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UPDATE: The owners of Zuccotti Park, home to Occupy Wall Street, released a set of rules this afternoon that, if enforced, will put an end to the occupation. It appears that suspicious of protesters who believed the cleaning was an excuse for eviction have been borne out. The park cleaning will take place in three stages starting at 7 am tomorrow, though it’s possible a police crackdown will happen sooner. I will be at the park starting this evening and will be posting constant updates on Twitter from @JoshHarkinson.

Just two days after announcing that Occupy Wall Street protesters can stay in Zuccotti Park indefinitely, New York Mayor Michael Bloomberg said last night that they’ll have to leave tomorrow, at least temporarily, while sanitation workers clean it up. Protesters say they plan to resist the move, with some viewing it as a ploy to permanently evict them.

Bloomberg briefly visited the park last night and later released a statement noting that the park’s owner, Brookfield Office Properties, was concerned about its cleanliness. He went on to outline the cleanup plan: “The cleaning will be done in stages,” the statement said, “and the protesters will be allowed to return to the areas that have been cleaned, provided they abide by the rules that Brookfield has established for the park.”

What is now known as Zuccotti Park was constructed in 1968 by the builders of the adjacent United States Steel Tower in exchange for being allowed to build a taller skyscraper than zoning rules would otherwise allow. The park is classified as “privately owned public space”–it’s open to the public 24 hours a day but maintained by Brookfield, the building’s property management company.

Protesters with Occupy Wall Street’s Planning Working Group told me earlier this week that they still weren’t clear on exactly what kinds of rules governed the park. Brookfield has not released anything in writing, and has mostly just raised sanitation concerns. In an effort to prevent the cleanliness issue from turning into an excuse for eviction, the Planning and the Sanitation working groups at OWS have been trying to obtain bins in which to store bedding during the day, making the park easier to clean. But the process has been slow. At a meeting on Sunday night, for example, the proposal was met with resistance by other protesters who wanted to try to obtain the bins on Craigslist, rather than purchase them, and wanted to make sure that they were “fair trade.”

Now that the cleanliness concerns have come to a head, OWS is organizing a massive cleanup effort today. Still, it probably won’t be enough to convince Bloomberg and Brookfield to leave sanitation to the occupiers, which means clashes with the police who’ll clear parts of the park tomorrow could be likely.

In the longer term, OWS is trying to apply some urban planning principles to the Zuccotti camp in order to make it easier to clean and navigate. Check out our interactive map of the camp that explains how the layout would work.