A Premature Plunge into the Gowanus Canal

By Elias Rodriguez

The Gowanus Canal harbors a legacy of industrial waste.

The Gowanus Canal harbors a legacy of industrial waste.

Last week, a gentleman garnered widespread media attention in New York by deliberately swimming in Brooklyn’s highly contaminated Gowanus Canal. This urban water body is on EPA’s National Priorities List of the country’s most hazardous waste sites. The Gowanus is scheduled for a cleanup under our Superfund program.

It seemed like every tabloid and television station in the Big Apple contacted us to ask if it was safe to swim in the Gowanus Canal. In a word: NO! As you can see from our color-coded hazard guide, direct contact with the water of the Gowanus should be avoided to reduce exposure risks.

Color Coded ChartWhat’s in the Gowanus? Data shows the widespread presence of more than a dozen contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and various metals, including mercury, lead and copper, at high levels in its sediment. PAHs and metals were also found in the canal water. PAHs in the canal come mostly from former manufactured gas plants which used coal to make gas. PCBs were used as coolants and lubricants in transformers, capacitors and other electrical equipment. PCBs are suspected carcinogens and can have neurological effects. PAHs are also suspected carcinogens.

The origin of the Gowanus Canal goes back to the 19th century. It was envisioned as a transportation route for goods and services and, after its completion in the 1860s, the canal became an important link for commerce in the city. Manufactured gas plants, coal yards, concrete-mixing facilities, chemical plants and oil refineries were established along its banks. The canal was additionally an outlet for untreated industrial waste, raw sewage and runoff. Fast-forward to 2015 and you’ll see in the Gowanus’ murky water a legacy of urban and industrial pollution in the midst of thriving Brooklyn neighborhoods.

EPA’s $506 million cleanup calls for the removal of contaminated sediment and the capping of dredged areas. The comprehensive plan also includes controls to reduce sewage overflows and other land-based sources of pollution from re-contaminating the waters and ruining the cleanup.

EPA’s progress to date at the Gowanus Canal has been faster than at any other site of comparable complexity anywhere in the nation. We are currently working on the remedial design for the cleanup project to be followed by the start of actual dredging in 2016. When all the work is done, circa 2022, the Gowanus will be in much better shape. In the meantime, the EPA’s No Swimming warning is serious and remains in effect.

About the Author: Elias serves as EPA Region 2’s bilingual public information officer. Prior to joining EPA, the proud Nuyorican worked at Time Inc. conducting research for TIME, LIFE, FORTUNE and PEOPLE magazines. He is a graduate of Hunter College, Baruch College and the Theological Institute of the Assembly of Christian Churches in NYC.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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PAHs in Urban Streams of Kansas City

By Laura Webb

The Water Monitoring Team at EPA Region 7 has been collecting samples in the urban streams of Kansas City since 2006 as shown in the map below.  During our non-field sampling season (when the water is generally frozen or near enough to freezing that we don’t want to wade in), we spend a lot of our time evaluating data and trying to figure out what it all means.

Locations of KCWaters urban stream sampling

One particular contaminant of interest of mine has been PAHs (not to be confused with PAW-PAWs  which we also find in streams from time to time). Polynuclear Aromatic Hydrocarbons (PAHs) are organic molecules found in oil and other fossil fuels which are released when fuels are burned. In my previous job as a bench chemist, I once analyzed samples collected on a filter from a charcoal production facility. The black, sooty residue was comprised of many, many PAH molecules. So, when charcoal is used to grill meat, the smoky flavor and blacked exterior of the meat contains, you guessed it, PAHs. Hopefully not a large concentration, though, because oh how I do love grilled steak! PAHs are found in auto exhaust, tire particles, gas residue, and coal-tar based sealant, such as is used on parking lots and road surfaces. In large enough doses, PAHs are toxic to aquatic species that live in streams. Studies have also shown that higher PAH concentration in urban areas can contribute to human health problems, including asthma, anxiety, and lower IQ scores.

In looking at our data, several things are clear. First, that there is not a clear single source of these compounds to our urban waterways in Kansas City. The ratio of PAH compounds to each other and the total can act as a type of chemical fingerprint of the source. Unfortunately for the urban environment, these prints are smeared and difficult to match up to their source.

Compounds can enter the stream water in many ways. For example, there are permitted discharges, storm water runoff, deposition from the air, and even illegal dumping. Some compounds stay dissolved in the water, some combine to form new compounds, some react with sunlight to decompose into other compounds and some, like PAHs, tend to attach to particulates in the water and “sink” down into the sediment (PAHs and many other organic chemicals don’t really like water; they prefer the rich gooey sediments that deposit as water flows around obstacles in the stream). The sediment is a sink, or trap, for these water-phobic compounds. When we collect samples, we obtain a single grab of water at a particular location at a particular time. While it is a single point in time, the flowing water changes every moment, so samples just a few minutes apart could represent completely different pictures of the stream. Sediment samples, on the other hand, are collected throughout the length of the stream site and really represent a depositional history of what was once in the water as it passed a particular spot. That is what causes the smeared chemical  fingerprint, and what causes me headaches when trying to figure out where the PAHs in stream sediment come from.

A prime suspect of urban PAH contamination is coal-tar sealant, and it appears to be a heavy contributor in stream sediments especially those related to large areas of impervious surfaces (roads, parking lots, roof tops, surfaces that water cannot penetrate but runs off of). As a matter of fact, the total concentration of PAHs in sediment is closely correlated with both the percentage of impervious surfaces and the percentage of development in the watershed. The fingerprint ratios of sealant versus many urban sediments, especially those with the highest levels of PAHs, match fairly well, although still keeping in mind that sediment is a collection of many sources.

Along with these sealed surfaces are mobile sources in the form of gasoline and diesel burning vehicles. The pollutants deposit from the exhaust, either in the water itself, on the sediment, or surrounding land and are then washed into the streams during runoff events. Some of the sediment fingerprints have traits from petroleum sources but because the sediment is a sink, there is no clear pattern match for this source (but I know it contributes). Along with vehicle exhaust, there is also power plant exhaust, perhaps smoke from nearby restaurants that grill their meat, fireplaces (although we do collect samples in the summer, the deposits occur all year long), waste water treatment discharge, and other industrial processes.There are plenty of sources, and when concentrated together in the urban core, they combine to increase the PAH concentrations in sediment to levels that may be problematic for aquatic life. So that’s a look at one class of compounds we find in the urban environment. For a more complete look, check out our website at

Laura Webb is a chemist with EPA Region 7’s Water Monitoring Team.  She spent her first 16 years with EPA in the regional laboratory, analyzing samples for everything from metals to dioxins.  Her current assignment involves ambient water sampling, laboratory analysis, operating the mobile bacteria laboratory, and participating in emergency responses as part of the Response Support Corp.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

Please share this post. However, please don't change the title or the content. If you do make changes, don't attribute the edited title or content to EPA or the author.