A unique environmental project will begin this month in Peninsula Harbour near Marathon.

Contaminated sediment in the harbour will be capped with about a 20-centimetre layer of clean sand.

The sediment is contaminated with mercury and PCBs from years of discharges of wastewater and storm water runoff from the now-closed pulp mill in Marathon.

The sand is used to accelerate the natural recovery process by reducing plant, animal and fish exposure to chemicals.

This is the first time in Canada that the thin-layer capping system will be used to manage contaminated sediments.

The provincial and federal governments are footing the bill for the $7 million project.

But the province says $3 million of it comes from a settlement with a former owner of the mill.

Peninsula Harbour has been designated a Great Lakes Area of Concern, one of nine on the Canadian side of the Great Lakes/St. Lawrence Seaway system.  An Area of Concern is a location that has experienced environmental degradation.