Mumbai: The proposed construction of the Borivali-Thane twin tunnel will involve diversion of 57.02 hectare of forest land from the Sanjay Gandhi National Park (SGNP), documents relating to the environmental clearance accessed by The Free Press Journal show.
The area involved is equivalent to almost 39 Wankhede stadiums. The SGNP’s total area is 106.5 sq km or 10,650 ha. That means the area sought to be diverted is 0.5% of the total area of the national park.
The analysis by forest department
In a letter, the Mumbai Metropolitan Region Development Authority (MMRDA) has requested the Principal Chief Conservator of Forests to recommend to the Union Ministry of Environment, Forests and Climate Change to divert 57.02 ha forest area and grant approval to the project.
In a cost-benefit analysis done for the project, officials put the environmental loss at a meagre Rs57.81 crore over a period of 50 years, which translates to a loss of just Rs1.15 crore each year.
The Forest Department has a thumb rule to ascertain the environmental value of a hectare of fully stocked forest. A forest with a density of 1.0 is said to accrue a value of Rs1.26 crore over 50 years. Hence, environmental value depends on the density of the forest and its area.
In the case of the Borivali-Thane twin tunnel project, the average forest density of the area to be diverted has been calculated at 0.8, which translates to a value of Rs1.01 crore per hectare. That is how the figure of Rs57.81 crore was arrived at.
The construction phase
During the construction phase, no noise-emitting works such as drilling or movement on the roads close to the park will be done after sunset. During daylight hours, vehicular speeds will be capped at 20kmph.
The MMRDA has floated bids to connect the two suburbs of the Mumbai Metropolitan Region via two tunnels underneath SGNP’s hill. Of the 11.84 km long project, 10.8 km will be the twin tunnels. In all, a total of 23.68 km of new road will be constructed in the next four years. Each tunnel will have three lanes.
The estimated cost of this east-west connectivity project has been pegged at Rs13,200 crore. The road will connect Magathane in Borivali with Tikuji-ni-Wadi in Thane.