A major part of works to determine whether the Cross Island MRT Line can go under Singapore's largest nature reserve has been completed.
The Land Transport Authority (LTA) told The Straits Times this week that soil tests for the 16 boreholes drilled within the Central Catchment Nature Reserve were finished last month.
The works, which will help engineers determine the soil and rock profile under Singapore's largest nature reserve, started in February and have been watched closely, especially by environmental groups who are urging the Government not to build the MRT line under the Central Catchment Nature Reserve.
Other than the drilling of boreholes - each about 10cm wide to extract soil samples - the soil investigation works also included geophysical surveys.
These involve surveyors going off-trail into the forest to collect data using handheld equipment. Such surveys are needed to supplement data, as LTA had reduced the number of boreholes drilled in the nature reserve from 72 to 16, in a bid to reduce impact within the sensitive habitats. "Geophysical works and post-site investigation fauna monitoring activities are still ongoing," said the LTA spokesman.
The works are expected to be completed by the end of this year, the authority had said earlier.
Expected to be ready in 2030, the 50km Cross Island Line will stretch from Changi to Jurong.
The authorities are considering two paths for the line - a 4km route, half of which would be under the nature reserve, and a "skirting alignment" that would take a 9km route around it.
While the latter option is expected to tack on $2 billion to the cost of constructing the line, it could allow for an additional station to serve Thomson residents.
It would also satisfy nature groups which have raised concerns about the environmental impact of running an MRT line under the reserve, which is a treasure trove of biodiversity and home to critically endangered animals such as the Sunda pangolin.
The LTA spokesman said that findings from the site investigation works will be used in the next phase of the Environmental Impact Assessment (EIA), which will assess the impact of the construction and operations for both alignments.
The Love Our MacRitchie Forest volunteer group said it appreciated the authorities' engagement with the nature groups, and hoped that it would continue.
"We would like to see the results of the monitoring activities made available for the public to view," said its spokesman Chloe Tan.
"Should the findings of the soil investigation works recommend that the Cross Island Line be aligned through the CCNR, we hope that Phase 2 of the EIA and monitoring activities will be conducted with the same (or even more) rigour to ensure that wildlife will not be affected by the construction works."
The first phase of the EIA, announced in February last year, had looked at the soil works and how to reduce their impact.
A key finding was that the works would have a "moderate" impact on plants and animals there, but only if measures to reduce impact are strictly implemented.
For the alternative route around the reserve, the impact of soil investigation works along Lornie Road was deemed to be "negligible", and "minor" for areas near Venus Drive and a golf course.