BC Land Reclamation
Waste rock dumps at an open pit coal mine after reclamation
Revision: November 2006
Author: Jack Caldwell
The Thirtieth Annual British Columbia Mine Reclamation
Symposium was held in Smithers,
I write this review in order to survey the current state-of-the-art in mine reclamation and to share BC advances and successes with the wider mining industry. I wrote this in the distinctly non-mining environment of a farm in Iowa, where for over 150 years man has been modifying the environment and molding it to needs: grow corn and soya beans, raise hogs to make Iowa the largest pork producer in the nation, and cut the timber for construction. I doubt there is any part of the vast horizon outside my study window that is unchanged from early times: fences and barns, gravel roads, power lines, houses every 80 acres, ponds formed by clay embankments across the creeks. Yet this is all very beautiful. The horizon is clear, unbesotted by mountains. The grasses are everywhere green. The fields are yellow and brown. The high corn is dry and awaits the harvester. If nothing else, this utterly unnatural environment proves that human activity is not inimical to beauty and peace and productivity. I hope to show by reviewing the symposium papers that the same conditions can be achieved when mined lands are properly reclaimed.
En route to
High up on an isolate plateau above the
All that remains of Uravan is an old boarding house and the community center. Both are boarded up and signed to advise no-entry. The Navaho told me the local historical society wants to keep the buildings, but the EPA wants them demolished; a complex conflict of interests here. He personally has no opinion, for he will retire and return to Shiprock, many miles away. For the rest, the mill and the town and all that they relied on and supported are gone—now incorporated into the tailings pile atop the hill. I quote this side trip as further evidence that reclaimed mine and mill sites can once again revert to nature if properly done. So let us proceed to see what is being done in this regard in BC.
S.J. Sibbick (AMEC) and R. MacGillivray (Barrick Gold Inc) describe the Snip Mine as it is now, seven years after closure. In 1999 portals to the lower underground workings were sealed, the lower third of the mine was allowed to flood, and discharges from the mine were routed into the tailings impoundment, which was covered with inert rock and provided with a spillway. Monitoring establishes that the tailings impoundment discharges into the receiving environment are below water quality criteria for the receiving waters; and this happy state is expected to continue.
Clem Pelletier (Rescan Environmental Services Ltd.) describes reclamation of the Trout Lake Molybdenum Property. Ignoring the complex history of the site: exploration, collapse of the market, portal closure, claim lapses, prospector staking, BC Ministry intervention, and finally $500,000 additional expenditure by Newmont to be indemnified from further claims, the following are some of the interesting physical activities undertaken to reclaim the site. (1) Assorted debris was removed from site or buried on site; (2) Hydrocarbon contaminated soil was excavated and hauled off site for disposal in Vernon, BC; (3) The upper adit was backfilled and sealed and the adjacent rock dump was recontoured and seeded; (4) The main adit was cleared, cleaned, and a concrete dam was built across the adit to direct flow from the adit to HDPE drainage pipes—then the adit was backfilled to the concrete dam and water discharged to the environment; (5) Acid generating ore piles were relocated and compacted in 500-mm lifts to increase water retention, limit infiltration, and thereby minimize oxidation leading to acid drainage; and (6) Disturbed areas were regraded, topsoil was placed where needed, and the areas seeded. Monitoring was undertaken from 2004 to 2006, but we are not told the results—maybe the topic of a future paper?
Peter Witt and Robert Hamaguchi (Highland Valley Copper) describe preparation of the Highland Valley Copper Mine tailings impoundment for final closure. Activities leading to closure have been ongoing since 1984 and the final phases of closure are to be undertaken. The impoundment covers 220 ha and is bounded by five rock-fill dams up to 47 meters high. The water in the tailings impoundment was pumped out periodically starting in 1994 and is now at or close to the elevation of the spillway invert of 1480.2 meters. It expected that with completion of the cover over the tailings, the pond water quality will improve to the point where free discharge is possible. Between 2003 and 2005 some 33 ha of the dam surface was capped with overburden. It is not entirely clear from the paper, but I presume this means the sloping part of the embankment, not the top of the tailings impoundment which it appears will be turned into a wetland. Seepage from the dams is captured in seepage ponds whence it is removed for use as process water in the Highland Mill. Some discharge is permitted from freeze-up until July 1. By far the most fascinating aspect of this paper is the report on studies of molybdenum uptake in cows and caves grazing at the mine. I quote: “Elimination studies on molybdenum conducted in 2003 and 204 demonstrate that muscle and fat tissues from cows grazing at Highmont could be safely introduced into the human food chain within one month of departure from the site. Liver tissue would require three months before acceptable clearance of molybdenum was evident.”
A remarkable paper by Price, Bellefontaine, and Ferris describes a review of the cost of maintaining closure works at the Equity Silver Mine. The authors are from, respectively, Natural Resources Canada, the Ministry of Energy, Mines and Petroleum Resource, and a local resident. If, like me, you are unfamiliar with the mine and its issues, here is a summary: Equity Silver operated between 1980 and 1994 producing silver and lesser amounts of gold and copper from three open pits and a small underground operation. At the end of operations there were, and remain, waste rock dumps, a flooded tailings impoundment, diversion ditches, ponds, dams and treatment works. The closure and long-term maintenance issues are described thus: “In addition to long-term collection and treatment by lime of large volumes of high strength acid rock drainage (ARD) produced by the waste dumps, other environmental concerns include elevated contaminants in the tailings impoundment water cover, elevated zinc and cadmium in the drainages from the backfilled Southern Trail Pit and in surface waters of the Main Zone pit lake, and the loadings of copper, zinc, and cadmium in treated drainage discharges to the receiving waters. Large volumes of mine drainage must be stored on site and can only be discharged to the environments during the spring and the fall when there is adequate dilution in the receiving environment.”
As a condition of the Mines Act permit,
In 2000 the Crown (the Federal Government of Canada) assumed
responsibility for the Coloma Mine after the former owners and their property were
placed into receivership. Left at the
site were three open pits, contaminated tailings water in a tailings
impoundment originally licensed as a “no-discharge” facility, several waste
rock dumps, and assorted mine structures.
Of immediate concern at the time of closure in 1997 was tailings water
contaminated with cyanide and rising levels of water that threatened to
overflow the tailings impoundment. This
did not occur. Natural breakdown of
cyanide and enhanced breakdown through the addition of phosphate has improved
water quality. Now only ammonia is of
concern when predicted discharges occur—in 2008. Selection of reclamation options involved the
affected First Nation, the Tlicho. The
papers details the process and notes these benefits from community
involvement: (1) the mine owner gained
timely regulatory approval [although how this occurs when the Crown is the
“owner” is not clear]; (2) the Tlicho advanced issues important to them,
including provision of a fence around the beached tailing to prevent caribou
from consuming [vegetation on the] tailings during the winter. This paper is by Tony Pearse,
Accolades and issues in mine reclamation in
There are other papers in the proceedings. I do not cover them in detail as they deal with technical issues associated with mined land reclamation, but which deserve their own technical summaries. Here are very brief summaries of some:
Finally there are what I call the exotics: papers on Indian [