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PROPERTIES OF TAILINGS DAMS

(last updated 28 Aug 2023)

Introduction
Upstream tailings dams
Comparison of tailings dam types
Bibliography
Related information sources

INTRODUCTION

What are tailings?

Tailings are the residue of the milling process that is used to extract metals of interest from mined ores. During this process, ores are first milled and finely ground, and then treated in a hydrometallurgical plant. Since the extracted metal represents only a small percentage of the whole ore mass, the vast majority of the material mined ends up as a fine slurry.
The tailings contain all other constituents of the ore but the extracted metal, among them heavy metals and other toxic substances. Moreover, the tailings also contain the chemicals added during the milling process. In addition, as a result of the milling process, all these contaminants now are much better available for dispersion into the environment than in the original ore. And, the mechanical stability of the tailings mass is very poor, due to its small grain size and the usually high water contents.

Tailings impoundments

Most of the mill tailings mass produced worldwide is dumped in large surface impoundments ("tailings dams"). The embankments forming these impoundments are earthfill dams. Although water-retention type dams would be very suitable for tailings dams, they are not used for their high cost.

Water-retention type dam for tailings storage

Other than water-retention type dams, tailings dams usually are not constructed initially to completion, but raised sequentially as the impoundment fills.

Types of sequentially raised tailings dams

UPSTREAM TAILINGS DAMS

Upstream-type embankments are the most popular embankments for tailings dams; new parts of the embankment are built on top of the slurries impounded during the previous stage - the dam crest thus moving "upstream".

Upstream tailings dam (click image to view animation of sequential raising)

(Click image to view animation of sequential raising of upstream tailings dam )

For its low cost, the upstream embankment type is used with most tailings dams worldwide, but it bears the highest risk. Dam stability is of particular concern with this type of tailings embankments:

The phreatic surface is critical for the dam stability. Dam failure can occur, if the beach width between the decant pond and the dam crest becomes too small - from flood inflow, or from improper mill operation, for example. While the determination of phreatic surface location is so important for upstream-type embankments, it is more complex by far for this embankment type than for any other type of tailings-retention structure.

k_L = permeability at the edge of the ponded water at the slimes zone
k₀ = permeability at the spigot point (dam crest)
k_F = permeability of foundation
k_h / k_v = anisotropy ratio (horizontal vs. vertical)
Upstream dams are particularly susceptible to liquefaction under severe seismic ground motion. This motion may result from earthquakes, from nearby mine blasting, or even from nearby motion of heavy equipment, for example.
Upstream dam stability is endangered if the raising rate of the dam is too high. Raising rates greater than 15 m/yr can be hazardous. They can produce excess pore pressure within the deposit, decreasing stability.

(see also Tailings Dam Safety)

COMPARISON OF TAILINGS DAM TYPES

Comparison of Surface Impoundment Embankment Types
Water Retention Upstream Downstream Centerline

Mill Tailings Requirements Suitable for any type of tailings At least 40-60% sand in whole tailings. Low pulp density desirable to promote grain-size segregation Suitable for any type of tailings Sands or low-plasticity slimes

Discharge Requirements Any discharge procedure suitable Peripheral discharge and well-controlled beach necessary Varies according to design details Peripheral discharge of at least nominal beach necessary

Water Storage Suitability Good Not suitable for significant water storage Good Not recommended for permanent storage. Temporary flood storage acceptable with proper design

Seismic Resistance Good Poor in high seismic areas Good Acceptable

Raising Rate Restrictions Entire embankment constructed initially Less than 4.5 - 9 m/yr most desirable. Greater than 15 m/yr can be hazardous None Height restrictions for individual raises may apply

Embankment Fill Requirements Natural soil borrow Natural soil, sand tailings, or mine waste Sand tailings or mine waste if production rates are sufficient, or natural soil Sand tailings or mine waste if production rates are sufficient, or natural soil

Relative Embankment Cost High Low High Moderate

Source: [Vick1983]

