Almost half a century after millions of tires were dumped into the waters off Fort Lauderdale, Florida, the massive underwater graveyard has been drastically reduced and is expected to be cleaned up even more in the coming months, state officials say.

In the last nine years, littering the seafloor off Hugh Taylor Birch State Park, the Sun Sentinel reports. Another 30,000 are expected to be removed by the fall, and another effort will start after that.

From 1967 to 1973, , the Osborne Tire Reef, according to the Florida Fish and Wildlife Conservation Commission. Tires were bundled into groups of eight with plastic scrapping designed to not rust or corrode in the water and were released at depths of 65 to 70 feet between two coral reef tracks running parallel to the beach.

Despite good intentions, what was supposed to be a reef essentially became an underwater uninhabited cemetery for the big rubber rings.

In 1974, the year after the last tires were dumped, a study showed there were a number of problems, according to the commission. Tires migrated over a large area because of the depth of the water, strong currents and haphazard dumping. Additionally, inaccurate navigational controls caused wrong placement of the tires, which led to some landing on and damaging the reef tract. Many of the plastic bands were broken when the bundles stacked on the barge were lifted and some of the steel-belted tires that were unable to be hole punched trapped air and floated instead of sinking to the sea floor as intended.

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By 1975, researchers said some of the tire towers rolled 1.25 miles north of the original site and had covered an area of about 600 feet by 1000 feet between the second and third reefs east of Sunrise Boulevard in Fort Lauderdale.

Because there was a lack of follow-up data monitoring the reef, state and local researchers knew very little about it. They stumbled across the reef during a separate search mission, bringing new attention to the harmful impacts of the migrating tires. According to the commission, the invertebrate growth was minimal, which suggests that the unstable tires’ constant flipping, flexing and/or abrasive contact with the seafloor made it difficult to sustain sea life. Needless to say, they weren’t good habitats.

"The ocean has ever-changing currents and storms, and ," Trash Free Seas manager Allison Schutes told Reuters.

to test diver retrieval productivity, loading and transportation methods and tire processing and disposal, according to the Florida Department of Environmental Protection. The first full retrieval was completed in 2008, after divers worked for 27 days and got rid of an estimated 44,000 tires. With clear conditions, divers were able recover about 2,500 tires within a day.

In this most recent effort, the state has budgeted $1.8 million for future work, the Sentinel also reports. Industrial Divers Corp. is performing the removal, retrieving only loose tires and not those embedded in the sand. Removing tires fixed onto the seafloor can do more harm than good, as the process could sit up sand and mud. Loose tires, which do consistent damage by rolling around in the water, are easier to get rid of.

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After being removed, the tires end up at Wheelabrator Ridge Energy Inc. near Tampa, Florida, where they are burned to produce electricity.

The tire cleanup is projected to last for years, but it’s unlikely all of them will be removed.

“There will probably always be tires there,” Quinn told the newspaper. “There are so many tires that are out there. It’s difficult to go diving in the county without running across tires."

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