The Sewer System
by Michael Markowitz
Oct 20, 2003
Sewage was probably the last thing on the minds of most New Yorkers during the August 14 blackout. But while millions of people struggled to get home or contact loved ones, city workers watched helplessly as untreated waste poured into the East River from a pumping station at Avenue D and East 13th Street. With no electricity, nothing could prevent the pressure of the water from pushing open the gates that control the discharge of untreated sewage and so it simply blasted out.
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By the time the power came back, 145 million gallons of raw sewage - water from toilets and sinks as well as storm runoff -- had flowed into the East River from 13th Street and another 345 million gallons had spilled from treatment plants along the Hudson River in Manhattan and Brooklyn.
Sewage accidents caused by blackouts are rare, of course. What most people do not realize, however, is that spills are quite common. Even after decades of expensive upgrades designed to curb pollution, raw sewage regularly pours into the waterways around New York City because the sewer system uses outdated technology.
Failing sewers are not a problem limited to New York City. On November 4, all voters in the state, including those in New York City, will be asked to approve a constitutional amendment (in pdf format). that would help some smaller upstate communities upgrade their wastewater facilities.
Construction of a Tunnel Sewer under 10th Avenue, 1938.
The measure will not help New York City control sewage spills or deal with the other problems of its massive sewer system. The city will be on its own when it comes to maintaining aged pipes, getting rid of environmentally harmful nitrogen, and dispelling the persistent belief that alligators live in its sewers.
FROM DITCHES TO DUMPING TO DECAY
New York City's sewer system, an engineering marvel and a murky source of urban legend, contains 6,600 miles of mains and pipes. Placed end to end, the city's sewers would stretch from Times Square to Fairbanks, Alaska and back. About 70 percent of that vast sewer system consists of combined sewers, which carry runoff from storms as well as waste from sinks, tubs and toilets. Some of the pipes still in use were laid 150 years ago when the modern sewer system began.
The city's first underground sewer of any kind goes back even further, to Dutch Colonial times, when a channel was dug down the middle of Broad Street and decked over. But well into the 19th century, most waste was typically disposed of in backyard outhouses, dumped into the gutter or poured into the ponds and streams that still existed in many parts of Manhattan.
Explosive growth in the early 1800s forced New York to finally confront its sanitation problems. In 1849, after years of haphazard planning and a series of deadly cholera outbreaks, the city started systematically building sewers. Between 1850 and 1855, New York laid 70 miles of sewers. In the second half of the 19th century, it expanded the network throughout the metropolis. By 1902, sewers served virtually all the developed sections of the city, and even tenement houses began offering private flush toilets. Today, sanitary sewers snake their way beneath all but a handful of outlying streets, and storm sewers crisscross just about every neighborhood.
Each day, the city's 14 sewage treatment plants handle 1.3 billion gallons of wastewater, roughly 162 gallons for every man, woman and child who lives in the city.
Whenever you flush or turn on a faucet, the wastewater flows through pipes that lead to sewer pipes, called mains, in the street. Sewer mains are typically three to five feet in diameter. Runoff from rainstorms (and all the stuff that collects in the gutter) joins it in combined mains.
Building a Trunk Sewer in Queens, 1938
The sewage and runoff flow into a series of progressively larger pipes until they reach the wastewater treatment plant. The system relies almost entirely on gravity to keep the waste moving, although pumps help where the topography is difficult.
For decades, the waste simply went from the pipes out into the waterways surrounding the city. Most treatment plants in the city were not built until after World War II, and the last of these, the North River plant in West Harlem and the Red Hook plant in Brooklyn, were not completed until the late 1980s. As recently as 1986, all the sewage from the Upper West Side of Manhattan flowed untreated into the Hudson River. Ending that sewage flow played a big role in the river's rebirth.
Now the sewage goes to a plant for several stages of treatment. In the first stage, known as primary treatment, the water flows through filters and then collects in pools, where solids settle to the bottom so they can be removed. Until 1992, the city dumped about five million tons a year of these solids, known as sludge, in the ocean. It now dehydrates the sludge at special de-watering facilities that reduce its volume dramatically. The sludge is then either carted to dumps out of state or processed into materials that can be used for landfill cover.
In the secondary treatment stage, the wastewater is sent to large tanks where bacteria consume nutrients and organic materials. After the bacteria do their job and die a natural death, they are allowed to settle out of the water in tanks and then the cleaned water is released. One of the byproducts of the bacteria processing the waste is nitrogen, which mostly comes from the breakdown of ammonia in the sewage.
That is what happens when the system operates properly, but all too often it does not. Whenever there is a significant rainfall, sewer pipes overflow, and trash and chemicals pour directly into rivers and bays. Normally, all the waste in a combined system - toilets, sinks and runoff -- flows into sewage treatment plants. But when it rains heavily, all the the pipes tend to become overwhelmed and spill their contents. Each year, about 40 billion gallons of wastewater pours out of the combined system " a seemingly large amount but far less than in the past," city officials say
"Any time you get over a tenth of an inch of rain per hour, there are overflows," says Terry Backer of Connecticut-based Long Island Soundkeeper, an environmental group. "Oil, garbage, ethylene glycol [antifreeze], dog poop and everything in the gutters comes blasting out of the system, and then we tell our kids to go swimming in it."
