Domtar is voluntarily undertaking a soil and groundwater sampling program to ensure there is no migration of legacy mercury from the Domtar site to the river.

"We're doing the work really to reassure ourselves and confirm the findings of previous studies that legacy mercury contamination is not leaving the site," explains Bonny Skene with Domtar.

The sampling plan has been approved by the Ministry of Environment, Conservation and Parks and is expected to take eight weeks.

"At which point we'll be following up with the Ministry and sharing the outcome," Skene added.

Since Domtar purchased the mill in Dryden, mercury hasn't been used in operations.