In order to ensure fast and smooth construction of the proposed twin tunnels at Bandra-Kurla Complex (BKC), which are expected to ease the flow of traffic between the Kalanagar and Kherwadi junctions, the Mumbai Metropolitan Region Development Authority (MMRDA) has asked prospective contractors to import an advanced tunnel boring machine (TBM) that can drill tunnels of 11 metre diameter.
So far, the MMRDA has used conventional drilling and blasting methods for the construction of tunnels. According to the MMRDA, the TBM will ensure smoother and faster construction than conventional methods. “One of the advantages of TBMs is the high excavation rate. This means that it can bore a tunnel with a speed about five to six times higher than conventional drilling and blasting methods. In addition, it significantly reduces disturbance to surrounding areas, making it suitable for use in BKC, which is a highly urbanised area,” said an MMRDA official, requesting anonymity.
According to the MMRDA, the 11-metre TBM costs Rs100 crore. This is the first time an 11-metre TBM will be used in the city. The civic agency has used tunnel boring machines for construction of underground water tunnels, but the diameter of these tunnels was only 3 to 6 metre.
One 1.6 km tunnel will start at the Central Bank in BKC and end at Kherwadi junction on the Western Express Highway, while another 700 m tunnel will stretch from the E block till the approach road to the Bandra-Worli sea link near Mahim Causeway. Both tunnels will help decongest traffic between the Kalanagar junction and Kherwadi junction stretch.
MMRDA officials said that tenders for the Rs360 crore project will be submitted by June this year and the contract will be awarded in October. Subsequently, the contractor will have to import the 11-metre TBM to construct the twin tunnels.
“In our pre-bid meeting, we conveyed to the bidders that the contractor will have to import the 11-metre TBM. Because of the cost of the machine, we expect the contractor will bring the TBM on rent. The contractor will be expected to construct the tunnels in 30 months,” the official said.