Covers are constructed on these facilities at mines sites: tailings impoundments, heap leach pads, waste rock dumps, sludge ponds, and solid waste disposal units (the equivalent of a landfill). Generally the cover is constructed as part of the closure and/or reclamation works. A wide range of cover types have been designed and constructed on mine facilities world wide. The specifics of the cover are dictated by the waste covered, the environment of the mine and in particular its climate, and the governing regulations. Accordingly, in this paper, we survey cover types by county, facility including ore type, and climatic zones.

Cover Design Criteria

General Criteria

Design and performance objectives for a mine waste disposal facility cover may include:

· Limit infiltration

· Control air entry

· Resist erosion by wind and water

· Remain stable statically, seismically, and in the long term not creep or slide down the sides of the pile

· Support vegetation including the climax vegetation and the biotic regime associated therewith (e.g., ants and termites)

· Endure for a defined period.

Cover Functions

Here is a list of soil cover functions, somewhat different but valid.

Control Radiation
Stabilize the Waste Pile
Limit Seepage and Leachate
Limit Thermal Influences
Promote Vegetation
Limit Access

Regulations

Relevant and appropriate laws and regulations are generally the basis of cover design criteria. The facility owner may impose additional criteria on the basis of corporate objectives and standards. The consultant has the obligation of knowing, advising on, and designing to standards and criteria established for a specific project.

With the exception of coal mining in the United States (1977 SMCRA Legislation; Nawrot et al 1988), the review did not find reference to prescriptive regulations for the design and construction of soil covers associated with the mining industry. In Australia, the Australian Best Practice Guidelines (Australian EPA 1995) presents a set of common closure objectives that a mining company planning waste rehabilitation should consider. The South African coal mining industry is subject to a set of closure recommendations posted by the Chamber of Mines (DWAF 1992). The MEND program in Canada has produced a number of reports that document cover practices (MEND5.4.2d 2001). MEND has provided guidelines based on these reports but these are considered to be guidelines, not prescriptive regulations. Similarly there are guideline regulations under which Wismut must operate. None of these guidelines prescribe what the cover should look like, but rather state certain minimum standards that must be achieved though the placement of a cover system.

Cover Design Life

MEND5.4.2d (2001) suggests that long-term cover performance integrity should be ensured though appropriate design for a period of 1,000 years. In Australia, Normandy Mining Ltd. has specified physical stability of their waste containment facilities for between 200 and 500 years. The Wismut practice is to design cover systems that will ensure physical stability for a 200 year life.

Most mine sites acknowledge that some form of cover maintenance and repair will be required; however, generally the understanding is that such commitments would be temporary, i.e. immediately following cover construction there would be an intensive monitoring period; however, over time, say 10 to 20 years no more maintenance will be required.

In countries with no relevant regulations and generally weak standards of practice, the cover design criteria may reflect or be influenced by one or more of these mine closure objectives:

Remove human and animal health and safety risks
Prevent, remove, or minimize environmental impacts
Reclaim the area to reasonable social and economic land value
Secure a release of bonds.
Enhance corporate image.

Cover Components

Covers may be constructed of soil borrowed from suitable sources that may include other mine wastes piles. Cover may include geosynthetics such as geomembranes. We identify the following common components of a cover, some or all of which may be present in a cover—note that sometimes a soil layer may function in two or more of the following capacities:

· Vegetation support layer

· Erosion resistant layer

· Percolation control layer

· Moisture retention layer

· Foundation layer

· Reinforcing layer.

Ancillary Facilities

The design, construction, operation, and performance of a mine waste facility cover are affected by these common ancillary facilities that are often an integral part of the cover itself:

· The waste, including its shape, topography, chemical characteristics, response to consolidation, performance in the event of an earthquake, and the requirements for limiting infiltration and air entry.

· Surface water management facilities that control run-on from precipitation and snowmelt, and which direct run-off of precipitation and snow melt.

· Access roads that may result from waste deposition or which may be required to maintain the cover.

· Irrigation facilities that may be installed to establish and maintain the design vegetation.

· Monitoring instruments that may be installed to measure the performance of the cover including soil moisture probes, deformation monitoring stations, and earthquake response instruments.

