TECHNOLOGY REVIEW

 

BC Land Reclamation

 

 

 

 

 

 

 

 

Waste rock dumps at an open pit coal mine after reclamation

(Photo: TRCR)

 

 

 

 

 

 

 

Revision:  November 2006

Author: Jack Caldwell

http://technology.infomine.com

 

The Thirtieth Annual British Columbia Mine Reclamation Symposium was held in Smithers, British Columbia in June of 2006.  By kind permission of Kim Bittman of Teck Cominco, I am able to prepare this review of the proceedings.  She provided me with a copy of the proceedings; you can get a copy from Bitech Publishers Ltd. 

 

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 Iowa I was detained in Grand Junction, Colorado by a great snow storm that swept down over southern Utah and the Rockies making passage across the Continental Divide dangerous.  Instead of tackling I70, I spent a day slowly driving down State Route 141, surely one of the most beautiful drives in all the world.  The spectacular scenery was not my only objective.  I headed for Uravan as I wondered through the mountains and valleys and along the rivers bounded by red and orange fall foliage. 

 

High up on an isolate plateau above the San Miguel River are five uranium mine tailings impoundments.  The first is the relocated pile from the Title II Bristol Mine.  Just above it at the head of a small local drainage divide are the Title I tailings relocated from Naturita many miles south on 141.   Dominating all, however are the three interlinked impoundments from the Uravan Mine and Mill.  I had just parked my car to look over the vast landscape when a van drew up, a fellow got out, and enquired my purpose.  I told him of my days on the UMTRA Project and my interest in the final Naturita Pile.  He quickly and proudly told me he is a full-blooded Navajo, and then recounted his fifteen years working as a QA/QC inspector on the UMTRA an other uranium mill pile stabilization projects.  We spent a good hour in the warm sun exchanging stories of acquaintances and projects we both knew well.  He is proud of his most recent project:  completion of closure of the Uravan tailings soon to become another Title II site. 

 

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, British Columbia requires provision of a financial security that is sufficient to provide interest payments equal to the predicted future liability and annual operating costs at the Equity Silver Mine.  Reviews of these cost are conducted every five years.  This paper describes the 2005 review.  I cannot possibly do justice to the paper’s details in this review; suffice it to say that the major issue was the quantity and the cost of the lime that would be required in the future for ARD treatment.  The review of factors that could increase or decrease ARD production and lime consumption should be required reading for all practitioners in the field.  More conservative quantities and cost were finally adopted because of “increased evidence of build-up and flushing of weathering product, lower confidence in the effectiveness of the dry cover and the high environmental risk and high uncertainty.”  Not being familiar with the total situation or the BC regulations and political process, I cannot say what the outcome of the review was; it is summarized thus in the paper: “Placer Dome committed to taking these suggestions under advisement and trying to incorporate them into future plans but cautioned that only a limited number of issues could be addressed each year.”

 

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, Technical Advisor Tlicho Government. 

 

Accolades and issues in mine reclamation in British Columbia are the topic of a fine paper by David Polster and Diane Howe of Polster Environmental Services Ltd and the Ministry of Energy, Mines and Petroleum Resources respectively.  I quote from the abstract: “British Columbia leads the world in mined land reclamation.”  The authors point to the following successes: (1)  Re-integration of the disturbed lands with the surrounding terrain; (2) Placement of soil for plant growth and isolation of wastes; (3) Revegetation of disturbed areas; and (4) effective reclamation monitoring and maintenance.   The authors note the following issues: (1)  Large waste dumps that do not blend into the topography; (2) Uncovered waste rock dumps and tailings; and (3) dense stands of agronomic grasses and legumes that preclude the re-establishment of appropriate successional trajectories on the disturbed lands.  The authors praise the concept of designing for closure and point to the cost benefits and reclamation advantages.  They point to the benefits of wrap-around waste dumps, the placement of sufficient thicknesses of suitable soil, and the sealing of reactive waste areas to minimize acidic drainage.  They plead for more monitoring and more ongoing maintenance, and continued research as many reclaimed sites mature and provide insight into the ecological processes associated with successful reclamation.

 

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:

 

  • Biosolids and lime were used as a slurred sprayable soil amendment (see Mattes et al.)
  • Airborne multispectral imagery was used to examine temporal trends of vegetation biomass at reclaimed mines (see Brown et al.)
  • The ability of an anaerobic bioreactor to deal with arsenic, cadmium, and zinc is examined (see Kawaja et al.)
  • The response of birds to mining and reclamation initiatives was observed (see Howie.)
  • The response of juvenile rainbow trout and benthic invertebrates to the effluent from molybdenum mine is described (see Galloway et al.)
  • The impact of mercury on the reproductive success of fish-eating birds is described (see Weech and Scheuhammer.)
  • The effect of selenium on fish and water birds is described (see Carmichael and Chapman.)

 

Finally there are what I call the exotics: papers on Indian [Asia—not First Nation] mine reclamation, mercury use by artisanal miners world-wide, and nationwide abandoned mine remediation activities.  Interesting but only peripherally relevant to BC mined land reclamation, so be aware of them if these are your interests.   And keep in mind the papers from decades of previous society symposia are available on one CD at this link.  Someday we may survey them all and write of the history of mined land reclamation in BC—another success story I am sure.