The Sandhogs begin construction on the first new subway tunnel expansion in over 20 years. Working in the heart of downtown Manhattan, Walking Boss Martin Hostetter and Foreman Ryan McGinty lead a gang of Sandhogs through a series of test blasts to determine the effect the explosions will have on the city above. At the Croton Filtration site in the Bronx, one of Walking Boss Morgan Curran's foremen loses his fingers in an on-the-job accident, and Morgan promotes his young Sandhog protégé Anthony Aviles to fill the position and lead the gang on the mole. In Croton's lower tunnel, the gang detonates an historic blast that successfully unites their new tunnel with the century-old New Croton Aqueduct tunnel, built by fellow Sandhogs over a hundred years ago.in over 20 years. Working in the heart of downtown Manhattan, Walking Boss Martin Hostetter and Foreman Ryan McGinty lead a gang of Sandhogs through a series of test blasts to determine the effect the explosions will have on the city above. At the Croton Filtration site in the Bronx, one of Walking Boss Morgan Curran's foremen loses his fingers in an on-the-job accident, and Morgan promotes his young Sandhog protégé Anthony Aviles to fill the position and lead the gang on the mole. In Croton's lower tunnel, the gang detonates an historic blast that successfully unites their new tunnel with the century-old New Croton Aqueduct tunnel, built by fellow Sandhogs over a hundred years ago.