An expert who investigated leaks in Boston's Big Dig project says he can no longer vouch for the tunnels' safety. The 14 point six billion dollar system is formally called the Central Artery and Third Harbor Tunnel project. According to a letter obtained by The Boston Globe, Jack Lemley wrote he's "unable to express an opinion as to the safety of" a portion of the Central Artery. He says new information shows there are construction defects in more than 40 large sections of the tunnels and that fireproofing material has been damaged by leaks. However, a state highway spokesman says officials believe the tunnels are "perfectly safe."