A five-foot-wide pipe has travelled 24km in three years between the Palta Waterworks on the northern city fringes and the giant overhead tank at Tallah, promising the city a steadier stream of filtered water and facilitating repair of the leaky conduits.
Once commissioned on Sunday, the 64inch diameter pipeline will push up the daily supply of water from Palta to the city by 58 million gallon to 230 million gallon. Salt Lake will get a part of the additional supply 10 million gallon from next week.
Work on laying the sixth water main connecting Palta Waterworks with Tallah was completed a few days ago, 10 months behind schedule. The delay resulted in an additional expenditure of Rs 15 crore, taking the project cost to Rs 320 crore.
So far it is the single largest investment of the Calcutta Municipal Corporation in a water supply infrastructure project in the past 25 years. The project also marks another first in Calcuttas history use of micro-tunnelling or trenchless method, which requires minimal digging, for laying an underground pipe.
Civic chief engineer (water supply) Bibhas Maity said the micro-tunnelling technique was employed on a 12km stretch under BT Road as digging up the busy artery that links the city to North 24-Parganas would have caused a traffic disaster.
Its good news for Calcuttans and the residents of Salt Lake, said former mayor Bikash Ranjan Bhattacharyya, during whose tenure the project had started.
The proposal to lay the sixth pipe was mooted in 2008 following a breach in a water main under BT Road, resulting in a water crisis across Calcutta for two days.
The Centre included the project under the Jawaharlal Nehru National Urban Renewal Mission and the civic body entered into an agreement with RITES, a subsidiary of the railways, in August 2008. A work order was issued on April 25 next year.
As required by the urban renewal mission, the Centre and the state government bore 35 per cent of the project cost each and the rest was shouldered by the civic authorities.
Mayor Sovan Chatterjee attributed the 10-month delay in finishing work to the armys initial refusal to let the pipe pass under the Barrackpore cantonment area.
The army finally withdrew its objection five months ago, said Chatterjee.
Once the sixth pipe starts supplying water, an existing conduit of 60inch diameter will be closed for repair.
The pipe has sprung thousands of leaks that have been plugged with wooden pegs. The other pipes, too, will be repaired in phases, said the official.