Geotechnical Risk, Regulation, and Public Policy€¦ · tailings dams is typically more regional than national. The failure rate for tailings dams has generally been proportionately

Geotechnical Risk, Regulation, and Public Policy

N.R. Morgenstern

Abstract. At this time, there is a crisis associated with concern over the safety of tailings dams and lack of trust in their de-sign and performance. This crisis has resulted from recent high-profile failures of dams at locations with strong technicalexperience, conscientious operators, and established regulatory procedures. It is the primary intent of this Lecture to assessthe underlying cause(s) for this crisis, review the response to it by various agencies, and to make recommendations on howto overcome it. The Lecture begins with a review of the evolving safety culture associated with slope stability problems asexemplified by the achievements in Hong Kong. This is particularly relevant here because Victor de Mello was a key con-tributor to the recommendations made in 1976 that initiated the development of the Hong Kong Slope Safety System. TheLecture then addresses the evolution of the safety culture associated with water dams. While there is a long history of con-cern with respect to water dam safety, these concerns were intensified by several catastrophic dam failures that occurred inthe USA in the 1970s. The evolution of regulatory systems from that time is recorded, as is the later trend to adoptrisk-based safety assessment and regulation. However, the process that has emerged has been much affected by theOroville Dam Spillway incident, and dam safety practice is being re-assessed by many. This Lecture summarizes some ofthe major findings arising from the analysis of this incident and makes recommendations to move to more performance-based risk-informed design and safety reviews that are constrained by reliable evidence to a greater degree than is currentlythe case. Turning to the evolving safety culture for tailings dams, this emerged with rational dam design procedures in the1970s, more or less as an appendage to water dam design. The growth of environmental legislation related to surface waterquality had a considerable impact as well. Hence, a twin regulatory regime emerged in the 1970s. The regulatory regime fortailings dams is typically more regional than national. The failure rate for tailings dams has generally been proportionatelyhigher than water dams and thus has received considerable attention in the technical literature, however without measur-able results. The recent failures of major dams in technically advanced regions of the world, operated by mature mining or-ganizations and designed by recognized consulting engineers, has created a crisis in terms of a loss of confidence and trustassociated with the design, construction, operation, and closure of tailings storage facilities. Responses to these failures areanalyzed, and all are found wanting, particularly since the widespread evidence for weak engineering is inadequately rec-ognized. The Lecture proposes a system for Performance-Based Risk-Informed Safe Design, Construction, Operation, andClosure of tailings storage facilities. It further urges the International Council on Mining and Metals (ICMM) to support theproposed system and facilitate its adoption in practice.Keywords: safety culture, slopes, water dams, tailings dams, risk analysis, performance-based design.

In Memoriam

Like my predecessors who have delivered this Lec-ture, I too was much influenced by my relationship withVictor de Mello. Victor was inspiring in his breadth of in-terests, his enthusiasm, and his accomplishments. Readingthe list of his consulting assignments is almost like readingthe history of modern Brazil. This relates not only to hisprowess as a consulting engineer, but also to his dedicationto our profession as both a teacher and a researcher.

Over the years we engaged in numerous discussionson both technical and professional matters. I owe much tohis guidance and support that encouraged me to becomePresident of our International Society (ISSMGE). Whilewe discussed a number of technical challenges over theyears, the one in which we collaborated closely was the as-signment from the Government of Hong Kong to partici-

pate in an Independent Review Panel on Fill Slopes, in1976. The photo below (Fig. 1) shows Victor in characteris-tic field-work mode. As will be discussed subsequently inthis paper, our report had a significant impact on slopesafety in Hong Kong and subsequently on internationalpractice.

Through engineering, Victor devoted his life to thebetterment of the people not only of Brazil, but also theworld at large. The central theme of this Lecture is publicsafety. I like to think that Victor would have approved of it.

1. Safe Slopes

1.1. Hong Kong slope safety management

The history of slope instability in Hong Kong iswell-documented. In the 1970s, during a period of intensiveconstruction, catastrophic landslides occurred in 1972 and

Soils and Rocks, São Paulo, 41(2): 107-129 May-August, 2018. 107

Norbert R. Morgenstern, Distinguished University Professor (Emeritus), University of Alberta, Edmonton, Alberta, Canada. e-mail: [email protected] Lecture, no discussions.DOI: 10.28927/SR.412107

1976. They are portrayed vividly in videos and animationreconstructions online (GEO, 2011). Following the 1976disaster, the Government of Hong Kong appointed an Inde-pendent Review Panel on Fill Slopes to advise on the causeand implications of the Sau Mau Ping failure. In addition toresponding to the technical issues, the Panel also recom-mended “that a central organization be established withinthe Government to provide continuity throughout thewhole process of investigation, design, construction, moni-toring, and maintenance of slopes in Hong Kong” (Knill etal., 1976, republished in 1999). The Government acceptedthis recommendation and established the GeotechnicalControl Office (GCO), which later became the Geotechni-cal Engineering Office (GEO).

The GEO was set up in 1977 to regulate slope engi-neering in Hong Kong. The initial efforts of the GEO werebased on the application of the then current state of practicein slope engineering in order to enhance the safety ofman-made slopes in Hong Kong, at a territory-wide level.Over the ensuing years this involved cataloguing slopesand development of suitable prescriptive design measuresand soil testing procedures, supported by considerablechecking of designs proposed for construction, all of whichcontributed to the evolution of a safety culture of excel-lence. Advances were made in characterizing regional soilsand geology, as well as carrying out slope stabilizationworks that were needed to bring priority slopes up to thenewly declared standards. Within a decade, enormousprogress had been made as reflected in a marked decline inthe annual landslide fatality rate. It was recognized earlythat to reduce risk, a Slope Safety System had to evolve thatnot only set standards for new slopes, but also embracedretrofitting substandard slopes, issued landslide warnings,advanced emergency disaster services, and encourage pub-lic education on slope safety. This has been described in de-tail by Malone (1997).

Although considerable progress in reducing the riskfrom landslides had been made by the mid-1990s, HongKong continued to grow and public expectations of slopesafety increased as the quality of life continued to improve.Unfortunately, several landslides occurred in the early tomid-1990s that generated a strong negative reaction fromthe community and the government administration. I re-turned to Hong Kong at that time to review the investiga-tion into the Kwun Lung Lau landslide and to comment onthe slope safety system as a whole (Morgenstern, 1994).This report resulted in a number of changes to GEO’s prac-tice, leading to more outward-looking perspectives in eval-uating slope stability assessments. Of far-reaching implica-tions, it also supported the adoption in Hong Kong of thedevelopment and application of Quantitative Risk Assess-ment (QRA) as a tool for landslide risk quantification, eval-uation, and mitigation. This was particularly timely as theGEO was beginning to address landslide hazards from nat-ural slopes where traditional approaches based on pre-scribed Factors of Safety are of limited value. Malone(2005) recounts the circumstances that preceded this im-portant step and the challenges associated with gaining ac-ceptance for it within public policy. The outcome for theGEO and Hong Kong has been entirely positive.

Figure 2 plots the history of landslide fatalities inHong Kong from 1948 to 2016. This history embraces a pe-riod of population rise, from about 2,000,000 to over7,000,000 today. The threat of extreme storms and cyclonesis ever present. Yet the impact of the GEO and its efforts onthe key fatality metric is clear. This remarkable achieve-ment is highlighted by the plot of the 15-year rolling aver-age annual fatality rate, recently updated by Wong (2017),that emphasizes the near elimination of fatalities due tolandslides in Hong Kong.

1.2. Learning from Hong Kong

The Hong Kong Slope Safety System increased its ef-fectiveness as it progressed through traditional geotechni-cal considerations to risk-based decision-making, togetherwith a parallel commitment to risk communication and en-hancing public awareness. Are there lessons to be learntfrom this experience that can be applied to enhancing safetyof water and tailings dams?

Hong Kong was the first jurisdiction that put into reg-ulation quantified tolerable risk criteria embracing geo-technical hazards associated with slope stability. While themethodology for QRA was well-established, and in someinstances was a recommended practice, making it a re-quired evaluation process in the law is much more complexthan adopting it to aid decision-making in the private sec-tor. Figure 3 presents the risk tolerance criteria adopted af-ter considerable evaluation, and many examples exist in theliterature to illustrate the calculations for risk associatedwith various scenarios.

108 Soils and Rocks, São Paulo, 41(2): 107-129, May-August, 2018.

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Figure 1 - Victor de Mello, 1976.

Hungr et al. (2016) undertook a review of currentpractice in various parts of the world related to landsliderisk management and found wide differences between thecurrent scientific understanding of risk acceptance and ac-

tual applications in practical circumstances. This is particu-larly marked by the absence of public jurisdictions to fol-low Hong Kong’s lead. Examples of legally bindingregulation in public policy were found only in Canada.

Soils and Rocks, São Paulo, 41(2): 107-129, May-August, 2018. 109


Figure 2 - History of landslide fatalities in Hong Kong from 1948 to 2016 (Wong, 2017).

Figure 3 - Societal risk tolerance criteria for landslides in Hong Kong (GEO, 1998).

Two cases in Canada involving QRA are summarizedin Morgenstern (2017). Both adopt the Hong Kong risktolerability criteria (Fig. 3) and both relate to debris flows.In order to calculate risk in terms of “Potential Loss of Life”(PLL) in both cases, it was necessary to develop the hazardmagnitude/frequency relationship based on complex geo-logical and geomorphological studies; conduct debris flowrunout analyses using advanced computational models; de-termine the spatial vulnerability reflecting both spatial andtemporal probabilities; and convert the outcome into PLLmetrics. QRA calculations are challenging undertakingsbut carry considerable weight if conducted carefully. Whilewe found in both cases that the utilization of the Hong Kongcriteria made sense, ultimately the stakeholders, jurisdic-tions and decision-makers have to select, ideally by meansof a suitable public process, the appropriate risk evaluationparameters for a particular situation or jurisdiction. This se-lection of risk tolerance has to balance the risks from land-slides with other societal values. Societal values includesuch things as public safety, affordable residential land, andreturn on investment. The geotechnical risk assessment canonly inform this process.

