Published in March 2008 Australian Longwall Magazine

But in true global miner fashion, Xstrata is tackling the freezing conditions at its prospective Donkin Mine in Canada’s Nova Scotia region with vigour as it moves towards completing its pre-feasibility study.

The Donkin project – 75% owned by Xstrata and 25% owned by Erdene Gold – is on schedule to complete its pre-feasibility study and hand it to Xstrata’s investment review committee in April 2008. The board will make a decision on whether the project will be pursued and taken to the full feasibility stage.

The ambitious under-ocean project holds an indicated resource of 101 million tonnes and inferred resource of 115Mt in the Sydney coal field. It is expected that should the project be given the green light, 109 million ROM tonnes could be extracted over a mine life of 30 years.

“Donkin is quite a unique project in that it is so geographically distant from other Xstrata Coal projects and presents many aspects that we wouldn’t have to deal with anywhere else,” project manager Darren Nicholls said.

While many aspects of the project are unique for Xstrata, the company will stick with familiar territory to develop the operation to the highest standards of health, safety, environmental and community expectation. The project is off to a strong start with 90,000 hours worked and 7000m of tunnel cleared without any incidents of note.

Already two 3500m long access tunnels to the mine have been dewatered and samples of the Harbour Seam taken.

According to Nicholls, 450 million litres of water was pumped from the tunnels over eight months. The water was treated and transported to one of Canada’s most valuable lobster fisheries which happens to be located directly off the Donkin Peninsula.

“From an environmental perspective it was extremely challenging but ultimately very successful,” Nicholls said.

“We are also very cognisant of the fact that we need to maintain this effort while ever we are doing business on this site; the fishery and community are too important to us and we have not only a legal but a moral obligation to ensure we have no impact in this regard.”

With dewatering out of the way, Nicholls is now concentrating on conducting an extensive inseam drilling program to determine gas levels and characteristics relative to Donkin’s ventilation modelling.

Interestingly the job is very much an international affair with expertise coming in from Nicholls based in Nova Scotia and people in Vancouver; out of Xstrata’s office in Sydney; ventilation expert Dr Roy Moreby working out of Portsmouth, England; and mine planners from Marston’s office in St Louis, USA. All this means plenty of phone calls across clashing time zones.

While the Donkin team already has a good feel for gas absorption rates from its exploration drilling, inseam drilling will detail how the gas will behave from a ventilation modelling perspective.

Nicholls said Xstrata Coal was committed to planning gas management at Donkin by reviewing the use of internal combustion gas engines to offset its greenhouse gas footprint.

One of the most interesting aspects of the current tasks at hand for Donkin are the divers who are working offshore locating old boreholes that were drilled 30 years ago into the virgin coal seam.

“It is very important that we know that the holes were surveyed accurately,” Nicholls said.

“They were triangulated using shore markers; there was certainly no GPS in those days so the method of the time was prone to some error with wind, tides and interpretation. This is critical to mine planning, as we take the view that any borehole may not be cemented and as such could provide a conduit to the Atlantic Ocean.”

Divers, using drysuits in the freezing conditions, are going to depths of up to 45m before they switch to remote cameras. A submarine-like underwater camera is used which shines a light on the sea floor to locate borehole positions, which are then marked up by GPS.

“Until we found a borehole we had no idea what they were going to look like, or even if they could be located,” Nicholls said of the challenging job.

The boreholes have a 2ft pipe (old drill casing) sticking out of the sea floor and a 1ft high cement “blob” where the borehole has been grouted. The blob is what the divers look for.

In addition, Nicholls noted the divers had located some old munitions.

“This is not unique – Halifax Harbour was the forming point for many of the Atlantic convoys of World War I and World War II. After the end of the war, munitions were dumped at sea and divers fairly regularly locate munitions on the sea floor,” he said.

Donkin can only undertake the diving until mid-March before pack ice floats down past the minesite from the Gulf of Saint Lawrence. The ice, which lasts for about two months, makes it impossible to access the boreholes.

“We can have ice six to seven kilometres offshore and there are harp seals and a whole range of stuff out there – it looks like a little mini Arctic sea,” Nicholls said.

The under-ocean aspect of the operation has been factored into Xstrata’s pre-feasibility plan with Ross Seedsman working on the geotechnical challenges that potentially may pertain to the face.