hurwitz: the city bought up land around the reservoirs to prevent it from development. it provides assistance to local residents to see that there's no pollution of the reservoirs. it's much more cost effective to prevent pollution and to protect a source of water than to remove it at the drinking water treatment plant. lloyd: what epa said to us was, "you can have an exemption from filtration "if you keep this undeveloped, "and if you can manage the wastewater so that it does not pollute your water supply." and we feel that we've reached the point where we can really keep it clean enough to drink unfiltered for the indefinite future. and new york city is in a small club of cities that actually have that filtration avoidance waiver. narrator: while municipalities are responsible for maintaining systems and source supply, the standards that protect water are established at the federal level. there are two important pieces of federal legislation that were both enacted in the early to mid-1970s. the first was the clean water act, which acts to protect rivers and lakes, and

hurwitz: currently, city tunnel 1 and city tunnel number 2 would be feeding each half of the city. so you'd lose half the city if you didn't have a replacement. narrator: without half of its water supply, the city would shut down. for nearly 40 years, new york has been in the process of constructing a solution. man: this project is water tunnel number 3. we started on this project in 1969. i'm a sandhog. i've been a sandhog for 37 years. narrator: sandhogs are the men of local 147, who work deep below the city. they began building the infrastructure of new york in 1872. from the subways to the sewers, the water tunnels to the highway tunnels, new york city thrives because of their work. ryan: you got one little hole in the ground, and nobody knows we're here. see the empire state building, right. that's 1,000 feet. so you figure, you go down 1,000. how high that is -- that's how far we go down. narrator: stretching more than 60 miles under the city, tunnel 3 is taking generations of workers to complete. ryan: i don't even want to imagine what my father had to go through. when we fi

hurwitz: we have the stock exchange, we have the united nations -- failure can have a dramatic impact on the nation, and even internationally. so there's a really keen awareness that you always have to be fixing the system. things corrode, they rust. they get to where you turn them on and nothing happens. but it is so totally used in every nook and cranny,

and the -- and the two young writer/directors, jon hurwitz and hayden schlossberg -- and these are the>> jimmy: yeah, and they -- and this is funny, because it's like -- it's -- everyone gets back together for a high school -- it's their ten -- no? >> well, yeah, that's the -- it's the ten-year reunion and the idea is just so simple, but it's brilliant. it's a high school reunion, which means, you know, you're bringing your current life back to your past life. you're bringing current relationships back to meet your past relationships. >> jimmy: now, people have kids and now, people are married. >> yeah, people have kids, people are married and -- >> jimmy: you're single in this movie. >> and the old flame. well, i -- i am single. they did -- i am a -- a widower. >> jimmy: yes. >> in this movie, which is a -- which is a -- a terrible thing for my wife and even worse for -- ever worse for her agent, but -- [ laughter ] i -- >> jimmy: she could go back as a ghost, maybe. >> yeah -- and she did. she does make an appearance. and really a wonderful, wonderful actress. and i had a lot fun wor