Two artificial reefs made from about 3000 tyres will be removed from Guam's Cocos Lagoon.
The Pacific Daily News reports the tyre reefs were created 50 years ago in the hope of increasing fish stocks.
Documents obtained from Guam's Environmental Protection Agency say the tyre reef project was started in 1969 but stopped four years later after failing to gather enough fish.
Studies later found elevated levels of toxins including zinc in the lagoon and its fish, which could have come from the tyres.
A figure of $US250,000 has been allocated to remove the artifical reefs.
The larger pile containing about 2500 tyres is about a mile south of Merizo pier, while the smaller pile has been lost, buried somewhere in the sediment.
The clean up is expected to take three years and will include the relocation of some coral that's grown on the tyres.