In a shadowy, cavernous passageway 600 feet below Midtown Manhattan, the temperature is about 55 degrees Fahrenheit year-round -- and it's always raining.
The ground is covered with a soppy muck that squishes and sucks at the bottoms of the rubber boots that are requisite gear for those who work there.
This is the world of the sandhogs -- urban miners drilling through deep layers of bedrock nearly half a billion years old to build a third tunnel connecting city faucets to reserves of fresh drinking water upstate.
City Water Tunnel No. 3 is a four-stage construction project begun by the New York City Department of Environmental Protection in 1970. It is expected to cost about $6 billion and stretch more than 60 miles when completed in 2020.
The tunnel is part of a broader improvement plan to revamp the city water system, which funnels 1.1 billion gallons of water daily throughout the five boroughs and is fed by two tunnels built in 1917 and 1936.
Each day, about 170 sandhogs laboring around the clock begin their workday with a rumbling, four-minute elevator trip straight down a narrow mine shaft to a metal mesh platform overlooking the blasted cavity they call the "bell out" area.
"You gotta be willing to work hard, be alert and like getting dirty," said Jim Donovan, who started working as a sandhog 20 years ago when he was 18.
The work is strenuous, and it can be dangerous -- 24 sandhogs have died working on Water Tunnel No. 3. Accidents are a risk, and despite ventilation improvements, many sandhogs suffer some degree of the dust-related lung disease silicosis.
Richard Fitzsimmons, 46, business manager for the tunnel workers union Local 147, says about 80% of his sandhogs are eligible for workers' compensation upon retirement -- mostly because of respiratory problems.
"DEP is pretty good when it comes to safety," Fitzsimmons said. "If we report a dust problem, they will try to eliminate it. But there will always be some dust when you are doing heavy construction."
Despite these dangers, many sandhogs say they love the job.
For some, it's the camaraderie and the paycheck -- they are among the highest paid construction workers in the nation, earning about $100,000 in salary and benefits.
"It's an interesting job," said Patrick Brady, a 30-year-old Bronx native. "I enjoy it. It's hard work, but it's good pay."
For others, it's a fascination with the ancient mineral layers exposed as the tunnel is drilled.
"I love the rock," said Pierre LeFrancois, a DEP inspector who has been working in tunnels since 1960. "I'm a geologist, and the only place you can actually see the bare rock formation is underground."
The hum of machinery is constant. Water drips from the jagged, rock ceiling and collects in puddles along railroad tracks that run nearly two miles through a 12-foot tunnel to the rock face -- the head of the tunnel excavation site.
Stage one of Water Tunnel No. 3 was activated in 1998. Sandhogs are working on stage two.
Sandhogging tends to stay in the family, and the men are often third, or even fourth, generation.
"I wish every person went to college and didn't have to do this kind of work, but the bottom line is somebody has to do it," Fitzsimmons said.
"We bring clean water, and nothing happens without clean water."