While quantifying risk is challenging, communicat-ing risk to inform public policy is equally challenging. Inthe case of the debris flow in North Vancouver, Canada,which was the first jurisdiction outside of Hong Kong toformally adopt the Hong Kong QRA criteria, extensivepublic involvement was a part of the process which ulti-mately resulted in legislation that places restrictions on in-creases of habitable area, rezoning, or redevelopmentwhere tolerable risk criteria are violated. Tappenden (2014)has summarized these processes that successfully utilized acommunity task force approach. The District of North Van-couver received international recognition for its innovationand community engagement.

Similar circumstances were encountered in Canmore,Canada, the second jurisdiction in Canada to formallyadopt QRA in legislation. This followed a catastrophic de-bris flow that created considerable damage, although, fortu-nately, no loss of life. Future risk mitigation was based onQRA. Risk communication had to be directed not only tothe population affected, but also to three levels of govern-ment who would fund risk mitigation measures. The deci-sions affecting public policy required consideration of“feasibility, fairness, and affordability.”

The limited adoption of QRA in public policy relatedto managing landslide risk is better understood by referenceto a Maturity Matrix for Assessing Community Engage-ment. This was published in studies undertaken to fostercommunity resilience after the Katrina disaster in New Or-leans (National Research Council, 2012). The matrix is pre-sented in Fig. 4. As indicated by the Table, adoption ofQRA into public policy requires a high level of Maturity(IV-V). Most jurisdictions worldwide operate in the rangeof I-III. Even with high levels of Maturity, the penetration

of QRA related to slope stability and related land manage-ment is slow.

In recognition of the fact that by far the greatest im-pact of landslide hazards occurs in the developing world,Hungr et al. (2016) were prompted to reflect that our ap-proach towards landslide hazard and risk control should bemade simpler and more transparent, so that it can be moreeasily exported to help people who most need it.

2. Safe Water Dams

2.1. History

A history of dams in society and their implications forpublic safety has been presented by Jansen (1980). Jansenobserves that about 200 notable reservoir failures occurredin the world in the 20th century to the date of publication,with more than 8,000 fatalities. Catastrophic loss of life isalways of great public concern, and, albeit in a reactivemanner, this has resulted in a wide recognition of the needfor governmental involvement in the supervision of damsand reservoirs.

Jansen (op. cit.) records how, in 1929, following thefailure of the St. Francis Dam, California placed dams un-der an effective system of governmental supervision withjurisdiction over all dams, except those owned by thefederal government.

In the United Kingdom, reservoir safety legislationcame into effect in 1930 (The Reservoirs (Safety Provi-sions) Act, 1930) following two major dam failures in 1925which led to the deaths of 21 people. This was subsequentlyupdated with the Reservoirs Act of 1975. The Malpasset(1959) and the Vajont (1963) disasters also contributed tothe trend in a number of countries to enact new or revisedlaws for the supervision of dams and reservoirs. However,it was the failure in the United States (US) of the BuffaloCreek Dam, in West Virginia, with 125 deaths and the fail-ure of the Teton Dam in 1976, with 11 deaths and $1 Billionin losses, which accelerated this process, not only in the US,but also elsewhere.

The Buffalo Creek Dam which failed in 1972, was ac-tually a coal slurry impoundment that burst four days afterhaving been declared “satisfactory” by a federal mine in-spector. The effects were catastrophic for the local commu-nity, not only due to fatalities and injuries, but also due todevastating property damage. One of the results of thisevent, together with the near failure of the Van NormanDam due to the San Fernando Earthquake and the failure ofthe Canyon Lake Dam, South Dakota, was the passage ofthe National Dam Inspection Act in 1972 which wouldhave authorized the US Army Corps of Engineers(USACE) to compile an inventory of all dams in the US andinspect them. For both financial reasons and other, this wasnever completed.

The Teton Dam, Idaho, designed and constructed bythe Bureau of Reclamation, failed during first filling. Fail-


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ure was rapid. Fortunately, it occurred during the day. Thepopulation affected by the flood was estimated to be around10,000, and, had the failure occurred at night, it is believedthat the majority of those people would have been killed.This failure, the responsibility of one of the premier damdesign, construction, and operation organizations in theworld, sent shockwaves through the dam engineering com-munity.

One positive outcome from the failure was the cre-ation by the Bureau of Reclamation of one of the most rig-orous and comprehensive dam safety programs in the US.

2.2. Evolution of regulatory systems

Public policy related to dam safety is established byregulations. It is of interest to observe the contrastingframeworks that have evolved. Some of the variations arisefrom differences in the legal structures in various countries,i.e., the common law system vs. the Napoleonic legal sys-tem. Scaletta et al. (2012) provide some concise summa-ries.

In the US there are both federal and state dam safetyregulations. Federal guidelines for privately ownedhydropower dams are summarized in the EngineeringGuidelines for Hydropower Projects (FERC, 2010). Theguidelines were developed in conjunction with the Federal

Power Act. Dams that are owned and operated by the fed-eral government through the USACE and the Bureau ofReclamation are regulated by their respective organiza-tions. State or privately owned dams that do not supporthydropower production, including tailings dams, are the ju-risdiction of the individual state where the dam is located.All states in the US, with the exception of Alabama, havedam safety regulations.

US regulations typically have a hazard classificationbased on the consequences of failure. This classificationcommonly relates the loading conditions and the requiredFactors of Safety for design as well as requirements formonitoring and inspection. For high-hazard, FERC-regu-lated dams, the engineering guidelines also require the fol-lowing:i. Supporting Technical Information Documentii. Emergency Action Planiii. Probable Failure Mode Analysisiv. Dam Safety and Surveillance Monitoring Planv. Dam Safety and Surveillance Reportvi. Dam Safety Inspection Reports.

Similar requirements are required for high hazarddams from other federal and state agencies. The tenor ofthis phase of regulatory development is decidedly prescrip-tive and standards based. In more recent years, risk-infor-



Figure 4 - Maturity Matrix for Assessing Community Engagement (National Research Council, 2012).

med decision making has entered into federal dam safetyevaluation processes, and this will be discussed below.

In Canada, the regulation of dams is on a provin-cial/territorial basis. The federal government has no man-date to regulate in this area. However, national dam safetyguidelines have been published by the Canadian Dam As-sociation (CDA), a professional organization which has noregulatory authority. A province may choose to adopt CDAguidelines which would then make them official standardsin the specific jurisdiction. Matters are made more complexbecause regulations may differ in some provinces betweenwater storage dams and tailings dams. CDA (2012) summa-rizes Canadian dam safety regulations by jurisdiction.Technical Bulletins published by the CDA provide addi-tional detail on suggested methodologies and proceduresfor dam analyses and assessments.

While Brazil contains a large number of dams of con-siderable economic importance in terms of water supply,power generation, and support for industry and mining,prior to 2010 Brazil did not have any laws or regulationsthat addressed dam safety at either the federal or state lev-els. However, guidelines such as CDA and US federalagencies were available as a general reference for damowners and hydropower plant operators. The lack of policywas remedied at the federal level in 2010 by the establish-ment of the National Policy on Safety of Dams and creationof the National System on Safety of Dams in Brazil (Presi-dente da República, 2010). The objectives of this law are toensure compliance with dam safety standards, regulate damsafety requirements during various phases of the dam pro-ject, promote monitoring and oversight, institute public in-volvement, establish technical guidance, and foster damsafety culture and risk management. Comprehensive damsafety plans are required for dams assessed to be in higherrisk categories.

The evolution of the regulatory system in Australia isof special interest. Like Canada, dam safety in Australia iscovered by state legislation, and there is no role for the Aus-tralian federal government. Design methods were tradi-tional until 1994 when the Australian National Committeeon Large Dams (ANCOLD) produced Guidelines on RiskAssessment, followed by revised Guidelines in 2003. TheDams Safety Act was passed in New South Wales (NSW)in 1978, and it established the Dam Safety Committee(DSC) as regulator. By 2002, the DSC had officially de-cided to pursue a risk-based approach to dam safety regula-tion. This was endorsed by the NSW Government in 2006,and in 2010 it was fully implemented by the DSC. It is note-worthy that the DSC appears to have been the first regulatorin the world to successfully incorporate the inclusion ofpublic safety tolerability criteria into regulatory practice(Graham, 2016).

2.3. Evolution of risk-based regulation

The first phase of regulatory control of dam safety re-lied primarily on a prescribed standards approach sup-ported by visual observations of behaviour amplified by in-strumentation. USACE criteria dominated much of thepractice. Spillway capacities were designed to safely passan inflow design flood; Factors of Safety were calculated tomeet required minimum values depending on various rec-ognized loading conditions; and stress in components or thestructure itself were compared with allowable levels and/orultimate strengths. Dam failures were rare, and the method-ology was underpinned by substantial experience. Brinded(2000) has provided an insightful analysis of the frame-work associated with risk-informed decision-making pro-cesses, summarized in Fig. 5. The description of the firstphase of regulatory control fits well with Type A.

As summarized by France & Williams (2017), theevolution of risk analysis has strengthened the dam safetycommunity in many ways by:i. Recognizing in a formal manner the many ways that a

dam can fail and the consequences of the failures;ii. Using risk as a tool for prioritizing risk reduction ac-

tions, particularly for dam portfolio analyses; andiii. Focusing monitoring programs and remediation ef-

forts on the highest risk dams and potential failuremodes.These are all laudable advances, although the means

of achieving them are not without pitfalls.As pointed out by France & Williams (op. cit.), dam

safety risk analysis in the US has its roots in the Bureau ofReclamation’s adoption of failure modes and effects analy-sis (FMEA) in the 1980s, which evolved into PFMA (po-tential failure modes analysis). This transformed the damsafety evaluation process into one of critically assessing theway dams could fail, along with the relative likelihoods ofthe different failure modes and their consequences. Steps inthe process vary from qualitative to semi-quantitative. De-tailed descriptions are found in Hartford & Baecher (2004)and FERC (2017). This methodology is utilized in practiceboth at the design stage and at subsequent performanceevaluation stages. The requirement of FERC to conductPFMAs as part of its mandatory inspection for hydropowerdams within its regulatory jurisdiction has resulted in wide-spread understanding and adoption of the procedures.

