Cobalt Mining Legacy

Environmental Studies in Cobalt

*** Updated November 4, 2007 ***

Several environmental studies have been carried out in the Cobalt area, documenting pollution levels in the area, as well as sources of pollution. This section lists these reports, providing brief summaries of each. Some of these reports are also available for download from this website, and more will be added as they become available.

If any visitors to this website are aware of additional studies which could be included in this list, please contact the author.

1916 – Fire Insurance Maps. These maps, while not related to the environment, are an excellent resource for those doing environmental research in the Cobalt area, particularly detailed work at the sites covered by these maps. Most of the mill sites operating at that time are covered by these maps.

»Beaver and Temiskaming mines (500 kB) »Buffalo mine (570 kB) »Coniagas mine (525 kB) »LaRose and Lawson mines (590 kB) »McKinley-Darragh mine (500 kB) »Nipissing site, including both the low grade and high grade mills (540 kB) »Nova Scotia mine (500 kB) »O'Brien mine, Northern Customs Mill and Crown Reserve mine (580 kB) »Penn Canadian mine (440 kB) »Townsite and Cobalt Lake mines (600 kB) »Trethewey mine (570 kB)

1967 – The Cobalt Camp: a preliminary assessment of water pollution by mining wastes in the Cobalt area. Prepared by the Ontario Water Resources Commission.

»Download report (800 kB)

1967 – Research in Geochemical Prospecting Methods for Silver Deposits, Cobalt Area, Ontario, 1966 by R.W. Boyle, A. Dass, D. Church, G. Mihailov, C. Durham, J.Lynch and W. Dyck. Prepared by the Geological Survey of Canada, Paper 67-35.

1977 – Report #2: A Report on the Continued Investigations into the Occurrence of Metals and Arsenic in Private Drinking Water Supplies of the TriTown Area. Prepared by the Ontario Ministry of the Environment.

»Download report (700 kB)

1980 - The Chemical Characteristics of Mineral Tailings in the Province of Ontario, 1979. Prepared by John Hawley, Ontario Ministry of the Environment.

1985 – The use of cattails to treat sewage in Northern Ontario. Prepared by G. Miller and M. Young for the Ontario Ministry of the Environment.

»Download report (300 kB)

1991 – Assessment of potential health effects of ingestion of garden produce containing arsenic and cobalt grown in Cobalt, Ontario. Unpublished report prepared by the Ontario Ministry of the Environment.

»Download report (160 kB)

1993 – The Occurrence of Arsenic and Heavy Metal Contamination from Natural and Anthropogenic Sources in the Cobalt Area of Ontario. Masters Thesis prepared by Charles Dumaresq, Carleton University.

This report, prepared by the author of this website, is the basis of much of the information on this site.

Abstract of Report

In the ore deposits of Cobalt, Ontario, silver is associated with arsenide and sulfarsenide minerals. These minerals occur in mine tailings, and oxidation of these minerals in tailings mobilizes As. Groundwater in tailings contains high As concentrations, and this groundwater discharges into surface waters. During the summer, water soluble As-rich crusts form on the tailings, and heavy rains dissolve these crusts, flushing As into surface waters. Erosion of tailings, and redeposition of tailings in downstream water bodies also contributes to surface water contamination. Thus, tailings are an import source of contamination for local surface waters. Surface waters around Cobalt contain high concentrations of As. Except for one lake, As concentrations in local water bodies range from 0.040 to 6.510 ppm, and the maximum acceptable concentration for freshwater aquatic life is 0.050 mg/L. Since As occurs naturally in the rock, some of the contamination is of natural origin. One lake unaffected by mining has a mean As concentration of 0.048 ppm. Some local groundwater also contains As, due to high As concentrations in various rock units. Most groundwaters used for consumption contain acceptable concentrations of As and heavy metals. Water from one well, in a campground, which is finished in a rock unit associated with high As concentrations in groundwater, has a mean As concentration of 6.970 ppm. Environmental contamination in the Cobalt area puts local ecosystems at risk, and there are a number of potential health threats to local residents, including: inhalation of dust from tailings, handling tailings and other solid materials, swimming in local lakes, and eating fish from these lakes.

»Download summary of report (4 MB) »Download complete report (21 MB)

1993 – Cobalt Mining Camp Tailings Inventory. Cobalt, Ontario. Prepared by Pat Anderson.

