If all goes as planned, Mumbai will receive its first underground train line. In South Mumbai, the Central Railway (CR) intends to dig underground to construct its fifth and sixth lines between Parel/Currey Road and Chhatrapati Shivaji Maharaj Terminus (CMST), taking inspiration from the Mumbai metro, whose Line 3 is the city's first-ever underground transport route. Along the Kurla-Parel-CSMT segment of the CR's suburban system, the route in question intersects Phase 2 of a project to construct a fifth and sixth railway corridor. A 7.4-kilometer route between Parel and CSMT is part of Phase 2. Phase 1 is now under way and spans 10.1 km from Kurla to Parel.
For large-scale projects like these, the railway thinks digging under the city will avoid the significant difficulties in acquiring land and rehabilitating project affected individuals (PAPs), making the journey more comfortable. After all, they contend, why can't the railways do it if the Mumbai metro can? Although it is still in its early stages, the proposal is ambitious. Central Railway and the Mumbai Rail Vikas Corporation (MRVC) have met a few occasions, however they have not yet developed a strategy for the proposed underground rail route. The agency that will carry out the project will be decided by the results of technical feasibility studies.
The line would be 7.4 kilometres long and constructed 20–25 meters beneath the overland train rails, said railway officials. It would align with them and avoid highways, buildings, and subterranean utilities, all of which are major obstacles for any underground project, reported HT.
A railway official told HT The feasibility of putting the fifth and sixth rail lines underground between Parel and CSMT stations is currently being examined, and the required research will be done before a decision is made. They will designate a consultant and are draughting the process's terms of reference. The study will determine the amount of land that is available for tunnel boring machines to access and exit at CSMT and Parel. Once underground, they can terminate the tube at the CSMT end using different alignments.
For the proposed tunnel at the CSMT end, there are two possible entry/exit points: one inside the terminus and one close to it. The official said in the first case, the tunnel can enter or exit CSMT inside the terminus, adjacent to the suburban railway corridor, or near the long-distance train stations, depending on what is practical.
An entry/exit point on the P D'Mello side of CSMT could be taken into consideration as a backup plan. But there are probably two difficulties here. It would be necessary to take into account the proposed Metro 11 line's route, which will run from Wadala to CSMT via an underground metro corridor. Metro 3's underground CSMT station would also need to be considered by the Central Railway. If the underground corridor is permitted, the estimated total cost of the project (Phase 1 and 2) will be ₹3,000 crore, which is about three times the initial cost of the upland lines alone. The anticipated cost was ₹890.89 crore when it was first approved in 2008. Since then, it has been changed to ₹1,337 crore, reported HT.