No blasting for Borivli-Thane underground tunnel project, say SNGP authorities

Using tunnel-boring machine option would drive up project costs: MSRDC

In a bid to protect the environment and natural wildlife in the Sanjay Gandhi National Park (SGNP), the park authorities have said no to the use of the 'controlled blasting method' for tunnelling in the Borivli-Thane underground tunnel project, according to an official from the Maharashtra State Roads and Development Corporation (MSRDC).

The SGNP's chief conservator of forests, Anwar Ahmed, said, “We have received a proposal on the project from MSRDC. However, we cannot respond, since the MSRDC must first obtain permission from the environment ministry. Asking us whether to use the controlled blasting method or any other method is premature.”

However, sources in the MSRDC revealed that at a recent meeting, park authorities were reluctant to consent to the use of the blasting method and had emphasised the use of tunnel boring machines (TBM), just as was being done in the Metro-III project.

The MSRDC had come up with this project in 2015 to ease traffic flow, after observing the increasing use of the Thane-Ghodbunder Road. The 11km-tunnel under the SGNP is expected to cut travel time between Mumbai and Thane by 20 minutes.

Despite the three-year delay in the onset of the project and the decision of the SGNP posing the latest roadblock, the official said, “There is no way this plan will be dropped. Since the controlled blasting method has been rejected, the other option is to use a tunnel-boring machine(TBM). However, the use of the TBM will more than double the cost of the project, estimated at Rs 3,000 crore,” the official said.

Following this development, the MSRDC will now revise its cost estimate and send the new detailed project report to the union ministry of environment and forests (MoEF) for final approval.

The tunnel will have three lanes on either side. The official added, the use of the TBM would also change the design plan.

"Earlier, we had planned a pathway, which could be used by both pedestrians and cyclists. But since the TBM has a set diameter, the width of the lane will reduce and eventually the pathway will shrink. Whereas in the controlled blasting method, there was no restriction on the tunnel diameter,” the official explained.