»Download report (1.5 MB) (note – this download does not yet include the many excellent maps included in this report)

1993 – Sonar profiling: A subbottom study of Gillies, Peterson, and Crosswise Lakes, Ontario. Undergraduate Thesis prepared by S.D. Wallis, Carleton University.

1995 – Analysing Arsenic, Mercury, Nickel and Cobalt Surface Water Contamination in Cobalt, Ontario, with a GIS. Undergraduate Thesis prepared by Anita Grossmann, Carleton University.

Abstract of Report

The purpose of this project was to analyse and spatially illustrate arsenic, mercury, nickel and cobalt concentrations in the surface water of the Farr Creek drainage basin encompassing Cobalt, Ontario. Maps of the study area were digitized for a Geographic Information System to include surface water, topography, surface geology and anthropogenic sources of contamination. Areas of highest risk to people and aquatic/wildlife were determined using previously collected data from 1967, 1988 to 1990, 1991 to 1992, and 1994. Statistics were calculated and results were reclassified into high, medium and low toxicity based on legal concentration limits. Then, maps were produced applying overlay analysis with the GIS to illustrate both the amount and type of contamination at each sample site for every period researched.

The GIS spatially displayed what statistical analysis had revealed, that arsenic levels were at a record high in 1994, and the Mill Creek system was still the area of highest risk. High mean arsenic levels were found throughout the Farr Creek system except for Sasaginaga Lake and Brief Lake. Because the Mill Creek system had the highest arsenic, mercury and nickel concentrations and areas of natural contamination, it was recommended that future research focus on the Mill Creek System. This should improve the statistical validity of results by increasing the number of samples where standard error was highest. The GIS analysis of sample data illustrated toxicity levels quickly and simply, enhanced the spatial interpretation of the data, delineated relationships and improved the management of information. Disadvantages were the simplified data, error introduced and time required. Overall, the GIS effectively demonstrated the complex and vast amounts of environmental research data and can now be used as an interactive tool for environmental and hydrological modeling and management.

1995 – The potential formation of a nickeloxyhydroxide layer surrounding a weathered niccolite (NiAs) grain. Undergraduate Thesis prepared by N. Nadorozny, Carleton University.

1996 – Arsenic in surface waters, Cobalt, Ontario. Prepared by J.B. Percival, C.G. Dumaresq, Y.T.J. Kwong, K.B. Hendry and F.A. Michel. Published in Current Research 1996-C, Geological Survey of Canada, pages 137-146.

Abstract of Report

Water samples from the Farr Creek drainage basin, Cobalt, Ontario, were collected to study the aqueous transport of As and other metals in a weakly alkaline environment. New data on downstream changes in total As, As(lli), and As(V) concentrations are presented. Temporal (1991-1995) changes in aqueous As distribution in the study area are also examined. Total dissolved As concentrations in surface waters range from 11 to 20 000 µg/L. Arsenic concentration generally decreases downstream, especially through wetlands, and appears to decrease with time. Widespread mine waste is undoubtedly the primary source of As in surface waters, but natural background levels in groundwater may also contribute and need to be assessed. Without mitigation, however, exposed tailings and waste rock will continue to release significant amounts of As and associated trace elements to the drainage system.

»Download complete report (200 kB)

1996 – An investigation of the fractionation of various metals associated with the low grade mill tailings at Nipissing Hill within the organic layer at Hebert Pond, Cobalt, Ontario. Undergraduate Thesis prepared by G. Andrews, Carleton University.

1996 – Detailed mineralogical analysis for the determination of alteration within the Nipissing low grade mill tailings, Cobalt, Ontario. Undergraduate Thesis prepared by A. Stoddart, Carleton University.

1997 – The occurrence and extent of arsenic contamination in surface waters in the area south of Cobalt, Ontario. Undergraduate Thesis prepared by R. Gombar, Carleton University.

1998 - Arcellaceans as Pollution Indicators in Mine Tailing Contaminated Lakes Near Cobalt, Ontario, Canada. Prepared by Eduard G. Reinhardt, Andrew P. Dalby, Arun Kumar and R. Timothy Patterson, Carleton University. Published in Micropaleontology, volume 44; number 2; pages 131-148.

