Every year, New York City dumps billions of gallons of raw sewage into its waterways. Not only is that unpleasant — but the city could face hefty fines if it doesn’t clean up its act. The city has recently come up with a new plan to address the problem — a plan based on so-called “green infrastructure.” It’s not going to stop sewage from overflowing entirely. But as Willow Belden reports, experts and community groups alike hope it will make a major difference.
Interactive graphic by Jonah Comstock.
Story by Willow Belden
Second Avenue in Brooklyn is a noisy, industrial street that dead-ends into the Gowanus Canal. There’s a maze of buses parked at the end of the cul de sac.
Hans Hesselein picks his way around the pot holes and steps out into a small, grassy park on the southeastern bank of the canal. A big green sign warns visitors not to swim. The Gowanus polluted with toxic chemicals, and this spot is a discharge point for sewage.
Hesselein says he was here last summer during a downpour — and he saw sewage pouring into the canal.
“There was just this huge, violent swelling of water rippling the surface,” Hesselein said. “And this pitch black cloud, filled with all kinds of floating debris just spread across the water like an oil slick.”
Most of it was human excrement.
“And it smelled,” Hesselein said. “Oh my goodness — You can imagine what it smelled like. It was all sewage.”
This spot on the Gowanus is one of more than 450 places across the city where raw sewage is discharged into the water. It happens whenever it rains hard.
Here’s how it works:
Step one: It starts raining.
Step two: The rain runs off of rooftops and streets and sidewalks … and flows into the sewers.
Most of New York City has what are called “combined sewers.” That means rainwater from the street mixes with wastewater from your bathroom and kitchen.
As a result, any time it rains, the sewage treatment plants have to deal with a lot more liquid.
“The systems — the treatment plants — in New York are generally able to treat twice what’s called the dry weather flow,” said Kevin Bricke, the director of environmental planning and protection at the regional office of the EPA.
Even with a moderate rainfall, the city gets significantly more than that.
When the capacity of the system is exceeded, the excess volume — i.e. rainwater mixed with raw sewage — overflows into the waterways around the city. That’s called “combined sewer overflow” — or CSO. The city’s waterways get about 30 billion gallons of it every year. That’s more than 45,000 Olympic swimming pools full of sewage.
Some of the release points are near beaches, so when it rains, swimming is off limits. And people who live and work near discharge locations say the smell is sometimes nauseating.
But there’s a bigger problem. A legal problem.
The Clean Water Act makes it illegal to dump contaminants — including sewage — into U.S. waters. Cities can get permits allowing them to discharge some waste — but they have to prove that they’re working to remedy the situation.
“The city of New York is already in the process of developing what are called long-term control plans,” said Bricke. “These are their plans to abate combined sewer overflows and achieve the goals of the act. … They’re doing that under an order that they have with the New York State Department of Environmental Conservation.”
Until recently, the plans focused on increasing the capacity of the sewer system — building more tanks and pipes. That’s what’s called a “gray infrastructure” approach.
It’s expensive, though. A recent upgrade to a plant in Brooklyn cost five billion dollars.
And there’s another problem. Carter Strickland, director of sustainability at the city’s Department for Environmental Protection, says gray infrastructure treats the symptoms — not the disease.
“The fundamental cause of our wet-weather issues in urban areas is the fact that when you build a dense city … you have a lot of impervious areas,” Strickland said. “You cover things with roads and roofs and whatnot. … So address the fundamental root cause of the problem, we need to make our impervious areas effectively pervious.”
In other words, we need to make New York City more like a natural environment, where the ground — not the sewer system — handles the rainwater.
That’s what the city is trying to do now: Not focus exclusively on gray infrastructure, but instead add what’s called “green infrastructure.” The new plan includes measures designed to stop storm water from entering the sewers in the first place.
“Green infrastructure gets to the root of the problem in a way that gray infrastructure doesn’t,” Strickland said.
There are several different types of green infrastructure.
One is being tested right now on a parking lot in New Jersey. The lot is made out of “porous pavement,” which is designed to let water seep through into the ground below.
Pat Pozzolano is in charge of testing the pavement for the EPA — to see how well it works. He picks up a plastic container with a precisely measured amount of water and empties the bucket onto the porous concrete.
The water disappears into the pavement almost instantly.
