by: Dr. A. Robertson and S. Shaw
Technical Audits and Reviews are completed in order to review the safety, stability and environmental liability of mine facilities such as tailings systems, sediment dams and waste dumps; to identify the safety, stability and environmental liability risks of each structure; and, to provide recommendations for the improvement of safety measures and procedures to enable appropriate international standards to be achieved.
These Audits and Reviews are typically completed by professional specialists and consist of:
- Information collection, review and analysis of all site investigation (geotechnical, hydrology, hydrogeology, geochemistry, environmental and socio-economic), design and 'as-built' plans and reports;
- Field inspection of the sites and structures;
- Review of the operating history and compliance of the structure/facility, operating plans, management systems, emergency response plans and closure plans;
- Identification of the relevant risks for each of the structures;
- Development of recommendations to mitigate the risks and address issues identified; and
- Preparation of a report summarizing the work.
There are various levels at which an Audit and Review can be completed. At a minimum, a level sufficient to determine the current status of safety, stability and environmental liability of the subject structures is completed. Also included in the Audit and Review is a definition of a path forward for the implementation of measures that would ensure achievement of international standards of good practice and to prioritize the items of an action plan. Recommendations for remediation or improvements are typically provided, in which the levels of concern or risk that are associated with deficient items are indicated. For this purpose review ratings that describe the assessment of where current structures or operational procedures meet appropriate standards, or should be improved, are provided.
The sections below provide more detailed descriptions of the key concepts, i.e.:
The description which follows provides an outline of the practice of audit and review as implemented by the authors. This practice is continually changing in response to increased requirements for assessment of additional environmental and social impact and liability concerns. The following links are to materials that provide some indication of the direction of changes being motivated.
Definitions for Audit and Review Levels and Terminology
Audit level: At this level the auditor performs sufficient investigation, documentation and analysis review to develop an independent opinion on both the general principles of designs, construction and operations and on the validity of the key elements of the design analyses, construction control and operating methods. For dams and critical mining structures, Audits are typically conducted at fairly widely spaced intervals of about 5 years. More frequent Audits may be appropriate if the structure and designs are undergoing rapid and substantial change. Generally an audit level review is required on initiation of the review process for any major structure. An Audit Report is produced which documents, generally against a check list, the reviewer's observations as to adequacy of the designs, construction and operations and indicates any recommendations that flow from these. The adequacy of the design is based on its achievement of a set of standards as defined below.
Review level: At this level the reviewer generally reviews all key documents and does at least 'reasonableness of results' checks on key analyses, design values, and conclusions. Design, construction and operational procedures are reviewed at a level sufficient to develop an independent opinion of the adequacy and efficiency of the designs, construction and operations. The reviewer generally relies on the representations made to the reviewer by key project personnel, provided the results and representations appear reasonable and consistent with what the reviewer would expect. A review report is produced which documents the reviewer's observations as to adequacy of the designs, construction and operations and indicates any recommendations that flow from these.
Review at Discussion level: At the discussion level the reviewer is not provided with all the relevant data required to perform an independent assessment or develop an independent opinion. Generally, only selective information is presented, often in meeting presentation form, and there is insufficient time to absorb and digest all the pertinent information and develop a through understanding of all pertinent aspects relating to the design, construction and operation. The reviewer relies on information selected by the presenter and substantially on the observations, interpretation and conclusions of the presenters. While discussion level reviews are valuable in that the reviewer can question results, conclusions and design aspects that raise issues in the mind of the reviewer, and make recommendations when applicable, the reviewer is often unable to develop an in depth understanding of all the issues that may arise or an independent opinion.
Interim Reviews: Interim reviews are conducted between more formal regularly spaced reviews. They are generally conducted during periods when there is rapid change in the designs or construction of major geotechnical structures and may be focused on only those parts of the design or structure which are undergoing change. They form a basis for regular exchange of information between the design/construction/operating personnel and the reviewer and for reviewer comments during the process of design/construction or operation.
The Audit or Review Process
The auditor and/or reviewer generally evaluates each structure and facility of a mine development and makes an assessment of the adequacy of the design, construction, operation and closure provisions for that facility according to some check list. Examples of checklists are available from a number of sources such as the MAC Guide to the Management of Tailings Facilities and the tables shown in Table 1 and Table 2 which are adoptions from a checklist provided in M.B. Szymanski, 1999 (Evaluation of Safety of Tailings Dams, BiTech Publishers Ltd., pp. 100). Additional checklists will be added to this section in due course.
For each structure or facility, the various design, construction, operation and closure elements are reviewed and an assessment made of the adequacy of standards achieved. This results in the assignment of a Review Rating as described below. Many reviews are concluded once the Review Rating is complete. The author recommends that in addition, a risk assessment be completed to enable a program and a prioritization of risk reduction to be implemented. The risk that is associated with any structure or facility that does not achieve appropriate standards is dependent on the likely consequences. The reviewer therefore assigns a Consequence Category in addition to the Review Rating. A definition of Consequence Categories is provided below. Finally, the reviewer considers both the Review Rating and the Consequence Classification and makes a judgement decision of the risk and assigns a Risk Management Rating as defined below. This rating allows the prioritzation of actions required to reduce and manage risk.
The review rating is an assessment of the extent to which the current status of design, construction, operation or closure measures meet typical international standards of good practice and design standards. The review is completed using the following ratings:
- Blank - Undone, or inadequate information for a rational assessment
- NA - Not applicable
- I - Improvement needed to meet current international good practice or standards
- I- - Large and urgent improvement needed to meet required practice or standards
- I+ - While inadequate against international standards, there are mitigating circumstances reducing concerns.
