The
North East Line (NEL) project, which was first proposed in 1984, received government approval in January 1996. Clarke Quay station was among the sixteen NEL stations announced by communications minister
Mah Bow Tan that March. The
Land Transport Authority (LTA) Deputy Chief Executive and his colleagues visited Clarke Quay in 1995. During their visit, they decided there should be a station built under
Ellenborough Market, which lay along the proposed NEL route. The
Urban Redevelopment Authority (URA) agreed, saying the proposed station would "realise the tremendous commercial and aesthetic potential" of the
Singapore River. Some property developers interviewed by
The Straits Times felt the station was not as "centrally located" to serve the developments near
Robertson Quay. Others, such as
DBS Land and
Far East Organisation, supported the proposed station as it would fill a "major gap" in transportation access to the area. The station opened on 20 June 2003 along with the other NEL stations.
Station construction The contract for the design and construction of Clarke Quay station and tunnels was awarded to a joint venture of Nishimatsu Construction, Lum Chang Building Contractors and Bachy Soletanche Singapore. Stallholders of the Ellenborough Market had to move out by 31 March 1997 as the market would be demolished for the station. Due to the soft marine clay, a dam was built around the station site, and the contiguous concrete wall panels were installed via diaphragm walling. The contractors had to monitor and minimise any ground movement of the heritage shophouses by the river and the Thong Chai building. Some of the perimeter walls were also installed near the river wall. The APG building located along New Bridge Road was detected to be settling unevenly because it had a separate foundations. Following a thorough survey of the building, the LTA engineers deemed it safe for use and made repairs and restorations.
Tunnels construction The NEL tunnels cross the Singapore River near
Coleman Bridge. This was the second MRT river crossing, though the first to use the
tunnel boring machine (TBM) beneath the riverbed. Compared to the cut-and-cover method, the TBM was considered less time-consuming, had lower risks of tunnel flooding, and minimised environmental damage to Clarke Quay and the river. As the tunnels were only below the riverbed, it was decided to further lower the tunnels and the station by . The TBM had to tunnel through a layer of marine clay with varying thickness, loose fluvial sands and weathered sedimentary rocks that could create varying resistance to the TBM. Hence, it was essential to maintain effective control of the excavation rate to keep the TBM in alignment. While initially opposed by the management of Clarke Quay, the launch shaft was located at the former Whampoa Garden due to optimal soil conditions. Explosives were used for the hard rock under
Fort Canning Hill when workers tunnelled between Clarke Quay and
Dhoby Ghaut. Sensitive structures, such as an underground enclosed reservoir atop Fort Canning and a telecom microwave tower, were closely monitored. A minor ground settlement at Fort Canning Country Club created a large void above the TBM. As a result, grout was pumped in to prevent further settlement. The tunnelling also encountered a huge inflow of water, and pipes were drilled into the rock face to channel the water out and prevent water from seeping into the rock cracks. The tunnel excavation also exposed a layer of sand in the rock face directly underneath the Oxley Rise flyover, causing slow settlement under the flyover. As survey teams established monitoring points at the flyover, pit bosses and miners hammered timber into the ground to stop ground loss. The ground was filled with chemical grout to add strength and cohesion to the soil before tunnelling resumed. Explosives were also used for another hard rock under the
North–South Line (NSL) tunnels near Dhoby Ghaut station as the manual excavation was too slow.
Jet-grout arches supported the NSL tunnels while tunnelling near Dhoby Ghaut station. ==Details==