Over the last decade, several prominent tailings dam failures have occurred, resulting in significant environmental damage and even loss of life. These incidents have led owners and regulators, and even investors, to increase their scrutiny of tailings storage facilities worldwide. As part of this greater scrutiny, commonly used standards—such as the Global Industry Standard on Tailings Management (GISTM), the International Commission on Large Dams (ICOLD), and the Canadian Dam Association (CDA)—recommend performing regular dam safety reviews (DSRs).
What is a dam safety review?
A DSR is an independent review that assesses the safety of a tailings facility from a technical, operational, and governance perspective. The DSR—a regulatory requirement in many jurisdictions—is carried out by an independent technical specialist and should be conducted according to established best practices. This review should be performed at regular intervals based on the complexity of the dam’s condition or performance, in addition to its “consequence classification,” as defined in the table below.
GISTM’s Consequence Classification Matrix
The GISTM states that an independent DSR should be conducted at least every five years for tailings facilities with “very high” or “extreme” consequence classifications and at least every 10 years for all other facilities. For tailings facilities with complex conditions or performance, the Independent Tailings Review Board (ITRB) may recommend more frequent DSRs. The DSR contractor cannot conduct consecutive DSRs on the same tailings facility and must certify in writing that they follow best practices for engineers in avoiding conflicts of interest.
ICOLD states that DSRs are “carried out to determine if the safety and management of the dams and associated facilities is current and adequate.”
In Canada, the CDA specifies that a DSR is carried out “to assess and evaluate the safety of a dam or system of dams against failure modes in order to make a statement on the safety of the dam. A safe dam is one that performs its intended function under both normal and unusual conditions; does not impose an unacceptable risk to people, property, or environment; and meets applicable safety criteria.”
What issues might a dam safety review uncover?
A DSR might reveal a variety of issues—including technical design, operational, or governance issues—and may provide a series of recommendations or actions to address those issues. For example, recommendations Barr has identified in past DSRs include:
Reexamine target factors of safety for various slope stability cases to be consistent with applicable guidance documents
Carry out more robust characterization of the shear strength of tailings and foundation materials
Determine instrumentation thresholds and specific actions pertaining to data review and/or geotechnical analysis
Assess static liquefaction using advanced constitutive models
Address the frequency of instrumentation monitoring data review by responsible parties
Add specific consideration of maintenance and surveillance activities into closure and post-closure
Develop a flow chart to direct communication with clear identification of internal and external lines, especially in the event of an emergency response
Develop documentation of the most recent emergency drills or exercises, including date, activity, and catalogs of internal and external participants
DSR findings help clients identify deficiencies in their design, operations, or governance activities for which the Engineer of Record, tailings management responsible person, or corporate counsel can take actions to mitigate.
Barr has extensive experience in performing DSRs and third-party peer reviews at tailings management facilities. We have performed multiple DSRs for tailings dams built using upstream, centerline, and downstream construction methods located throughout the U.S., Canada, Mexico, and Brazil. Similarly, we have performed design peer reviews for mining projects in Russia, Jordan, and Brazil (tailings dams, retention dikes, etc.).
Interested in learning more? Connect with Barr staff at the upcoming Tailings and Mine Waste 2023 conference taking place November 5 through 8 in Vancouver, British Columbia.
Contact us to discuss your specific needs, degree of progress toward GISTM or other standard compliance, and to decide if DSR or peer review is appropriate for your situation.
About the authors
Iván Contreras, vice president, senior geotechnical engineer, has more than three and half decades of experience in multidisciplinary projects in the United States, Canada, Central America, Europe, Middle East, and South America. Iván’s expertise includes mine tailings-dam design and management; embankment, slope, foundation, tunnel, and underground structure design; landslide stabilization; cutoff walls, seepage control, and mitigation; ground improvement and grouting; soil dynamics and earthquake engineering; dredged material management; and in-situ testing. He serves clients in the mining, public, fuels, manufacturing, and power sectors, and is also active within the geotechnical and civil engineering communities. Iván serves on the Embankments, Dams, and Slopes committee for the American Society of Civil Engineers (ASCE). He is board-certified as a Diplomate of the ASCE’s Academy of Geo-Professionals and has earned a certification from the Dispute Resolution Board Foundation (DRBF). He has authored or coauthored more than 50 technical papers and presented at numerous conferences.
Jed Greenwood, vice president, senior geotechnical engineer, has 20 years of geotechnical engineering experience. He has worked extensively on the investigation and design of tailings dams for U.S. and Canadian mining clients and on flood-protection levees and dams for municipalities. Jed's projects have ranged from design and analysis of levees, floodwalls, and dams to forensic analysis of landslides and seepage analysis and stabilization measures for natural and constructed slopes. He is board-certified as a Diplomate of the ASCE’s Academy of Geo-Professionals.
Suncor Energy Inc. operates and develops a few oil sands mining and processing facilities near Fort McMurray, Alberta. These sites have several ponds and embankment dam structures that provide containment for tailings and process water—some of which are registered as extreme consequence dams under Alberta’s Water (Ministerial) Regulation. The regulation requires that a DSR be undertaken every five years for "Very High" and "Extreme" consequence structures. In 2022, Barr conducted a DSR for one of the external tailings facilities and its containment structures, which is registered as an extreme consequence facility. The DSR included review of dam risks inherent in the design, operation, and performance of the structure, as well as review of associated external risks that could impact the safety of the facility and its dams.
Barr was commissioned by a confidential client to conduct an independent DSR of a very large tailings-storage facility (TSF) in Mexico. This external TSF, built using centerline construction, is classified as an extreme consequence facility based on the highest potential consequence and/or the failure scenario that would result in the worst consequences, which requires a DSR be completed every five years. The DSR was conducted in general accordance with standard practices and regulatory requirements. Among the primary topics addressed were shear strength characterization of the tailings and foundation soils, deformation of the dam, instrumentation thresholds, and static liquefaction, in addition to operational and governance topics.