RSF Disclosure

Firestone Diamonds

Liqhobong Mining Development Company

Tailings Facility Disclosure (Principle 15)

Country:                                             Lesotho

Mine:                                                   Liqhobong Mining Development Company

GISTM classification:                        High

Status:                                                Operational

Deposition method:                          Spigotting

Raising method:                                Waste Rock section (Bottom-up Construction) and

Coarse Tailings section (End tipping Construction)

Current height:                                 168 m

Planned max height:                         2606 masl

 

 

  1. Description of Facility
  • Liqhobong Diamond Mine is in the southern region of the Butha-Buthe district, Lesotho’s northern-most district. The mine is located approximately 116 km west, northwest of Maseru and 87 km south, southwest of Bethlehem in South Africa. The mine’s coordinates are approximately 28°59’10” S, and 28°37’03” E.
  • The mine’s elevation varies significantly from one part of the mine to another due to the steep topography on which it is built. This range is between approximately 2 450 mamsl and 2 720 mamsl, with upstream watersheds varying between 2 762 mamsl and over 3 100 mamsl.
  • Residue Storage Facility 3 (RSF3) is a valley-fill Kimberlite tailings residue storage facility as shown in Figure 1. RSF3 is the only active residue storage facility on the mine. RSF 3 consists of fine tailings deposited behind an impoundment embankment constructed with waste rock and coarse tailings. Slurry is pumped to the fines basin and deposited through multiple open-end delivery stations.
  • Within the fine’s basin, the coarser fraction of the slurry settles closest to the point of deposition. The finer fraction migrates to the pond area where settling takes place before the water is decanted through a floating barge to be returned to the processing plant.
  • The diamond recovery process relies on X-ray sorting, and no chemicals are added to the process to assist with extraction. The tailings product is therefore a mixture of water and fine host rock particles.

 

Figure 1 Mine Layout 

     

    1. Consequence Classification

    The GISTM consequence classification is “HIGH”. The categories are listed in Table 1.

    Table 1 GISTM Consequence Classification

    Category Classification
    Potential population at risk High
    Potential loss of life High
    Environment High
    Health, Social and Cultural High
    Infrastructure and Economics Significant
    Overall Classification High

     

    1. Risk Assessment Summary (MC)

    3.1. Risk management consists of selecting and implementing those risk reduction measures, which are cost effective i.e., the expected reduction in system risk outweighs the implementation “cost” of the risk reduction measures.

     

    3.2. Risk management must incorporate a continuous improvement principle i.e., by periodically monitoring system conditions and performance, updating the risk assessment as new information is obtained, and identifying, evaluating, and implementing additional risk reduction measures, when required.

    Constant surveillance is conducted to ensure that RSF3 is operated and managed at a controlled level of risk.

    3.3. Risks associated with RSF3 are evaluated through the lifecycle of the facility and include risks associated with the design, construction, operation, and closure of the facility.

    3.4. The material unwanted event is the failure of downstream impoundment embankment of the facility. The current controls implemented to mitigate this risk are:

    3.4.1. Adoption of the company tailings management policy which commits LMDC to the implementation of the GISTM principles.

    3.4.2. Implementation of a company tailings management procedure.

    3.4.3. Appointment of individuals responsible for the roles of Accountable Executive, Independent Review Board, Responsible Tailings Facility Engineer and Engineer of Record.

    3.4.4. Periodical external reviews of operational and engineering systems.

    3.4.5. Use of construction methods as approved by the Engineer of Record.

    3.4.6. Monitoring of facility parameters through a hierarchical inspection process. The results from these inspections are evaluated against trigger action points for parameters such as free board, beach lengths, wall heights, piezometer levels, drain flows etc; and

    3.4.7. Development of emergency response plans informed by the dam break analysis.

     

    1. Impact Assessment

    4.1. LMDC contracted iLanda Water Services CC to conduct a failure analysis on RSF3. The analysis did not only focus on determining the area of inundation but identified sensitive receptors and calculated the hazard to these receptors as well as determining the GISTM hazard classification. The impacted area was evaluated from a safety and environmental impact, health, social and cultural impact, infrastructure and economics. The GISTM consequence classification is HIGH as reflected in Table 1.

    4.2. LMDC implemented its human rights policy which is aligned to the United Nation’s Guiding Principles. This policy provides guiding actions to prevent infringements of human rights. LMDC further conducted a Human Rights Due Diligence Assessment (HRDDA) in line with requirement 1.1 of the GISTM. The scope of the assessment was limited to tailings management and not all mining activities. The methods adopted are contained in the ICMM Human Rights Due Diligence Guidance and the United Nations Guiding Principles on Business and Human Rights as the GISTM which dictate amongst other community consultations and engagements. The assessment involved review and analysis of LMDC policies and benchmarking against international standards, site inspections and community visits and assessment on the rights of surrounding communities. The identified human rights risks (actual and potential) were further mapped in order to assess the level of impact as well as the likelihood of such occurring.

    4.3.  The Safety, Health and Environmental and Corporate Social Responsibility Policies guides actions towards environmental impact assessment of the inundation area e.g. water quality assessments.

    4.4. The potential impacted area forms the basis of identifying potential stakeholders that will be represented in the local disaster forums and communication forums towards the community. LMDC is a member of the Butha Buthe District Disaster Management Committee  which meets every month to discuss all the potential and actual district disaster risks.

