It was assumed that additional toll hikes--beyond those already tentatively scheduled for this coming year--would be required to cover the costs of the overruns. But Rita Strazerri, spokesperson for the Turnpike Authority, tells GlobeSt.com that a portion of the project would be funded by selling real estate along the Massachusetts Turnpike.

According to the plan released by the Authority, the base cost of the project is $13.981 billion with a $494 million contingency fund that comes to the $14.475 current price tag. Last year's cost estimate was $14.075 billion. The primary funding sources for the cost overruns will be a $175-million transportation infrastructure fund, which will be a restructuring of the fund for registration and motor vehicle licensing fees. An additional $150 million will be provided by the state bond cap and $75 million will come from the future sale of Big Dig headquarters at 185 Kneeland St. The Authority states the property's appraised value is $100 million.

Unconfirmed reports say the state bond cap was made possible because $150 million in Federal highway funds that couldn't be spent on the Big Dig were given to the statewide road and bridge project and exchanged for the $150 million in additional debt capacity. The Federal Government has mandated an $8.5 billion cap on its spending for the Big Dig but reportedly, Big Dig officials state that the Federal Highway Administration signed off on the exchange.