Black Mayonaise

What Exactly Is the Black Mayonnaise at the Bottom of the Gowanus Canal?

Photo by Susan De Vries  by Craig Hubert

There are numerous mysteries about the Gowanus Canal. But the most baffling, not to mention terrifying, is the thick dark sludge that makes it way through the oily waters, that which has been called black mayonnaise.

Aside from its gross name — which is a pretty good descriptor, to be honest — there has rarely been an acceptable explanation of what black mayonnaise is, exactly, and how it is formed. So we reached out to Christos Tsiamis, the EPA’s Senior Project Manager for the Gowanus Superfund cleanup, and asked him to explain.

gowanus canal black mayonnaiseA core sample from the former First Street Basin near the BRT Power Station. Photo via EPA’s Gowanus Canal Facebook Group

Black mayonnaise is the “result of chemical waste that was discharged from the industries that operated along the canal as well as by New York City sewage and street runoff,” wrote Tsiamis in an email.

“The combination of the chemicals and sewage gave the sediment the soft texture of mayonnaise, while the combination of liquid tar from the manufactured-gas plants, petroleum products (such as motor and lubricating oils), decomposed organic matter and sewage gave to this sediment its black color.”

gowanus canal brooklyn superfund sitesPhoto by Hannah Frishberg

A 10-foot-high layer of black mayonnaise lays over the original native sediment at the bottom of the canal. But is it dangerous?

The answer is a resounding yes.

“It contains a multitude of chemicals (in the dozens) many of which are toxic and dangerous to human health upon repeated exposure or from consumption of fish that is caught at the canal (or at close proximity to it) over time,” wrote Tsiamis. This was determined by a risk assessment study conducted by the EPA in 2010.

Will the cleanup cleanse the canal of black mayonnaise forever? Two months of dredging, starting in December, is expected to permanently clean the bottom of the canal, according to Tsiamis. Meanwhile, the Gowanus’ two new underground holding tanks are expected to keep a good part of sewage and street run-off from overflowing into the canal during storms. “After the storm passes, the liquid held by these tanks will be pumped for treatment to the city’s treatment facilities,” he said.

Tsiamis says these measures will free the canal of black mayonnaise forever. But the EPA will be checking every five years anyway, just in case the substance inexplicably returns.

Until next time,

Garbage Girl


Is It A Waste?


The strangest sight of other worldly lumps and bumps planted with a variety of grasses and a smattering of young trees along the perimeter has been evolving under the Whitestone Bridge now for many years.

On a former landfill, closed in 1963, sits a World Class Golf Course. The New York Parks Department and Donald Trump have put years into its realization.

I have blogged a few times about repurposing landfills such as Fresh Kills and redeveloping Superfund Sights such as the Gowanus Canal. As the engineering gets more sophisticated and the understanding of toxic pollution over time gets known, we are creating some interesting solutions.

A few weeks ago, I attended a lecture on the Gowanus Canal.  I learned that its status as a Superfund sight puts the financial burden for the pollution primarily on National Grid and New York City.  This means that they are responsible for funding the clean up of the water, the sediment and the surrounding land.  The costs are staggering and may never be known.  So the city is giving incentives to developers in exchange for cleaning up the portion of land they want to build on.  Whole Foods was the first to step in and it took over five years.

a  - gowanus_0

There was even a pair of swans fishing in the water when Martin and I were there this weekend.  I hope they survive!  Eventhough, the reality was not quite as spectacular as the renderings full of open park land and people picnicking along the canal, it was a nice experience with its brick walls and greenhouse glass roof.  All creating the feeling of potentially good things to come.

The challenge for Gowanus will be our sewer system and heavy rain. We have a one use system that was built more than a hundred years ago.  All storm water, sewer water and household water goes into the same pipes.  These old pipes have a limited capacity to deliver the water to the treatment plants and clean it before it goes to the Gowanus that feeds into NY Harbor and the Atlantic Ocean.

You have been warned!  The following video is really bad!