     

     

     

     

    1. Description of the Design over the Lifecycle of RSF3

    5.1. The facility was constructed to contain coarse and fine tailings generated during processing of kimberlite ore. The coarse tailings and waste rock form a downstream containment embankment. The fine tailings from the processing plant are contained behind this containment embankment. The fine tailings are deposited through spigot pipes located on the perimeter of the facility.

    5.2. Supernatant water and stormwater are decanted off the facility through a floating barge, which pumps to a return water dam (RWD1). Recently, the barge decant has been directed to the plant thickener header box.

     

    1. Summary of Findings and Mitigations from Annual Performance Review

    The following conclusions and recommendations were recorded in the latest

    annual report from the Engineer of Record

    • Freeboard: The existing beach freeboard in the basin is sufficient to accommodate a 1 in 10 000-yr, 24-h storm event. There is adequate beach and total freeboard to ensure legal compliance.
    • Slurry Densities: during the year the slurry relative densities ranged between 1.35 and 1.42.
    • RSF3 has a large external catchment area. Should the storm water trenches fail at the start of the probable maximum precipitation (PMP) event, the potential storm water volume that would accumulate in the RSF3 basin is approximately 1.25 million m3. This volume exceeds the basin capacity and water will pond against the impoundment embankment (constructed from waste rock or tailings). Overtopping of the impoundment embankment is not considered a credible failure mode, due to the high vertical freeboard, but the impoundment embankment is not designed as a water retaining structure. Excessive seepage through the embankment can therefore result in piping failures.
    • The GISTM overall consequence classification is High. The GISTM flood and seismic criteria (annual exceedance probability) is 1:2 475 and 1:10 000 for active care and passive care respectively.
    • The remaining airspace to final height (excluding freeboard) is 11.0 million m3, or 13.2 million tonnes (assuming an average dry density of 1.2 t.m3). The remaining design life for RSF3 is approximately 12.2 years @ 30% slimes and 10.5 years @ 35% slimes.
    • The side slope stability analysis results indicate that the factors of safety are 1.67 (excl. seismic loading) and 1.43 (incl. seismic loading). These exceed target factors of safety of 1.5 (excl. seismic loading) and 1.1 (incl. seismic loading).
    • The risk management system ranks the following items against a colour-coded system: Green – negligible risk, Blue – low risk, Yellow – medium risk, Orange – recognizes/acknowledges that the integrity of the RSF is at risk, posing a threat to parties beyond the boundary, triggering the stand-by mode of the emergency preparedness and response plan (EPRP), Red – recognizes/acknowledges that the failure of RSF3 is imminent and un-avoidable, triggering full evacuation.
      • Side Slope Instability – Yellow
      • Overtopping – Blue
      • Foundation Instability – Blue
      • External Erosion – Green
      • Internal Erosion – Green
      • Environmental (non-compliance) – Blue
      • Overall – Yellow

     

    1. Summary of Findings and Mitigations from Environmental and Social Monitoring

     

    7.1. Environmental and social monitoring is conducted through the Safety, Health, Environmental and Community (SHEC) Management system and Environmental and Social Management system, which is governed and guided by the NOSA SHE management standard , and Equator Principles.

    7.2. Monitoring activities conducted include monitoring of:

    7.2.1. The surface water quality.

    7.2.2. Chemistry of both downstream and upstream of the mine as well as all the water storage facilities.

    7.2.3. Biomonitoring of downstream rivers.

    7.2.4. Online live weather station to monitor all weather parameters applicable to our operations.

    7.2.5. Air quality.

    7.3. LMDC has a Stakeholder Engagement Plan and Grievance Management Procedure in place governed by the CSR Policy.

     

     

    1. Emergency Preparedness and Response Plan

    8.1. A site-specific Emergency Preparedness and Response Plan is in place for the

    Facility (the Plan).

    8.2. The Plan includes:

    8.2.1. Ranking of potential emergency situations and actions to address

    foreseen situations.

    8.2.2. A list of stakeholders involved to assist with immediate response.

    8.2.3. Individual responsibility matrix.

    8.2.4. Establishment of an emergency control centre and associated procedures; and

    8.2.5. An emergency alarm (warning system) procured specifically for RSF3 emergencies.

    8.3. In case of an emergency, down-stream residents within the zone of influence will be informed if evacuation is required through various public forum (including e.g. public gatherings).

    8.4. Awareness of the site specific emergency preparedness and response plan is provided to the neighbouring community.

    8.5. Installation of emergency assembly points in the neighbouring community.

    8.6. Presentation of the site specific emergency preparedness to the District Disaster Management Committee and ensure that they are aware of the potential disaster risks in their district.

     

    1. Independent Review Plan

    9.1. An annual review of the RSF3 is conducted by the Engineer of Record which includes a review of progress of previous actions and a record of new conclusions and recommendations.

    9.2. The Senior Independent Tailings Reviewer does a further annual review and prepares a report for the accountable executive. The review covers compliance to GISTM and identifies areas of improvement.

    9.3. In addition to the above, status updates on the facility are presented at quarterly inspection and status monitoring meetings.

     

    1. Financial Capacity

    10.1. LMDC recently appointed Digby Wells Environmental to update the Life of Mine Rehabilitation and Closure Plan.

    10.2. The details of the financial provision cover the estimated costs of planned closure, early closure, reclamation and post-closure monitoring and maintenance of the facility.