It had been hoped the Ministry of Defence (MoD) clear up of Dalgety Bay beach would have been completed by last month,
But that has now been pushed back to next June.
Removal of radioactive materials from beaches in the town - thought to be Scotland's worst area of radioactive pollution - began in November 2020, 30 years after they were first discovered.
Private contractor Balfour Beatty is handling the clean-up on behalf of defence chiefs, and aim to make Dalgety Bay's beaches fully accessible to the public for the first time in years once they are finished.
The latest update given to councillors on Fife Council’s South and West Fife area committee last week said work had progressed “but not as quickly as anticipated resulting in less work being completed.”
One of the main reasons was the restrictions on when teams can move in.
They are limited to between April and September to avoid impacting on wintering birds in the area.
During the second working window, - which expired last week - the contractor has advanced the works, but the initial delays mean it will require a third session which, according to a report to councillors, will take until June for the decontamination and associated construction to be completed.
The rep[ort added: “Whilst this is not ideal, the nature of the work requires the time to complete the work to the satisfaction of SEPA.
“The MoD commitment to address the public health situation as agreed in the management strategy remains and will do until the work is complete. “
Areas out with the construction site continue to be monitored by specialist consultants, and the MoD has undertaken to carry on monitoring the entire area after completion of the works to make sure the decontamination exercise has been successful.
Discussions are being held with Fife Council over a reduction in the constraints to allow work to progress beyond the end of September.
SEPA has also carried out monthly drone tests on the work being done on the shore.