The Gowanus Canal Flushing Tunnel, originally built in 1911, is a 12-foot wide structure that runs beneath Degraw Street through Boerum and Cobble Hill, between the Gowanus Canal and the New York Bay. Following activist Chris Swain's icky dip into the canal's putrid waters, urban explorer Steve Duncan shared with us his extensive knowledge of the canal's turgid history. Click on the photos for a tour!


When it was first built, the Gowanus Flushing Tunnel pumped or flushed the dirty water from the canal out into Buttermilk Channel (the part of New York Bay between Red Hook and Governor's Island). This worked fine until the pump—an old ship's propeller—broke down in the 1960s, causing the canal to become stagnant and polluted once more.

Some repairs were made in 1999, and the flow of the tunnel was reversed now to pump water from the Buttermilk Channel into the Gowanus Canal so as to "flush" the canal with clean water again. In 2012 and 2013, the tunnel was drained and new turbines were installed. The Flushing Tunnel enters the Gowanus Canal at Degraw Street, and at low tide you can see the water from it spraying into the canal.

Other features of the tunnel: When a nearby sewer line broke in the 1980s, the city laid a "temporary" line inside the large flushing tunnel—this has become a permanent fixture, and can be seen in some of the above pictures in the form of a pipe on the floor of the tunnel.

This area of Brooklyn also had natural streams and springs, some of which can be seen as small trickles of water flowing into the Flushing Tunnel through the bricks.

Where did the tunnel come from?

In 1906, Charles F. Breitzke undertook “An Investigation of the Sanitary Condition of the Gowanus Canal” as part of his university work, which involved sampling the water at various points and analyzing it. The investigation was published in 1908, and concluded that on average, the canal was 25 percent raw sewage. At the head of the canal—where most of the sewer outlets were, and where the ebb and flow of the tide did least to wash it out—the canal water was actually 65 percent sewage. This helps explain why it was worthwhile to the city to invest a million dollars in something that would be invisible and underground for the next century.

However, even with the essential idea in place, there was still plenty of work in hashing out the details. Because most of the sewage was at the head (north end) of the canal, the first idea was for the Flushing Tunnel to pump the disgusting sludge directly out from that end, into the Buttermilk Channel and thus into the New York Bay. This was what ultimately happened when the tunnel opened in 1911, as pumping in the other direction would have flushed the mess down the length of the canal before sending it into the ocean.

However, merchants and shippers who had interests along the East River and the Brooklyn waterfront quickly complained that the tunnel would move the sludge into their front yards, and the newspapers from 1909-1911 were filled with their back-and-forth. Today, with the re-opening of the Flushing Tunnel, the flow has been reversed. Now water is pumped from Buttermilk Channel into the Gowanus Canal, so that clean water flushes into the canal and flows through the canal down into Gowanus Bay.

Also, there's a sewer in the Flushing Tunnel


One of the oddest things about the Flushing Tunnel as it exists today is that it's not just one tunnel, but two, each going in opposite directions. After the collapse of a sewer that had run beneath nearby streets, the Department of Environmental Protection (DEP) installed a “temporary” sewer pipe inside the (at the time non-working) Flushing Tunnel. Once the Flushing Tunnel was brought back into service, the “temporary” fix was still the cheapest option— though hardly the most elegant. The end result is an undersized sewer line (33 inches in diameter, called a “force main” because the sewage has to be forced through at speed in order to move sufficient amounts) plonked down in the middle of the otherwise quite sightly brick Flushing Tunnel.

The clean water in the Flushing Tunnel moves from west to east from the Buttermilk Channel to the Gowanus Canal. The sewage in the force main moves from east to west, from Park Slope and Carroll Gardens toward Red Hook.

A skeptic might say the sewer has literally paved they way for future catastrophe—as millions of tons of water batter away at its concrete encasement, how long before the sewer springs a leak and feeds sewage into the relatively clean water stream flushing out the canal? A historic preservationist might have a slightly different viewpoint; it’s just a shame to have the tremendous engineering and aesthetic accomplishment of the tunnel marred by something as ugly and non-reversible as a huge chunk of concrete, complete with a sewer pipe running down the middle.

For now, though, expediency has won. And since both the Flushing Tunnel and the sewer are running for now, it’s time—just as in 1911—to celebrate.

Steve Duncan is an urban historian, geographer, and a photographer of the urban underground. He has photographed sewers and underground rivers in cities from Antwerp to Yangon (but he's still working on exploring in a city that begins with "z"), with particular focus on the underground hydrological and wastewater infrastructure of New York City, Los Angeles, Paris, and London.