General Sources of Information

The literature on mine waste disposal facility cover is immense and growing daily. The follow are some of my favorite sources of information, available via Infomine Publications Pages, Infomine Links, or web searches:

· The Proceedings of the International Conference on Tailings and Mine Waste. The proceedings of this annual conference generally held in Colorado are an excellent source of papers on covers (and other topics) for tailings impoundments and mine waste dumps.

· The many publications on mines and waste covers that may be accessed through the University of Reno’s Mining Life-Cycle Center

· O’Kane and Wels “Mine Waste Cover System Design – Linking Predicted Performance to Groundwater and Surface Water Impact” describes a method to develop site-specific criteria for covers for acid-forming mine waste.

· Also in the Infomine Library are other publications by Wels who describes design, construction, and performance monitoring of covers at mine waste disposal facilities form New Mexico to Canada. Not all his papers are discussed in this State-of the-Art review but they are recommended for clarity and insight.

· Although rather outdated, Caldwell and Reith in “Principles and Practice of Waste Encapsulation” discuss in detail covers for uranium mill tailings and other very low level radioactive wastes. (Still available to my surprise from Amazon)

· Any of the many sites accessed by keywords landfill covers; the design, analysis, construction, and monitoring of covers for landfills is of interest to those charged with covers for mine waste. I particularly like the University of Nevada’s Desert Research Institute Alternative Cover Assessment Program, the Sandia National Laboratories Alternative Landfill Cover Demonstration, the California Integrated Waste Management Boards Alternative Final Landfill Cover Program, the EPA fact sheet on evapotranspirative covers, and the volume “Landfill Covers for Use at Air Force Installations”

Cover Design Approach

Yanful and Lin (1998) present a flow chart for soil cover design. Wels and O’Kane (2003) present a “typical” approach to the design of soil covers. Wismut developed an in-house design approach that focuses on the selection and testing of suitable cover soils, and on the development of appropriate quality assurance and quality control procedures for the cover placement.

As a result of the review undertaken by SRK, a formalized approach to cover design is proposed.

Cover Design Procedures

The complete formalized approach (Steps 1 through 12 in Figure 1) has been followed successfully in a number of actual case studies; Kidston Gold Mine (Durham 2002), AA Heap Leach Pad (Zhan et al 2001), Les Terrains Auriferes (MEND2.22.4a 1999), Whistle Mine (Ayres et al 2002) and Wismut being good examples. Sites where this approach has been adopted, but not yet fully implemented (i.e. only up to Steps 7, 8 or 9), include Mt. Whaleback (O’Kane et al 2000), Grasberg, Kestrel Coal, Syncrude (Meiers et al 2002), Kaltim Prima Coal, Questa Mine (Wels et al 2002) and Greens Creek.

Beyond these case studies, pilot-scale work appears to be limited to research studies in the form of experimental test plots which has not led specifically to a detailed full scale design of any particular waste facility cover; for example at Waite Amulet (Yanful and St-Arnaud 1991), Sullivan Mine (Gardiner et al 1997), Heath Steele Mine (Yanful et al 1993), Myra Falls (O’Kane et al 1998), Bersbo Mine (Lundgren 1997), Key Lake Mine (Lee 1999), East-Sullivan Mine (Aubertin et al 1997) and the Potash Corporation of Saskatchewan (Haug et al 1991).

There are a number of case studies where the cover construction has been completed without pilot scale work, with the cover performance based solely on uncalibrated numerical modeling (i.e. skipping Steps 6 though 8). For these case studies cover performance monitoring is implemented in tandem with cover construction with a view to proving the design. Examples of this approach include Equity Silver (Aziz and Ferguson 1997), Golden Sunlight (Wilson et al 1995), and Rum Jungle (Bennet et al 1988).

Most full-scale covers are constructed without pilot scale testing or calibration monitoring (i.e. moving straight from Step 5 to Step 9). Examples of this approach include the Vangorda waste rock pile (SRK 1994a, 1994b), Yankee- and Coral Gold heap leach pads, and the Glamis waste rock dumps and heap leach pads. Drummond et al (2003) reports on the cover designed for the Tonopah heap leach pad, where no design was done at all. Their approach was simply to adopt a design similar to those in the surrounding areas and apply that – the premise being that if it works elsewhere, it is good.

Cover Performance Analysis

Erosion

Control of cover erosion is generally best effected by:

· Vegetation which may be preferable in a moist climate.