PFMA follows thought processes familiar to engi-neers; it can be applied to a variety of consequences (fatali-ties, property damage, environmental, etc.) with ease, and itcan be conducted in a timely and economic manner underthe right circumstances.

In the 1990s the Bureau of Reclamation advancedfrom PFMA to quantitative risk analysis as a key tool indam safety decision making. This aided them in assessingthe urgency of dam safety concerns and, particularly, therelative priority of concerns for different dams. Quantita-tive risk analysis consists of estimating annual probabilities


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of failure, failure consequences such as expected life loss,and annual life loss risks for failure modes of significance.Guidelines were needed to help evaluate the results of theanalyses, typically expressed in terms of tolerable loss oflife. This marks a significant change in metrics that mightbe acceptable internally to a large dam owner, but theyshould require extensive consultation if the criteria are to beadopted by the public at large. As observed by Bowles(2007):

“From the outset it is emphasized that judgementsabout the adequacy of dam safety, which are fundamentallyjudgements about public safety, are intrinsically valuejudgements and not technical matters, although they shouldbe informed by sound technical information.”

The vocabulary of “tolerable loss of life” is provoca-tive and should require stakeholder engagement as well asspecial risk communication efforts before the criteria be-come legal regulations. The appropriate balance between“value judgements” and technical matters also requires re-flection.

While quantitative risk-informed decision making isundoubtedly informative, it involves its own, sometimeslarge, uncertainties. It is also time-consuming and costly.Embracing these uncertainties in a regulatory framework ischallenging. This observation is also a finding arising fromthe previous discussion on the contribution of quantifiedrisk analysis and its application to slope safety.

2.4. Dam safety after the Oroville Dam spillway incident

“Although the practice of dam safety has certainlyimproved since the 1970s, the fact that this incident hap-

pened to the owner of the tallest dam in the United States,under regulation of a federal agency, with repeated evalua-tion by reputable outside consultants, in a state with a lead-ing dam safety regulatory program, is a wake-up call foreveryone involved in dam safety. Challenging current as-sumptions on what constitutes “best practice” in our indus-try is long overdue” (Independent Forensic Team Report,2018).

After the Oroville Dam Spillway incident in February2017, FERC required the California Department of WaterResources (DWR) to engage an Independent ForensicTeam (IFT) to develop findings and opinions on the causesof the incident. Anyone who cares about dam safety and isinterested in the theme of this Lecture owes an enormousdebt of gratitude for the outstanding report that has beenproduced. It is neither practical nor necessary to summarizethe report in any detail before drawing conclusions from it.However, a brief description of the event is necessary be-fore doing so.

The following points are extracted from the summaryof the IFT report of the Incident which led to the mandatoryevacuation of at least 188,000 people on February 13, 2017:i. The inherent vulnerability of the service spillway de-

sign and as-constructed conditions reflect lack of pro-per modification of the design to fit the site conditions.

ii. Almost immediately after construction, the concretechute slab cracked above and along underdrain pipes,and high underdrain flows were observed. The slabcracking and underdrain flows, although originallythought of as unusual, were quickly deemed to be“normal” and as simply requiring on-going repairs.



Figure 5 - Risk decision framework (Brinded, 2000).

iii. The seriousness of the weak as-constructed conditionsand lack of repair durability was not recognized duringnumerous inspections and review processes over thealmost 50-year history of the project.

iv. Over time, a number of factors contributed to progres-sive deterioration (see Report for details).

v. Due to the unrecognized inherent vulnerability of thedesign and as-constructed conditions and the chuteslab deterioration, the spillway chute slab failure, al-though inevitable, was unexpected.

vi. Once the initial section of the chute slab was uplifted,the underlying poor-quality foundation materials weredirectly exposed to high-velocity flows and were qui-ckly eroded.

vii. Although the poor foundation conditions at both spill-ways were well documented in geology reports, thoseconditions were not properly addressed in the originaldesign and construction, and all subsequent reviewsmischaracterized the foundation as good quality rock.As a result, the significant erosion of the service spill-way foundation was also not anticipated.

viii. In limiting service spillway discharge to reduce thelikelihood of powerhouse flooding, the additional damsafety risk associated with use of the emergency spill-way was not appropriately considered. Once the emer-

gency spillway was allowed to overtop, this additionalrisk was soon realized, and the evacuation order be-came a necessary precaution.

Figure 6 presents a picture of the net result of the Inci-dent.

The IFT report makes a number of observations andrecommendations related to the operation of DWR relatedto dam safety evaluation and with respect to the process as awhole. Two are particularly germane to the contents of thisLecture:

i. “Shortcomings of the current PFMA processes indealing with complex systems must be recognized andaddressed. Evolution of ‘best practice’ must continueby supplementing current practice with new ap-proaches, as appropriate.

ii. Compliance with regulatory requirement is not suffi-cient to manage risk and meet dam owners’ legal andethical responsibilities.”

Vick (2017) has made a timely and important contri-bution by emphasizing how “normalization of deviance”(Vaughan, 1996) has been a major contributing factor in anumber of dam failures or near failures. The Oroville Inci-dent is clearly another example to be added to the list.Improvements to dam safety evaluation processes must


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Figure 6 - Oroville Dam Spillway incident (Independent Forensic Team, 2018).

recognize this organizational risk and measures must beimposed to eliminate it.

2.5. Toward safer water dams

In the previous presentation summarizing the evolu-tion in practice of risk-based perspectives for evaluatingdam safety, the common regulatory requirements were de-scribed as standards based, albeit supported by observation.This is not an accurate description of geotechnical practicein design and construction for all but the simplest struc-tures. It is common risk management in geotechnical engi-neering to employ the observational method, whichrequires not only making observations, but also planningfor intervention and mitigation of risk if needed. As dis-cussed in Morgenstern (1995), the observational methodimplies risk analysis, but of a consequential kind. Its appli-cation enhances robustness, adaptability, and the capacityfor intervention which are important considerations to en-hance reliability.

Current practice does require conformance to certainstandards, some prescribed and some recognized empiri-cally as sound practice. As such, the design process basedon the observational method is precautionary and wouldbest be described as a “precautionary risk-informed designprocess.”

The geotechnical aspects of current dam design, atleast for major projects, is rapidly being transformed by ad-vances in instrumentation, real-time monitoring, and inter-pretation of data, all supported by increased capacity, inreal-time, to model and interpret deformation and seepageregimes. As observed by Morgenstern (2017), this will leadto design procedures that overcome some of the conceptuallimitations associated with the Factor of Safety conceptand, by sequential history-matching of performance andimplicit Bayesian updating, will result in a more reliablebasis for projecting future performance. This can be de-scribed as a “performance-based risk-informed design pro-cess.”

Whether precautionary or performance-based, oreven utilizing subjective judgements based on experience,it is essential that the risk assessment process be con-strained by evidence and its evaluation to a higher degreethan is currently the case. Based on the IFT report on theOroville Dam Spillway Incident and experience from fo-rensic investigations into two major tailings dam failures(Mount Polley Internal Panel, 2015; Fundão Tailings DamReview Panel, 2016), the following are recommended:i. Design Basis Memorandum (DBM): The DBM con-

tains the design criteria for all aspects of the facilityand the methods of analysis. It should contain enoughdetail to support a forward projection of all observa-tional performance data once the project is completeand in service. Such an analysis should be undertakento provide a reference basis for in-service expecta-tions.

ii. Construction Record: Experience reveals that whenproblems occur, the record is everything. Constructionrecordings should be expanded to develop a compre-hensive GIS-based retrievable system that willdocument all aspects of construction history chrono-logically, as well as any written or photographic docu-ments associated with the specific components.

iii. Quality Assurance (QA): The role of QA is to docu-ment whether the facility has been constructed as in-tended. This is much more than simply collectingas-built drawings and some corroboration of labora-tory procedures. More extensive reporting is neededtied to the expanded Construction Record.

iv. Deviations: Deviation from the design/specificationsare common. Major deviation may result in a formaldesign change which would be captured in the QA re-port and changes to the DBM. However minor devia-tions may accumulate. To avoid the risks associatedwith normalization of deviation, a Deviation Account-ability Report (DAR) should be implemented to vali-date the acceptance of the deviations.

Implementing the above and carrying the related doc-umentary references and criteria through the future damsafety evaluation process should contribute to improve reli-ability, accountability, and transparency, and therebystrengthen the safety cultures associated with the long-termperformance of water dams.

3. Safe Tailings Dams

3.1. Regulatory framework

The industrial antecedents for the development oftailings dams differ markedly from those for water dams.Water dams, for millennia, created value by facilitatingflood control, enhancing water supply, and subsequentlyexpanding power supply. The disposal of tailings was anecessary evil in the mining industry, to be carried out atminimal cost. This typically meant disposal in streams orother bodies that would minimize accumulation. As pro-duction capacity increased in the mining industry, or aque-ous disposal was not economical, surface stacking evolved.All aspects of tailings disposal added to the cost of produc-tion, and it was natural, at the time, to adopt procedures thatwere as economical as possible. This resulted in the up-stream method of construction which became the standardprocedure for many decades. By the mid-1960s changeswere becoming evident.

The transformation is evident in the paper by Casa-grande & McIver (1971). It provides a clear recognition ofthe differences between tailings and water dams as well asspecial geotechnical risks associated with upstream con-struction. The references reveal considerable related geo-technical studies being undertaken in the years precedingpublication.



