IRMA Standard for Responsible Mining (Draft 2.0)
Chapter 3.3 Mine Waste Management

This chapter has been flagged. IRMA Steering Committee members are aware of recent and emerging efforts by others to define critical safeguards related to mine waste/tailings management. Such efforts have been initiated in the wake of two recent failures of major tailings dams that led to significant worker and community loss of life and environmental degradation.

This draft of Chapter 3.3 has incorporated some of the findings from a 2015 expert review panel that examined the failure of the Mount Polley tailings storage facility in Canada. IRMA expects to also learn from the recent findings of the Mining Association of Canada’s Tailings Review Taskforce, as well as the impending findings of the ICMM global tailings management expert review, a United Nations Environment Program review on tailings management, and other investigations and efforts launched in the wake of the 2015 Samarco tailings dam tragedy. IRMA respects the efforts of these expert review panels, and recognizes that the Standard will benefit from the knowledge gained through these important reviews.

N.B. Industry participants in IRMA have not yet provided comments on this revised chapter, but will do so based on the lessons arising from the aforementioned reviews
.

 

Background

Most of the material removed from the ground at a mine will remain on the site as waste.  The waste takes two general forms: waste from processing the ore into a concentrate or final product (tailings, spent heap leach materials, etc.), and waste rock from the mine that is not processed for minerals (called overburden, waste rock, sub-economic ore, etc.).  All of this material can contain sub-economic concentrations of the mined mineral and other minerals including sulfidic minerals. In addition, tailings will contain process chemicals, and in the case of hard rock mining waste rock may contain nitrogen based explosives compounds, both of which may contaminate water resources.

It is through waste characterization and management that the operating company has the most control over both the short- and long-term environmental contamination. Geochemical testing can be utilized to determine whether wastes have the potential to generate acid drainage and/or metals leaching contaminants, but the control and management associated with these waste materials is a major challenge. Water contamination is the most prevalent problem, but air quality/dust can also be an issue.  Impacts can continue over very long timeframes. Similarly, there are legacy problems from old mines that were operated and closed/abandoned under different environmental standards than are applicable today.

Information and concern about contamination problems may not become apparent until a mine has closed, when there is no longer an operator or responsible party in place to address the problems.

Objectives/Intent of this Chapter

To eliminate off-site contamination, minimize short- and long-term risks to communities and the environment, and protect future land uses.

Scope of Application

Chapter Relevance:  This chapter is relevant for all mines applying for IRMA certification.

New vs. Existing Mines:  The requirements in this chapter are applicable to all new mines, new facilities at existing mines, and existing mine facilities where practicable.  However, at existing mines where compliance with the requirements are judged not to be practicable, non-compliance, even though not practicable, may result in the mine being non-certifiable under the IRMA Standard.  Examples on non-certifiable practices are:  Riverine, Lake, and Submarine Mine Waste Disposal (3.3.1.3); and Tailings Dam expansions where it is practicable to meet the requirements of (3.3.4).

Existing mines may qualify for IRMA certification without strict compliance to the following requirements: Liners and Effluent Control Systems (3.3.3); Tailings Dam (3.3.4); Tailings Impoundments (3.3.5); Heap Leach Facilities (3.3.7); Process Water Facilities (3.3.8); Stormwater Facilities (3.3.9); and Underground Mines (3.3.10).

NOTES TO READERS ON MAJOR CHANGES TO THIS CHAPTER:

  • Supplementary text was added, or revisions were made to existing language in the sections on engineering plans, liners, Independent Tailings Review Boards, stormwater facilities, and wildlife monitoring, to add clarity.
  • Removed requirement for reporting toxics following the rules of the USEPA Toxic Release Inventory; companies may now use other approaches.
  • Allowed for alternatives to liners to manage seepage from wastes (see 3.3.3).
  • Non-critical stormwater design requirements are now required to use the 200-year/24-hour storm event, instead of the 100-year/24-hour event.  This is primarily due to the uncertainty associated with climate change (and is being utilized in many new mine proposals).
  • Added a requirement for and Independent Tailings Review Panel (3.3.5.2).
  • Monitoring of surface water seeps from waste rock dumps is now required. (This is simply a presence-absence determination, not a pass-fail determination – i.e. Are there seeps, and if so, are they being monitored?)
  • The means of verification (MOV) have been removed from this version of the draft IRMA Standard. If you would prefer to review and comment on a version of the draft Standard that has the means of verification, you can download a pdf version of the Standard with MOV.
     