· Placement of rocky soil which may be preferable in a dry climate.

· Contouring to limit runoff lengths—benches at 20- to 50-ft vertical intervals are commonly used.

· Disking to create paddocks, i.e., a series of vertical and horizontal surface on the otherwise overall slope sideslope.

Infiltration

There is a considerable body of data and many technical papers on quantifying infiltration on mine waste facilities in the InfoMine technology sections and systems. In addition, the procedures and practices developed by the landfill industry for infiltration control and cover construction are readily available and applicable to mine waste disposal facility covers and infiltration control.

In 2003 we looked at 177 case studies in 14 countries of covers for mine waste. We subsequently updated the study to include more than 200 case studies. This paper summarizes our findings.

Cover performance data (Figures 2 &B 3) illustrate reliable cover performance data for four case studies. In all cases there has been a significant increase in infiltration over time. The increased infiltration appears to be as a result of increasing hydraulic conductivity of the cover material. Differences of one to three orders of magnitude between design and measured values are not uncommon: soil properties should change over time, especially when these soil covers are subjected to wet/dry and freeze/thaw cycles.

Figure 2. Long-term Infiltration Through Four Covers

Figure 3. Field Hydraulic Conductivities Variations with Time

Cover Performance Monitoring

There are two approaches to evaluating and monitoring cover performance. These have been defined as “macro” and “micro” monitoring. Macro monitoring entails measurement of water quality and flow data from seepage or overland flow discharged from waste facilities (i.e. a measurement of site wide waste load), independent of the actual cover system, whilst micro monitoring entails actual monitoring of the cover system itself.

In most cases, the standard against which cover performance is evaluated is the downstream water quality. The onus is on the mining company to prove that their design will ensure compliance to the water quality standards set for that site. The South African coal industry is a good example of this system in practice. Receiving water bodies in watersheds impacted by the mining industry are monitored and an assimilative capacity for each is determined based on the downstream water use. It is therefore recognized that the mining industry has an impact on the environment, and the maximum allowable contaminant load that any receiving water body can receive without impacting the downstream water use is calculated. Each mine in the watershed is assigned a pro-rated portion of that waste load, based on production numbers. The system is regulated through measurement of the contaminant loads emanating from each site. The mine must ensure compliance with this assigned contaminant load, by whatever means, including possibly soil covers.

For some sites compliance are also measured via other mechanisms, i.e. achieving low radon emissions for radioactive waste (DOE 2002) or specific final land use requirements, i.e. pasture (Rykaart et al 2002).

Direct performance monitoring of the cover system in the form of flux measurements through the cover (MEND5.4.2d 2001) is generally used to evaluate the processes that influence the cover system performance, and to assist in setting target performance criteria for downstream water quality monitoring. The review did not identify any case studies where this level of performance monitoring is used for the purpose of compliance monitoring.

Many case studies list the use of lysimeters to directly measure infiltration though the cover system and these measurements are used to evaluate the cover effectiveness. Bews et al (1999) illustrated the complexities involved in lysimeter design, and showed that in order for a lysimeter to correctly measure infiltration though a cover it has to be specifically designed for each application. We conclude that many cover performance results are based on inadequate lysimeters, often making the interpretation of data difficult.

Long-Term Cover Maintenance

Some covers have specific maintenance plans, for example the Richmond Hill cover has to be regularly inspected and any trees that has germinated must be removed (van Zyl 2002). DWAF (1992) reports on annual grass cutting of covered coal spoil heaps in South Africa. There are also numerous examples of covers that have undergone annual repairs due to erosion; however, there does not appear to be any particular maintenance standards.

The general approach to maintenance is to “deal with the problems if and when they occur”. Furthermore, the only aspects of cover maintenance that are addressed are erosion and vegetation. Aspects that have found to require maintenance, but that are rarely acknowledged upfront include sediment transport, settlement (both from consolidation and thaw) and physical degradation (as a result of wet/dry or freeze/thaw cycles).

Complex Covers

Simple Covers

Reclamation Covers

Cover Construction Costs

Australian Cover Practice

Uranium Waste Rock Dumps

The cover placed in 1984-1985 on the Rum Jungle uranium mine waste rock dumps has three layers: (1) a low-permeability clay layer to control infiltration; (2) a storage-release layer to provide moisture to the vegetation in the long, dry season and prevent the clay drying out; and (3) an erosion resistant layer that supports vegetation. The covers were designed to limit infiltration to less than five percent of incident precipitation. For the first ten years the covers performed as designed, but by 2003 the infiltration rate was in excess of the design criterion.

