Chennai Metro Rail Limited (CMRL) has implemented a significant cost-cutting measure in its phase-2 project by shrinking the size of underground stations by nearly 40%. This decision, driven by the need to tighten purse strings, has resulted in a reduction in station length from 240 meters in phase-1 to 150 meters in phase-2.
The key to this cost-saving strategy lies in the redesigned tunnel ventilation system. Engineers have successfully reduced the number of exhaust fans from eight in phase-1 to just two in phase-2, without compromising safety. This has brought down the length of the station and saved over ₹2,000 crore in project cost on system procurement alone. Experts estimate that this optimization could save several thousand crores in overall construction costs.
The new tunnel ventilation system involves strategically placing two large exhaust fans at either end of the stations on the concourse level. These fans utilize a duct system built below the platforms, equipped with steel nozzles, to effectively push or draw smoke during fire emergencies. Simultaneously, fresh air is pumped into the tunnels through ventilation shafts. This design also significantly reduces the electrical load and cabling requirements, contributing to the overall reduction in station size.
CMRL officials have highlighted that the new ventilation system meets all functionalities in both normal and emergency modes. They have also emphasized that the size of the platforms remains consistent at 140 meters across both phases.
The optimization of the tunnel ventilation system, along with other cost-cutting measures, has led to a reduction in the project cost from ₹89,000 crore to ₹63,432 crore. The average construction cost of one kilometer of underground line is ₹500 crore.
The new tunnel ventilation system, conceptualized by CMRL officials and designed by international experts, adheres to guidelines set by the National Fire Protection Association and the National Building Code. The design has also undergone rigorous validation by general consultants and external experts.
While the average length of metro stations in India is typically between 220 and 230 meters, experts note that metro projects are increasingly incorporating smaller underground stations due to space constraints in densely populated areas.
CMRL’s efforts to reduce the size of underground stations in phase-2 have set an example for other metro projects across the country, demonstrating the feasibility of achieving cost savings without compromising safety or functionality.
