Nova Scotia has an unknown financial liability on its hands as it begins to remediate abandoned mine sites, the province's auditor general said Tuesday.

Michael Pickup's newest financial audit found the Department of Lands and Forestry hasn't sufficiently investigated potential contamination at many of the province's old mines.

Without that analysis, the department can't assess the province's financial risk relating to remediating and monitoring the sites.

"I think, you know, the danger is that there could be significant changes as this work gets done on these sites," Pickup said of potential cleanup costs.

Earlier this year, the province announced it would spend $48 million to remediate two historical gold mines. Montague Gold Mines in Dartmouth and Goldenville near Sherbrooke have been contaminated with arsenic and mercury since a gold rush first hit the province in the 1860s.

But those are just two of 69 abandoned gold and coal mine sites on Crown land that the province may be responsible for cleaning up.

The province's auditor general, Michael Pickup, speaks with reporters about the release of his office's financial report on Tuesday. (CBC)

"We've been pushing the government to say, 'You need to do that work,'" Pickup said. "And that's why we gave them a significant deficiency this year to say, 'OK, time is up. You need to do this work and you need to figure out, you know, whether you have contamination, what the extent of that might be, what you have to do and if you have to record it [in the accounting].'"

Due to what the report calls a significant weakness in the department's financial reporting of abandoned mine sites, the auditor general's office is now conducting a performance audit, with a report expected next spring.

In addition to the financial risk, Pickup's report notes that the lack of studies at old mine sites also means there are potential human health or ecological risks.

Department responds

Lands and Forestry Minister Iain Rankin said he agrees "we can always move faster" to address contamination concerns, but he couldn't give a timeline on when the sites will be remediated.

"It'll be a number of years to address these sites. There's a lot of analysis and work that has to go into it and then looking at what the priority is and how we find the money to make sure that we're addressing them."

Iain Rankin, Nova Scotia's minister of Lands and Forestry, says the department plans to comply with recommendations in the report. (Robert Short/CBC)

Rankin said staff plan to meet with other relevant departments, including Energy and Mines and Nova Scotia Lands, and then present a plan to the Treasury Board.

The next sites on the province's list to study are the former gold mines of Caribou Mines, near Upper Musquodoboit, and Oldham, near the Halifax Stanfield International Airport, and two former coal mines in Sydney Mines on Halfway Road and Ocean Street.

Rankin said he welcomes the auditor general's report and the department plans to comply with his recommendations.

Financial liability for contaminated sites $372 million

Nova Scotia's financial liability for contaminated sites this year sits at $372 million, up from $285 million last year, and up from $107 million five years ago. This year's figures include $230 million for the cleanup of Boat Harbour, $48 million for abandoned mine sites and $94 million for other projects, including the cleanup of the Harrietsfield salvage site.

Despite Pickup's concerns about the lack of studies on abandoned mines — and the financial implications of that — he said the province has followed proper accounting procedures for the sites it has studied.

In 2010, the auditor general's office audited the management of contaminated sites and made 17 recommendations. When the office last followed up, in 2014, 10 of the 17 recommendations had not been implemented, Pickup said.

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