As described by Taylor et al “Determination of the Reasons for Deterioration of the Rum Jungle Waste Rock Cover” testing of the cover materials showed that they no longer met the construction specifications. The clay permeability was several orders of magnitude more permeable than specified. The authors conclude that the increased permeability is the result of galleries formed by termites and ant, root growth from pasture grasses and trees, and extensive shrinkage and desiccation cracking. The authors state that acidification of the soil at the base of the covers may also affect cover performance.

The authors also noted that at some locations the upper layers of the cover were not as thick as specified possibly due to poor construction. The authors attribute some of the poor cover performance to the thinner cover sections.

Measurement of the oxygen flux in to the heap indicted that the full cover reduces the flux to about 20 percent of that into bare rock. The flux is about four times higher at the end of the dry season than at the end of the wet season primarily due to the moisture content changes in the soil of the cover.

Canadian Cover Practice

Copper Tailings

Following closure of the Falconbridge Mill, Sudbury, Ontario, the 90-hectare tailings impoundment was flooded and covered with a water cover by construction of a series of dams. Hall “New Tailings Area Closure: A Case Study” [Infomine Library] describes a water cover where no there are thriving colonies of minnows, performance has exceeded expectations, and the mine is heading to a walk-away closure scenario. Swedish covering of mine waste by water is described by Eriksson et al “A quantitative evaluation of the effectiveness of the water cover at the Stekenjokk tailings pond in Northern Sweden: Eight years of follow-up” [Infomine Library]. Canadian covering of tailings by water is described by Aziz and Ferguson “Equity Silver Mine - A Case Study.” And by Amyot and Vezina “Flooding as a reclamation solution to an acidic tailings pond”.

Acid Generating Tailings Piles and Waste Rock Dumps

You may significantly underestimate the infiltration through the sideslope cover if you consider only the one dimension effect; runoff down the sideslopes and downslope seepage in the soil of an evapotranspirative cover may increase the infiltration rate in the lower reaches of the sideslope cover relative to the upper reaches of the sideslope cover. Christensen and O’Kane “The Use of Two-Dimensional Soil-Atmospheric Modeling in the Design of Dry Cover Systems for Mine Waste” [Infomine Library] describes the effect of the long sideslopes on the infiltration through what they call a dry cover, or what is more commonly called and evapotranspirative cover. The authors used the computer code VADOSE/M to model sideslope evaoptranspirative covers and examine the increase in infiltration that results from the downslope effect of the cover—they conclude that one dimensional modeling of sideslope covers can significantly underestimate the infiltration through a cover and that the designer may have to change the cover design in the lower reaches of the slope.

Can you control the flux of oxygen through a cover to the acid generating wastes below? Shelp et al. “Electrochemical Cover for the Prevention of Acid Mine Drainage—A Laboratory Test” [Infomine Library] describe the use of steel mesh cathode installed in a cover’s oxygen barrier of the top layer of thickened tailings to reduce oxygen migration to the acid generating wastes. Laboratory testing indicates this may work, but confirmation awaits field tests in Montana.

The carbon in a wood-waste cover in a wet environment may consume atmospheric oxygen passing through the cover and thereby reduce acid seepage generation. This possibility is described by Germain et al. “Treatment of Acid Mine Effluent Using a Wood-Waste Cover” [Infomine Library]. The authors describe the efficacy of a wood-waste cover at the East Sullivan mine tailings pile in Quebec. They conclude: an organic cover can act as an oxygen barrier and can be integrated into a strategy for efficient treatment of transient acidogenic waters.

European Cover Practice

Uranium Mill Tailings

Germany is designing and constructing covers on the uranium mine waste facilities in the east of the county. As described by Deissmann et al “Design Constraints on Engineered Dry Covers for Waste Rock Dumps” the design life is 200 years with 1,000 years being a “secondary” consideration. The authors note that if trees are likely to grow on the cover, there must be at least 1.5 m of soil for the roots and this layer must incline at no more than three horizontal to one vertical. The authors note that collection and treatment of contaminated seepage forms an integral part of “after-care” of the remediated dump.

