RE-GREENING THE ANVIL RANGE

Curragh Resources’ environmental people have shepherded approvals through the regulatory process several times now — for the Vangorda and Grum deposits two years ago, for Westray in Nova Scotia and for Sa Dena Hes more recently. Now they are working on the Stronsay project in northern British Columbia and have geared up for the Faro pit de-commissioning review process.

But all that experience doesn’t make it any easier, says Gerry Acott, Manager, Environmental Affairs. If anything, it’s getting tougher.

Approvals are sought for land use under the Territorial Lands Act and for water use under the Northern Inland Waters Act. The Yukon Territory Water Board reviews water license applications for the mining industry and makes recommendations to the federal minister of Indian Affairs and Northern Development (DIAND). The public hearings include “intervenor” groups that make it their business to critique Curragh’s and any other company’s environmental effort. These include DIAND, the Environmental Protection Service, the federal Department of Fisheries and Oceans, the Yukon Territorial government, Yukon Conservation Society, Ross River Dena Council, and Selkirk First Nations.

Additionally, the federal government, through its Environmental Assessment Review Process (EARP), looks like it’s jumping into the environmental arena with both feet. Some people would argue that in the Yukon, at least, EARP is attempting to assume more of a regulatory than an assessment role.

“So now the industry is faced with two fairly redundant reviews,” Acott told The Northern Miner Magazine during a visit to his Whitehorse office. While EARP’s main focus is water quality, it also delves into land use and the socio-economic effects of development.

The key considerations of the water license are discharge standards, tailings disposal, water use, monitoring requirements, stability of physical structures, and de-commissioning. Currently, the major effluents of concern at Faro are ammonia, mill reagents, particularly cyanide, and metals such as zinc, copper and lead.

In having diverted several creeks (Faro, Rose and Vangorda creeks), Curragh has minimized contamination. Contaminated water is collected and treated at the Faro tailings pond or the Vangorda/Grum treatment plant.

In the Faro tailings, the mine discharge is mixed with the high-pH mill tailings to precipitate the soluble metals. A retention time of a minimum 25 days also allows for the natural breakdown of cyanide and ammonia.

But the big question for Curragh today revolves around how it will safely dispose of the Faro tailings at shutdown. The tailings area has three components — the first, a downstream polishing pond, will be removed, as will the contaminated sediment beneath.

Two options exist for the remaining two ponds, which contain virtually all the tailings, said Acott. In the preferred option, Curragh removes approximately two-thirds of the tailings by a hydromonitoring technique and reprocesses the tails to recover the residual Pb/Zn metal. Final tailings disposal will be in the Faro pit.

“We’ve got a billion dollars worth of metals in those tails,” Colin Benner, President, Operations, said in a recent interview. The reserve in the upper section of the pond is 37.7 million tonnes, grading 0.79% Pb, 1.23% Zn, 0.15% Cu and some silver and gold. If Curragh can recover 25% of that metal, this tails disposal option would cost it $7-$8 million. Without metal recovery, removing and pumping the tails to the pit would cost up to $40-million, a price tag that makes this option unfeasible.

Option No. 2 utilizes a dry, 1.5-m cover of non-acid generating material (slimes, till and waste rock). Six pits currently are testing different cover materials — organic, composite (unsaturated and saturated), till and water. The dry-cover alternative would cost $28 million.

Ever since 1986, Curragh has been contributing 25 per wet tonne of concentrate to a de-commissioning fund. It now has $750,000 and by the year 2008, there will be $8 million. As a condition of the Vangorda Water Licence, Curragh put up an initial $1 million, and another $560,000 is put every year into a de-commissioning fund. Additionally, DIAND required a supplementary $4.4 million be placed in trust as a result of the EARP review of the project. In total, about $2.00 per tonne is invested in a trust fund dedicated to final closure.

At Sa Dena Hes, closure should be far less onerous, said Acott. “There is no acid generation. De-commissioning the tailings area will simply involve a top dressing and seeding for erosion control.” He estimates the closeout will cost $1.3 million.

At Faro, the previous mine operators, working under the less stringent rules of the day, didn’t consider the implications of acid mine runoff. Now, of course, it constitutes a costly environmental headache. Curragh has established collection ditches around its potential acid-generating waste dumps and will treat the water using a natural biological sulphate reduction process.

Steffen Robertson and Kirsten are assisting Curragh in evaluating in-situ sulphate reduction in the underground workings adjacent to the Main Faro pit and rock-filled Zone II pit.

On the Vangorda Plateau, any sulphide wastes will be completely encapsulated in basic rock and till so that acid runoff will be kept to a minimum. A water treatment plant has already been installed between the Vangorda and Grum deposits to treat minewater and waste-dump runoff. (Cominco Engineering Services Ltd. was involved in the project.) Contaminated water is treated with lime and then flocculated and settled in a clarification pond. The plant has a capacity of 2,000 gal. per min., and the sludge settling pond has a 10-year capacity before dredging is required. The treatment plant cost $4.5 million.