Hundreds of feet below one of the world's most famous cities, a different breed of men dig and blast their way through solid rock. These urban miners create the tunnels that ensure the survival of the city above. Meet Walking Boss Morgan Curran and the Sandhogs of Local 147. Under great pressure, these men work to complete the Croton Filtration Plant, a facility that will help ensure the safety of the city's water supply. In one tunnel they use the "Mole", an enormous tunnel-boring machine that relentlessly eats away at the rock. In the other tunnel, they're using large quantities of dynamite to blast their way through the earth. When a void develops along one of the tunnel walls, the hogs race to put up ring steel to prevent a cave in. And while the Brooklyn Bridge celebrates its 125th anniversary, the Sandhogs continue to toil below, preparing and detonating their next blast.
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.
Discover a world under New York City where injury and death on the job are common occurrences. Watch as these workers toil underneath the streets of New York City just as they have for the past 150 years--they are an instrumental part of the development of the city. Their union, their identity and their culture have been forged in iron and steel, and it is a bond that is truly shared as a brotherhood.
As the tunnel-boring machine cuts through Croton's upper tunnel, morale is at an all time low. Temporary Foreman Anthony Aviles' aggressive leadership style has forced Walking Boss Morgan Curran to monitor the situation closely and he's beginning to fear for the worst. Meanwhile at the #7 Subway line extension in Manhattan, Walking Boss Martin Hostetter and Foreman Ryan McGinty work to perfect their blasts as they move deeper and deeper beneath the city streets. Back at Croton, Morgan moves to the lower tunnel where he and Forman Repete Moore prepare to blast out a section of "tights" -- outcroppings of rock that must be eliminated for work to continue. Just as Morgan is about to set off the blast, the situation with Anthony in the upper tunnel worsens. Distracted from the task at hand, Morgan takes decisive action to keep the Sandhogs on track.