Ten years after placing a cover over uranium mill tailings in Ranstad, Sweden, the concentrations of most metals in the seepage have decreased, but water treatment is still needed to meet discharge criteria. Sundblad “Ten years experience of a multi-layer cover system for uranium mill tailings” describes the performance of the cover that consists of these layers, from the top down: top soil – 0.2 m; moraine – 1.2 m; crushed limestone – 0.2 m; clay moraine – 0.2 m; mill tailings. The author notes that no environmental goals for the remediation of the mill tailings were proposed when restoration work began, but due to 1997 water quality requirements imposed for the downstream lake, studies for alternatives to the treatment plant proceed.

The construction of soil covers on very weak, compressible fine tailings is complicated by the low shear strength, poor trafficability, and large settlement of the unconsolidated tailings. Wels et al. “A review of dry cover placement on extremely weak, compressible tailings” describe how to analyze and how best to place a cover over unconsolidated tailings. The analytical and construction approaches they described are based on practice at the Wismut GmbH uranium mill tailings impoundments in the eastern part of Germany. They describe these steps in placing a cover: (1) remove pond water; (2) place an interim cover; (3) enhance tailings consolidation by de-watering; (4) flatten embankments and sideslopes; (5) fill and grade the tailings surface; and (6) construct the final cover.

Basic Ores

The base metal and iron ore mines of Sweden have been mined since the ninth century. Remediating the tailings impoundments to the standards of the twenty-first century is described by Johansson et al. “Garpenberg—Mine Site Reclamation Using Alternative Cover Methods.” Methods include placement of paper mill sludge, soil covers, and flooding via dams.

United States of America Cover Practice

Uranium Mill Tailings

The U.S. Department of Energy’s Uranium Mill Tailings Remedial Action (UMTRA) Project. At each of the twenty four sites in ten states a cover was constructed over the uranium mill tailings. The covers were designed to last for a 1,000 years to the extent reasonably achievable and at least for 200 years. Many papers on the design, construction, and performance of the covers are available in the Infomine Library and on the web.

Gold Tailings

The Cannon Mine was operated between the mid-1908 and mid-1990 as an underground gold and silver mine on the outskirts of Wenatchee in central Washington. The mine was closed in 1994 and reclaimed over a period ending in 1996. The tailings facility was built as a valley fill structure with a 300-ft high earth and rockfill embankment. The closure cover includes these layers, from the top down: (1) vegetation; (2) a 1-ft thick topsoil layer; (3) 2.5-ft thick well-graded sand and gravel base; and (4) a geotextile support layer. A superb presentation on closure of this impoundment and the cover is available.

Anaconda Mine

The U.S. EPA is moving fill from part of the Anaconda Mine site in Yerington, Nevada to build a soil cap over sulphide tailing contamination at the site, along with using soil sealant on areas of wind erosion in adjacent evaporation ponds. The emergency action was the second removal action initiated as a result of requested the assistance of EPAs emergency response group to address two problems that posed an imminent threat to human health and the environment: PCB contamination from electrical transformers and fugitive dust from mine tailings. EPA has taken steps to address the imminent dangers to human health and the environment from PCBs and fugitive dust.

During the removal assessment, EPA determined that the PCB contamination and fugitive dust needed to be addressed as soon as possible. Because the sulphide tailings were exposed, there was the potential the wind could spread the dust across the property or even carry it off-site. The emergency response was necessary to prevent the contaminants from migrating. To address the PCB contamination, EPA removed and disposed of 119 PCB-containing electrical transformers. EPA asked potentially responsible party Atlantic Richfield Co (ARCO) to complete the removal actions, but the company declined. EPA is completing the emergency cleanup and seeking reimbursement from ARCO and other potentially responsible parties.

EPA is using a number of safeguards to prevent the spread of contamination during the placement of the cap, including air monitoring and using water trucks to help reduce the risk of the tailings becoming airborne. Once complete, the soil cap and sealant will cover eight basins across nearly 120 acres at the site. The emergency response has cost approximately $600,000 to date.