Klohn (1972) summarizes the evolution of tailingsdams in British Columbia (BC, Canada), where methods oftailings dam design and construction were coming undercritical review as both government regulatory bodies andthe mining industry became more aware of the need forbetter tailings dams. This culminated in the Government ofBritish Columbia enacting regulations which, historically,were precedent setting in North America. The BC regula-tions appeared in 1971, but were preceded by the Chileandecree in 1970 that banned upstream construction of tail-ings dams (Valenzuela, 2016).

In BC, two separate approvals were necessary: thefirst from the Department of Mines which was specificallyconcerned with the design, construction, and operation oftailings dam; and the second from the Department of Lands,Forests, and Water Resources, Pollution Control Branchwhich was concerned that the effluent escaping from a tail-ings storage pond would not cause pollution. The earlyguidelines related to dam safety were not prescriptive inany way, retaining confidence in the professional commu-nity to meet its obligations. At the time, practice proceduresand other supporting documentation were being publishedto indicate what was considered acceptable practice.

The evolution of tailings dam regulation was muchinfluenced by these two emerging regulatory concerns: i)environmental concern over pollution of water bodies, andii) concern with respect to safety of dams. The history of thedevelopment of the Grizzly Gulch Tailings Dam, in SouthDakota, is an example of the first, while Tar Island Dyke,the first tailings dam in the Alberta oil sands industry, is anexample of the second.

In the US, the enactment of the Federal Water Pollu-tion Control Act Amendment of 1972 brought an end to thestandard practice of merely depositing tailings in the mostconvenient place. This legislation set a deadline of 1977 forcompliance with standards that totally precluded disposalof industrial waste into the waters of the US. TheHomestake Mine, which had at the time been operating forabout 100 years, had been depositing most tailings into lo-cal creeks. To comply with these regulations, the Mine un-dertook the design and construction of an impoundment towater dam standards with an ultimate storage capacity of 50years of gold production. Inflow flood design criteria weredeclared by the Mine Enforcement Safety Administration(MESA), but geotechnical design criteria relied on the ex-perience of the dam design engineers. Site investigationwas performed in the mid-1970s. The design was finalizedin 1975, and the facilities were completed in 1977, withsubsequent raises at later times. Details are provided inCarrigan & Shaddrick (1977). I was involved with this fa-cility at the end of its service life and was pleased to assessthe safe design created at the outset.

A contrasting evolution of tailings dam regulation isprovided by the experience in the Province of Alberta aris-ing from the expansion of dam safety regulation, discussed

in Section 2, above. In 1978, the Government of Alberta en-acted specific dam and canal safety regulation establishingthe first formal dam safety regulatory program in Canada toensure safety of the public and the environment. This fol-lowed from recommendations of a Committee formed bythe then Association of Professional Engineers, Geologistsand Geophysicists of Alberta in 1972, that recommendedthat the Province of Alberta take action in this regard. Theinitial application of this new regulatory program was toTar Island Dyke, the first tailings dam under construction inwhat was a relatively young oil sands industry. This firstcomprehensive safety review conducted by a team of well-known experts in the field expressed concern about move-ments in the foundations of the structure that had beendetected by inclinometers that had been installed, and rec-ommendations were made to restrict rate of construction byobservational means. As noted by McRoberts et al. (2017):“This first review significantly strengthened the ability ofthe geotechnical engineers to insert on the budgetary sup-port for appropriate monitoring with such new-fangled de-vices such as slope inclinometers and pneumaticpiezometers.”

The positive interaction between the new regulatoryprocess and the growing challenges in the oil sands industrycontributed to the evolution of dam safety reviews, nowregularly being undertaken, and the early adoption in the in-dustry of external tailings review boards.

Both the catastrophic failure of the Aberfan CoalWaste Dump in England in the 1960s and the equally cata-strophic failure of the Buffalo Creek Coal Waste Dam inthe US in 1972 resulted in the recognition in the dam designcommunity that tailings dams and related structures re-quired better design to increase their safety. A committee toaddress these issues was formed by the International Com-mission on Large Dams (ICOLD) in 1976 which produceda design manual in 1982 (ICOLD, 1982). This publication(Bulletin No. 40) contained a summary of the status of in-ternational regulations that revealed that only limited prog-ress had been made related to tailings dam safety by thetime of completion of the manual.

ICOLD (1989) issued Bulletin No. 74 in response tothe increasing number of large tailings dams that were be-ing constructed around the world and in recognition of thesevere consequences that would result from failure. TheStava catastrophe that occurred in Italy in 1985 was cited asan example. This publication, in an Appendix on Guide-lines on Tailings Dam Legislation, recognized that whileregulation of water dams had advanced, only a few coun-tries had similar measures for tailings dams and that the ju-risdictional issues for regulation of tailings dams werecomplex. They could vary from national to regional andeven local responsibilities. Recommended guidelines werepublished but, to my knowledge, are not commonly cited.

Failures persisted in the following years and the envi-ronmental impact of tailings dams also attracted the atten-


Morgenstern

tion of the United Nations Environmental Programme(UNEP) who joined forces with ICOLD to support a sub-stantial revision of Bulletin No. 40 in the form ofICOLD/UNEP (1996). Progress was identified in recogniz-ing jurisdictions that had regulations covering tailingsdams, particularly with respect to environmental matters.Regional jurisdictions were the norm in North America andAustralia where strong mining industries existed. However,national regulations also prevailed elsewhere at this time,such as in Chile.

3.2. The emerging crisis

Recorded failures of tailings dams persisted throughthe 1980s and 1990s with even an increase in rate in themid-1990s as reflected in the WISE inventory(www.wise-uranium.org/mdaf.html). This attracted the at-tention of not only geotechnical and mining engineers, butalso other organizations such as the UNEP.

In 1996, I presented an overview of the multiple con-tributions that geotechnical engineering can make to thechallenges of mine waste management (Morgenstern,1996). This presentation emphasized the changes in designand performance requirements that have evolved in recentyears, and it provided examples of complex tailings dambehaviour, both favourable and not, as illustrations of theneed to avoid over-simplification.

Toward the end of the decade, the UNEP combinedresources with the International Council on Metals and theEnvironment (ICME; now the International Council onMining and Metals, ICMM) to convene international meet-ings on managing the risks of tailings disposal. At the meet-ing in 1998, I drew on the previously published assessment,aided by additional experience, to conclude the following(Morgenstern, 1998):i. The standard of care associated with mine waste reten-

tion structure was too low.ii. The standard of care associated with mine waste reten-

tion structures should move towards those of wa-ter-retaining structures.

iii. Establishing the standard of care is the responsibilityof senior mine management who should set design ob-jectives, risk management policy, and the associatedlevels of safety.

iv. Consultants should involve Failure Modes/EffectsAnalysis or equivalent risk analyses at an early state ofproject development.

v. Regulatory Agencies should devote more concern tothe details of corporate policy regarding mine wastemanagement procedure as opposed to being riskdriven.

vi. ICME (now ICMM), as the industrial interface, shouldcontribute to improved risk management by draftingmodel corporate policy codes of practice and modelregulations for consideration by individual corpora-tions and regulatory agencies.

As will be borne out by this Lecture, it is disappoint-ing to reflect that these recommendations are as meaningfulto-day (2018) as they were when presented twenty yearsago (1998).

I re-visited the issue of the safety of mine waste im-poundments in 2010 (Morgenstern, 2010). In the precedingdecade, failures continued to accumulate at approximatelythe same rate as in the recent past although some analysissuggested the possibility of a correlation between the timeof failure with commodity price peaks. The inference im-plied here would be the suggestion that economic prizescreate compromises in the diligent management of tailings.There was no socio-economic pattern among the cases,with regulatory environments ranging from weak to strong.

I was able to draw attention to some positive develop-ments, namely:i. The efforts made by the Mining Association of Can-

ada (MAC) to foster improvements in the safe and en-vironmentally responsible management of Tailingsand mine waste. This culminated in the document“MAC Guide to the Management of Tailings Facil-ities” which provided a framework of managementprinciples, policies and objectives, checklists for im-plementing the framework through the life cycle of atailings facility, and lists of technical considerations.This document was followed by the guide on “De-veloping an Operation, Maintenance, and Surveillan-ce Manual for Tailings and Water Management Facil-ities” and “A Guide to Audit and Assessment ofTailings Facilities Management.” The MAC guide-lines were readily adaptable to non-Canadian jurisdic-tions and site conditions of any kind.

ii. Improvements in regulatory guidance documents hadbeen produced, particularly with respect to the coal in-dustry in the US where serious problems with the in-tegrity of coal waste impoundments had developedearly in the decade. Nevertheless, the limitations of re-lying on regulatory processes alone to ensure damsafety were becoming increasingly clear.At the time, I offered the opinion that in my experi-

ence the dam safety system that had been developed in Al-berta applied to the oil sands industry was the best in theworld. It is worth repeating its components:i. Each owner is cognizant of its responsibilities to pro-

vide a tailings management consistent with the MACguidelines.

ii. Each owner has staff qualified in the management oftailings dams.

iii. Owners retain consulting engineers for design andconstruction supervision who are well-known for theirexpertise in tailings dam design with special referenceto the circumstances associated with the oil sands in-dustry; the designer acts as the Engineer-of-Record atleast for design; senior internal review of design sub-missions is expected.



iv. Designs rely on the detailed application of the obser-vational method for risk management.

v. Designs are reviewed by the Alberta Dam SafetyBranch, the regulator, who have staff well-versed indam design and construction.

vi. An annual report is submitted to the regulator by theowner, supported by the Engineer-of-Record, that thedam is behaving as intended; if not, actions that havebeen or need to be taken are indicated.

vii. In accordance with CDA Guidelines, approximatelyevery five years the owner retains an engineer, otherthan the Engineer-of-Record, to undertake an inde-pendent assessment of dam safety.

viii. Each owner retains an Independent Geotechnical Re-view Board, comprised of senior specialists, to pro-vide on-going third-party review of geotechnical is-sues of significance to the operation. One of the majorresponsibilities of such Boards is to review all aspectsrelated to safety of tailings dams over the life cyclefrom design, construction, operation, and closure.

