There’s something unique about each one of Mumbai Metro Line-3’s 26 underground stations which are being built throughout the length of the city to connect South Mumbai with the western suburbs.
This post is all about Sahar Road Station which is located on the 4.45 km package UGC-06 (CSIA T1 – CSIA T2), towards the northern-end of the line, and is under construction by J Kumar – CRTG JV with just one tunnel breakthrough pending at CSIA T1 Station.
The station is 218m long, 25m wide and 29m deep. When ready, this cut & cover station will have 3 entry/exit points to provide connectivity to Airport Colony, Sahar Village and JB Village.
Besides the 227m NATM Crossover Cavern on its east where excavation was completed last Friday, this station has historic water pipelines, some as old as 50 years, running right across the middle of it. These highly pressurized utility pipes supply water to the entire region and run from Upper Vaitharna Dam all the way to the southern tip of the island city.
Typically underground stations are planned away from such pipelines or the pipelines are diverted, but given the strategic location of the station and other reasons, the pipelines had to be kept intact.
A unique steel support structure was designed by Tandon Consultants. Here’s what one of its senior designers had to say:
Typically an underground station will be re-planned away from such hindrances or the pipeline will be diverted around the station. But, the station location is strategically placed to have maximum catchment of riders and due restriction in tunnel alignment because of Mumbai International Airport runway and land makes shifting infeasible.
Diverting these pipelines was also not feasible due to space constraints because of the presence of public buildings and airport land near it. Providing a bend in the pipes to route it around to the other side of the station was also not feasible as it will lead to creating bend in pipe thus lowering the pressure of the water pipe. Also diversion cannot happen without interrupting the flow of water until diversion is completed.
Thus these larger diameter water mains had to be supported at its place before commencement of excavation to enable construction of Sahar Road Station.
As the station is constructed using bottom-up method, the water pipes have to be supported before excavation for the station or water pipes. The utility support system consists of a series kingpost planned on the envelope of the water pipe system along the length of pipe at certain spacing.The king posts are connected with longitudinal girders and on top of it trusses are erected.
A series of 36 nos of steel truss of 20m span each supports the entire pipe line along the length. Water pipelines are suspended from the truss using a steel section as a suspender connecting a cross girder and pipe cradle at the bottom of the pipe and the truss at the top. The water pipeline support system being a sensitive and critical structure is being monitored daily during construction progress for this performance and safety.
Here are some historic images shot at the station over the past 24 months:
Satellite imagery of the station with the pipelines can be viewed here on Google Maps.
For more updates, check out the Mumbai section of The Metro Rail Guy!