Environmental Engineering Reference
In-Depth Information
At this depth, I sensed the weight and density of the city's bedrock. My eyes slowly
adjusted to the gloom, and I saw muddied yellow drill rigs mounted on Caterpillar
tracks. The rigs were armed with twin hydraulic bits and stood next to a long, mud-
spattered conveyor belt. Giant air ducts and thick, looping power lines carrying 13,200
volts of electricity to power the tunnel-boring machine snaked along the wall beneath a
line of dim bulbs. In either direction, the massive tube seemed to recede to infinity.
Dowey, a tall, lean man with a dark goatee, pointed straight ahead, along the tunnel.
“That way is north,” he shouted over the roaring fans that supplied fresh air. “From here,
the tunnel runs straight uptown to Sixty-Eighth Street, with no stop signs.” Then he
turned downtown. “Let's go this way and see if we can find some sandhogs.” Sandhogs
is the nickname for the tunneling specialists who have excavated New York's subways,
sewers, and skyscraper foundations since the mid-1870s, when they dug out the cais-
sons for the Brooklyn Bridge.
Manhattan is a relatively dry island in a relatively wet region. Viewed through the lens
of water supply, New York City has more in common with dry Western cities such as
Denver, Phoenix, and Las Vegas than it does with most places in the East. Just like those
cities, New York has responded to its water demands by building a gigantic siphon to
bring water into the city from rural sources far away.
Tunnel No. 3 is a project of the New York City Department of Environmental Pro-
tection (DEP), which comprises the largest and most complex municipal water sys-
tem in the country—known to many engineers as “the eighth wonder of the world.”
The DEP's exquisitely engineered network of dams, reservoirs, aqueducts, and tunnels
draws from a watershed stretching across 1,972 square miles—an area about the size of
Delaware—and contains 580 billion gallons of water. The distribution system supplies
roughly 1.3 billion gallons of freshwater to 8 million city dwellers and 1 million suburb-
anites every day. The DEP system encompasses sixty-five hundred miles of water mains
and sixty-six hundred miles of wastewater pipes; 95 percent of the water it carries flows
dozens of miles into the city by gravity alone. Dropping from aqueducts as high as four-
teen hundred feet above sea level down to pipes a thousand feet below sea level, the wa-
ter builds up so much pressure that when it reaches Manhattan's water mains, where it
flows at roughly ninety-five pounds per square inch, it will rise to the sixth floor of most
buildings unaided by pumps. Pressure in the system is so great that in some parts of the
city it must be lowered mechanically by regulator valves.
New York City's water system was well designed and robustly built but has grown
leaky and decrepit with age. Parts of the system are 140 years old and require significant
upgrades. The city's drinking supply has had a higher profile under Mayor Michael
Bloomberg, but much of the system suffers from years of underinvestment and deferred
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