For 280 m tunnel i think two to three months are enough time. If they will use modern science and technology target can be easily achieved. Delhi metro is using such high level of advance TBM machine and completed so many project before time frame. Eastern railway has given one and half year it is very shocking and they are claiming it will be constructed by one of the world best technology. It is joke of the day and system. Britishers completed tunnel in 3 years before 150 plus years earlier and if we will take one year and more than a year it is a black spot on eastern Railway.