Mine Waste Management Requirements

3.3.1.  General Requirements

3.3.1.1.  The operating plan, or its equivalent shall provide a detailed physical description of the mine facility, the geology and hydrology, and other physical elements that could reasonably affect design specifications.

3.3.1.2.  A report disclosing the annual and cumulative mass balance of toxic constituents generated, stored or released from mining and processing operations shall be published at least annually on the mine or company website.

3.3.1.3.  Riverine, Lake, and Submarine Mine Waste Disposal:  At this time, IRMA will only certify operations that utilize land-based mine waste disposal. Rivers, streams, lakes and oceans shall not be used for the disposal of mine waste.

3.3.1.4.  Mine Waste

a. All waste material at a mine facility shall be evaluated for its potential to generate acid generating and/or metals leaching and to release water contaminants at levels in excess of the standards.

b. All mine rock used for construction outside of a waste facility shall be free of acid/metals leaching contaminants, and shall be tested before use as construction material.

c. Testing shall follow the guidelines published in the Global Acid Rock Drainage (GARD) Guide issued by the International Network for Acid Prevention.

3.3.2.  General Engineering Requirements

3.3.2.1.  Engineering plans for critical mine structures, including tailings and water supply dams, and waste rock facilities bear the seal and signature of a qualified licensed professional engineer.

3.3.2.2.  Surveys that require the employment of professional surveyors shall bear the seal and signature of a licensed professional surveyor.

3.3.3.  Liners and Effluent Control Systems

3.3.3.1.  Newly constructed waste rock and tailings disposal facilities shall be lined if:

a. Acid generation/metals leaching/cyanide or other contaminated leachate is predicted; and

b. Contaminants are predicted to leach to the environment off the mine site at levels above the IRMA or other relevant water quality criteria or goals.[1]

3.3.3.2.  Newly constructed liner systems shall:

a. Achieve an equivalent liner fluid-transit time of one year or longer; and

b. Have a drainage collection layer on top of the liner, and/or a leakage collection system under the liner.

3.3.3.3.  A natural in-situ layer, for example clay or bedrock, may be utilized as a liner if it meets the requirements in 3.3.3.2.

3.3.3.4.  A constructed or natural effluent control system to prevent off-site contaminant migration may be substituted for a liner if it can be demonstrated that relevant water quality standards will be met off-site.[2]

3.3.3.5.  Effluent control systems, including source control, covers, underdrains, liners, and slurry cutoff walls shall be employed before a mixing zone is utilized to dilute contaminants.

3.3.4.  Tailings Dams

3.3.4.1.  Tailings dams shall be designed to withstand potentially long-term catastrophic events. Designs shall incorporate the following:

a. Apply the guidelines of the Canadian Dam Association Dam Safety Guidelines (or equivalent) for design;[3]

b. The maximum credible earthquake shall be used for long-term seismic stability design for the tailing embankment; and

c. The probable maximum precipitation event shall be used for the design of operational holding capacity.

3.3.4.2.  An Independent Tailings Review Board (ITRB), composed of at least three independent experts, shall be formed to review all tailings impoundments constructed to retain wet tailings during mine operation in order to provide third-party recommendations on the design, construction, operation and closure of tailings impoundments.[4] The ITRB shall meet at a frequency that it deems necessary to ensure safety, but no less frequently than every five years.

3.3.5.  Tailings Impoundments

3.3.5.1.  The following requirements shall be implemented at new facilities:[5]

a. Tailings impoundment design and operation shall place safety as the primary consideration; and

b. Tailings impoundments designs shall incorporate liners and/or drainage collection underdrains or systems that can be used to dewater impoundment tailings after closure.

3.3.5.2.  Tailings impoundments shall be designed for dry closure. Wet closure of tailings may be considered if it can be demonstrated, through a risk assessment and a failure modes and effects analysis or its equivalent, that wet closure poses less long-term risk to environmental and social considerations than a dry closure.