Now that the city has upgraded its sewage treatment plants to comply with the federal Clean Water Act, it will focus on stanching such overflows and limiting the amount of nitrogen discharged from the sewer system into waters feeding Long Island Sound. "The key sewer-related issue right now for us is definitely the decrease of overflows," says Ian Michael, press secretary of the Department of Environmental Protection. The city has embarked on a 10-year overflow reduction program that will cost $2 billion, he says.
Environmentalists have been pressing the city about this. The current situation is "outrageous," Sarah J. Meyland, executive director of Citizens Campaign for the Environment, told The New York Times recently. "Across the board there often is a very casual feeling about allowing raw sewage back into the environment under sporadic circumstances, as if sewage is really not that bad."
Construction Crew at a Storm Sewer in Queens, 1938
Many see the combined sewers as the culprit. Only about 800 U.S. cities still rely on combined systems. The rest, some 20,000 municipalities, carry wastewater and storm runoff in separate pipes. The separate sewer systems prevent overflows and are more efficient because treatment plants do not have to accommodate storm runoff along with wastewater.
But building separate sewers in New York would be prohibitively expensive. Instead the city is constructing huge underground reservoirs where the overflow can be held until water levels subside and the waste can be safely pumped into the treatment plants without spilling.
Poor equipment poses another problem. The 13th Street plant had emergency generators to prevent spills but they failed during the blackout. Some in the community have opposed the generators because the neighborhood already has a Con Edison plant in addition to the pump station. But the city is ready to install new backup power systems.
THE NITROGEN PROBLEM
The city is also under pressure to reduce the amount of nitrogen it discharges along with treated sewage water. Nitrogen feeds huge growths of algae, which deplete the supply of oxygen in the water as they die and decompose, choking fish and other marine life. Environmental groups say that excessive nitrogen levels in New York City's wastewater have undermined efforts by other Long Island Sound communities that have spent hundreds of millions of dollars to clean up discharges and restore the marine ecosystem.
One such group, Soundkeeper, filed suit in federal court in 1998 accusing the city of failing to comply with nitrogen regulations and trying to delay a clean up. After the states of New York and Connecticut joined the environmentalists' action, the city in late 2001 agreed to begin nitrogen reduction, using natural chemical reactions.
But some environmentalists think this is not enough. At a hearing before an administrative law judge in Nassau County on October 2, Soundkeeper argued that the city should be held to stricter standards under its permit to discharge wastewater. The city, which has invested heavily in nitrogen removal in recent years, says it is doing plenty and should be able to seek the most cost-effective solutions. The hearing process could take four to six months.
In the sewer pipes, age is a continual and critical issue. The heavily used system still includes 1850s-vintage pipes below parts of Lower Manhattan. Sewer workers regularly send remote-controlled video cameras through the pipes to try to spot leaks and cracks and patch or replace damaged pipes before they break. But replacing whole stretches of old pipes is not an option, because officials believe that even a major water or sewer main break is less disruptive than ripping up miles of streets to lay new pipes. "We know for a fact that they'll continue to last," Michaels says. "It is not just a matter of crossing your fingers and hoping they keep working."
The city is also repairing one of its oldest treatment plants, Sheepshead Bay, Brooklyn, where a fire in August damaged the odor-control system and sent foul-smelling gases wafting over the surrounding residential neighborhood.
The measure on the ballot this fall is designed to help smaller communities fund some of the projects New York City has already undertaken. If passed, it would allow counties and municipalities to exclude the cost of building or refurbishing sewers from municipal debt limits until 2014. Assemblymember Robert K. Sweeney of Suffolk County, who sponsored the measure in the Assembly, says it will help communities that have small tax bases by allowing them to borrow for sewer projects without having to postpone building roads and schools. The debt limit is pegged to the size of the tax base,
"In the past 10 years there have been less than two dozen communities statewide, most of them upstate, that have been covered by this," says Sweeney. The measure, which sailed through the state legislature earlier this year, renews a provision first enacted in 1963.
Whatever the problems facing New York's sewer system, video inspections of the sewers do not turn up colonies of alligators.
Contrary to popular mythology, there are more alligators living in Manhattan apartments than underneath the city.
The alligator story is an old one, but it got a big boost in 1959, with the publication of Robert Daly's otherwise credible book, The World Beneath the City. Daly relied a bit too heavily on an imaginative former sewer inspector named Thomas May who said that, as he went on his rounds, he encountered reptiles of "alarming sizes."
A new sewer-related urban legend has been born in recent years. The story goes that marijuana, hurriedly flushed down toilets to keep it from police and prying parents, has taken root in the sewers. Fed by nutrient-rich sewage but deprived of sunlight, it mutated into an extremely potent albino form. Known as New York White, this pot is said to be incredibly expensive. That's because to harvest it, you have to get past, yup, alligators.
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