How You Can Help:

  • Be aware that everything going down your drains has the potential to end up in the waterways around our city, especially during storms.
  • As hard as it is to support commercial development at times; if they come with resources to clean up our biggest mess. . . how bad can that be?
  • Take up golf?  Yes, the grounds are covered with pesticides and fertilizers to keep that course green and inviting for the wealthy few. . .it looks better than a landfill and the birds love it!
  • For more information about concerns due to gentrification and bad development. 
  • Look for  Joseph Alexiou has a new book coming out.     Gowanus: The Rise and Fall and Rise of Brooklyn’s Curious Canal.

Until next week,

Garbage Girl


Toxic Waste Spurs Development Boom


Brooklyn’s own Gowanus Canal was designated a Superfund Site in 2009. This means the EPA will force the polluting companies to pay for the clean up of the canal.  Potentially Responsible Parties that were served notices are Con Edison, Honeywell, Kraft, ExxonMobil, Unilever, Viacom, Coca-Cola, Sears, their predecessors, or their affiliated businesses. The worst offender is National Grid due to decades of coal tar pollution. Also, the City of New York.

Residential and commercial buildings add to the problem by draining their sewage downhill and storm water collecting all sorts of runoff from 19th and 20th century industrial Brooklyn all end up in the canal. The natural tides from Upper New York Bay do not flush the canal out so the water stays put. Without movement, there is no oxygen.  Life died out, changed color from clear to brown to its current gray-green, and it began to smell.  Bubbles of foul air breach the oily surface due to decomposing sewage far below. Dense swirls of oil, at times, can become beautiful in the changing light.  In 2007, a 12-foot-long baby minke whale swam into the Gowanus. Healthy at first, it was soon nicknamed “Sludgy” due to a coat of slimy muck and sediment that covered its body.  Its health deteriorated rapidly and it died after a few days.  In 2013, a dolphin swam into the Gowanus and perished.

Dan Nosowitz wrote in Popular Science,  “The Gowanus is one of the most creatively and massively pathogenetic waterways on the planet. Water taken from different parts of the canal and from different depths will have totally different levels of contaminants, microbes, radioactive materials, or carcinogenic materials. It’s polluted and dangerous in an entirely different way than most other water because you have a huge, 1.8-mile waterway that’s completely stagnant.”

“We don’t really know what’s in there, we don’t know what’s in the soil and air around it, and we don’t know how it affects the tens of thousands of people who live within a few blocks of it.”   Nasreen Haque, a microbiologist who taught at the City University of New York attempted to study the microbial makeup of the Gowanus. She decided to have her students test for microbes in the canal.  “We found that everything we threw at it, every kind of imaginable pathogen, was growing there,”  she said. But here’s where it gets nuts: in the stagnant water of the canal, fed by chemicals from raw sewage, tar, and rotting garbage in the sludge at the bottom of the canal, they’re breeding and evolving into new forms we’ve never seen before.  In 2008,  Haque conducted a study revealing the white clouds of “biofilm” that float just above the sludge at the bottom of the canal.  The clouds aren’t microscopic; they’re giant clumps of white gunk that nobody had ever seen before.  Haque discovered the white clouds of biofilm because she is one of very few to have actually gone into the water.  Hague made her dive with the help of the Urban Divers Estuary Conservancy   This organization supplies Open Accessible Space Information System to NYC.

Cleaning up the Gowanus is a project of immense difficulty.  Companies dumping sewage and waste materials will have to be stopped.  A giant retention tank will need to stop the sewage tanks at the blocked end of the canal from overflowing and sending raw, untreated sewage directly into the Gowanus.  The sludge and the toxic soil around the canal will need dredged and removed.  Methods for treating the dredged soil, depending on the level of contamination, will need burned or treated and put to reuse.  The bottom will need sealed to contain whatever leaked down further.  Then layers of absorbent materials, sand, gravel, and rock, and clean sand will be needed to attempt restoring the canal bottom as a habitat. The current pump can circulate between 200 and 300 million gallons of water daily through the canal to remove water.  The area along the canal will get planted with native trees, grasses, and plants playing a vital role in preventing erosion, fostering a healthy ecosystem and improving its appearance.

So, after all of this bad stuff!

Ways You Can Help:


Until next week,

Garbage Girl