The 20-km Colaba-Bandra underground corridor has been designed to run underground Metro between Colaba and Mahim. But in the new proposal from the MMRDA to the state government, the former has suggested the stretch between Colaba and Mahalaxmi (10 km) remain underground while an elevated stretch should be constructed between Mahalaxmi and Bandra.

“Both the proposals have been submitted to the state government. They will take a call on the alignment of the third corridor,” said G R Madan, Director, Mass Rapid Transit System, MMRDA.

An entire underground corridor was estimated to cost around Rs 12,000 crore with a viability gap fund of nearly Rs 9,000 crore. As the VGF was huge, the nodal agency had planned to take up the corridor on the lines of the Delhi Metro Rail Corporation (DMRC). Since no bidders have come forward for the Rs 6,192-crore Charkop-Bandra-Mankhurd corridor, the state government would now want to opt for a cheaper option.

According to a senior official, if the government takes up the shorter underground corridor, the MMRDA would easily save around Rs 3,000 crore from the corridor.