The success of the dam safety system applied to theAlberta oil sands industry relies on responsibilities sharedby the owner, the Engineer-of-Record, the regulator, andvarious levels of independent review. I am aware that inmany jurisdictions, not all of these components will be ma-ture. Under these circumstances, the remainder of thesafety management team should exercise additional cautionto compensate for regional limitations. As many case histo-ries continue to remind us, a permit to operate is not a guar-antee against failure.

It is of interest to note that this same regulator has nothad the same degree of success with a different set of indus-trial clients, strengthening my view that improving thesafety of mine waste impoundments relies on shared re-sponsibilities and cannot be achieved by regulation alone.

In this same presentation, following my experiencewith the oil sands industry and with water dams, I advo-cated for increased use of Independent Tailings Dam Re-view Boards (ITRB) in the mining industry and providedsome guidance on their operations. It is of interest to notethat McRoberts et al. (op. cit.) confirm the value of ITRBsin their experience in the oil sands industry.

Following on from 2010, tailings impoundment fail-ures continued to recur at approximately a constant rate, asreflected by the WISE catalogue, which is recognized to beincomplete. For example, Li et al. (2016) report four majorfailures of upstream dams in China over the period 1962-2010 that involved 249 fatalities and are not included in theWISE catalogue. Moreover, Li et al. (2017) reveal that fol-lowing a period of eliminating particularly hazardous facil-ities, at the end of 2015, 8,869 tailings facilities existed inChina. Most are upstream constructions with design Fac-tors of Safety less than commonly used elsewhere. Detailsare not readily available.

However, outside of China, the record for 2010 to2018 was not “business as usual.” In 2014, the MountPolley Mine tailings dam in British Columbia failed, fortu-nately with no loss of life, but with substantial outflow ofboth water and tailings. This was followed by the failure ofSamarco’s Fundão tailings dam in 2015, with multiple fa-talities and huge environmental and social consequences. Itis located in Minas Gerais, Brazil. These two events at-tracted special attention not only because of their scale ofconsequences, but perhaps more so, because of their prove-nance. Both were operated by responsible mining compa-nies, retaining experienced consulting engineers, and bothwere located in regions with mature mining experience andadvanced regulatory regimes. The conjunction of the twoevents, building on a long history of inadequate perfor-mance has created to-day’s crisis. There is a loss of confi-dence and a loss in trust in the safety of tailings dams.Moreover, there is a lack of transparency in the way thatsafety-related issues are communicated to stakeholders.

In its commentary on risk reduction in the MountPolley Report (Independent Expert Panel, 2015), the Panelexpressed the following:

“In risk-based dam safety practice for conventionalwater dams, some particular level of tolerable risk is oftenspecified that, in turn, implies some tolerable failure rate.The Panel does not accept the concept of a tolerable failurerate for tailings dams. To do so, no matter how small, wouldinstitutionalize failure. First Nations will not accept this,the public will not permit it, government will not allow it,and the mining industry will not survive it.”

As this manuscript is being written, Newcrest MiningLimited (NML) has just announced the failure of a portionof its tailings dam at the Cadia Mine in New South Wales,Australia. NML is one of the largest and most experiencedgold mining companies in the world; its Cadia Mine is itsflagship producer; and New South Wales has had for sometime one of the most comprehensive dam safety regulatoryprocesses in the world. Clearly the crisis is not over.

3.3. Responding to the crisis

3.3.1. Introduction

As a result of the two main incidents a few years ago,many commentators and agencies addressed the issues andprovided guidance to resolve the crisis. This involved indi-viduals, mining organizations, NGOs, government, and theUNEP. This section summarizes and comments on the mostnoteworthy of these recommendations and actions and asksthe overarching question whether enough has been done.

3.3.2. Prescriptive recommendations

Examples of prescriptive recommendations followwith commentary on their effectiveness.


Morgenstern

3.3.2.1. “Ban upstream dams, particularly where subjectedto seismic loads.”

This prescriptive solution has appeal because of thelarge number of upstream failures in the case historyrecords, and it is policy in Chile where, since 1970, the con-struction of upstream dams has been prohibited. Thisresults in higher costs. Nevertheless, the policy was re-affirmed in 2007 with no exceptions. Valenzuela (2015)summarizes the successful performance of downstreamtailings dams in Chile when subjected to large earthquakes,hence, apparently, vindicating the policy.

However, I side with the views of Martin &McRoberts (1999) and others before them (e.g., Lenhart,1950; Vick, 1992) that there is nothing wrong with up-stream tailings dams provided that key principles are ad-hered to in the design, construction, and operation of suchdams. Some 12 principles are outlined that should be recog-nized when upstream dams are proposed. In my practice, Iadvocate for purposes of preliminary design that lique-fiable deposits that can liquefy be assumed to do so and thatcontainment be provided by a buttress of non-liquefiableunsaturated tailings and/or compacted dilatant material. Inaddition, it is essential to continually demonstrate by moni-toring that the assumed unsaturated conditions in the but-tress persist if relied upon in the design and that the buttressis behaving as intended.

Some upstream dams are surprisingly seismic resis-tant. Morgenstern (1996) cites studies into the DashiheDam that survived the catastrophic Tangshan earthquake in1996. At the time of the earthquake, this dam was 36 m highand the downstream slope was 5:1. It developed somecracking and sand boils during the earthquake, but did notcollapse. Investigation carried out by a joint Sino-Canadianresearch team revealed surprisingly high densities. Thesewere attributed to the low solids content during depositionand long beach slopes facilitating enhanced seepage-indu-ced densification. The capacity to pump higher solids con-tent slurry did not exist in China at that time. While arational explanation of behaviour exists, the survival of theDashihe Dam was more accidental than founded in geo-technical principles.

If upstream construction can be executed safely, evenin seismic areas, does that contradict the logic of the Chil-ean regulation? The Chilean regulation, as with most na-tional/regional regulation, reflects more than designprinciples. It must reflect the maturity of the design com-munity, procurement policies, quality assurance, land ten-ure, the degree of seismicity, and many other aspects ofpractice. Only the Chileans have the capacity to make theseintegrated judgments with respect to public safety in theirown country.

3.3.2.2. “Ban clay foundations.”

There are numerous examples of successful construc-tion of large tailings dams on clay foundations. From the oil

sands industry alone, one can cite the successful comple-tion of Tar Island Dyke, 90 m high, in part on a normallyconsolidated alluvial clay and other structures, albeit withflat slopes, on some of the weakest foundation ever encoun-tered.

The application of geotechnical principles adequatelyprovides for accommodating clay foundations. The chal-lenge resides in ensuring that these principles are properlyunderstood and applied in design.

3.3.2.3. “Require a Factor of Safety of at least 1.5 duringoperations.”

The prescription of the Factor of Safety (F of S) is at-tractive to regulators, but experience with case histories,such as Samarco, reveal that over-reliance on prescribedvalues is not adequate to eliminate failure. In my experi-ence, we have been using F of S = 1.3 during operations onvery challenging sites in the oil sands industry for manyyears. At the other end of the spectrum, I have encounteredcases where F of S = 1.5 may not be adequate due to eitherenhanced ductility or enhanced brittleness. The prescrip-tion of F of S in regulation, if necessary, requires thoughtfulinput from experienced designers and recognition of thecharacteristics of regional practice.

This leads to a wide choice in regulatory perspectivesfrom that adopted in Chile where upstream construction isbanned regardless of calculated F of S, to that currently be-ing adopted in the revised Alberta Dam Safety Guidelineswhere no specification of minimum F of S is made. In thisinstance, existing industry guidelines are referenced, butthe selection of the F of S must consider influencing factorssuch as:i. Consequence of failureii. Uncertainty of material properties and subsurface con-

ditionsiii. Variable construction and operating conditionsiv. Comprehensive site investigation, and geotechnical

monitoringv. Soil response (contractive/dilative) and its variation

with confining stress and shear stress laws), includingpotential for brittle failure

vi. Time-dependent, deformation-dependent, and stress-path dependent processes that may affect the criticalmaterial properties

vii. Strain incompatibility of different materialsviii. Seismic loading as appropriateix. Implementation of an effective risk management sys-

tem (e.g., observational method).

3.3.2.4. Concluding remark

No set of simple prescriptions will resolve the crisis.As emphasized by McRoberts et al. (2017): “One of themost important learnings can be seen in failure of otherstructures in the world. This is that a highly integrated teameffort and success of an individual structure relies on the



operational discipline of planning, technology, operations,geotechnical engineering, and regulatory bodies.”

3.3.3. Response in British Columbia (BC) to the MountPolley incident (2014)

The breach in the Mount Polley Tailings Storage Fa-cility (TSF) resulted in two inquiries:i. Independent Expert Engineering Investigation and

Review Panel(https://www.mountpolleyreviewpanel.ca/fi-nal-report).

ii. Investigation Report of the Chief Inspector of Mines(https://www2.gov.bc.ca/gov/content/industry/min-eral-exploration-mining/further-information/direc-tives-alerts-incident-information/mount-polley-tailings-breach/mount-polley-investigation).The first had terms of reference to report on the cause

of failure of the tailings storage facility and to make recom-mendations to government on actions that could be taken toensure that a similar failure does not occur at other minesites in BC. The Panel concluded that the dominant contri-butions to the failure resided in its design and operation. Inaddition, it recommended that the industry establish a pathto zero failure, as opposed to some tolerable failure rate. Todo so, it should adopt a combination of Best AvailableTechnology (BAT) and Best Available Practices (BAP).BAT argued for an emphasis on technologies that minimizethe consequence of failure by reducing fluidity and/or pro-vide more positive containment. BAP included a number ofrecommendations to reduce the probability of failure byimproved governance, expanded sensitivity to risk assess-ment in design, the introduction of Quantitative Perfor-mance Objectives in the declared design, the increased uti-lization of independent tailings review boards, and otherrelated aspects of professional practice.

