History of the subterranean connections between Calcutta and Howrah

Abstract

The first metro railway started operation on London’s Metropolitan Railway line using steam locomotives and wooden carriages (1863). Although Calcutta, India, acquired its metro in 1984, its connection with Howrah through an underwater tunnel under the River Hooghly was first conceived in 1921. Plans for this were laid out by Sir Harley Dalrymple-Hay, and he prepared the blueprint of a railway from Calcutta to Howrah with ten stations over its 10·6 km stretch. Unfortunately, the project was abandoned by the government of Bengal on financial grounds. Then, in 1928, Calcutta Electric Supply Corporation, to cater for increasing power demand on both sides of the river, consulted Sir Dalrymple-Hay to provide a tunnel below the lowest scour level of the river. It was planned to provide a conduit for electrical cables with inspection facilities, and this tunnel was built in 1931. Calcutta’s East–West metro line, including the underwater stretch below the River Hooghly, was reconceived in 2006, and construction started in 2009. This line now crosses the River Hooghly with a rail level at a depth of 19 m below the riverbed with 13 m of water depth at average tide, and its projected daily commuters will be almost 1 million by the year 2035.