Reference a Great (Railroad) Engineer:
Isambard Kingdom Brunel for his sheer, unmatched versatility: he could add bonuses to tunnels, bridges, canals, shipbuilding (shipyard bonus?)
Jawn Henry for the specific railroad tunnel reference, and for the music
But for the quintessential (and real) railroad tunnel engineer, may I present:
Samuel S. Montague
He was the Chief Engineer in the building of the Central Pacific Railroad through the Sierra Nevada Mountains out of California - the western 'end' of the first North American transcontinental railroad. Without dynamite or power machinery, he probably directed the building of more railroad tunnels in a shorter time than any man before or since. If you've ever ridden the Amtrak route from Oakland to Chicago you will get an awe-inspiring view of his work.