Abstract of Report

Six assemblages resulting from Q-mode cluster analysis of 27 arcellacean taxa in thirty-nine sediment-water interface samples collected from two small lakes heavily polluted by mine tailings near the town of Cobalt, northeastern Ontario, Canada, correlated well with various distinct polluted and remediated environments. Results of R-mode cluster analysis indicated that arcellacean strains within the same species often discriminate among environments, thus utilization of infraspecific categories increases resolution when studying lake microenvironments, pollutants, and rates of lake remediation. Results of this study suggest that successful lake remediation in these and similarly polluted lakes is best achieved by leaving the tailings undisturbed to be buried naturally, or to speed the process by addition of an allochthonous sediment cap.

Summary and Conclusions

  1. Six arcellacean assemblages were recognized that characterize distinct highly contaminated to remediated environments. As arcellaceans live at the sediment-water interface, they are highly responsive to environmental stimuli.
  2. Characterization of infraspecific strains is useful to distinguish subenvironments not recognizable using species.
  3. Only a thin veneer of sediments is required to protect the biota from underlying tailings in neutral pH settings. In places where this layer has been artificially removed (eg. the DWRT Assemblage), exposed contaminated substrate has not recovered as indicated by the arcellacean fauna despite the passage of 31 years (1965-1996).
  4. The most effective way quickly to bring about remediation is to either leave the tailings alone or to add clean sediments to these lakes and bury the tailings.

1999 – Silver at an Old Mining Camp, Cobalt, Ontario, Canada. Prepared by James Kramer, Nicholas Adams, Helen Manolopoulos and Pamela Collins. Published in Environmental Toxicology and Chemistry Journal, volume 18, issue 1, pages 23-29.

Abstract of Report

Aqueous Ag(I) in different size fractions, ‹5 µm, ‹0.2 µm, and ‹10 kDa, was analyzed in a low dissolved organic carbon (DOC) and a high DOC environment. The sediment and tailings, contacting the water, were elevated in silver (10–100 mg/kg) from mining. The area is buffered at pH 6 to 8 by carbonate mineral gangue. Aqueous Ag(I) is present at nanogram per liter levels. Significant amounts of Ag are found in the colloidal (0.2 µm to 10 kDa) and are nondetectable (‹0.3 ng/L) or a few nanograms per liter in the ‹10-kDa fraction. Acid-volatile sulfide (AVS) was found in most (oxic) water samples at the nanomolar level. Ag(I) does not accumulate in plants probably due to the strong binding of Ag(I-) with S(II-). One exception occurs for cattails, when the aqueous AVS concentration is less than the colloidal Ag(I) concentration.

»Download report from publisher’s web site

2003 – Phytotoxicology Technical Memorandum. Interim Report. 2003 Soil Assessment Program, Cobalt National Historic Site. Cobalt, Ontario. By Randall Jones and Kyle Davis. Ontario Ministry of the Environment. Report No. Phyto - s5053 – 2005.

»Download Executive Summary (34 kB)

2004 - Transport and attenuation of arsenic, cobalt and nickel in an alkaline environment (Cobalt, Ontario). By Jeanne Percival, John Kwong, Charles Dumaresq and Fred Michel. Geological Survey of Canada Open File Report 1680.

Abstract of Report

Understanding the behaviour of arsenic in natural waters is important because arsenic and its compounds are toxic to humans and aquatic organisms. The Cobalt area, once renowned for its bonanza silver deposits, is now characterized by numerous deposits of arsenic-rich tailings, waste rock piles and remnant historic mine workings. Very limited mitigation has been undertaken since the cessation of mining. Thus, despite its slightly alkaline character, the surface drainage system continues to be contaminated from leaching of the widespread mine wastes. This Open File documents the transport and attenuation of arsenic and associated elements in the surficial environment from mine wastes (tailings and waste rock) through surface waters to wetlands of the Farr Creek drainage basin in Cobalt, Ontario.

»Download complete report from Natural Resources Canada

2005 - TECHNICAL REPORT: Screening Level Health Risk Assessment of the Historical Mining Tour of Cobalt, Ontario. Ontario Ministry of the Environment

»Download Executive Summary (100 kB) »Download full report (1.2 MB)

2005 – A Grey Wee Town: An Environmental History of Early Silver Mining at Cobalt, Ontario. By Douglas Baldwin and David Duke. Published in Urban History Review; Fall 2005; 34; 1; Research Libarary.

