Engineering design work will soon get underway for cleanup of what are believed to be the last three remaining toxic hot spots in the St. Clair River south of Sarnia.

The St. Clair River Conservation Authority has received $1 million from the federal and provincial governments and Dow Canada for the project.

The funding will help create a detailed engineering design to remove historic mercury pollution from sediment in three specific sites in the river between Sarnia and Stag Island.

The conservation authority says a project manager will be hired to oversee development of an engineering plan.

The design process is expected to begin in early 2019 and last for two years.

The actual removal of contaminants, using a hydraulic vaccum, is estimated to cost between $10 million and $30 million.