Comparison of Surface Impoundment Embankment Types
	Water Retention	Upstream	Downstream	Centerline
Mill Tailings Requirements	Suitable for any type of tailings	At least 40-60% sand in whole tailings. Low pulp density desirable to promote grain-size segregation	Suitable for any type of tailings	Sands or low-plasticity slimes
Discharge Requirements	Any discharge procedure suitable	Peripheral discharge and well-controlled beach necessary	Varies according to design details	Peripheral discharge of at least nominal beach necessary
Water Storage Suitability	Good	Not suitable for significant water storage	Good	Not recommended for permanent storage. Temporary flood storage acceptable with proper design
Seismic Resistance	Good	Poor in high seismic areas	Good	Acceptable
Raising Rate Restrictions	Entire embankment constructed initially	Less than 4.5 - 9 m/yr most desirable. Greater than 15 m/yr can be hazardous	None	Height restrictions for individual raises may apply
Embankment Fill Requirements	Natural soil borrow	Natural soil, sand tailings, or mine waste	Sand tailings or mine waste if production rates are sufficient, or natural soil	Sand tailings or mine waste if production rates are sufficient, or natural soil
Relative Embankment Cost	High	Low	High	Moderate

BIBLIOGRAPHY

Planning, Design, and Analysis of Tailings Dams, by Steven G.Vick, John Wiley & Sons , New York, 1983, 369 p., ISBN 0-471-89829-5
[the textbook on the issue !]
A reprint was published in 1990 by BiTech Publishers Ltd. , Richmond B.C., Canada (ISBN 0-921095-12-0)
> Download complete book (29.9MB PDF)
Technical Report: Design and Evaluation of Tailings Dams, U.S.EPA Office of Solid Waste, EPA/530-R-94-038, NTIS/PB94-201845, August 1994, 69 p. [Provides an overview of the various methods used to dispose of mine tailings and the types of impoundments that are used. Describes the basic concepts used in the design of impoundments, including a number of site-specific variables of concern. Report also discusses tailings embankment and stability and briefly discusses water management in tailings impoundments. Includes a case study on a lined tailings impoundment. The report relies heavily on Steven G.Vick's book (see above). Watch out: Figures 8-11 are mixed up!]
Order address: National Technical Information Service
Also available for Download (307k PDF).
Seminar on SAFE TAILINGS DAM CONSTRUCTIONS, Gällivare, 20-21 September 2001, Technical Papers. Swedish Mining Association, Naturvårdsverket, EUROPEAN COMMISSION
> Download full text (800k PDF) of selected papers
Proceedings of the Workshop on Risk Assessment and Contingency Planning in the Management of Mine Tailings, Buenos Aires, Argentina November 5-6, 1998. ICMM , Ottawa, Ont., 1998, 314 p.
> Download full report (ZIP archive containing PDF file)
Proceedings of the International Workshop on Managing the Risks of Tailings Disposal, Stockholm, Sweden, May 22-23, 1997. ICMM , Ottawa, Ont., 1997, 264 p.
> Download full report (ZIP archive containing PDF file)
Dynamic safety of earth and rockfill dams. Proceedings of a course, New Delhi, 16-20 August 1993. by T.Ohmachi, J.Kuwano (Eds.), A.A. Balkema, Rotterdam 1994, 160 p. ISBN 90-5410-265-9
International Symposium on Safety and Rehabilitation of Tailings Dams, (Sydney) 23 May 1990, Vol.1: Presented Papers. International Commission on Large Dams, Australian National Committee on Large Dams (Eds.), Sydney 1990, 339 p.
Upstream constructed tailings dams - A review of the basics, by M.P.Davies and T.E.Martin, In: Tailings and Mine Waste '00, Proceedings of the Seventh International Conference on Tailings and Mine Waste '00, Fort Collins, Colorado, USA, 23-26 January 2000, ISBN 90 5809 126 0, Rotterdam/Brookfield 2000, p. 3-15
Some considerations in the stability analysis of upstream tailings dams, by T.E.Martin and E.C.McRoberts, In: Tailings and Mine Waste '99, Proceedings of the Sixth International Conference on Tailings and Mine Waste '99, Fort Collins, Colorado, USA, 24-27 January 1999, ISBN 90 5809 025 6, Rotterdam/Brookfield 1999, p. 287-302
Regulatory and technical tailings design considerations in Chile, by Alan J. Krause. In: Tailings and Mine Waste '97, Proceedings of the Fourth International Conference on Tailings and Mine Waste '97, Fort Collins, Colorado, USA, 13-17 January 1997, ISBN 90 5410 857 6, Rotterdam/Brookfield 1997, p.51-55
