CHENNAI: The proposed 18.4-km elevated corridor from Kilambakkam bus terminus to Chettipunniyam near Mahindra City on GST Road is likely to get delayed by another year, as the state government has requested the National Highways Authority of India (NHAI) to prepare an integrated design for a double-decker viaduct comprising a six-lane elevated highway on the lower deck and a metro rail corridor on the upper deck.
In December last year, the state government granted in-principle approval for the extension of the metro rail corridor from KCBT to Chettipunniyam.
Sources said the Detailed Project Report (DPR) prepared earlier for a 18.4 km single-deck elevated corridor on the GST will have to be revised, as the load-bearing capacity of the piers must now be redesigned to accommodate both the highway and the metro line.
“The cost-sharing arrangement between the NHAI and the state government will also have to be reworked before the DPR can be finalised. The design finalisation process is expected to take nearly five months. Only after that will we be able to determine the state government’s share of the project cost,” an official said.
Another senior official from NHAI told the TNIE once the elevated corridor is constructed on the lower deck, there will be practical constraints in building a metro corridor above it at a later stage. “Constructing both the flyover and the metro line simultaneously, as was done on the Mugaliwakkam-Ramapuram stretch of the Mount-Poonamallee Road, would be more feasible,” he said.
However, he pointed out the NHAI is prepared to proceed either way, by constructing the elevated highway first and developing the metro corridor later, as the latter requires approval from the Union government, which could take additional time.
If the state government chooses to develop the civil infrastructure required for the metro project as part of the elevated corridor construction, including the installation of pier caps and the launching of U-girders and I-girders, its financial contribution to the project would increase.
“Such an arrangement would help avoid future complications, as traffic using the lower deck would not have to be disrupted during metro construction. The subsequent laying of tracks and installation of overhead electrical systems could then be carried out smoothly with minimal inconvenience. However, the decision now rests with the state government,” the official explained.
With the state government’s proposal to extend the Blue Line metro from Airport to KCBT, Kilambakkam still awaiting approval from the Union government, the proposed further extension from Kilambakkam to Chengalpattu is also expected to be delayed.
Rail enthusiast and activist Dayanand Krishnan said it has been more than a year since the DPR was submitted to the Union government for approval. “The Centre should grant approval at the earliest and commence the work,” he added.
Quick look
The Tamil Nadu government granted in-principle approval in December last year for extending the Metro rail corridor from KCBT to Chettipunniyam
The proposed Metro extension will be incorporated into the DPR being prepared by NHAI for the 18.4-km double-decker viaduct between KCBT and Chettipunniyam
The project envisages a six-lane elevated highway on the lower deck and a metro rail corridor on the upper deck
The DPR prepared earlier for a single-deck elevated corridor will be revised to accommodate the metro line on the upper deck
The Tamil Nadu government’s share of the project cost will be determined based on the revised DPR
NHAI has suggested the elevated highway and metro corridor be constructed simultaneously to ensure smooth execution of the project
Alternatively, the state government may opt to develop the civil infrastructure required for the metro corridor during the construction of the elevated highway