The Ministry of the Environment, Conservation and Parks says work to remediate three areas of the St. Clair River is underway.
The areas contain mercury contaminated sediments, left behind by historic industrial processes.
In an email to Sarnia News Today, ministry spokesperson Gary Wheeler said Dow Canada will lead the work to place an erosion resistant cover in the identified areas starting on Monday, November 18.
"The work is anticipated to take up to seven weeks to complete," Wheeler said. "An extensive sampling campaign in 2019-2020 showed that mercury levels in the sediment have decreased significantly since the last samples were taken and the existing levels do not present a measurable risk to aquatic species."
The contamination is believed to have come from Sarnia's former Dow Chemical operation, which closed in 2009.
The priority areas are near the TransAlta (formerly Dow Canada) and Suncor’s sites, near property owned by Enbridge and Shell and near Guthrie Park in St. Clair Township.
Wheeler said the cover will mitigate future risk.
"To further reduce the risk of contaminated sediment moving downstream, project consultants recommended an erosion resistant cover -- made up of double washed gravel -- be placed on areas with the highest mercury concentration," he said.
Wheeler added "sediment management is one of the key remaining actions required for the St. Clair River to be de-listed as a Great Lakes Area of Concern (AOC)."
The St. Clair River was designated a binational AOC in 1987 under the Canada-U.S. Great Lakes Water Quality Agreement.
The AOC stretches from the Blue Water Bridge to the north shore of Mitchell’s Bay on Lake St. Clair and includes the immediate drainage basin of the St. Clair River.