Cleaner, Greener NYC Waterways

The City of New York has invested over $10 billion since the early 2000s on projects to protect and improve water quality in New York’s rivers and creeks. Building on the legacy of innovation and investment, today the New York City harbor is the cleanest and healthiest it’s been in over 100 years of testing. While water quality continues to improve, there are still challenges to address—particularly the pollution that is caused by stormwater runoff. 

In 2015, the New York State Department of Environmental Conservation (DEC) issued a permit to the city to manage stormwater runoff, protect overall water quality and improve water quality in impaired waters. As part of the integrated Stormwater Management Program that the city is developing, new legislation and programs will address stormwater management from construction sites.

To gather substantive feedback in the development of the new program, the New York City Department of Environmental Protection (DEP) asked Urban Green Council to convene industry stakeholders to discuss their experiences managing stormwater from construction sites. The goal was to add minimal extra burden to the already expensive and complex process of construction permitting in New York, while getting the biggest environmental “bang for the buck.” Perhaps regulators could even remove barriers (often around permitting) that make it harder for people to do the right thing. The focus was municipal separate storm sewer system, or MS4, areas.[1]

The Cost of Runoff Reduction

In MS4 areas, rainfall runs off roofs, lawns, sidewalks, streets and parking lots before heading to the storm sewer to be discharged into a nearby waterway. On its way, it picks up contaminants from silt, fertilizers, herbicides and heavy metals in motor oil. Unlike in combined sewer areas, the rainwater doesn’t get treated, so all that gunk is going right into the waterway.[2]But there are many stormwater control measures that could be implemented to reduce pollution runoff into waterways in MS4 areas. DEP prioritizes keeping and treating the stormwater onsite through vegetation, rain gardens, permeable pavement or a green roof. Sometimes it’s impossible to do so—the building site may be “space constrained” with no room to build these features, or “soil constrained” if bedrock or the water table is right below the surface, with no place onsite for water to be absorbed into the ground. But in that case, water may be treated onsite through a sand filter or other means.

Not all stormwater management techniques are appropriate for all sites, and they also vary widely in price. DEP did extensive cost modeling to determine the overall and average cost of implementation for sites across the city. They started the process by checking their cost assumptions with engineers, consultants, owners and developers. This included both construction (capital) costs and ongoing (operational) costs.

Defining the Policy and Permitting System through Stakeholder Engagement

Permitting stormwater management work can be complex since projects that disturb soil must apply for wastewater discharge permits from the city and state. Wisely, DEP has taken significant time to work through the development of the MS4 policy, procedures and permitting process with industry representatives. Feedback obtained from stakeholders is informing DEP’s development of this new program, which aims to maximize compliance while streamlining the process for new development and redevelopment sites.

Looking Forward

The city’s regulatory authority on sites one acre or greater will roll out first, in 2019, with the regulation of smaller lots to follow. New Yorkers will see further improvements toward achieving cleaner water at that point—the DEP program is predicted to keep over 10,000 tons of suspended solids out of our waterways, with similarly impressive reductions for other pollutants.

So, is this regulation worth the work? In just 30 years, our waterways have become cleaner than one could have imagined in 1985. Hopefully, in 2047, we’ll remember the sights and smells of our waterways in 2017and think the same thing.


[1] This is different than the combined sewer overflow (CSO) issues that everyone has heard of. In combined sewer areas, the stormwater drains feed into the same pipes as the sewers that take wastewater from the sinks, showers, toilets laundries and more. These pipes lead to the wastewater treatment plant—yes, New York City handles much of its rainwater at a treatment plant before discharging it to a waterway! The City’s Waste Water Treatment Plants are designed to handle twice the amount of dry weather flow but, depending on the rain event or the location, there may be too much water for the plant to treat all at once. When that happens, the sewer system is designed to discharge the mixture of raw sewage and stormwater at a CSO outfall.

[2] That doesn’t mean MS4 isn’t a new and better system; it is, and cities newer than New York tend to do it this way. Even old York prohibits combined sewers at this point. In fact, the issues with MS4 areas are not as pressing overall as CSO issues. Less of the city area is MS4 and most of the population (and therefore, sewage) is in CSO areas. That’s why CSO areas have gotten attention for a long time now, but you may not have heard of MS4—it’s not as much of a problem, so CSOs got attention first. However, after the 2015 city-state agreement, New York City must regulate MS4 areas.