage process before its projected completion in 2030:
Stage 1: Feasibility studies before a decision is made on CRL's final route (24 to 30 months)
Stage 2: Detailed engineering design (24 to 30 months)
Stage 3: Construction (72 to 78 months)
Stage 4: Testing and commissioning (30 to 36 months)
The process is still at Stage 1 because an Environmental Impact Assessment had to be done on soil testing, which is required to study the viability of tunnelling since the line will run through the Central Catchment Nature Reserve at MacRitchie.
The 1,000-page assessment showed that soil testing would have a "moderate" impact on the environment.
Impact of massive weight on plants
The estimated number of plant species found in the Central Catchment Nature Reserve (CCNR) which houses Singapore's second largest primary forest
Plant expert Lahiru Wijedasa believes that installing boardwalks to distribute the weight will be unlikely due to the space constraints around the bore sites, but there are other options that can be put in place to minimise damage.
"It would help if a pump is installed outside the CCNR and forest area to pump water in instead of having water-filled ancillary machines move in daily," he said.
He said that placing sandbags across the areas where machines will move could also mitigate the weight.
species of birds
types of mammals
species of freshwater fish
types of amphibians
Enclosures will be put up to reduce noise impact on fauna that can move away from the work sites, with tanks used to collect discharge from the boring machines to reduce impact on water bodies.
Risks in affecting underground water table
Tunnelling under the Central Catchment Nature Reserve could affect the underground water table and impact the whole ecosystem.
"(The eventual) tunnelling works will happen some 40m below ground and while that will have little impact on vegetation, it is a question of hydrology of the area," said Singapore Arboriculture Society president Rick Thomas.
The effects of disturbing the hydrology of an area could surface only later in the future, but plant expert Lahiru Wijedasa believes that should not make preserving it any less important.
"A potentially big effect is what if hydrology does affect our forests, it is not going to affect just the stretch above the (proposed) tunnel but the entire catchment area," he said.
"Yes, this is something that will be studied in detail in the subsequent assessment but worthy of pointing out at this stage."