BANGOR, Maine (AP) — A new report estimates cleanup of a Penobscot River estuary polluted by mercury from a defunct plant could cost up to $333 million.

The report filed Tuesday in court in Bangor is far higher than a previous estimate of $130 million for mercury removal. The Bangor Daily News reports the filing was made by Portland-based Amec Foster Wheeler Environment & Infrastructure, Inc.

The firm recommendations include dredging and replacing the riverbed soil near the former Holtrachem chemical manufacturing site in Orrington with new soil. It also calls for sediment replacement and capping off much of Mendall March. The plan also calls for monitoring mercury levels for 25 to 45 years.

Former plant operation company Mallinckrodt says it will challenge some of the recommendations for cleanup.