What lies beneath one of Nova Scotia’s most polluted sites will support aquatic life

One of Nova Scotia’s worst contaminated sites should be able to recover from decades of pulp mill pollution, according to a new study that determined pre-industrial sediment found underneath lagoons at Boat Harbour can support aquatic life.

The results bode well for the cleanup planned at the Northern Pulp mill wastewater treatment facility, which shut down earlier this year.

Scraping away decades of accumulated toxic sludge at the 150-hectare Boat Harbour site in Pictou County and returning it to a tidal estuary is now forecast to cost $292 million.

Will it support marine life? 

Researchers from St. Francis Xavier University in Antigonish, N.S., wanted to know if salt marsh and eel grasses would grow in the clay bottom that was in place at Boat Harbour before 1967 when effluent started arriving from the nearby pulp mill at Abercrombie Point.

Researchers took dozens of core samples from underneath the toxic sludge that has accumulated in lagoons at Boat Harbour. (Submitted by Megan Fraser)

“We had really promising results,” said lead author Megan Fraser, who carried out the field research as an undergraduate.

“We found that these plants were able to grow and they were able to survive.”

The study, published in the Canadian Journal of Fisheries and Aquatic Sciences, was commissioned by the Nova Scotia government, which is responsible for the cleanup.

What they did

The researchers took 55 core samples from beneath a contaminated layer — averaging 21 centimetres thick — in the Boat Harbour stabilization lagoons.

Megan Fraser is a co-author of the study, recently published in the Canadian Journal of Fisheries and Aquatic Sciences. (Dave Laughlin/CBC)

That is where effluent was discharged after being churned by aerators. The wastewater stayed in the lagoons for about three weeks before making its way into the Northumberland Strait through the Pictou Landing First Nation.

The stabilization lagoons make up about 85 per cent of the overall Boat Harbour footprint.

The core samples were transplanted 80 kilometres away in Pomquet harbour where the grasses were grown and compared with those in local conditions.

What they found

The study found no significant difference in plant growth or survival levels. Later analysis in both types of sediment and plant tissues showed similarly low levels of contaminants.

Sample cores were contained under these cages in the clam experiment plot. (Submitted by Megan Fraser)

Clams and mussels were also tested for growth and contaminants in the samples.

Those findings have not yet been published but Fraser said the results were the same.

“The shellfish were able to grow. They were able to survive. And once again, they had very low levels of these contaminants of concern that we see in an environment such as Boat Harbour,” she said.

The project manager for the Boat Harbour cleanup project said he was encouraged by the findings.

“What this is telling us, is once we get the remediation completed, Boat Harbour will restore itself naturally,” said Ken Swain. 

“It’s good news. It’s good news for us. It’s good news for the community. It’s good news for A’Se’k.”

A’Se’k is the Mi’kmaw name for the Pictou Landing First Nation, which has lived next to Boat Harbour for 50 years.

New bottom sludge?

While the findings are encouraging, there is new uncertainty about the sludge at the bottom of the aeration lagoon.

Northern Pulp is responsible for removing all contaminated sediment accumulated in the aeration lagoon after it took over in 1997. The company is now insolvent.

A researcher inserts a core for salt marsh grass. (Submitted by Megan Fraser)

Northern Pulp claims its own independent testing discovered 194,000 cubic metres of sludge that existed before it bought the mill in 1997, according to documents filed in British Columbia by the court-appointed insolvency monitor.

The monitor’s report suggested Nova Scotia has agreed to clean up the recently discovered “bottom sludge.”

Swain said the province is investigating and has not yet conducted testing to verify the claim.

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