Big Dig's costs spiral

In all, the project will cost an additional $7 billion in interest for a grand total of $22 billion, according to a Boston Globe review of hundreds of pages of state documents.

The debt will not be paid off until 2038.

Though popular belief was that the federal government subsidized much of the project, in actuality almost three-fourths of costs were paid by Massachusetts drivers and taxpayers.

Big Dig payments have already taken maintenance and repair money away from deteriorating roads and bridges across the state, forcing the state to float more highway bonds and to go even deeper into debt.

The state is in financial distress, as it is currently paying almost 80% of its highway workers with borrowed money, and the costs of debt have pushed the Massachusetts Turnpike Authority, which manages the Big Dig, to the brink of insolvency.

Massachusetts spends a higher percentage of its highway budget on debt than any other state.