CHICAGO (CBS) — With sunny skies and hot temperatures, Chicago’s beaches proved a popular destination for Memorial Day weekend revelers, but lakefront visitors didn’t leave the sand as pristine as they found it.

Chicago Park District crews moved in early Tuesday to clean up all the junk left behind in the sand at North Avenue, 31st Street, and other beaches along Lake Michigan.

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Workers used huge surf rakes towed by tractors to pick up all the empty water bottles, food wrappers, and other trash left behind by the huge crowds that swarmed the lakefront over the long weekend.

Someone even left a portable grill behind at 31st Street Beach, which is typically the most crowded spot on the lakefront on the South Side.

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At North Avenue beach, one worker was spotted carrying away several towels and blankets picked up from the beach Tuesday morning. The wide sandy beach is one of the most popular spots on the lake on the North Side.

Chicago Park District officials urged beach visitors to help keep the beaches clean in the summer.

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“Crews were on duty all weekend, and the 4,000 trash cans and recycling bins were dumped multiple times daily. We’d like to remind patrons that keeping the beaches clean is the key to enjoying them. Bacteria that can adversely affect water conditions can come from many sources, including bird waste, pet waste, or people at the beach,” spokeswoman Jessica Maxey-Faulkner said in an email. “Help us keep the beach clean by throwing your trash and recycling in the cans provided. Do not feed birds or other wildlife. Pets are not allowed on the beach, and please pick up after your pet if you are walking it in the park. If you have small children in diapers at the beach, please use waterproof swim pants.”