There are environmental concerns for the planned 8 kilometres long tunnel under Matheran Hill. But the union environment ministry’s regional empowered committee (REC) recently issued a directive to the state forest department for construction of the tunnel.

https://www.hindustantimes.com/cities/mumbai-news/state-government-gets-green-signal-to-build-tunnel-under-matheran-hill-101673205293290.html