The Conservation Conversation: Sewers Vs. No Sewers (Part II)

Last time, I described the extraordinary improvement in public health and water quality that was accomplished during the 20th century - particularly, the last quarter of that century after the 1972 federal Clean Water Act required secondary treatment for sewage systems that discharged into rivers, lakes, and the ocean.

New York City’s sewage system is a marvel of engineering, with over 6,000 miles of pipes carrying wastes to 14 treatment plants with a combined capacity of two billion gallons per day.

Its construction is responsible for huge improvements in the quality of the water that surrounds us. Unfortunately, there is a big flaw in the system and that flaw represents the major remaining source of water pollution confronting our urban aquatic environment today. 

Years ago, New York, like most older cities, built combined sewers. That means the same pipes that carry “sanitary” sewage - wastes from our toilets, sinks, bathtubs, showers, dishwashers and washing machines - also carry storm water from the streets whenever it rains. In newer systems, sanitary and storm sewer pipes are separated. 

The problem with the older combined sewers is that when it rains more than just a little bit, the pipes - and, more importantly, the sewage treatment plants at the ends of those pipes - can't handle the extra load. So, the system was designed with overflow points, where billions of gallons per year of this rain-water-and-raw-sewage mixture gets discharged into creeks, bays and inlets all around the city. 

Several combined sewer overflows (CSOs) empty into Little Neck Bay. The largest was located on Alley Creek, just south of Northern Boulevard and east of the . During many summers, the bay would be closed to swimming for weeks at a time because of unhealthy bacteria levels attributable to sewage.  

The federal Clean Water Act requires that pollution from CSOs be addressed, but doing so is complex and costly. Separating the sanitary and storm sewer systems is the best solution, but it would be incredibly expensive and disruptive if done city-wide.

An alternative approach is to build extra storage capacity into the system before the pipes reach the treatment plant. When it rains, the excess water and sewage gets stored instead of going into the bay. When the rain stops, the stored wastes are pumped back into the pipes and on to the treatment plant.

During the past several years, the city built one of these storage facilities for the Alley Creek CSO. A large-diameter, rectangular pipe was installed under Northern Boulevard and under the open park land directly across the street from APEC.  The pipe goes nowhere. Instead, it becomes wider and deeper and doubles back on itself. Essentially, it becomes a large underground storage tank with a capacity of about five million gallons. This is enough to hold the excess water from small rain storms.  

Even during larger storms, much less sewage ends up in the bay. When it starts to rain, the “first flush,” which is the most heavily contaminated, is captured in the underground tank. And floatables – plastic garbage and the like – are screened out from the dilute sewage that gets discharged.

The $130 million project, which was put into operation in May of 2011, will reduce the total amount of CSO discharged into Little Neck Bay by about 134 million gallons annually - a reduction of nearly 55 percent from previous levels. That's not enough to completely solve our water pollution problems, but it will effect a dramatic improvement.

The construction area is now being restored and will be returned to park land. Native trees and shrubs are being planted and a large tidal basin has been constructed. The basin is easily visible from the entrance ramp to the northbound Cross Island Parkway. When the tide is high, water fills the basin to within a stone’s throw of the bicycle path along the parkway.

Thousands of plugs of spartina salt marsh grass were planted around the new tidal basin. This type of grass thrives in salt water and provides excellent habitat for aquatic animals and birds (more about spartina in my next post). During warmer weather, you’ll see egrets, herons, bitterns, geese, ducks of various kinds and the occasional swan. You may even see an osprey dive from the air into the tide pool to catch a large fish.  

When the replanting of the upland area between the basin and Northern Boulevard is completed, other animals will return and you'll be able to walk through the area to view the wildlife.

In this case, a sewer pipe to nowhere is a very good thing.