Anaconda mine site is a massive 3,400-acre site approximately 105 km from Reno. Copper was discovered in the region in 1865, and the site began operating as Empire Nevada Mile in 1918. Between 1918 and 1978, Anaconda continued mining operations at the site. ARCO purchased the property in 1977, operated the facility for just one year, and sold it to Don Tibbals, who leased portions of the property for use. Arimetco purchased the property from Tibbals and conducted leaching operations at the site; the company went bankrupt in 2001 and abandoned the property.

Covers to Control Acid Mine Drainage

Covers to control Acid Mine Drainage should control infiltration of water and also inflow of air. Here is a brief discussion of some covers proposed and/or used for Acid Mine Drainage control.

This is a simple cover of soil over the rock. The permeability depends on the soil gradation and the density and crack pattern in the soil.

A slightly more complex cover where a relatively high density soil is placed directly over the rock, followed by a lower density soil selected and placed to support vegetation.

The cover used at the Gray Eagle Mine Tailings Impoundment.

Below we summarize come comparisons of the infiltration and runoff for a variety of covers.

A comparison of runoff and percolation from a variety of covers.

Yet more covers and calculated infiltration and runoff.

Quebec Covers

The performance of covers on tailings piles to limit oxygen migration to the acid generating materials beneath is the topic of an abstract in the latest CIM magazine. In brief, the abstract tells us that the measurements of a cover in Quebec since 1996 establish that, except in the upper parts of the sideslopes, the soil of the cover remains moist enough to limit the entry of air to the encapsulated tailings. About five percent of the cover is cover is susceptible to desaturation in dry periods, presumably as a result of downslope migration of the moisture in the cover.

Sadly we cannot access the papers—need to be a CIM member for that. Or see a paper on the same topic from 2003, unless you subscribe to the Canadian Geotechnical Journal. As most TechnoMine readers are not CIM members, and cannot afford the Canadian Geotechnical Journal let me tell you what I did find out on this topic from free sites on the web.

Natural Resources Canada describes the site closure. See similar information about the site and others in Quebec at this link. Hong Kim and Craig Benson have written on the theoretical aspects of the phenomenon—their paper is readily available and worth reading if the topic concerns you. Another good paper that deals more with the practical aspects of acid drainage control including the use of moist covers is my Murphy and Leake of Earth Systems. The most practical and case history oriented is the 1999 Environmental Progress Report from The Mining Association of Canada

One of the delights of trawling the web is to find a superb volume you had not previously seen—here are my picks from this trawl—not much to do with the topic of the CIM paper, but worth you time, nevertheless:

Ø Sustainable Improvement in Safety of Tailings Facilities (2004) and see page 27 for information relevant to moist covers designed to limit air flow.

Ø Engineering Guidelines for the Passive remediation of Acid and/or Metalliferous Mine Drainage and Similar Wastewaters (2003). See page 91 and following for information of covers.

Miscellaneous References

Aubertin, M., Bussière, B., Barbera, J.-M., Chapuis, R.P., Monzon, M. and Aachib, M. (1997). Construction and Instrumentation of In Situ Test Plots to Evaluate Covers Built with Clean Tailings. Proceedings of the 4th International Conference on Acid Rock Drainage, Vancouver, British Columbia, Canada. 31 May to 6 June. Vol 2, pp. 715-730.

Australian Environment Protection Agency (EPA) (1995). Rehabilitation and Revegetation. Module in series on: Best Practice Environmental Management in Mining. Australian Federal Environment Department, June 1995.

Ayres, B.K., O’Kane, M.O., Christensen, D., Lanteigne, L. (2002). Construction and instrumentation of waste rock test covers at Whistle Mine, Ontario, Canada. Proceedings of Tailings and Mine Waste ’02, Fort Collins, Colorado, USA. 27-30 January, pp. 163-171.

Aziz, M.L. and Ferguson, K.D. (1997). Equity Silver Mine - Integrated Case Study. Proceedings of the 4th International Conference on Acid Rock Drainage, Vancouver, British Columbia, Canada. 31 May to 6 June. Vol 1, Pp. 181-196.

Bennett, J.W., Harries, J.R. and Ritchie, A.I.M. (1988). Rehabilitation of Waste Rock Dumps at the Rum Jungle Mine Site. Proceedings of the Mine Drainage and Surface Mine Reclamation Conference, Pittsburgh, PA, USA. 17 to 22 April. Vol 1, pp. 104-108.

