The homeless encampment Whac-a-Mole continues.

The city cleaned out a filthy East Side homeless encampment under the FDR Drive Monday, leaving behind a stomach-turning mess — while locals said the vagrants will likely come back anyway.

“[The encampment] could start again as soon as, like, the end of the day,” Dina Elkan, senior director of events at Solar One, told The Post. “It’s not just about over here. They have to check all the way down to make sure that people haven’t just relocated.”

The scene resembled a garbage dump on Monday, with luggage, chairs, coolers and piles of trash strewn about under the FDR near 23rd Street — and it’s been going on for weeks.

“It looks like their living room and everything is over there,” complained Matthew Condah, who works at a nearby BP gas station. “That’s where they sleep. And they come over here for water and stuff. They walk around all the time causing a whole lot of headaches over here.

“But for the past two weeks, they’ve always been there,” he said.

The Big Apple has been plagued by unsightly shantytowns in recent months, including a blocks-long row of tents and shelters that wreaked havoc on the West Side near the Intrepid Museum, with sidewalk squatters stealing city electricity and peddling drugs and sex.

In February, The Post exposed an illegal encampment in Queens, with rows of mobile homes and trailers under the Whitestone Expressway in Queens in the shadow of City Field.

Now, another batch of homeless vagrants have set up shop on Manhattan’s East Side.

“From 23rd to 18th, they will come and do a cleanup. Let’s say they’ll clean this part. By the time that cleaning is done, they would have already set up shop on 18th and have started a whole new encampment,” Solar One worker Liz Parades told The Post. “So, it happens instantly.”

Ridding neighborhoods of the disheveled shantytowns is hampered by City Hall.

Mayor Zohran Mamdani’s approach to the encampments calls for the NYPD to be shut out when a new site is reported — with city outreach workers instead given a week to coax vagrants off the streets.

Only then are sanitation workers and cops allowed to clear out the encampments — a process that has typically just forced the vagrants to relocate and return when the police are gone.

“The cadence is this,” Elkan said. “You set up your encampment, somebody needs to report it, somebody needs to respond to that report. Then there’s a seven-day warning period during which you can figure out where you’re gonna shift to.

“In fact, to the point, we’re trying to get them to understand this entire area should constitute a zone,” she said. “It’s not just about over here. They have to check all the way down to make sure that people haven’t just relocated.”