We don't have synonyms for big dig yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are big rig, big dog and big wig.
(N) :
a megaproject in Boston that rerouted the then elevated Central Artery of Interstate 93 that cut across Boston into the O'Neill Tunnel and built the Ted Williams Tunnel to extend Interstate 90 to Logan International Airport.
(N) :
a collection of various civil engineering projects in Liverpool to regenerate the city.
(N) :
a megaproject in Boston that rerouted the then elevated Central Artery of Interstate 93 that cut across Boston into the O'Neill Tunnel and built the Ted Williams Tunnel to extend Interstate 90 to Logan International Airport.
(N) :
a collection of various civil engineering projects in Liverpool to regenerate the city.