Geotechnical Risk, Regulation, and Public Policy

N.R. Morgenstern

Victor de Mello Lecture

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


Abstract

At this time, there is a crisis associated with concern over the safety of tailings dams and lack of trust in their design and performance. This crisis has resulted from recent high-profile failures of dams at locations with strong technical experience, conscientious operators, and established regulatory procedures. It is the primary intent of this Lecture to assess the underlying cause(s) for this crisis, review the response to it by various agencies, and to make recommendations on how to overcome it. The Lecture begins with a review of the evolving safety culture associated with slope stability problems as exemplified by the achievements in Hong Kong. This is particularly relevant here because Victor de Mello was a key contributor to the recommendations made in 1976 that initiated the development of the Hong Kong Slope Safety System. The Lecture then addresses the evolution of the safety culture associated with water dams. While there is a long history of concern with respect to water dam safety, these concerns were intensified by several catastrophic dam failures that occurred in the USA in the 1970s. The evolution of regulatory systems from that time is recorded, as is the later trend to adopt risk-based safety assessment and regulation. However, the process that has emerged has been much affected by the Oroville Dam Spillway incident, and dam safety practice is being re-assessed by many. This Lecture summarizes some of the 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 currently the case. Turning to the evolving safety culture for tailings dams, this emerged with rational dam design procedures in the 1970s, more or less as an appendage to water dam design. The growth of environmental legislation related to surface water quality had a considerable impact as well. Hence, a twin regulatory regime emerged in the 1970s. The regulatory regime for tailings dams is typically more regional than national. The failure rate for tailings dams has generally been proportionately higher than water dams and thus has received considerable attention in the technical literature, however without measurable results. The recent failures of major dams in technically advanced regions of the world, operated by mature mining organizations and designed by recognized consulting engineers, has created a crisis in terms of a loss of confidence and trust associated with the design, construction, operation, and closure of tailings storage facilities. Responses to these failures are analyzed, and all are found wanting, particularly since the widespread evidence for weak engineering is inadequately recognized. The Lecture proposes a system for Performance-Based Risk-Informed Safe Design, Construction, Operation, and Closure of tailings storage facilities. It further urges the International Council on Mining and Metals (ICMM) to support the proposed system and facilitate its adoption in practice.


Invited Lecture, no discussions. DOI: 10.28927/SR.412107