Bews, B, Barbour, S.L., Wickland, B. (1999). Lysimeter Design in Theory and Practice. Proceedings of Tailings and Mine Waste, Fort Collins Colorado, USA. January 24-27. pp. 13-21.

Cabalka, D, Newton, P. (1998) Fire and Ice. Geotechnical Fabrics Report. pp. 30 - 35. January - February 1998.

Department of Energy (2002). U.S. Uranium Production Facilities: Operating History and Remediation Cost under Uranium Mill Tailings Remedial Action Project as of 2000. April 12. www.eia.doe.gov

Department of Water Affairs and Forestry (DWAF) (1992). Rehabilitation Principles for Coal Waste Dumps Arising from an Audit of Rehabilitation Works on Coal Wastes in Northern Natal. Report No. 1622, prepared by Wates, Meiring & Barnard Consulting Engineers, Edited by Wates et al., December 1992.

Department of Water Affairs and Forestry (DWAF) (1998). Minimum Requirements for Waste Disposal by Landfill. Waste Management Series, Second Edition, ISBN 0620-22993-4.

Drummond, S., Smith, M., Robison, N.E. (2003). Equatorial Tonopah, Inc. Copper Heap Leach Closure. Presentation delivered at Heap Leach Closure Workshop, March 25 and 26, Elko Convention Center, Elko, Nevada, USA, 2003.

Durham, A.J.P. (2002). Optimization of a Waste Rock Cover System in an Arid Environment M.Sc. Thesis. Department of Civil Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

Gardiner, R.T., Dawson, D.B. and Gray, G.G. (1997). Application of ARD Abatement Technology in Reclamation of Tailings Ponds at Cominco Ltd., Sullivan Mine. Proceedings of the 4th International Conference on Acid Rock Drainage, Vancouver, British Columbia, Canada. 31 May to 6 June. Vol 1, pp. 47-63.

Haug, M.D., Wong, L.C. and Johnston, K. (1991). Design and Construction of a Compacted Earth Test Cover for a Potash Tailings Pile. Proceedings of the First Canadian Conference on Environmental Geotechnics. 14 May. pp. 185-192.

Lee, N. (1999). Evaluation of Cover Materials for a Large Scale test Facility at Key Lake. M.Sc. Thesis, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

Lundgren, T. (1997). Bersbo Pilot Project Physical Behavior Seven Years after Covering the Waste Rock Piles. Proceedings of the 4th International Conference on Acid Rock Drainage, Vancouver, British Columbia, Canada. 31 May to 6 June. Vol 3, pp. 1419-1434.

McKenna, G.T. (2002). Sustainable mine reclamation and landscape engineering. PhD Thesis in Geotechnical Engineering, Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Canada. Fall, pp. 661.

Meiers, D.E., Barbour, S.L. (2002). Monitoring of Cover and Watershed Performance for Soil Covers Placed over Saline-Sodic Shale Overburden From Oilsands Mining. Paper presented at 2002 National Meeting of the American Society of Mining and Reclamation. Lexington KY, USA. June 9-13, 2002. Published by ASMR.

MEND 2.22.4a (1999). Construction and Instrumentation of a Multi-Layer Cover Les Terrains Aurifères. February.

MEND 5.4.2d (2001). MEND Manual, Volume 4 – Prevention and Control. Ed. G.A. Tremblay and C.H. Hogan, February.

Münnich, K. (1993) Reduction of the Migration of Contaminants through Mineral Barrier Systems by Hydraulic Means. Proceedings of Fourth International Landfill Symposium, Sardinia, Cagliari, Italy. October 11 — 15, 1993.

Nawrot, JR, Sandusky, J and Klimstra, WB. (1988) Acid Soils Reclamation: Applying the Principles. Proceedings American Society for Surface Mining and Reclamation and the U.S. Department of the Interior, Mine Drainage and Surface Mine Reclamation Conference, Pittsburg, PA, USA. April 17 - 22, 1988. pp 93 - 103.

O’Kane, M., Porterfield, D., Weir, A. and Watkins. A.L. (2000). Cover System Performance in a Semi-Arid Climate on Horizontal and Sloped Waste Rock Surfaces. Proceedings of the 6th International Conference on Tailings and Mine Waste ’99, Fort Collins, CO, USA. 24 to 27 January. pp. 1309-1318.

