Report says humidity affects roof stability in Nova Scotia mine under stop work order

A group of miners. Photo: Adobe Stock

By Keith Doucette

Production at Cape Breton’s idled Donkin coal mine can’t resume until recommendations contained in a consultant’s report are implemented, says the Nova Scotia Labour Department.

Until the measures are adopted, the underground operation will remain under a stop work order that was put in place by the province following a rockfall in mid-July, officials said Wednesday.

The department provided a status update that highlighted a report by Andrew Corkum, a geological expert at Dalhousie University.

Corkum told reporters that seasonal weather and humidity affect roof stability at the mine. He said engineering work would have to be done to upgrade two access tunnels before the mine can safely resume operations.

“The issue in the tunnels is primarily related to mudstone rock in the roof in many locations,” said Corkum, adding that the rock “has a tendency to degrade with the presence of water.”

He said the problem is worst during the high humidity seasons of spring and summer with “little or no record of any problems in low humidity seasons like the winter.”

Corkum recommended that the mine improve its safety measures — including its roof reinforcement work — and add to its monitoring system in the tunnels.

“They (tunnels) are complex engineering structures, and we have lots of ways of doing calculations, but monitoring performance is really the gold standard and best way to determine if it’s performing well,” he said.

Once that work is done, department officials said production operations could resume during the winter, although a third-party engineer with experience in mining and tunnelling would have to review the mine’s ground-control plan before operations could continue in the spring and summer.

Scott Nauss, the department’s senior executive director of safety, said the third-party review will have to be completed by the end of February for mine owner Kameron Coal Management Ltd., to be in compliance.

Nauss said the company is aware of the recommendations and had “given us every indication that they intend to comply with the orders.”

“We’ve laid out a clear path to compliance and lifting of the stop work order, and now the ball is in the mining company’s court,” he said.

There was no immediate response to a request for comment from Morien Resources, which has a royalty interest in Kameron Coal. The mine has laid off its 130 workers and placed its operation in an “idled state.”

The province’s stop work order was issued after a July 15 rockfall inside the mine that was characterized by government officials as “significant.”

The rockfall was the second within a week and resulted in no injuries. Provincial officials have said the fallen rock covered a distance of about 15 metres and was 4.5 metres wide and nearly a metre deep. It occurred approximately 1.5 kilometres from the entrance to the mine in the tunnel providing primary access for the mine’s workers.

The company had made repairs and installed reinforcements for the roof, officials said in August.

Meanwhile, a temporary closure had also occurred when inspectors found that a small amount of roof material had fallen inside the mine on July 9. Approval to reopen was given following repairs and an inspection by the Labour Department.

The early July rockfall followed an underground fire on April 30, which investigators determined was caused by an overheated ball bearing in a conveyor belt used to extract coal from the mine. No workers were in the mine when that fire started.

Donkin resumed operations in September 2022 after it was shuttered in March 2020 amid slumping coal prices and roof collapses that led to repeated stop-work orders. The mine first opened in 2017 and is described by the province as the world’s only operating subsea coal mine.