The Gowanus Canal Flushing Tunnel is operating again after four years and $177 million worth of repairs. At full capacity, the tunnel will pull 252 million gallons of fresh water from Buttermilk Channel (the sliver of harbor that separates Brooklyn from Governors Island) into the head of the Gowanus Canal every day.

Officials say this infusion of oxygenated water will dramatically improve the aesthetics (including the smell) of the canal, and provide more suitable habitat for aquatic and other wildlife. Will it work? Residents and canal advocates say they aren’t holding their breath.

History of a Troubled Tunnel

Map of the Gowanus Flushing Tunnel
Photo credit: New York Times

The brick-lined tunnel was originally constructed in 1911 as a seemingly simple solution to a complex problem: using a giant propeller, pump the dirty, toxic sludge filling the Gowanus Canal into the Buttermilk Channel. Out of sight, out of mind.

Almost immediately after opening in the mid-1800s, the Gowanus Canal had become a dumping ground for the tanneries, gas plants, and cement works that lined the bulkheaded banks. Coal tar, mercury, lead, and other toxic metals were regularly discharged into the water—along with the neighborhood’s raw sewage, a common practice at the time. As early as 1910, the Gowanus was described as “almost solid” with with the stuff.

The flushing tunnel was the city’s attempt to deal with the noxious smell and appearance, but it was plagued by mechanical problems and never particularly effective. Despite that, it continued running until the 1960s, when the pump system was damaged and the city opted not to repair it.

For nearly forty years after, the waters of the canal remained stagnant—even as the landscape of the area changed dramatically. Today trucking has replaced shipping and residential developments are replacing factories, yet the industrial legacy of the Gowanus remains. Coal tar continues to leach from abandoned, below-ground storage tanks, and the bottom of the channel is coated in a 10-foot-thick layer of sludge, vividly described as “black mayonnaise.”

Photo credit: Joe Holmes / Creative Commons

The raw sewage hasn’t gone away either. With any significant amount of rainfall, the city’s combined sewer overflow system sends millions of gallons of untreated waste into the canal — a situation dubbed by residents as the “poo-nami.” Today the canal is a federally-designated Superfund site and recognized as one of the most polluted bodies of water in the United States.

A Fresh(er) Start

Photo credit: Tamas Neltz via Creative Commons

For the last four years, the New York City DEP has focused on what they call The Gowanus Facilities Upgrade in order to “improve the capacity, function, efficiency, and reliability of the Gowanus Canal flushing tunnel system … with the aim of improving the water quality in the Gowanus Canal over the long term.”

The project, which is being conducted in tandem (though separately) from the federal Superfund cleanup plan, has consisted primarily of reconstructing the motor pit and replacing the century-old propeller with three vertical turbines.

As of May 2014, the tunnel is running at full capacity and the water flow has been reversed, pumping some 250 million gallons of fresh water from Buttermilk Channel daily into the stagnant canal.

This time, the focus of the flushing is not necessarily to move pollution out of the canal, but to bring oxygenated water into it. Water quality studies have found the concentration of oxygen in the canal to be just 1.5 parts per million, well below the minimum 4 parts per million needed to sustain life. DEP officials say that bringing in cleaner water with more dissolved oxygen should reduce smells and make the canal more hospitable to fish, plants, and mollusks.

In June, the DEP will also reactivate a pump station which will allow it to send up to 30 million gallons of wastewater to the Red Hook Wastewater Treatment plant each day. The City claims this will reduce the amount of raw sewage overflows during rain storms by 34 percent.

A Post-Flush Plan?

It’s clear that the City believes these dual upgrades are a significant milestone in improving the condition of the canal. But residents and local officials caution that while these improvements are necessary and welcome, they are also just the first step in a much larger Superfund cleanup plan.

“This needs to be effective,” Gowanus Alliance president Paul Basile told The Brooklyn Paper. “This is the first key element of the clean canal. It will never been sustainable without this.”