The Chief Inspector of Mines has the statutory au-thority to investigate any incident that occurs on mine sitesin the Province of British Columbia. His investigation dif-fered from that of the Independent Panel in that it includedthe determination of the root and contributory causes of theevent as well as developing findings to address the account-ability of the industry, the regulator, engineering practices,and any other contributions to the event. The investigationwas also concerned with reducing the risk of such an eventin the future, as well as making recommendations for regu-latory changes.

The technical explanation of the failure was similar tothat presented by the Independent Panel, but it went furtherin attributing the root cause to weak engineering, wastemanagement issues, and risk management. It is of interestto note that the facility, from a structural perspective, wasapparently not in contravention with the then-extant regula-tions, clearly prompting a need for a reassessment. Arisingfrom the lessons learned from this inquiry, multiple recom-mendations for improved practice were made to mining op-

erations, the mining industry, professional organizations,and the regulator. There was a strong alignment betweenthe recommendations arising from the two investigations.

The Government of British Columbia responded pos-itively to the recommendations from the two inquiries. Inparticular all of the recommendations arising from the In-dependent Panel have been addressed, and a major revisionof the Code has been completed and published (Health,Safety and Reclamation Code for Mines in British Colum-bia; revised June 2017 https://www2.gov.bc.ca/as-sets/gov/driving-and-transportation/transportation-infrastructure/contracting-with-the-province/docu-ments/12811-2018/t3-10-health-safety-and-reclamation-code-for-mines-in-british-columbia-2008.pdf). Chapter 10(Permitting, Reclamation and Closure) in the Code dealswith tailings storage facilities. The revised Code reflectsthe response of a multi-stakeholder committee to the find-ings from the inquiries. This is an important document and,in my view, constitutes the best revision of any regulatorydocument in response to the crisis. It is evident that bothBAT and BAP need formalized response and that regula-tion needs to be more prescriptive than in the past to mini-mize recurrence of the failures that are being encountered.This Code strikes a sensible balance in this regard withoutintruding into the responsibilities of both the operator andthe design engineer.

It is of interest that it is having influence elsewhere.For example, the State of Montana has recently adopted aregulatory process that draws considerably from the exam-ple of the BC Code.

3.3.4. Response in Brazil to the Samarco incident (2015)

The Report on the failure of the Fundão Dam (FundãoTailings Dam Review Panel, 2016) was limited to an evalu-ation of the technical causes of failure. It drew attention toflaws in both design and operation. However, it conscious-ly did not address roles and responsibilities. Public discus-sion of these issues is limited by ongoing litigation. How-ever, this has not prevented agencies in Brazil fromassessing changes in both professional practice and regula-tion, intended to prevent future reoccurrences of such inci-dents.

The Brazilian National Dam Safety Policy was firstestablished in 2010 and constitutes the regulatory frame-work for dams in the country. Oliveira & Kerbany (2016)provide a brief summary of the evolution of tailings damrisk in Brazil and their regulations up to the Samarco inci-dent. ABNT NBR 13028:2006 appears to have been thefirst regulatory instrument explicit for tailings storage facil-ities. Following Samarco, a committee was formed to re-vise the existing regulations, and in November 2017, a newversion 13028:2017 was produced. It expands considerablyon the technical requirements to support approval of the de-sign of a tailings dam and draws on relevant internationalpractice in this regard. In addition, the National Department


Morgenstern

of Mineral Production (DNPM) has expanded substantiallyits regulatory requirements with respect to the operation oftailings facilities (Alves, 2017) and additional requirementsmay be forthcoming.

The role of the State in Brazil from a regulatory as-pect is not immediately clear. Bogossian (2018) reflectsdisappointment with the rate of change of regulations gov-erning tailings dam safety.

3.3.5. Response of United Nations EnvironmentProgramme (UNEP)

The UNEP has demonstrated a long-term concern re-garding the high incidence of inadequate performance ofmine tailings storage facilities. In response to the emergingcrisis, it undertook a Rapid Response Assessment to look atwhy existing engineering and technical knowhow to buildand maintain safe tailings storage facilities is insufficient tomeet the target of zero catastrophic incidents. It examinedthe ways in which the established best practice solutions tointernational collaborative governance, enhanced regula-tions, more resource-efficient approaches, and innovationcould help to ensure the elimination of tailings dam fail-ures. Case histories were utilized to highlight efforts in thisregard (Roche et al., 2017).

This report has not been prepared by technical spe-cialists, and it has been obliged to adopt some of the pub-lished literature at face value. Nevertheless, it is generallybalanced, well-produced with helpful photographs, refer-encing, and historical summations. It concludes with tworecommendations and identifies a number of actions to im-prove regulation and practice. The two recommendationsare:

i. The approach to tailings storage facilities must placesafety first, by making environmental and human safe-ty a priority in management actions and on-the-groundoperations. Regulators, industries, and communitiesshould adopt a shared zero-failure objective in tailingsstorage facilities where “safety attributes should beevaluated separately from economic considerations,and cost should not be the determining factor” (cita-tion from Mount Polley Expert Panel Report, p. 125).

ii. Establish a UN Environment stakeholders report to fa-cilitate international strengthening of tailings dam reg-ulation.

A number of actions recommended in past publica-tions are also summarized. Clearly the first recommenda-tion is consistent with the emerging safety culture withinthe mining industry. However, it is difficult to envisagemuch support for the second recommendation, given thecomplexity of jurisdictions responsible for tailings damregulation and widespread evidence that failures continueeven with mature and experienced regulators. This will bediscussed in more detail in a subsequent section of thisLecture.

3.3.6. Response of Mining Association of Canada (MAC)

The first edition of MAC’s Guide to the Managementof Tailings Facilities was released in 1998 in response to aseries of international tailings-related incidents that oc-curred in the 1990s, several involving Canadian miningcompanies. The overarching objective of this documentwas to help mining companies to implement safe and envi-ronmentally responsible management of tailings facilities.This was followed in 2003 with a companion document on“Developing an Operation, Maintenance, and SurveillanceManual for Tailings and Water Management Facilities.”Tailings management was further embedded in the “To-wards Sustainable Mining” (TSM) initiative established in2004, which provided clear guidance on governance issues.There has been strong external recognition that implement-ing the tailings management component of TSM is a bestpractice for tailings management. This was recognized inthe report on the Mount Polley failure.

Following the Mount Polley incident, the Board ofDirectors of MAC initiated a review of the tailings manage-ment component of TSM which culminated in the revisedGuide to the Management of Tailings Facilities (Third Edi-tion), issued in November 2017 (MAC, 2017). This is anoutstanding document particularly in its contribution togovernance structure within companies which is necessaryto underpin a commitment to safe design, construction, op-eration, and closure of tailings storage facilities.

MAC processes emphasize the value of conductingaudits to verify commitment and effectiveness. There arethe three levels that corporations aspire to. Numerous com-mitments are required to achieve each level. In the new edi-tion, new guiding principles are introduced to include:i. Risk-based approachesii. BAT and BAP for tailings managementiii. The roles of independent reviewiv. Design and operating for closurev. Revised roles and responsibilities.

This new Guide provides an outstanding document toinfluence the organization and governance protocolsneeded to ensure safe tailings management from the con-ceptual stages through to closure.

3.3.7. Response of International Council on Mining andMetals (ICMM)

The ICMM and its predecessor organization, theICME, has long recognized the significant role that minetailings management plays in the overall risk profile ofmining operations worldwide. This is of special signifi-cance since the ICMM represents the majority of theworld’s largest mining and metals companies. In responseto the crisis, ICMM undertook a global review of tailingsstorage facility standards, guidelines, and risk controls. Thereview was conducted by member company representa-tives, assisted by external experts. The focus was on corpo-rate-level surface tailings management across the



membership, including standards, guidelines, risk controls,and governance and emergency preparedness related to theprevention of and response to sudden catastrophic failure oftailings storage facilities. The report arising from this im-portant review and the recommendations based on its find-ings has been produced by Golder Associates (2016).

Before engaging in the review that concentrated ongovernance issues, the study team reflected on learningfrom recent high-profile failures and concluded:

“If one were to focus on these and other such case his-tories through consideration of a greater number of failureand investigation results over the last 20 or so years, andask the question is there anything missing form existingstandards and guidance documentation that if known andapplied could have forestalled such events, then the answermight be as follows:

“Existing published guidance and standards docu-mentation fully embrace the knowledge required to em-brace such failures. The shortcoming lies not in the state ofknowledge, but rather in the efficiency with which thatknowledge is applied. Therefore, efforts moving forwardshould focus on improved implementation and verificationof controls, rather than restatement of them.”

Based on this justification, it was concluded that ahigher level of governance and assurance is required for theeffective implementation of good practice. To this end, thestudy focussed on the following core elements of goodpractice:i. Tailings management frameworkii. Governanceiii. Minimum requirements for design, construction, ope-

ration, decommissioning, and closure (includingpost-closure management).Arising from the review of member company docu-

ments, five areas of improvement were identified and rec-ommendations were made with respect to the following(see Report for details):i. The need for a tailings storage facility classification

system based on the consequences of failure.ii. The need for a formal change management process re-

lated to material changes to the life of the facility plan.iii. The need for improved communication between the

Engineer-of-Record and operator/owner.iv. Expanded utilization of formal risk assessment pro-

cesses.v. The need for more independent review by suitably

qualified and experienced professionals.Additional details were provided regarding the rec-

ommended governance and tailings management frame-work, supported by the necessary assurance protocols.

