DTL2e - Tidbits from the EIS

 

An aerial render of the DE2/NS6 interchange station.
Source: LTA

An aerial render of the DE1 station.
Source: LTA

As part of the Downtown Line 2 extension (DTL2e) project, an Environmental Impact Study (EIS) report was generated under contract 9175 for the advanced engineering study to develop the extension. The Land Transport Authority (LTA) has put up the EIS for public viewing and feedback from yesterday (6 Jan 2025) to 3 February 2025 on its website. You may view the reports and submit feedback here. So what exactly does the EIS cover? There are a few tidbits that can be gleaned from going through the report, which is rather detailed and technical in many aspects. But they always say that the devil is in the details, no?

The EIS covers multiple aspects that pertain to the impact of the project on the environment - be it to humans, flora or fauna. The reports cover different phases of the project as well, from pre-construction, to construction & operational phases. Specifically, the project looks at the impact in terms of emissions, impact to air & water quality, impact to flora & fauna within the proposed sites, any species of conservational importance (both plant & animal), impact from lighting, noise & vibrations and makes assessments of these impacts. Measures to combat the impacts are suggested and recommended. Phew, that was a lot to cover, but important nonetheless. For most of us, the more interesting bits lie in the project description. More on that after the jump!

So here are some of the more interesting tidbits gleaned from the project description portion of the EIS reports for DTL2e:

1. A reception track connecting the North-South Line (NSL) with Gali Batu Depot was included as part of the project evaluation
The project outline for DTL2e not only included a reception track connecting the DTL to Gali Batu Depot, the main depot for the line. It also included an elevated reception track connecting the NSL with the depot to allow operational flexibility, such as when maintenance machines need to be loaned across lines. Based on the EIS, a decision had not been made yet whether to proceed with this NSL reception track though.

A view of the worksites along the DTL2e project. The elevated reception track can be seen in
green, running along Sungei Kadut Avenue.
Source: LTA

Excerpt from the EIS report on the elevated NSL reception track connecting with Gali Batu Depot.
Source: LTA

2. DE1 station may have 2 exits
In line with our expectations, the intermediate station - DE1 - may have two exits, one on either end of the station. While the EIS report refers to the stations as completely designed, there remains potential for this to be changed through subsequent design reviews and/or value engineering exercises.

An additional render of DE1 station exit, facing the JTC industrial estate.
Source: LTA

Excerpt from the EIS on DE1 station's exit count.
Source: LTA

3. Tunnel Boring Machines (TBMs) will be used to construct most of the extension
Can you recall the massive upheaval experienced along Woodlands Road during the construction of DTL2 in the vicinity of Bukit Panjang station? The process was disruptive, noisy and generally an inconvenience to many. To minimise such impacts, tunneling via the use of TBMs was recommended for the DTL2e project, especially so as the extension runs near to more ecologically sensitive and less developed areas. Cut & cover sites will still be required, nonetheless, at several key areas - the DE2/NS6 Sungei Kadut station site, the DE1 station site, at Gali Batu Depot & an interface with the existing DTL2 over run tunnels near Senja Way.

It is uncertain how many machines or drives will be used currently. However, given that there would be at least 5 drives to be completed, 2 machines will need to be procured minimally. In particular, it should be noted that the shaft at Senja Way will only be meant for docking (i.e. receiving) the incoming TBM, but not for retrieval purposes. In comparison, the shaft at Gali Batu Depot will be used for extraction (i.e. retrieving) of the TBM as well.

An overview of the tunneling concept for the DTL2e project.
Source: LTA

4. The extension will use a twin-bore tunnel for its alignment
A recent trend with other lines being constructed has been the used of large diameter single bore tunnels, especially through stretches of ecologically sensitive land. The upcoming Cross Island Line (CRL) will see four such machines being used along various stretches, including a section through the Central Catchment Nature Reserve.

Excerpt from the EIS mentioning the use of twin bored tunnels.
Source: LTA

In addition to the above notes gleaned from the EIS report, two additional renders of the stations could be seen, which we have placed at the top of this article. The renders provide additional aerial perspectives of the stations, until more information comes forth as the project progresses along. Stay tuned as we'll cover some pre-construction updates in time to come.

This post will also be available on Instagram & Facebook on 8 January 2025.