- P - Passes test of adequacy (generally reasonable international standards)
- P- - While passing there are substantial concern issues
- P+ - Passes well to consistent high standards
- O - Has been optimized to beyond standards, to minimize risk
- O- - Optimization is preliminary or not well done
- O+ - Optimization is extensive and risks have been minimized.
Review ratings do not include the assessment of the failure risks associated with the current state.
Consequence Classification Category
Consequence categories consider only the severity of the potential impacts should failure occur. They provide some indication of the importance of applying an appropriate level of design, construction, operation and closure engineering and management to the particular element or system being evaluated. High levels of risk management must be applied to avoid failure where there are severe consequences.
The consequence is similar to the 'hazard ranking' and may include for financial, investor and public relations consequences in addition to human health and safety and environmental impacts.
The scale is a 1 to 5 scale as follows:
- very low impacts: No injuries or identifiable health effects, insignificant property damage or environmental impact
- mitigatable low to moderate impacts: only minor injuries and minor property damage, small temporary environmental impacts
- moderate impacts: injuries anticipated, reversible health and environmental impacts of moderate extent and moderate property damage.
- severe impacts: severe injuries, possibly a fatality, large property damage, substantial but reversible environmental impacts or irreversible but moderate environmental impacts.
- extreme impacts: multiple fatalities, extensive property damage, and extensive environmental impact
There are numerous other hazard and consequence category scales that may be used to obtain a ranking which may then be used assigned a 5 point scale as listed above.
Risk Management Ratings
The risk management ratings provide an assessment of the current and future failure risk that exists for the current state of the element or system. It is the objective of a risk management program to reduce risks to levels consistent with regulatory requirements and corporate objectives.
For the purposes of risk management a Risk Rating is required. In the conducting of Reviews and Audits the authors have found the Concern/Risk Rating provided below to be useful for conveying to the mining company or stakeholders an understanding of the level of risk and concern, and the urgency for risk reduction. Such a risk rating, provided for each major element of the tailings pond, indicates to the operator and stakeholders the reviewers opinion of the degree of concern/risk and provides a priority list and time scale for correction.
The following risk rating is bases on the assumption that risk is proportional to:
- Site specific or inherent risk;
- Application of Internationally accepted criteria, standards, guidelines and methods;
- Demonstrated precedent;
- Capability, ability and commitment of design, construction and operating staff;
- Monitoring for unexpected behaviour;
- Available response time and methods; and
- Operational and risk management
At the most comprehensive level of risk assessment, a conventional risk assessment (considering likelihood of occurrence, consequences and potential mitigation for each identified failure mode, see FMEA) can be performed for elements of the facility to determine site specific or inherent risk. This establishes the appropriate design, construction and operating criteria, standards and methods. In the absence of a formal risk assessment, an experienced practitioner makes a judgment of risk.
Level 1: Low Risk/Concern
- Failure has only very low impacts, or
- Design, construction and operations are to appropriate high standards.
- Only normal care and management are required to maintain low risk.
Failure of the facility will not result in significant injury, loss of life or environmental damage: or risk is low as determined by all of the following evaluation criteria:
- Site specific and inherent risks have been identified and provided for in design, construction and operations.
- Design, materials, construction and operating methods are in accordance with internationally accepted design criteria, standards, guidelines and methods for facilities of this type.
- The facility is designed, constructed and operated by personnel with appropriate experience, training, commitment and authority.
- There is precedent for all facility elements (size, materials, performance levels, etc), construction and operating conditions.
- Facility performance is monitored, and detection of unexpected behavior is expected with a high level of confidence.
- Potential instability or unexpected behavior will develop sufficiently slowly to allow reliable corrective measures to be implemented.
- A reliable, informed management structure and procedures are in place to implement and control all aspects of facility design, construction and operation.
This is the lowest level of risk. Risk management is primarily aimed at maintaining this level while optimizing opportunities for further reduction.
Level 2: Small Risk/Concern
- Failure would result only in mitigatable low to moderate impacts, or
- Design, construction and operation have minor deficiencies that are correctable.
- Some increased risk management is required during period of correction.
Risk reduction to level 1 is desirable and should be implemented as part of the on-going design, construction and operating optimization program for the facility.
Level 3: Medium Risk/Concern
- Failure would result in only moderate impacts, or
- Design, construction and operation have moderate deficiencies that are correctable with directed management
- Committed risk management is required during period of correction.
Continued implementation of design, construction or operation should proceed under a specific risk management plan that ensures risks can be managed to acceptably low levels while corrective measures are implemented. Reduction to Risk Level 1 should be planned for.
Level 4: Substantial Risk/Concern
- Failure could result in severe impacts, or
- Design, construction and operation deficiencies are major but correctable with directed management.
- Comprehensive and committed risk management is required during period of correction. Correction is required urgently but not on a crisis level.
Continued implementation of design, construction or operation should proceed under a specific risk management plan. It may not be feasible to manage risks to acceptably low levels while corrective measures are implemented. Aspects for which acceptably low levels of risk cannot be achieved should be delayed or ceased until corrective measures are implemented. If this is not feasible (due to facility conditions) then specific risk minimization measures must be defined and implemented. Reduction to Risk Level 1 should be planned for.
Level 5: High Risk/Concern
- Failure could result in extreme impacts, or
- Design, construction and operation deficiencies are major and it is uncertain if they are correctable with directed management.
- A high level of focused and committed risk management is required during period of correction.
- Correction is required on a very urgent, possibly crisis level.
Continued implementation of design, construction or operation should proceed under a specific risk management plan. It may not be feasible to manage risks to acceptably low levels while corrective measures are implemented. Aspects for which acceptably low levels of risk cannot be achieved should be delayed or ceased until corrective measures are implemented. If this not feasible (due to facility conditions) then specific risk minimization measures must be defined and implemented. Reduction to Risk Level 1 should be planned for.
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