Cross Island Line: Option 3?

Let’s compare both available options with summarized information proposed for these options:

	Option 1: Direct Alignment	Option 2: Skirting Alignment
1.       Length of Impact	2km tunnel below the CCNR	9km under homes and businesses
2.       Depth of tunnel	40m Deep	Unknown
3.       Presence of physical structures	No Physical Structures	Supporting Ventilation facilities at the surface level

 According to this site:

There is something called the Railway Protection Zone (RPZ) and the Railway Safety Zone (RSZ). 

Perhaps, one can deduce that the depth of tunnel in Option 1 is 40m, was proposed such that the CCNR is 40m away from the tunneling works and the drone of vibration from the moving trains, based on the RPZ.

The question is:  Is applying the RPZ to the CCNR adequate?  Or should we be looking at the RSZ, which is 60m?

Another site shed some light of concerns within the RSZ:

On the same site, the following excerpt shows that there is still some impact for such items to be considered restricted activities:

Option 2 does not clarify the depth of tunneling works, so let’s assume that the depth is simply 20m, let’s look at the impact of applying the RSZ to the CCNR:

Option 1:

Option2
 

 

And translating the above section to plan, we see the impact of both options applying the RSZ:

 We also know from the following site that the ground of the CCNR has layers comprising:

Humus; Topsoil; Eluviation Layer; Subsoil; Regolith; Hard Bedrock

Perhaps then, a third option could be further studied and considered.   Let’s say, hypothetically, the RSZ needs to avoid the subsoil layer as this layer may contain the deepest roots of some trees, and the subsoil layer may be say 10m, these will require tunnel works for both options to be deeper at say 75m both schemes to have minimal impact. 

And what would Option 3 cost? 
Would the entire 50km length need to be deepened, affecting all station depths? 
Or could this depth also serve other functions such as civil defence shelters or even connect to the various underground rock caverns where Singapore’s future underground community may be?

There is no doubt that the cross-island line will help support the 6.9 million population by the year 2030.   However, this same 6.9 million people will also need pristine green spaces for their well-being.  In time to come, these remaining primary rainforests may even be gazetted as a world heritage site under UNESCO.  Floodgates to further diminish Singapore's remaining bits of nature should hence ever be opened.