Abstract of Report

Cobalt was Ontario's first mining-boom town and at its height was the world's fourth-largest producer of silver. The initial discovery of silver in 1903 led to a rush that saw the town grow to several thousand inhabitants within a decade. In this period, land values rose to astronomical heights, thousands of claims were laid, and the town was hemmed in by mining operations. Initially the mines were relatively small-scale and used simple technology, but soon major mining interests impinged on the town geographically and severely affected it politically and economically. The mining-boom story of Cobalt takes the form of a conflict between the town council on the one hand and powerful mining concerns on the other. The former struggled to provide a reasonable standard of living for Cobalt's inhabitants, while the latter attempted to extract as much silver as quickly as possible from the surrounding land, from beneath neighbouring lakes, and even from within the townsite itself. In this struggle both the urban and natural environments suffered: financial constraints and nearunrestricted mining production resulted in a thoroughly inadequate urban infrastructure, especially in the provision of water for the town's inhabitants, while unhindered mining systematically deforested and denuded the land around the town and even drained the town's original main source of water, Cobalt Lake. Today, almost a century after the silver industry began to decline, the Cobalt region still displays the environmental impact of the mining activities of those early, rush years.

2006 - Biogeochemical Characterization of a Wetland Impacted by Alkaline Mine Tailings Located in North Cobalt, Ontario. Masters Thesis prepared by Jenifer Kelly, Carleton University.

Abstract of Report

The wetland area studied in the Farr Creek drainage basin in North Cobalt is entirely floored with alkaline mine tailings containing elevated concentration levels of metals including As, Co, Cu, Zn, Pb, and Sb. This system was studied to assess its effectiveness in immobilizing metals and to characterize the biogeochemical interactions governing metal attenuation within this system. The results from this study clearly indicate that this wetland is a net sink for metals, with over 75% (by mass) of the metals being retained in the sediments. Also, up to 25 % (by mass) of the metals were retained in the leaves of Typha latfolia. Both oxidizing and reducing bacteria were quantified throughout the wetland and it was found that both types of bacteria were prevalent throughout the wetland at similar population levels. This would suggest that both oxic and anoxic geochemical processes are prevalent throughout this system. It is likely that the presence of localized oxic zones in the vicinity of root zones of Typha latfolia, supported the APB populations observed. The modeling data further supported the occurrence of concurrent oxic and anoxic conditions throughout the study area as both Fe, Mn and Al oxides and/or oxyhydroxides and metal sulfide precipitates were reported throughout the wetland system. The porewater chemistry also reported consistent sulfate reduction profiles. The sequentially extracted metals (SEM) results indicated that much of the metals retained in the sediments are associated with the residual and organic matter (OM) fractions. Select metals, mainly Co and Pb showed substantial associations with the carbonate fraction of the sediment. This was not surprising since both Co and Pb have known affinities for carbonates and as such there was likely competition between OM and carbonates for sorption sites.

These results have highlighted the geochemical processes prevalent in alkaline drainage systems which are quite different from those observed in acid drainage systems, These results indicate the importance in considering both the geochemical conditions of the wetland or system being used to treat the mine drainage, as well as to have a detailed understanding of the metals of concern within the mining waste because different metals will have different geochemical interactions based on redox conditions, presence of sulfides, Fe and Mn oxides, and organic matter.

»Download complete report (5.2 MB)

2006 - Impact of redox conditions on arsenic mobilization from tailings in a wetland with neutral drainage. S. Beauchemin and Y.T.J. Kwong. Environmental Sciences & Technology 40:6297-6303.

Abstract of Report

More than 80 years of silver mining in the Cobalt area (Ontario, Canada) has led to widespread contamination of water with arsenic. The objective of this study was to determine the impact of changes in redox conditions on the stability of As in samples collected from a tailings wetland in the historic mining camp. Dissolved metal concentrations were monitored while tailings samples (≈1300 mg of As kg-1, pH 7.4) were subjected to 30 days of reduction. Reoxidation of the samples was accomplished by air drying. The As oxidation states in the original, reduced, and reoxidized samples were determined using X-ray absorption spectroscopy (XAS). Arsenic speciation was affected by changes in redox conditions, resulting in rapid mobilization of As during reduction. Glucose input had a significant impact on the dissolution and speciation of As, suggesting that the As transformation was microbially mediated. When carbon was not limiting, the combination of reducing conditions and lower pH favored the formation of As(-I) species.