Assisted by the Golder Associates (2016) study,ICMM also issued a Position Statement on Preventing Cat-astrophic Failure of Tailings Storage Facilities (ICMM,2016). All members of ICMM are obliged to implement intheir businesses the ten principles associated with the

ICMM Sustainable Development Framework. A number ofthese principles are of particular relevance to the need forpreventing catastrophic failure of tailings storage facilities.The specific commitments related to an enhanced tailingsgovernance framework require the following:i. Accountabilities, responsibilities, and associated com-

petencies are defined to support appropriate identifica-tion and management of tailings storage facilities risk.

ii. The financial and human resources needed to supportcontinued tailings storage facilities management andgovernance are maintained throughout a facility’s lifecycle.

iii. Risk management associated with tailings storage fa-cilities, including risk identification, an appropriatecontrol regime, and the verification of control perfor-mance.

iv. Risks associated with potential changes are assessed,controlled, and communicated to avoid inadvertentlycompromising facility integrity.

v. Processes are in place to recognize and respond to im-pending failure of facilities and mitigate the potentialimpacts arising from a potentially catastrophic failure.

vi. Internal and external review and assurance processesare in place so that controls for facilities risks can becomprehensively assessed and continually improved.It is of interest to note that members of ICMM are ex-

pected to implement the commitments required by this po-sition statement by November 2018.

3.3.8. Commentary

Positive and productive responses to the crisis havebeen made by revisions of regulatory requirements at boththe regional and national levels as well as recommenda-tions for improved corporate practice, with emphasis ongovernance, as made by both MAC and ICMM. All arewelcome. However, the question remains whether they areadequate to overcome the crisis.

3.4. The causes of catastrophic tailing incidents

3.4.1. Introduction

One cannot answer the question that asks whether themeasures taken so far by the industry and the various regu-lators are sufficient to address the crisis and resolve it with-out understanding the causes of catastrophic tailings inci-dents.

I have been involved to various degrees in 15 publictailings incidents over the last 30 years, not all involvingdam failures, but all involving safe tailings management. Inthe following, I have personally assessed the basic causesof each incident in terms of whether it was engineering, op-erations, or regulatory related. By engineering related, Imean related to the matters of design, construction, qualitycontrol, and quality assurance. By operations related, Imean deviations from an operation manual that would


Morgenstern

guide such matters as water management, tailings place-ment, and care and maintenance and would usually be cov-ered by an Operations, Maintenance, and Surveillancemanual (OMS). By regulatory related, I mean decisionsmade, or not made, by a regulatory authority that contrib-uted significantly to the incident that occurred. In some in-stances, it is not possible to discriminate clearly betweenone or the other basic cause, and in such cases, I nominateboth (see Table 1).

It should be made clear that these attributions are per-sonal judgments and are not to be confused with root causesthat are more complicated to assess. I make no attribution ofroles and responsibilities in the basic cause assessment. Inmost cases, a brief Internet search will provide supportingdetails and photographs. Therefore, in general, no detailedreferences are provided here. Where this is not the case, abrief commentary and extra referencing is provided. My in-volvement in these cases covers the range from participat-ing in detailed forensic investigations through knowingenough from files managed by others to form an opinion.

3.4.2. Commentary

The first case, Tyrone, is mentioned in Martin &McRoberts (1999) who reference a more-detailed backanalysis of the failure first presented by Carrier (1991),which is neither well-known nor readily accessible. It de-serves wide-spread recognition because it highlights thelimited understanding of the role of undrained analysis ap-plied to tailings dam stability, which was extant at that timeand continues to this day.

The second case, Ok Tedi, was not a failure of an op-erating tailings storage facility, but a failure during con-struction due to a large landslide that occurred in the easternabutment of the dam. As a result, tailings storage conceptswere abandoned in favor of riverine discharge solutions.This decision had disastrous environmental, social, and fi-nancial consequences, which are a matter of public record.Substantial litigation developed with respect to liability as-sociated with the abandonment of the tailings storage sitewith conflicting expert reviews. Respected expert opinionsvaried from the view that the circumstances around thelandslide were too complex, given the local conditions, forthe hazard to be identified, to the alternative, that the stud-ies were deficient. Fookes & Dale (1992) provide a sum-mary of alternate views. It is not the intent here to favourone side or the other, but to draw attention to the fact thatgeological and geotechnical complexity in some instancesmay be too great to support site selection at all, which is nota comforting observation.

The third case, Stava, resulted in the loss of 269 lives,the destruction of two villages, and extensive propertydamage. This incident has received considerable attentionin the literature and was the subject of extensive litigation.It will come as a surprise to many that I attribute the basiccause to regulatory decisions. The detailed support of thisattribution is presented in Morgenstern (1996). This paperrecords that the mine was shut down in 1978, and the damswere abandoned, except for a pond in both dams to manageprecipitation runoff. The local authorities encouraged newownership, and mining recommenced in 1982 by an organi-zation with, limited mining experience. Construction and



Table 1 - Basic causes of tailings incidents.

Name Year Place Basic causes

Engineering Operations Regulators

Tyrone 1980 New Mexico, USA �

Ok Tedi 1984 Papua New Guinea �

Stava 1985 Italy �

Omai 1995 Guyana �

Golden Cross 1995 New Zealand �

Marcopper 1996 Philippines �

El Porco 1996 Bolivia �

Pinto Valley 1997 Arizona, USA � �

Los Frailes 1998 Spain �

Inez 2000 Kentucky, USA � �

Kingston 2008 Tennessee, USA �

Keephills 2008 Alberta, Canada �

Obed 2013 Alberta, Canada � �

Mount Polley 2014 British Columbia, Canada � �

Samarco/Fundão 2015 Minas Gerais, Brazil � �

tailings operations were substantially modified by the newoperator. In particular, mobile cyclone placement of tail-ings was abandoned in favor of single point dischargewhich allowed pond water to encroach on the beach of thedam, ultimately triggering static liquefaction. It appearsthat had the regulator not interfered in the fate of the facil-ity, without prescribing operational restraints, the failurewould not have occurred.

Not much information regarding the Pinto Valleyfailure is available in the public domain. It involved thestatic liquefaction of an old tailings facility that had beendecommissioned in the 1970s while the second lift of awaste dump was being placed on it. From my limited famil-iarity with the files, both engineering and operational issuescontributed to the incident.

The failure of the Inez coal tailings impoundment inKentucky, USA, reflected technological and operationalperspectives that appear peculiar to the coal industry in thatpart of the US. The technical challenges have been evalu-ated by a special committee established by the US NationalResearch Council (Committee on Coal Waste Impound-ments, 2002).

The Keephills incident is not well-known, primarilybecause it did not result in loss of containment. Instabilityof the wall of the impoundment occurred during dyke rais-ing. Fortunately, the crest of the slide did not penetrate intothe fluid contents of the pond. The slide was attributed todeficiencies in assessing the shear strength of the complexfoundation conditions beneath the embankment.

The Obed incident is also associated with the coal in-dustry. A water retaining dyke failed due to inadequacies insite-wide fluid management, indicating an operational Ba-sic Cause. However, even though the operation was li-censed as a mine, the retaining structure had not beenreviewed by the dam safety regulator. This appears to havebeen a lapse in the approval of mine operations and hence acontribution from the regulator to the basic cause of failure.

3.4.3. Reflection

From a technical perspective, it is of interest to notethat inadequate understanding of undrained failure mecha-nisms leading to static liquefaction with extreme conse-quences is a factor in about 50% of the cases. Inadequaciesin site characterization, both geological and geotechnical,is a factor in about 40% of the cases. Regulatory practice,considered appropriate for its time and place, did not pre-vent these incidents. However, the most important findingis that the dominant cause of these failures arises from defi-ciencies in engineering practice associated with the spec-trum of activities embraced by design, construction, qualitycontrol, quality assurance, and related matters. This is avery disconcerting finding.

There is an unwritten covenant in our professionalpractice with the assumption on the part of an operator that,given reasonable resources, and on the part of the regulator

that, given technical guidelines and a modicum of inspec-tion, the engineering team can be relied upon to produce atailings storage facility that will perform as intended. Theexperience summarized here leads to the conclusion thatthis covenant is broken.

The conclusions in the ICMM-sponsored study oftailings management guidelines (Golder Associates, 2016)and the recommendations embraced in the Tailings Gover-nance Framework issued by ICMM (2016) are not adequateto resolve the crisis.

3.5. Toward zero failures

3.5.1. Introduction

The responsibility for improving the safety culture as-sociated with the performance of tailings storage facilitiesthrough all cycles of their life resides primarily with the op-erators. While regulators also have a role, it is necessarilysubordinate to the role of operators. Experience reveals thatthe advance of this safety culture to the goal of zero failuresrequires intrusion into not only the activities of the opera-tor, but also into the activities of the engineer(s). However,this intrusion must not be so prescriptive that it needlesslylimits the creative input from both the operator and the en-gineer. To this end, it is recommended for any specific pro-ject that the operator be required to develop, for regulatoryapproval and subsequent execution, a tailings managementsystem for Performance-Based, Risk-Informed, Safe De-sign, Construction, Operation, and Closure of the proposedtailings storage facility (PBRISD). Many single elementscombined in PBRISD have been identified before, but therequired integration presented in the following is perceivedas necessary to impose more rigorous direction, supportedby critical levels of review at various stages of the process.

3.5.2. Outline of PBRISD

For convenience, the organization of PBRISD is bro-ken down into various stages of the life cycle of the project.Actual projects will develop the proposed system with ref-erence to their own specific details.

3.5.2.1. Stage 1: (Conceptual)

This stage is associated with site and technology se-lections that generally are intended for application for ap-proval by a regulatory process. The following elements arepart of this stage:i. Qualified Operator (QO). Any proponent must estab-

lish itself as a QO. This is achieved by declaring thatits safe management system will be compatible withthe MAC 2017 Guide. In addition to prescribing to thisexcellent guide to the management of tailings facili-ties, the establishment of the following three criticalpositions becomes a commitment: i) Accountable Ex-ecutive Officer, ii) Responsible Person(s), and iii) En-gineer-of-Record.