3.3.6.  Heap Leach Facilities

3.3.6.1. Heap leach facilities shall incorporate the following:[6]

a. Heap leach facilities and associated solution channels within the heap shall have a synthetic liner with a low permeability subgrade of a minimum of 12 inches of soil that has a minimum re-compacted in-place coefficient of permeability of 1x10-6 cm/sec;

b. Heap leach facilities shall be equipped with a leak collection recovery system and/or underdrain system; and

c. Heap leach liner integrity shall not be intentionally breached on closure.

3.3.7.  Waste Rock Facilities

3.3.7.1.  Waste rock facilities shall be designed to minimize seepage of contaminated water to groundwater. 

3.3.7.2.  Waste rock facilities that contain potentially acid generating or metals leaching (PAG/ML) rock shall be designed and constructed to insulate the PAG/ML waste rock from the environment with non-acid-generating waste or a liner before a reclamation soil cover is applied.

3.3.7.3.  Surface seeps from waste rock dumps that exceed IRMA or other relevant surface water quality criteria or goals[7]  shall be monitored at least quarterly during operation, and at least annually during closure, for contaminants and flow, with sufficient data to determine chemical loading.

3.3.8.  Process Water Facilities

3.3.8.1.  New facilities designed to store process waters shall:

a. Be constructed and operated with no planned discharges of contaminated process water to the environment;

b. Be constructed and operated to minimize seepage to groundwater; and

c. For contaminated process water storage facilities, incorporate a seepage collection and/or leak detection systems into the facility design.

3.3.8.2.  Process water holding ponds for new and expanded facilities, and other mine facilities open to precipitation that involve the storage of contaminated water, shall be designed for the 200-year/24-hour maximum precipitation event.

3.3.9.  Stormwater Facilities

3.3.9.1.  New stormwater conveyance and storage facilities shall be designed:[8]

a. For critical facilities the probable maximum precipitation event; and

b. For non-critical facilities at least the 200-year/24-hour maximum precipitation event

3.3.9.2.  New stormwater conveyance and storage facilities built for closure/permanent containment or treatment shall be designed:

a. For critical facilities the probable maximum precipitation event; and

b. For non-critical facilities at least the 200-year/24-hour maximum precipitation event.

3.3.10.  Underground Mines

3.3.10.1.  New and expanded mine workings shall be designed so that there will be no drainage after mine closure, if practicable.

3.3.11.  Monitoring

3.3.11.1.  The operating company shall monitor pit lakes, tailings impoundments, process solution ponds and any other non-enclosed facilities storing potentially toxic wastes for mortalities of migratory birds, threatened species, and local wildlife or livestock species:

a. All mortalities shall be recorded, including location, species,[9]  number, and date of incident.

b. If there is any mortality involving migratory birds or threatened species, and it is followed by two separate incidents within the following one-year period, measures shall be taken to prevent future mortalities,[10]  including water treatment and/or cyanide destruction if required to reduce toxic contaminants.

c. Mortalities of any species shall be calculated on at least a quarterly basis, and the results publicly reported by the company at least annually.

3.3.12.  Climate Change

3.3.12.1.  The design of all mine facilities that store or control the flow of water shall make quantitative estimates of the potential impacts of climate change over the facility design life.

Notes

This chapter was developed with guidance from the best practices for waste management provided in the Global Acid Rock Drainage (GARD) Guide, and regulations from Arizona, Nevada and New Mexico guidance and regulations.  In drafting the proposed standard IRMA did consider the fact that the conditions of the Standard would need to be technically practicable all over the world.  IRMA realizes that in most instances one-size does not fit-all.  However, as much as is possible, IRMA would not only like to standardize the requirements, but also provide a level playing field for all potential mines.

The IRMA guidance document for Chapter 3.3 “Mine Waste Management Additional Background and Guidance” is referred to throughout the Means of Verification as a source of additional information for companies and auditors. The guidance document was developed to conform with recommendations from:

  • The best practices for waste management provided in the Global Acid Rock Drainage (GARD) Guide;
  • Standards derived primarily from Arizona, Nevada and New Mexico guidance and regulations.

Marine and Lake Disposal
IRMA participants have divergent views on the issue of waste disposal into lakes and oceans. Further work is required to determine the specific requirements under which such disposal methods could be considered, and comments are invited on this point.