O’Kane, M., Stoicescu, J., Januszewski, S., Mchaina, D.M. and Haug, M.D. (1998). Design of Field Test Plots for a Sloped Waste Rock Surface. Proceedings of the 15th National Meeting of the American Society for Surface Mining and Reclamation, St. Louis, MO, USA. 16 to 21 May. pp. 368-378.

Rykaart E.M. (2002). A Methodology to Describe Spatial Surface Flux Boundary Conditions for Solving Tailings Impoundment Closure Water Balance Problems. Ph.D. thesis submitted to Department of Civil Engineering, University of Saskatchewan, Saskatchewan, Canada.

Rykaart, E.M., Fredlund, D.G., Wilson, G.W. (2002). Spatial Surface Flux Boundary Model for Tailings Impoundments. Proceedings of Tailings and Mine Waste ‘02, Fort Collins Colorado, USA. January 27-30. pp. 283-291.

Savage River Rehabilitation Project (2001). Summary of SRRP Technical Reports to 31 January 2002. December. 50 pp.

Shepperd Miller (2001). North Waste Rock Storage Facility Acid Rock Drainage Mitigation and Final Phased Permanent Closure Plan, Rain Mine, Carlin, Nevada. Report prepared for Newmont Mining Corporation by Shepperd Miller Inc., Fort Collins, Colorado, USA. May 2001.

SRK-Robinson Inc. (1994a). Construction Report, Vangorda Rehabilitation PWGSC Project 760831, Vangorda Plateau, Faro Mine, Yukon Territory. Consultants report prepared for Public Works and Government Services Canada, Project P225101, November.

SRK-Robinson Inc. (1994b). Final Design Report Report, Vangorda Rehabilitation GSC Project 760831, Vangorda Plateau, Faro Mine, Yukon Territory. Consultants report prepared for Public Works and Government Services Canada, Project P225101, March.

Suter, G.W., Luxmoore, R.J., Smith, E.D. (1993). Compacted Soil Barriers at Abandoned Landfill Sites are Likely to Fail in the Long Term. J. Environ. Qual. 22:217-226.

Van Zyl (2002). Richmond Hill Mine. Personal communication with Prof. Dirk van Zyl, McKay School of Mines, University of Reno, Nevada, USA.

Wates, J.A., Rykaart, E.M. (1999) The Performance of Natural Soil Covers in Rehabilitating Opencast Mines and Waste Dumps in South Africa. Water Research Commission Report 575/1/99, ISBN No. 1868456139.

Wels, C., Fortin, S., Loudon, S. (2002). Assessment of Store-and-Release Cover for Questa Tailings Facility, New Mexico. Proceedings of Tailings and Mine Waste ’02, Fort Collins, Colorado, USA. 27-30 January, pp. 459-468.

Wels, C., O’Kane, M. (2003). Design of Mine Waste Cover Systems, Linking Predicted Performance to Groundwater and Surface Water Impacts. Paper presented on HydroMine website.

Wilson, G.W., Barbour, S.L., Swanson, D. and O’Kane, M. (1995). Instrumentation and Modelling for Saturated/Unsaturated Performance of Soil Covers for Acid Generating Waste Rock. Hydrogéologie. No 4, pp. 99-108.

Yanful, E.K. and St-Arnaud, L.C. (1991). Design, Instrumentation, and Construction of Engineered Soil Covers for Reactive Tailings Management. Proceedings of the 2nd International Conference on the Abatement of Acidic Drainage. Montréal, Québec. 16 to 18 September. Tome 1, pp. 487-504.

Yanful, E.K., Bell, A.V. and Woyshner, M.R. (1993). Design of a Composite Soil Cover for an Experimental Waste Rock Pile near Newcastle, New Brunswick, Canada. Canadian Geotechnical Journal. Vol. 30, pp. 578-587.

Yanful, E.K., Lin, M. (1998). An Integrated Approach to Designing Soil Covers for Reactive Mine Waste. Proceedings of the 51^st Canadian Geotechnical Conference, Edmonton, Alberta, Canada. Oct 4-7. Vol I: pp. 141-148.

Zhan, G, Mayer, A B , McMullen, J, and Aubertin, M, (2001), Slope Effect Study on the Capillary Cover Design for a Spent Leach Pad. Proceedings of Tailings and Mine Waste ‘01, Fort Collins, Colorado, USA.