»Publishers website to purchase a complete copy of the report

2007 - Transformation and mobilization of arsenic in the historic Cobalt mining camp, Ontario, Canada. Y.T.J. Kwong, S. Beauchemin, M.F. Hossain, W.D. Gould. Journal of Geochemical Exploration 92:133-150.

Abstract of Report

More than eight decades of silver mining in the Cobalt mining camp of northern Ontario, Canada, have left large volumes of As-bearing mine wastes widely distributed in and along watercourses in the Cobalt area. Metal leaching from these mine wastes has led to the contamination of the area drainage with dissolved As concentrations at least an order of magnitude higher than the Canadian drinking water criterion of 0.025 mg/L. To clarify the transformation and mobilization of arsenic in the historic mining camp, a portion of an extensive wetland located in northeast Cobalt and partially filled with historic tailings has been sampled for detailed characterization, chemical analysis and extraction tests. Field deployment of anionic exchange membranes, As sorption isotherm and desorption analyses in conjunction with chemical and mineralogical analyses indicate that: (1) the submerged tailings are likely a source instead of a sink of arsenic to the local streams; and, (2) Al-minerals are the main sorbents for As with significant P competing for the available sorbing sites. Subjecting selected samples to a laboratory redox experiment complemented with X-ray absorption spectroscopic analyses confirms that changes in arsenic speciation readily occur with changes in redox conditions in the surface sediments, resulting in rapid mobilization of arsenic. Preliminary enumeration of iron and sulfur reducing bacteria at selected sites coupled with scanning electron microscopic analyses show that microbial sulfate reduction occurs locally in the wetland with probable co-precipitation of arsenic as a sulfide in associated with framboidal pyrite. Further detailed study of the bacteria responsible for the arsenic transformation in conjunction with arsenic speciation analysis is recommended.

»Publishers website to purchase a complete copy of the report

Sudbury 2007 - Mining and the Environment International Conference

In October 2007, an international conference on mining and the environment was held at Laurentian University in Sudbury, Ontario. Known as "Sudbury 2007", this conference built on the successes of previous Sudbury conferences in 1995, 1999 and 2003, and brought together about 520 technical experts, policy makers and regulators from over 20 countries to address mine, land and waterways rehabilitation and related environmental protection issues.

The technical sessions of Sudbury 2007 included a session with four presentations related to Cobalt, and a fifth presentation in another session. In addition, a 2-day post-conference northern Ontario mining tour included a full day visit to sites in the Cobalt area. This field trip, which included almost 20 participants from Canada, Japan, South Africa and Australia, provided an excellent opportunity for participants to explore, first hand, the various challenges in the Cobalt area.

The author wishes to acknowledge the organizers of Sudbury 2007 for allowing the posting of the technical papers on this website. A complete copy of the proceedings of Sudbury 2007, on CD, is available for purchase.

Sudbury 2007 - Technical Presentations

2007 - Distribution of Heavy Metals in Typha Latifolia in a Wetland Environment on Alkaline Tailings at Crosswise Lake, Cobalt, Ontario. F. Michel and P. Champagne.


Crosswise Lake hosts the largest accumulation of alkaline tailings in the Cobalt silver mining camp. Tailings were deposited in the north end of the lake by at least five different mills operating between 1908 and 1970. Tailings now blanket the entire lake floor and a lowland through which Farr Creek drains Crosswise Lake and Mill Creek drains surface water bodies from the Cobalt Lake part of the camp. The northern portion of these tailings has been flooded by construction of a water-control dam to form a permanent wetland in which Typha latifolia is the dominant species.

Water flowing through this wetland carries elevated concentrations of arsenic and many heavy metals, including cobalt, copper, lead, molybdenum, nickel, and zinc. Sampling of T. latifolia leaves and roots in the wetland indicate that the plants are elevated in most elements compared to background samples, with the roots generally being higher than the leaves. Element concentrations in the roots were less than 15% of the average values for sediment surrounding the roots, while most metals in the leaves generally had concentrations less than 15% of the root values. Molybdenum concentrations were the exception, averaging 85% of the tailings sediment value in the roots and 5x the sediment value in the leaves. The average Mo concentration in the background sediment was twice that of the tailings sediment and leaf values averaged 50% of the sediment average value. For some elements (Ag, Cd, Cr, Cu, Pb, Sb and Zn) the concentrations in the background leaf samples were as high as the tailings leaf samples, even though the background sediment had lower concentrations than the tailings.