Dam-break studies for mine tailings impoundments, by Jey K.Jeyapalan. In: Geotechnical Engineering Program, Civil Engineering Department, Colorado State University (Ed.), Uranium Mill Tailings Management. Proceedings of the Fifth Symposium, December 9-10, 1982, Fort Collins, Colorado 1982, p.39-53
Earthquake effects on uranium mill tailings impoundments, by W.A.Charlie, R.E.Wardwell. In: Geotechnical Engineering Program, Civil Engineering Department, Colorado State University (Ed.), Uranium Mill Tailings Management. Proceedings of a Symposium, November 20,21, 1978 Vol.II, Fort Collins, Colorado 1978, p.69-85
Critical parameters for tailings embankments, by G.B.Baecher, W.A.Marr, J.S.Lin, J.A.Consla. U.S. Bureau of Mines (Ed.), BUMINES-OFR-135-83, 1983
Seismic Hazard Analysis of Title II Reclamation Plans, by D. Bernreuter, E. McDermott, and J. Wagoner; Report prepared by Lawrence Livermore National Laboratory for the U.S. Nuclear Regulatory Commission, UCRL-ID-121733, 1995, 145 p.
Recommendations Regarding Seismic Design Standards for Uranium Mill Tailings Sites in Wyoming, by James C. Case, Hazards Report 96-1, Wyoming State Geological Survey , Laramie, Wyoming, February 28, 1996, 9p., HTML text (32k - WMA)
Mine and Industrial Tailings Dams and Dumps - Bibliography, Bulletin 44a, International Commission on Large Dams, 1982- 1989; 290 pages.
Tailings Dams Safety - Guidelines, Bulletin 74, International Commission on Large Dams, 1989; 108 pages bilingual (French/English).
[The Bulletin examines the safety aspects relating specifically to tailings dams in terms of design, construction, operation and rehabilitation, which are different and usually more complex problems than those encountered in connection with more conventional dams. The 2 appendices deal with environmental safety and recommended legal requirements applicable to this type of structure]
Tailings Dams - Design of drainage, Bulletin 97, International Commission on Large Dams, 1994; 120 pages bilingual (French/English).
Tailings Dams and Seismicity: Review and Recommendations, Bulletin 98, International Commission on Large Dams, 1995; 60 pages bilingual (French/English).
[By ICOLD's account, almost two hundred tailings dams "have failed during earthquakes, releasing liquefied lagoons of tailings that have caused serious damage and loss of life... Tailings dams are very susceptible to earthquake damage."
This brochure, in French and English, explores the reasons for these failures and puts forth solutions for strengthening current dams and building more stable dams. The main aspects covered in the bulletin are: "Seismic performance of tailings dams; seismicity assessment; geotechnical evaluation; design and construction of tailings dam; seismic stability analysis; and remedial measures to improve the safety of existing tailings dams."]
Tailings Dams. Transport, Placement, Decantation - Review and Recommendations, Bulletin 101, International Commission on Large Dams, 1995, 97 pages
Tailings Dams and Environment: Review and Recommendations, Bulletin 103, International Commission on Large Dams, Paris 1996, 103 pages
A guide to tailings dams and impoundments: design, construction, use and rehabilitation, Bulletin 106, International Commission on Large Dams, Paris, 1996, 239 p.
> Download full report (PDF)
Design, Construction, and Inspection of Embankment Retention Systems for Uranium Mills, Regulatory Guide 3.11, U.S. NRC, Dec. 1977, 10 p.
Full text available through ADAMS , Accession No. ML003740223 (1M TIFF)
Operational Inspection and Surveillance of Embankment Retention Systems for Uranium Mill Tailings, Regulatory Guide 3.11.1, U.S. NRC, Oct. 1980, 8 p.
Full text available through ADAMS , Accession No. ML003740229 (0.6M TIFF)
UNEP MRF - Mining and Environment - Technical Issues: Tailings
InfoMine TailingsMine

> see also bibliography on Decommissioning & Tailings Management !

RELATED INFORMATION SOURCES

International Commission on Large Dams - ICOLD
Commission Internationale des Grands Barrages
151, boulevard Haussmann
75008 Paris, France
Tel: +33-1-40425438, Fax: +33-1-40426071
United States Society on Dams - USSD
(formerly United States Committee on Large Dams - USCOLD)
- USSD Committee on Tailings Dams
Australian National Committee on Large Dams - ANCOLD
Canadian Dam Association - CDA
Tailings.info
Tailings News Alerts