A new report shows the Ontario government knew nearly 30 years ago that a mill site upstream from Grassy Narrows First Nation was contaminated with mercury.

"There's a continued liability on the province," Grassy Narrows chief Simon Fobister said. "They said it's going to clear itself up, but they never informed us that there's still mercury in the soil and they were aware of it."

"We'll consider all our options right now, whether it's political or legal."

The confidential report was done by True Grit Consulting in 2016; the firm was tasked with determining whether mercury is still leaching into the Wabigoon River from the nearby Dryden mill site, which is located upstream from Grassy Narrows, where residents have shown signs of mercury poisoning for decades.

Mercury visible in soil at site

The report was independently reviewed by CBC News.

The report states that the Ontario government was informed about visible mercury in the soil at the site as early as 1990, and that 2016 data is insufficient to determine with any certainty if mercury is still present and leaching into the river. True Grit recommends a followup investigation.

"Very disappointed that the Ontario government hasn't continued monitoring the leakage of mercury at the old Dryden mill," said Fobister. "We've always been informed that the mercury is contained, but to our surprise, according to this report, mercury is still in the soil and leaching into the river."

"We have been misinformed by the ministry."

The mercury issue goes back decades, with reports that Reed Paper dumped several tons of mercury into the Wabigoon River in the 1960s and 1970s (the mill is currently operated by Domtar, which purchased the site in 2007 and commissioned the True Grit report).

The elevated mercury levels in the river led to mercury poisoning among residents of downstream Indigenous communities, Grassy Narrows First Nation and Wabaseemoong Independent Nations, who consumed fish caught in the Wabigoon River.

Research done by Japanese experts shows that more than 90 per cent of the population in the communities show signs of mercury poisoning.

Drums of contaminated soil removed

The True Grit report states that in 1990, mercury was observed in the soil beneath the mill's chemical plant building as repairs were being made to a floor there. The Ontario Ministry of the Environment — currently the Ministry of the Environment and Climate Change (MOECC) — was notified, and conducted an inspection.

Sampling was conducted and 35 drums of mercury-contaminated soil was removed. Further testing showed that contaminated soil remained in the area in amounts that exceeded MOECC criteria for cleanup activities, but further excavation was not considered feasible.

The MOECC subsequently said that no further excavation would be needed, provided:

an excavation policy be developed

the contaminated area be registered with the land titles office

a plastic barrier be installed between the contaminated soil and clean backfill, and

a study be undertaken to estimate the amount of mercury present.

The True Grit study states that "it appears that these requests were largely addressed by December 1991."

Two potential contamination sources

The study identifies the contaminated soil found in 1990 as one potential source of ongoing mercury contamination of the Wabigoon River. Monitoring wells were installed in the vicinity; some of them have shown elevated levels of mercury, although data is only available for certain years.

It's affecting the health of our people, and also it destroyed our commercial fishing and tourist operations - Simon Fobisher, chief of Grassy Narrows

For example, sampling from some wells showed elevated mercury levels from 1999-2006, then testing stopped. The report does note that the mercury levels in the wells were generally decreasing during those years.

The second potential source is a former effluent ditch, where "mercury-contaminated effluent was discharged before entering the Wabigoon River in the 1970s."

The ditch was closed and sealed in 1977 or 1978, and its precise location is unknown. No monitoring wells were installed in the ditch, the report says.

Socio-economic damage to Grassy Narrows

"How many generations of our children are going to be affected by it?" Fobister said. "It's affecting the health of our people, and also it destroyed our commercial fishing and tourist operations."

"There's a lot of socio-economic damage to our community."

Overall, the report states that generally, True Grit found that available historical data indicates elevated levels of mercury were present in groundwater on the mill site, particularly around the former chemical plant building.

However, the available data is limited, and "it is not presently possible to make a firm conclusion" whether or not mercury is still leaching into the Wabigoon River.

True Grit recommended a supplemental investigation be conducted, one that would include the review of existing background information, a site inspection, the drilling of boreholes to facilitate the installation of new monitoring wells, and the collection of soil samples.

In June, the province announced an $85-million cleanup of mercury near Grassy Narrows First Nation and Wabaseemoong Independent Nations.

Fobister meeting with cabinet ministers

Fobister will be also be meeting with provincial and federal cabinet members at the end of November, and will be speaking with them about the report.

MOECC representatives couldn't immediately be reached for comment.