with the water pumped out, upon which the tunnels and the station were to be built. The tunnels were then covered with another layer of concrete before the seabed was refilled. During the construction, a World War II-era bomb was found at the work site and was safely detonated elsewhere by the Singapore Armed Forces Bomb Disposal Unit. The station opened on 4 November 1989 and was the southern terminus of the North South line (NSL) until the extension to Marina South Pier station opened in 2014. On 8 January 2006, this station was one of the four stations that participated in Exercise Northstar V, a large-scale emergency preparedness exercise. Circle Line An extension of the Circle line (CCL) to this station was first announced in April 2007. Contract 901 for the construction and completion of Marina Bay CCL station was awarded to Hock Lian Seng Infrastructure Pte. Ltd. for in February 2008. The scope also included addition and alteration works to the existing NSL station, road diversions of the East Coast Parkway and Marina Street and the demolition of a vehicular underpass. Construction of the station started in February 2008 and was completed on schedule by January 2012. During the construction, Exit A of the station had to be relocated for construction works for the Circle line station. As announced on 28 November 2011, the station opened on 14 January 2012 as part of the two-station, extension from Promenade, with an opening ceremony the day before. On 17 January 2013, transport minister Lui Tuck Yew announced that the CCL would be extended from Marina Bay station to HarbourFront station as part of CCL Stage 6. Contract 886 for the construction of cut-and-cover tunnels at Marina Bay Area between the Prince Edward and Marina Bay stations was awarded to Koh Brothers Building & Civil Engineering Contractor (Pte.) Ltd. at in September 2017. Construction began in 2017, and was expected to be completed by 2025. However, with the COVID-19 pandemic in Singapore, the completion date was pushed to 2026. Thomson–East Coast Line On 29 August 2012, it was announced that Marina Bay station would interchange with the 22-station Thomson line (TSL). Contract T226 for the design and construction of Marina Bay TSL Station and associated tunnels was awarded to Taisei Corporation for S$425 million (US$ million) in February 2014. Construction started in 2014, with an expected completion date in 2021. On