“That was 3.6 liters, and that flowed through at a little over five seconds,” Pozzolano says as he scribbles numers in a notebook.
Mike Borst, a chemical engineer with the EPA, says the pavement is tested every month.
“None of these have ever demonstrated runoff,” Borst said. “All the water that has hit it has gone in.”
Up to 960 inches of rain per hour can flow through porous concrete, which Borst says is 100 times more than almost any rain event.
There’s another way to get water to go into the ground: Get rid of the pavement, and replace it with “rain gardens.”
Rain gardens are gardens that are specifically designed to absorb stormwater.
Hans Hesselein, who works for the Gowanus Canal Conservancy, is about to install a series of rain gardens, not far from where he saw the sewer overflow last summer.
He walks up the street away from the Gowanus.Workers bustle around the open doors of warehouses. Vehicles stand idle on the sidewalks. There’s not a tree in sight. Not yet, anyway.
The Gowanus Conservancy is planning to put in seven long, narrow gardens along the edges of the street.
“We hope to absorb all of the rain that falls on the sidewalk and the street itself, and channel it into basic rain gardens with street trees and shrubs,” Hesselein said.
The beds will be slightly lower than the surrounding areas, so water will flow off the pavement and into them. They’ll only take up half the width of the sidewalk. But if Hesselein’s calculations are right, the two and a half blocks where they’re installed won’t send any water into the sewers.
The city’s Department of Environmental Protection is funding this project and several others that community groups are undertaking.
The city also has more than 30 green infrastructure projects of its own in the works. It’s making green roofs — which are basically rain gardens on top of buildings. And blue roofs — where they essentially turn the roofs into swimming pools.
“We have pretty much every technology that’s practical built on a pilot scale, and we’re starting the monitoring this spring,” Strickland said.
Monitoring — to see how effective green infrastructure is.
The city expects that it will actually work better than gray infrastructure — and cost less.
DEP has estimated that building more tanks and pipes would reduce CSOs by 30 percent. Add in green infrastructure, and they say we’ll reduce sewer overflows by 40 percent.
Environmental experts say that’s plausible.
“Green infrastructure can be very effective in terms of volume reduction for stormwater management,” said Robert Roseen, director of the Stormwater Center at the University of New Hampshire.
Roseen is working on a study about green infrastructure, and he says cities like Chicago and Portland, Oregon are successfully reducing their CSOs — and saving money — through green measures.
“Cost savings for CSO management with green infrastructure are often in the 20 to 30 percent ranges,” Roseen said. “And when you’re talking billion dollar price tags, that’s a lot.”
But green infrastructure isn’t a panacea.
Porous pavement may be good at keeping water out of the sewers. But Mike Borst, the EPA engineer, says that in the few places where it’s been used on roadways, it’s fallen apart three times as fast as normal pavement.
Some environmental groups also worry that the city’s green infrastructure plan doesn’t go far enough.
Katie Schmid, director of the Newtown Creek Alliance, likes the idea of green infrastructure. In fact, her group is redoing a park in Bushwick to add more soil and trees.
Schmid says the trees will help soak up stormwater in the Newtown Creek watershed. But she’s concerned that initiatives like this won’t be enough to solve the creek’s problems.
“You can make a huge difference with green infrastructure if you commit to it, you make every street tree pit capture stormwater, if you green enough city property as you can,” Schmid said. “But the caveat to that is that we need more than a big difference on Newtown Creek. We are radically under any sort of attainment standards. … And you have decades and decades of sewage just sitting on the bottom of the creek.”
The city’s green infrastructure plan would only keep ten percent of the rainwater out of the sewers. And environmental officials like Kevin Bricke say that even that is going to be hard to achieve.
“It’s much easier to implement green infrastructure measures when you’re doing new development, which you’re not going to find a lot of in New York City,” Bricke said. “When you’re retrofitting in an existing area, you can still achieve some objectives but not the same level of objective.”
The city is trying to encourage private individuals to help out by adding green infrastructure to their property. There’s a tax break for green roofs, and a fee that parking lot owners have to pay if they don’t manage their stormwater runoff.
The DEP is also giving out grants for green infrastructure projects, like the rain gardens by the Gowanus Canal. The deadline for applications is next Friday. And the groups that are selected will have a year to carry out the projects.