Friday, November 1, 2013

Challenges to Construction

The Eastern Region Line poses a challenging alignment, also in part due to its location and geography. Today we look at some of the challenges that LTA is faced with in implementing this line. Firstly, the alignment runs along the east coast corridor of Singapore, intending to serve estates along the eastern stretch that do not currently have easy access to the MRT network. These include Tanjong Rhu, Marine Parade and Siglap areas.

Part of these areas are estates built on reclaimed land, presenting an additional challenge which we'll go into deeper later. The part at Marine Parade is pretty straight, thanks to the presence of Marine Parade Rd, a long a straight boulevard that stretches from the Laguna area to Parkway Parade near Amber Rd.

Marine Parade Rd towards Parkway Parade

But beyond this, the line has to cut through dense condominium developments or thread through narrow roadways. Once such potential roadway is Meyer Road, which happens to be a single lane dual-carriageway road that runs from Tanjong Rhu to Tanjong Katong South. Lined with condominium developments on one side and landed properties on another, this winding road is a pretty narrow corridor that the LTA may be exploring to run the ERL from Tanjong Rhu on to Marine Parade.

A shot showing the width of Meyer Rd.
Should the line go under Meyer Rd, therein lie several challenges to planning and subsequently construction of the line. Firstly, the width of the corridor would dictate that the line's tunnels be stacked one over the other to fit into the tight confines of the roadway above without running into any building foundations. In doing so, there need to be sufficient provisions for emergency egress, in other words, means of escape from tunnels during emergencies. Typical tunnels which run parallel to each other, and therefore side-by-side, have passages connecting the tunnels together allowing commuters to transfer over to an unaffected tunnel during emergency.

Stacked tunnels however, usually feature intervention or emergency exit shafts which are stairways leading to the surface through which commuters can evacuate the tunnels during emergency. With such dense development on both sides of Meyer Road, finding a suitable location itself will prove difficult.

Adding on to the list of challenges besides routing and finding space for facilities lies the geo-technical aspect. As mentioned earlier, much of Marine Parade estate sits on reclaimed land. This means that the line would have to cross the boundary between the original shore line of the island (which is relatively rocky) into the new, compacted reclaimed soil. With detailed records, this task alone can be tedious. But unfortunately for LTA, it seems that the records for the original rocky shoreline are not readily available, leading to either an intense study of the soil along the suspected shore line or coming up with alternatives to keep as far away from it as possible without changing the serving radius of the stations planned (in other words, without changing the number of people served).

Sea wall mole removal in Marina Bay

The above two images show you what a herculean task removing the sea wall can be in a relatively undeveloped area - Marina Bay. However, Marine Parade is a developed estate with established roadways, commercial and residential hubs and educational institutes dotting the stretch. Thus, this provides an additional challenge for the line planners. To combat this, planners and consultants had to come up with 4 alignment options and with results from studies, determine which is the most effective in terms of construction time and challenges against the ability of the line to move commuters efficiently.

A summary of work by an individual on LinkedIn shows that consultants
had to propose 4 alignment options
With 4 options to, not only choose from, but also study, it is understandable that this extends the time taken to properly interpret the information and therein make an informed decision. There are numerous challenges that face the ERL before it enters the construction phase, with more to come once actual building work begins. Best to iron out as many as possible before work begins on moving the soil.

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