Gowanus Canal Cleanup: Tanks or tunnel? It’s up to the EPA

The Environmental Protection Agency is casting doubt on a competing plan put forth by the city to keep untreated sewage from entering the toxic Gowanus Canal.

While federal employees were furloughed last month, the New York City Department of Environmental Protection presented a new idea for the canal’s cleanup: Install a tunnel to collect waste underneath the waterway instead of building two massive tanks along the canal — the EPA’s long-established plan.

The city’s proposal would be more costly and stall the project by at least three years.

EPA officials did not attend January’s Community Advisory Group meeting due to the government shutdown, but they were present at Tuesday’s gathering — and they made it clear that whichever choice is made will be theirs, and theirs alone.

“The decision lies with the EPA,” said Christos Tsiamis, EPA project manager for the federal Superfund site. “We will decide to pursue it or not. We have not endorsed this tunnel,” he added. “We’re still asking a lot of questions.”

Whether tunnel or tanks, both options would collect combined sewage overflow (CSO), which is rainwater and sewage that can overwhelm waste facilities during heavy downpours, causing it to be dumped — untreated — into waterways.

The CSO retention tanks along the canal are one part of the EPA’s overall plan to clean the Gowanus Canal, which also includes dredging contaminated deposit that has accumulated due to industrial and sewer discharges.

The half-mile, soft-ground tunnel would be constructed similarly to the waterway’s flushing tunnel, holding 16 million gallons of waste. The EPA’s current plan calls for an 8 million and 4 million gallon tank to be installed at two sites along the canal.

While the tunnel has the capacity to hold four million more gallons of waste, Tsiamis said the size of the two tanks could still increase as the project proceeds.

Once the tanks or tunnel fill up, rainwater and some waste will still flow into the canal, but that “second flush” will be cleaner. After the rain stops, the liquid in those containers will flow back into the sewers.

Although the city DEP highlighted the tunnel’s potential ability to extend in size, Tsiamis called the city’s presentation “simplified” and the issue “more complex.”

“Not all ideas are good for every place,” he said. “[The city] goes deep. We think deep before we go,” he added.

Tsiamis said the tunnel could also delay the cleanup by as many as three years. The tanks are estimated to be in the ground by 2027, while the city predicts the tunnel could be in place by 2030.

“We have some concerns about whether that [timeline] is real,” he said.

If the tunnel is ultimately selected, the EPA would also have to do another round of public hearings — a process already completed for the tanks.

The entire plan to install the two tanks would cost roughly $1.2 billion, according to Kevin Clarke of DEP. If the tunnel option is ultimately chosen, that price tag would increase by an additional $50 million.

Until the EPA makes a decision on which route to take, resources will be dedicated to exploring both options. The city is obligated to present a nearly complete design of the retention tanks by April.

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