IRMA recognizes that there are some specific instances where marine or lake disposal of mine waste might be the environmentally preferable method of waste disposal.  Riverine mine waste disposal has never been demonstrated to be environmentally sound. 

There are two fundamental problems with the disposal of mine waste in oceans and lakes that have led IRMA to take its present position. First, the necessary science of the impacts to existing resources is not in place, nor is there any defined program prepared to collect this information.  We just don’t know the nature of the impacts to areas that would be affected by deep sea disposal. Lake disposal has been justified by regulatory bodies as appropriate on the basis that many of these natural water bodies can be restored to some or all of their former function after the cessation of mining.  This presumption has not been confirmed by appropriate research. Second, the economic advantage of utilizing a natural body of water for waste disposal, over construction of an engineered impoundment for this waste, is so large that it presently distorts the evaluation of the social and environmental factors involved in a waste disposal location decision. 

Until appropriate regulatory guidelines and proper technical analysis are developed/employed for making decisions about the use of a natural water body can be demonstrated, IRMA will only certify land-based tailings disposal.

Cross Reference to Other Chapters

 Chapter

 Issues

1.1—Legal Compliance As per Chapter 1.1, if there are host country laws governing waste management at mine sites, the company is required to abide by those laws. If IRMA requirements are more stringent than host country law, the company is required to also meet the IRMA requirements, as long as complying with them would not require the operating company to break the host country law.
3.1—Water Quality IRMA water quality criteria, which are mentioned in 3.3.3.1, 3.3.3.4 and 3.3.7.3 can be found in Chapter 3.1., Tables 3.1.a, 3.1.b and 3.1c. If Approaches A and C are taken to protect water quality as per Chapter 3.1, the numerical water quality limits may differ from IRMA water quality criteria.
Chapter 3.1 contains monitoring requirements in 3.1.3. Post-closure Monitoring, and 3.1.5. Mixing Zones that are relevant to waste management facilities.
3.2—Water Quantity Chapter 3.2 contains monitoring requirements in 3.2.8 that are relevant to waste management facilities.
4.2—Reclamation and Closure See this chapter for discussions of financial sureties, long-term/perpetual water treatment, and monitoring of waste facilities and groundwater.

 

Endnotes

1. IRMA criteria are found in Chapter 3.1, Tables 3.1a, 3.1b and 3.1c. If Approaches A or C are taken to protect water quality as per Chapter 3.1, then the numerical water quality criteria may differ from IRMA water quality criteria.

2. Ibid.

3. Canadian Dam Association. Dam Safety Guidelines. 2007. See also, Application of Dam Safety Guidelines to Mining Dams. 2014. Both publications are available at: www.imis100ca1.ca/cda/Main/Publications/Dam_Safety/CDA/Publications_Pages/Dam_Safety.aspx?hkey=52124537-9256-4c4b-93b2-bd971ed7f425  

4. This applies to new and existing tailings impoundments, and to all tailings dams 25 meters or greater in height. The World Bank and other lenders groups require the formation of a similar “independent panel of experts” to review the investigation, design, construction and filling of new large dams, and includes reviews for high hazard cases involving significant and complex remedial work on existing dams. (World Bank.Operational Manual. OP 4.37)

5. These requirements were added as a result of the Mt. Polley Expert Review Panel findings. (Source: Independent Expert Engineering Investigation and Review Panel. January 30, 2015. Report on Mount Polley Tailings Storage Facility Breach. Province of British Columbia).  

6. 3.3.6.1.a and b apply to newly constructed heap leach facilities.

7. IRMA criteria are found in Chapter 3.1, Tables 3.1a, 3.1b and 3.1c. If Approaches A or C are taken to protect water quality as per Chapter 3.1, then the numerical water quality criteria may differ from IRMA water quality criteria.

8. Critical facilities include dam spillways, stream channels re-established on closed tailings facilities, tailings and waste rock diversion structures, etc.

9.  E.g. migratory or non-migratory birds, threatened species, local wildlife, cattle, pigs, etc.

10. Separate mortality incidents means that the incidents resulting in mortalities were separated in time (there may be one or more deaths per “incident”).

 

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