opening, private developers constructed newer buildings that re-established Raffles Place area as a financial hub. The presence of the MRT station near these buildings also created additional convenience for corporations and banks operating in the area. Construction of tunnels The contract for the construction of four tunnels between the City Hall and Raffles Place stations was awarded to a joint venture between Kajima Corporation and Keppel Shipyard in October 1983 at S$35.65 million (US$ million in ). Another contract for the construction of tunnels between the Maxwell (now Tanjong Pagar) and Raffles Place stations was awarded to a joint Japanese consortium including Taisei, Shimizu and Marubeni in December that year. The S$63.388 million (US$ million in ) contract included the construction of the adjacent Maxwell station. The tunnel route between Raffles Place and Maxwell stations goes along Robinson Road. Cement grouting was used to strengthen the soil along the road. This is to ensure the buildings above ground were unaffected by the works underneath. Ground treatment of the soil began on 28 May 1984 and completed by April the following year. The construction of tunnels between the City Hall and Raffles Place stations required the draining of the Singapore River. The contractor used the cut-and-cover construction method since the tunnels, which cross over one another, would pass through a shallow part of the river. The tunnel boring machine was launched from Empress Place, which is just by the river bank. Due to the acidity of the Singapore River, a layer of concrete was added to the concrete frame around the tunnels, with a waterproofing additive for the base slab concrete. The concrete frame was designed to prevent any corrosion or floatation of the tunnels. Due to requirements from the Ministry of Environment that the work site does not occupy more than 40% of the river width, the work proceeded in three stages. The cofferdam in the first stage occupied about of the river width from the riverbank at the Immigration Building site. However, this restriction led to a limited work area. The piles installation was hindered by the boulders in the river, which had to be drilled through. The works were close to the historical monuments of the Immigration Building and the Cavenagh Bridge. These two sites had to be closely monitored for any ground movement. Monitoring instruments such as inclinometers and levelling pins were used for any structural movement.