New York is a unique city with unique problems, and probably one of the only places you’ll find a triumvirate of water managers named Paulie, Jimmy and Vinny. Paul Rush, James Roberts and Vincent Sapienza — the New York City Department of Environmental Protection’s Deputy Commissioners for the Bureaus of Water Supply, Water and Sewer Operations, and Wastewater Treatment, respectively — addressed a group of engineers and students at Columbia University Tuesday afternoon. Part of a list of speakers presenting at this year’s New York City Water Summit, the trio of water czars laid out for conference participants their agency’s plan for the future of all things liquid in the Big Apple.
As with any sizeable water and sewer system, DEP has a number of challenges before it in the coming decades. With 9 million people relying upon the agency for water deliveries and wastewater disposal, that’s no easy task. The city’s water supply and sewage systems are both expansive and complex, and from a major leak upstate to the continuing puzzle presented by combined sewer overflows there are a few key areas needing attention. City water managers explained why water and sewer usage rates have gone up — they increased 12 percent for 2011, and are set to step up another 7.5 percent next year.
“The city is really spending money purposefully, and these are big investments,” said Roberts of DEP’s capital improvement program.
- The Leak -
Three separate watersheds — Croton, the Catskills, and the Delaware River — 19 reservoirs supply New Yorkers with water. Nestled in green hills and mountains far from New York City’s paved hustle and bustle, water flows by gravity through concrete-lined tunnels drilled through bedrock. One of these, the Delaware Aqueduct — completed in 1945, is listed in the Guiness Book of World Records as the longest continuous underground tunnel in the world — and it is leaking…a lot. DEP estimates that anywhere from 15 and 35 million gallons per day ooze into the surrounding rock.
DEP employees discovered the leak in the 1990s in a section of the Delaware Aqueduct known as the Rondout West Branch Tunnel. Some sections of the tunnel are up to 1,500 feet below the surface, making detection and repair extremely difficult, but pictures taken in 2002 and 2009 with an Autonomous Underwater Vehicle operated by a team of scientists from Woods Hole Oceanographic institute pinpointed the leak. It is located in a segment that bores through relatively porous limestone.
“The last time anyone really looked at the tunnel was in 1957, when it was de-watered for inspection,” said Rush.
The Delaware Aqueduct, which connects Cannonsville, Neversink, Pepacton, and Rondout Reservoirs to urban taps, has been in constant use since then. It supplies nearly 50 percent of the city’s drinking water. City engineers have decided to fix the leak by using a three-mile bypass tunnel in order to take the faulty pipe section out of service. The project, slated to begin in 2013, has an estimated cost of more than $2 billion, and will take six years to complete.
- From Gray to Green -
Perhaps one of the most daunting problems DEP faces is combined sewage overflows, known as CSOs. Incredibly complex, the warren of sewage pipes beneath the city slithers through 6,600 slimy miles, delivering sewage and storm water to the city’s 14 treatment plants, and ultimately back into the watershed. Unfortunately, during heavy rainfall, rainwater — which flows through the same pipes as raw sewage — swells the amount of liquid in the system. With no place to go, rainwater mixed with sewage spills from any one of 450 sewage outfalls. Ideally, the only water issuing from the outfalls would already have been treated, but not so for the overloaded pipes.
A host of problems greet planners as they cope with what is considered a major pollution issue. First, the city’s byzantine web of aging sewage pipes wasn’t standardized until 1970, so maintenance can be tricky. But Roberts highlighted a vigorous effort by the city to keep sewage lines clean — grease reduction, regular cleaning, and public education for users to reduce the amount of damaging material entering the system were among the methods employed.
Until now, DEP has been required to build an expensive system of storage and treatment tanks to deal with CSO effluent. Dubbed gray infrastructure, the costly setup consists of 28 million gallons of storage capacity. City engineers have increasingly relied upon mother nature to solve their problem, studying bioswales, blue and green roofs, and gradual elimination of some non-permeable surfaces (such as blacktop parking lots) as potential ways to reduce runoff and lower the volume of water in the sewage system during storm events. DEP estimates a runoff reduction of up to 12 billion gallons per year with adoption of a green infrastructure system. Although planners expect long term savings, the development comes at a cost. DEP has committed $1.5 billion to the project over the next 20 years, and expects $900 million in private investment.
“The green infrastructure strategy is a lot cheaper than concrete and steel,” said Sapienza, quoting $1.5 billion in savings for New Yorkers. He gave the Staten Island Bluebelt — a stormwater management system that makes use of natural drainage corridors — as an example of what’s being done right. “The bottom line is that we want to leave the city better for our children and grandchildren than we got it.”