Georgia Power said Tuesday it will cost more than half a billion dollars above previous estimates to clean up its toxic coal ash ponds across the state.

Those charges eventually will wind up in customers’ monthly utility bills.

In a semiannual report filed with state utility regulators, Georgia Power said “several market factors” have driven up project costs to $8.5 billion, up from $8 billion in a previous report. The electric company collects the money as part of a monthly charge previously approved by the Georgia Public Service Commission.