The EPA is set to scoop toxic sludge known as "black mayonnaise" from the Gowanus Canal's Fourth Street Basin starting the first week of December — prep work for the excavation will begin next week, EPA officials said Tuesday. View Full Caption DNAinfo/Leslie Albrecht

GOWANUS — Workers with the U.S. Environmental Protection Agency are set to start scooping toxic sludge from the bottom of the Gowanus Canal the first week of December and will begin prepping for the excavation next week, officials said.

Starting on Oct. 5, barges will cruise into the heavily polluted canal's Fourth Street Basin, where dredging will clear the way for EPA equipment to access the sludgy sediment, known as "black mayonnaise," marking a key step forward in the canal's $506 million cleanup, said Christos Tsiamis, the EPA's remediation project manager.

"You're not seeing a lot now, but starting October you will," Tsiamis announced Tuesday. "We are ready to go."

Before work on the Superfund site begins, the EPA will "stabilize the shore" with bulkheads along the basin's blighted banks, with that work likely to occur during the last week of October, depending on when supplies for the barriers arrive, Tsiamis explained.

Consultants with Langan Engineering, who were brought in last month to investigate two bulkhead collapses along the southern portion of the canal, determined it was "just time for that infrastructure to go," as Tsiamis put it, based on old age and exposure to the elements.

Langan will restore the walls as the EPA works to reinforce those along the Fourth Street Basin.

Come December, workers will begin scraping muck from the basin's floor for a pilot study that will work out the projects logistics and inform the EPA's final plan for the entire 1.8-mile waterway.

"Once we start doing the pilot study, the aim of the pilot study is to learn. Take lessons from that small segment of the canal and apply it to the cleanup of the entire area of the canal," Tsiamis said. "Then we will finalize the 100 percent design for the canal."

The pilot dredging is expected to last until the spring of 2018 and will culminate with a report to help shape the EPA's overall plan, including where excavators will eventually dredge the canal.

It is possible that the agency will unearth some hidden gems, or at least buried junk, during the work. Last year, debris removal from the the Fourth Street Basin yielded two boat wrecks, eight support pilings, a tree and 25 other items that measured greater than 5 feet across, according to EPA officials.

Toxic sediment removed from the canal will be ferried down the waterway and mixed with cement to ensure it does not leach contaminants, Tsiamis added.

EPA officials anticipate finalizing plans for cleaning up the northern portion of the canal by February 2019. The cleanup for that portion of the canal won’t be completed until at least 2022, Tsiamis told DNAinfo New York Thursday. But the pilot dredging still marks a milestone in the process, he said.

"Right now we are at the critical mass of information that will propel the project forward," he said.