»Download technical paper (0.5 MB) »Download presentation (1.7 MB)

2007 - Fluctuating Redox Conditions and Phosphorus Competition: Contributors to Arsenic Release from Wetland Tailings in Cobalt, Ontario. S. Beauchemin and J. Kwong.


In the summers of 2002 and 2003, two successive sampling campaigns were carried out in the wetland area at the confluence of Mill and Farr Creeks in Cobalt (Ontario, Canada). The goal of these studies was to (i) characterize the geochemistry and mineralogy of the tailings, (ii) assess the spatial variability of those properties and (iii) relate them to water quality. A laboratory study supplemented the investigation by taking a detailed look at the impact of changes in redox conditions on the mobilization and speciation of As in these tailings. The objective of this presentation is to review part of the results showing two factors that might contribute to arsenic release from these tailings: the change in oxidizing/reducing conditions and phosphorus competition. The laboratory experiment showed that arsenic in mine tailings readily responded to changes in redox conditions and was remobilized during reduction. In the absence of added soluble C, reducing conditions in the mid-layer sample resulted in the transformation of As into more soluble As(III) species and an increase in dissolved P. When an external source of soluble C was added, solid-phase As(-1) species formed and dissolved P was apparently consumed and remained low. On the field scale, dissolved P in stream water is high and often exceeds the water quality criteria for surface waters. Indirect evidences from the chemical characterization of the tailings suggest that P sorbs more strongly on the substrate than As. Overall, these results suggest that prolonged flooding periods and the presence of sufficient soluble C could stimulate the microbial reduction of As and favour the stabilization of As into As(-1) species. Increased microbial activity might in turn help maintain lower dissolved P concentrations.

»Download technical paper (0.2 MB) »Download presentation (6.8 MB)

2007 - Distribution of As, Ni and Co in Tailings and Surface Waters in the Cobalt Area, Ontario. J. Percival, Y.T.J. Kwong, C. Dumaresq and F. Michel.


From 1904 until the mid 1930’s and intermittently until 1989, over 450 million troy ounces of silver was mined from the Cobalt area, Ontario. Currently there is no active mining of silver, but the area has seen recent exploration activities for other commodities such as diamonds. Cobalt, however, has not only a renowned mining history, but also an environmental legacy. The area is characterized by remnant historic mine workings and numerous waste rock piles and tailings ponds. Several elements of concern including arsenic, nickel and cobalt continually enter the local watershed from the tailings and waste rock piles. These elements are transported through surface waters to the wetlands in the Farr Creek drainage basin and ultimately enter Lake Timiskaming.

Tailings samples are composed of abundant plagioclase with subordinate quartz, chlorite, calcite and dolomite. Less common are K-feldspar, amphibole and mica as well as trace minerals such as erythrite, scorodite and pharmocolite. When efflorescent mineral crusts form on tailings surfaces they are dominated by either gypsum or thenardite. The tailings may contain up to 3.5 wt % Co and 2.2 wt% Ni. Lake sediment and tailings cores show concentrations up to 1.8 wt% As, 0.62 wt% Co and 0.27 wt% Ni in the solids, and 160 mg/L As, 74 mg/L Co and 42 mg/L Ni in the pore waters. One core collected from the infilled Hebert Pond situated within the Nipissing Low Grade Mill tailings impoundment show pore water concentrations in excess of 1,500 mg/L As associated with an organic-rich layer. The concentrations of these elements sustain significant aqueous transport through the drainage basin as tailings are continually weathered, eroded or leached. Surface waters contain up to 20 mg/L dissolved As which decreases downstream through the wetlands with a mean annual discharge of over 10,000 kg to Lake Timiskaming.

»Download technical paper (0.3 MB) »Download presentation (2.4 MB)

2007 - Natural Re-vegetation or Arsenic-bearing Alkaline Tailings at Cobalt, Ontario. F. Michel and K. Henein.