Morgenstern

ii. Establish Independent Review Board. This will re-quire creating a risk-based classification of facilities toprovide guidance on the extent to which external re-view boards are required. Clearly there are instanceswhere, either by past experience or by limited risk, noexternal independent review is necessary. At the otherextreme, a three- to four-person board is required.Guidance is also required to assist the QO in formingsuch a board. Examples of terms of references areneeded as well as a discussion on dealing with confi-dential matters, while also assessing safety issues thatshould be available in the public domain. Hence, re-porting structures for boards need summarizing as dolegal/commercial issues such as indemnification ofboard members for potential legal actions beyond theirremit.

iii. Uncertainty Assessment. It should be recognized atthis early stage that safe design and operation relies ona large number of models (e.g., the geological model,the hydrogeological model, the geochemical model,the geomechanical model, the stability model). All ofthese models possess uncertainties which either areaddressed or become irrelevant with time. A first as-sessment of all uncertainties should be conducted inthis stage for all options under consideration.

iv. Potential Problems Analysis (PPA). The first formalrisk analysis for all options under consideration shouldbe a PPA which is a systematic method for determin-ing what could go wrong in a plan under development.It is not anticipated that all issues would be addressedin Stage 1. However, the analysis might influence therecommendations arising from Stage 1 and residualconcerns would be addressed in Stage 2.

v. Multiple Account Analysis (MAA). The options fortailings technology and site selection considered inStage 1 and recommendations arising from the assess-ments should be supported by an MAA. This is a struc-tured decision-making process that makes transparenthow both corporate and other stakeholder values havebeen considered in the assessment process. It is of con-siderable value in both documenting process as well aspromoting trust. The MAA procedure has long beenadvocated by the federal regulators in Canada and isalso outlined in MAC (2017).

3.5.2.2. Stage 2: (Feasibility)

This stage is associated with advancing the design ofthe selected option to a level both appropriate for making afinancial commitment to proceed and to submit a design insufficient detail to receive approval from the dam safetyregulator. The following elements are part of this stage:i. Engineer-of-Record (EoR). The position of EoR is

widely recognized as an integral part of the tailingsmanagement team dedicated to safety performance ofthe facility. The role of the EoR is to verify that the

facility has been designed in accordance with perfor-mance objectives and is supported by applicableguidelines, standards, and regulatory requirements.When constructed, it will perform, throughout the lifecycle, in accordance with the design intent, perfor-mance objectives, applicable guidelines, standards,and regulatory requirements. The EoR is generallyperceived to be a person and not a firm. While thefunctions of the EoR are important, there is still somedebate in practice as to how these functions are bestfulfilled, particularly if the QO has substantialin-house geotechnical and construction capability, aswell as increasingly automated instrumentation andinterpretation capacity. This is made more complexwhen the life of the facility is long and change of theEoR is inevitable. Guidance is required to assist theQO in evaluating the best way to fulfill the require-ments of the EoR.

ii. Designer. The designer selected for Stage 2 has a cru-cial role in all aspects of this stage. Some regional pro-curement practice places a strong emphasis on com-petitive costs which can result in breaking the designinto small segments for either economic or other per-ceived management objectives. The QO needs guid-ance on procurement policy and the risks that might begenerated by multiplying design interfaces.

iii. Design Basis Memorandum (DBM). The DBM is thecritical document that supports all design criteria andrelated methodology. It is subject to change based onevolving experience and methodologies. Documenta-tion of change to the DBM must be formalized in acomprehensive manner. While the review board willparticipate throughout this stage, it is expected that re-view of the DBM and related matters will receive spe-cial attention. It is expected that all geotechnicaldesign will adopt the observational method where pos-sible. This is a precautionary-based design, to verifythat no significant departures from design assumptionhave been identified. It requires prior identification ofpractical mitigation measures in the event that obser-vations reveal that they are prudent or necessary. It isalso expected that geotechnical design, at least for themore challenging undertakings, will increasingly uti-lize performance-based design. With advances in per-formance modeling, monitoring, and interpretation ina timely manner, it is now practical to move in this di-rection. The outcome is improved safety assessmentand increased opportunities for optimization.Morgenstern (2017) discusses the merits of this trans-formation in more detail.

iv. Risk Assessment. Risk assessments will be carried outas the schedule for Stage 2 dictates. For planning pur-poses, risk assessments at 30% and 70% completionshould be in the development plan. The PFMA meth-odology is recommended. Some guidance is provided



in the MAC 2017 Guide, but additional documenta-tion may be warranted for the QO.

v. Quality Management. Detailed quality managementplans will be developed distinguishing between Qual-ity Control (QC) and Quality Assurance (QA). Whenconstruction is performed by the mine itself, ambigu-ities often arise. It is necessary to emphasize the inde-pendence of QA and, if conflicts arise with QC, tohave resolutions at a senior level to ensure that pro-duction concerns do not overwhelm quality concerns.QA should also be responsible for the construction re-port which is an indispensable document, both for sup-porting the EoR requirements as well as constituting abasic resource to inform future long-term safety as-sessments.

vi. Documentation. Experience with recent failure inves-tigations highlights the need to have complete as-builtdata and other records compiled, preferably on a GISplatform, and accessible so that a technical audit couldbe conducted at any time. This is a valuable insurancedocument for all involved in the project and meritsdedicated planning and support.

3.5.2.3. Stage 3: (Construction and operations)

Both construction and operations tend to overlap inthe evolution of tailings storage facilities. Managing theconstruction follows naturally from the processes thatevolved in Stage 2. However, additional considerations areneeded to guide safe operations.

i. Operations. Both safe construction and safe operationare guided by an Operation, Maintenance, and Sur-veillance Manual (OMS). This document requires cri-tical reviews from the review board and periodic up-dating. The MAC 2017 Guide also provides valuableguidance on the development of this document.

3.5.2.4. Stage 4: (Closure implementation)

Modern project planning recognizes the need to inte-grate mine planning, tailings planning, water planning, andclosure planning at the outset. It is assumed here that inPBRISD closure planning will be considered in all of theprevious stages, at increasing levels of detail with time.From a geotechnical perspective, the primary concern iswith the physical and chemical integrity of the ultimatelandforms and release fluids. Closure design should recog-nize that the construction as-built record constitutes a basicreference for landform design under closure conditions.The evolution of closure design should emphasize the needfor a new DBM to identify closure design criteria and meth-odology for the physical and chemical aspects of the clo-sure landscape. Ongoing safety assessments must be able torely on the as-built record as reliable to avoid the circum-stances that occurred at Oroville Dam.

3.6. Guidance

The design, construction, operation, and closure ofmodern tailings facilities to acceptable standards of safetyand environmental impact is a complex undertaking. Bothexperience and system analysis indicate clearly that it is notpossible to meet acceptable standards by regulations alone.It is the primary responsibility of the proponent to put for-ward an acceptable waste management plan that meetsthese standards. The evolving crisis related to trust and con-fidence, discussed here, has also revealed a high rate oftechnical deficiencies as a significant factor in the failuresthat have been documented. It is tempting to conclude thatincreased prescriptive measures controlling the engineer-ing works are required. However, the intrinsic complexityand diversity of the undertakings reduces the reliability ofthis perspective. Instead, the underlying principle for thetailings management system advocated here (PBRISD) isaccountability. This is achieved by multiple layers of re-view, recurrent risk assessment, and performance-basedvalidation from construction through closure.

The regulator also has a vital role. It is the responsibil-ity of the regulator to review the proposed waste manage-ment plan and indicate how it is to be validated. This willinvolve some combination of inspections concentrating onquantified performance objectives, receiving review boardreports, and other measures deemed necessary. The regula-tor is also the custodian of prescribed regional practice. Forexample, the regulator in Chile may continue to ban up-stream construction even though technical arguments canbe advanced that they can be designed and operated in asafe manner.

3.7. Recommendations

In order to turn the system recommended here into areality, it is necessary to expand the skeleton outline into aguidance document that would help individual operators indeveloping a tailings management system for their specificoperations based on PBRISD. The principles involved inPBRISD are entirely consistent with the ten principles thatare the foundation of ICMM’s Sustainable DevelopmentFramework. In addition, supporting the adoption ofPBRISD can be regarded as a natural extension of the ac-tion already taken by ICMM in their 2016 Position State-ment.

This Lecture concludes with the recommendation thatICMM support the tailings management system based onPBRISD, as outlined here, and fund the development andpublication of a guidance document that would facilitate itsadoption in mining practice.

4. Concluding RemarksThis Lecture has explored the evolution in practice of

a safety culture in several important aspects of geotechnicalpractice. The range covers examples of success to examplesof failure related to public aspects of geotechnical practice.


Morgenstern

The example of success is the Slope Safety System inHong Kong, to which Victor de Mello contributed in itsearly development.

The intermediate example relates to water dam safetywhere the recent Oroville Dam incident in California hasexposed disconcerting practice in dam safety evaluation.Some of the learnings from this incident are presented andrecommendations have been made to improve practice inwater dams safety assessment.

Currently, the weakest safety culture is associatedwith tailings dams. Here, several high-profile failures have,in recent years, created a crisis due to loss of trust and confi-dence in the design, construction, and operation of such fa-cilities. The Lecture reveals that this appears to be justified,particularly due to weak engineering in many instances (de-sign, construction, QC, QA). Recommendations are made,primarily to operators, as to how to develop an improvedtailings management system to maximize reliable perfor-mance.

Acknowledgments

I would like to recognize the valuable discussions onthese matters with numerous colleagues in both profes-sional practice and academic studies over the years. Theyare too numerous to list in detail, but important to remem-ber. In the short term, the preparation of this Lecture andpublication owes much to the organizational and communi-cation skills of Vivian Giang to whom I am grateful.

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Documents

Geotechnical Risk, Regulation, and Public Policy€¦ · tailings dams is typically more regional than national. The failure rate for tailings dams has generally been proportionately