Federal officials warn that the Big Dig's cost may rise by an estimated $75 million, forcing state taxpayers to cover any increase. The projected hike, outlined in a memo drafted by the U.S. Department of Transportation's inspector general, would be the first increase in the project's price tag since 2001. There are numerous reasons for the possible hike, federal officials told The Boston Globe: Officials may have miscalculated the cost of settling disputes with Big Dig contractors and underestimated how much money the state will recover from contractors that performed late or shoddy work. A spokesman for Transportation Inspector General...