DTL is a new MRT line currently under construction,- see complete route map

and today (15/9/10) a report about one of the downtown stations Promenade, which the new line will pass, was published in the papers; from the Chinese paper I retrieved the following diagram

which I reproduce because it shows something odd: the vertical cross section of the Promenade station shows that the DTL tracks run lower than the neighbouring Circle Line tracks; I would have thought they should be on the same level, and in fact the DTL tracks should be right next to the existing Circle Line platform so that you change from one line to the other by simply crossing from one side to the other. This is clearly not the case in the construction design.

In fact, when Circle Line Promenade.station first opened, people were confused by the fact that its two opposing platforms are on two different levels rather than on both sides of the same level; the following diagram shows on level, with train on track one side and blank wall the other

the only way to make sense of it is that another line will share the two platforms, with each level providing train changing in one direction.

Today gave a brief report on this, ST a longer one but Zaobao gave the most details including the diagrams, but the following quote is from Today

Promenade Station at Marina Bay where 40 per cent of the excavation work has been done.

This will be Singapore's deepest train station at 43 metres underground, some 15 storeys below ground level. This is about 8 metres lower than the deepest station in operation, Bras Basah station.

Group director, Circle and Downtown Lines/Land Transport Authority, Sim Wee Meng said the Promenade Station is going to be an interchange station with Promenade Circle Line station.

He said heavy machinery would have to be brought in because of the challenges posed working at such a depth.

This includes the $10 million 500-tonne tunnel boring machine which works like a giant mechanical worm. .

It would seem that seem that the need to go deep, and to bring in new equipment (note the wording "would have to be brought in") was not originally in the plan;

If you look at the map, you realize that the DTL and Circle Line tracks cross each other near the station: DTL comes from the Marina station to the south, then turns westward towards Bugis; the Circle lines from Esplanade in the north west, turning north east towards Nichol around Promenade; since the two tracks must be at different levels at the crossing, it is not possible for them to go level so quickly, if the crossing was further north, a bit away from the station, it might have been possible, but DTL tracks at the stations would have to be to the east of Circle Line tracks, not to the west as present.

Another issue that struck me as curious was the side by side presence of City Hall and Esplanade stations, with just the Raffles City building separating them. I would have thought it quite simple to build a pedestrian tunnel between the two, making them parts of the same station and allowing people coming from the west who wish to go to Suntec Carrefore, Golden Mile, Stadium, Mounbatton etc, to change from EW line to Circle Line without having to change to NS line, go past CityHall to Dhoby Ghaut and then come back through Bras Basah and Esplanade, saving one change and 3 stations travel length. (People coming in from the far west could also change to NE line at outram park, go to Dhoby Ghaut then change to Circle Line - the train distance is slightly shorter but the change in Outram requires a long walk and the NE line runs less frequently than NS line; those from the east can change from EW line to Circle line in Paya Lebar but those living in the area from Kallang to Bugis have the same problem - those around Aljunid would go east first to paya lebar then come back westward)