Mining and milling of silver and arsenic-rich carbonate veins have resulted in the deposition of tailings in many lake basins and other depressions of the Cobalt area. In some places where the tailings are exposed and salt crusts form in the summer, no vegetation has been able to grow 60 years after mill operations ceased, even when seeding was attempted. The largest tailings deposit, at the north end of Crosswise Lake, received effluent from five mills over a 60 year period (1908 to 1970) and covered the Farr Creek valley floor over a length exceeding two km. Construction of a water level control dam at the north end of the valley created a wetland that grades southward into drier exposed tailings.

Vegetation surveys conducted by Carleton University Environmental Science students at Cobalt since 2004 included uncontaminated forest, meadow, and wetland, as well as tailings sites at Cobalt. Soil pH ranges from slightly acidic (mean of 6.14) at forested sites to alkaline in tailings (mean of 8.04). The high tailings pH is due to the abundance of crushed calcite and dolomite vein material. On the Crosswise Lake tailings, only 8 plant species were found that were not observed in the other ecosystems and only 2 of these were abundant (Juncus balticus and Equisetum pratense). They dominate the exposed tailings and aid in the prevention of tailings erosion and in moisture retention. Within the Crosswise Lake wetland, Typha latifolia and Eupatorium maculatum dominate and form a thick growth. Major limiting factors for plant growth on the tailings include availability of moisture and nutrients, and to some extent toxicity of the tailings.

»Download technical paper (0.1 MB) »Download presentation (2.5 MB)

2007 - Canada’s Mining Heritage – Balancing Heritage Preservation with the Environment, Health and Safety. C. Dumaresq.


When developing and implementing mine closure plans at most mine sites in Canada, there is no need to consider the heritage value of mining structures or other features, such as mine head frames. In general, structures are removed at the end of the mine life, and sites returned to something resembling the pre-mining state. However, at some sites, heritage considerations can make mine closure more complex. In Cobalt, Ontario, abandoned silver mines are subject to a mine closure plan and at the same time many of the mines are part of a National Historic Site and are the focus of efforts to increase tourism in the area. This presents challenges for reclamation and can leave those concerned about reclamation at odds with those concerned about heritage. However, the two need not be seen as mutually exclusive. In Cobalt, efforts have been made to preserve historic head frames, mill foundations, and other signs of Cobalt’s heritage. At the same time, efforts have been made to assess the potential health risks to visitors to these sites, due to concerns about contaminated soils and other materials. In Cobalt, there is much work still to be done, and lessons still to be learned and applied. Examples from other sites may help inform future work in Cobalt and other areas in Canada where the needs of heritage and reclamation need to be balanced. Relevant experiences at the Britannia Mine Site in British Columbia and heritage sites in the United Kingdom could be considered in planning and implementing future reclamation activities in Cobalt.

»Download technical paper (0.5 MB) »Download presentation (2.5 MB)

Sudbury 2007 - Northern Ontario Mining Tour

The Timmins portion of the tour included visits to the abandoned Kam Kotia Mine (copper), one of the most studied acid mine drainage sites in Ontario, and undergoing extensive remedial work under the direction of the Ontario Ministry of Northern Development and Mines (MNDM). Other stops included an examination of mine subsidence and associated reclamation efforts at the Hollinger Mine site and other sites, reclamation efforts at Goldcorp Canada's closed Coniaurum Mine, the unique thickened tailings "cone" waste management system at Xstrata's Kidd Creek mine (copper/zinc). From Timmins, the field trip went on to Cobalt, and October 26 was spent visiting several sites in the Cobalt area, before returning to Sudbury. The Cobalt portion of the tour started with a visit to the Welcome Centre in the train station, and then went on to visit the Lion's Club Park in Cobalt Lake, the Nipissing low grade mill and tailings, the Right-of-Way Mine, and the Townsite Mine. The tour ended with an underground tour at the Colonial Mine, and finally a visit to the Mining Museum. The tour of Cobalt provided an opportunity for participants to learn more about the environmental and human health risks posed by arsenic-bearing tailings and waste rock in the Cobalt area. The tour also provided an opportunity to learn more about some of the unique mine hazards and associated remediation efforts in the Cobalt area. Participants viewed some of the sites in the area which have been reclaimed and discussed the challenges to reclamation efforts in Cobalt.

»Download field trip guide book (9.4 MB) »Photos from the field trip - Cobalt »Additional photos from the field trip