CONTACT: Lindsay Newland Bowker
A real page turner!!! The expert panel technical cause of failure report commissioned by Vale was released yesterday (December 12, 2019).

This is a very  distinguished  panel but as with all such commissioned  works it is contractually limited to technical causes of failure and does not address the quality and competence of the Vale geotechnical team or the consultants and contractors involved over the life of the TSF or otherwise address prevailing practice or best practice.

It makes the point that the particular characteristics of the tailings in combination with an unsuitable design allowed the TSF stack to hover in a continuous state of  not fully understood or clearly recognized vulnerability over its entire operating life.  Applying standard tests and following standard guidelines for stability analysis and other assessment produces false and misleading results which on the whole wrongly state the stability condition and state of the tailings mass.  In one test the panel themselves did in the laboratory the tailings showed a compliant 1.5 factor of safety  in undrained conditions immediately pre-failure.

This mineralogy is significantly different from most natural soils that are predominately composed of quartz (i.e., silica-based minerals). The mineralogy also is significantly different from the soils used to develop the traditional empirical correlations used to interpret in situ tests, such as the CPTu, which would indicate that these empirical correlations may not provide reliable results in these tailings. p16

Historical stability calculations using LEM performed prior to the failure that used an undrained strength ratio of su/σ’vo = 0.26 calculated an FS close to 1.0.( TUV SUD 2018) However, if the FS was very close to 1.0, the dam would be expected to show various signs of distress, such as cracking and deformations, because the materials must strain (deform) to reach their peak strength. The fact that the dam showed no signs of distress prior to failure suggests that the results of traditional LEM were misleading. P59

Re-analysis of the stability of Dam I using the peak undrained strength values determined from laboratory testing performed by the Panel, which reflect the additional strength due to bonding, resulted in a FS close to 1.5. However, this ignores possible regions of high shear stress where the local FS can be less than 1.0. The additional strength due to bonding essentially allows a steeper slope to be constructed without signs of distress, even though it could be potentially unstable

Bonding here refers to an apparent tendency for iron particles to almost immeditaely bond with other particles creating a brittleness that adds a strength easily lost in un drained conditions ( the chronic state of the Brumadinho dam 1) resulting in sudden abrupt failure under  only a very small increase in strain. Brittleness is long understood to be a characteristic associated with abrupt and complete flow slides and is currently frequently referenced in connection with oil and gas wastes .

The overall conclusion is that it was something called a “creep rupture” ( a cumulative increasing strain within the mass deriving principally from the unusual weight  of the tailings). In the case of Brumadinho the additional strain was brought on, according to their modeling, by increasing saturation of the previously unsaturated layer above the chronically , critically high water table within the structure.

The report settles some long speculated attributes of the failure itself and causes .
(1) the failure of the dam was caused by the flow failure of the tailings contained within it.( a failure of the dam itself did not precipitate the flow failure)
(2) the failure began at the top of the dam not at weak lower layers as some experts opined on viewing the video.
(3) there were no external triggers( explosions, earth tremors)
(4) the horizontal drilling program , the main element of Vales several year effort to de water the dam,was not the cause and the the structure recovered quickly from the June 11 2018 hydro fracture event
(5) no drilling or other work on the dam contributed to or triggered the failure.
(6) there were no deformations one would associate with a normal tailings dam about to fail and Vale’s very high tech monitoring system detected none of any concern.

The report settles the widely held speculation that something more could have been done to prevent failure because the main conditions of concern were known pre-failure. The panel specifically noted  that little change had occurred in the water table over Vale’s focused and intensive 3 year effort to de water  due to  continuous influxes and the poor hydraulics of the stack itself .

The panel confirms that Vale did conduct a stability analysis for every raise, a basic of good practice. But  the limitations in “sophistication” , suitability to actual conditions and reliability of results on which Vale in house and consulting engineers based their conclusions and decisions are noted.

Vale’s geotechnical team insisted on  one model for all stability analysis which is not correct procedure. Tuv Sud complained about that in their 2017 stability report.  Vogbr complained about Vale requiring a specific model and supplying the data for that model at Samarco. It is important to select the correct method for liquefaction analysis for the conditions, stress and loading concerns at that moment in time and having the technical capacity at hand to apply and interpret the results of those analytic methods. One model for all situations, as Vale required does not satisfy that requirement.  Further, the specific model Vale insisted be used for all government required stability analysis is only appropriate for assessment of prospective changes in the structure, for example dam raises.  It is not appropriate for assessing actual conditions of a structure at any point in time.

The panel, because of the contractually imposesd limitations  on “technical causes” does not mention Vale’s imposition of a particular  model on all its consultants for all official stability analysis . The panel due to this limitation on its inquiry was not in a position to offer comment on Vale’s policy of one model for all situations or to comment on whether a licensed engineer functioning as an independent expert ( as required under Brazilian Law) should agree to  use of a model it does not feel is suitable to actual conditions.

TUV SUD, after failure refused to certify any more dams under Brazilian Law where its checklist risk of failure lead to a proforma result of “little risk of failure”.  No engineer should be required to put its name and signature on a conclusion that is not its own.

The report in general does not conflict with any of the analysis  we had posted at World Mine Tailings Failures.    It does though add many new insights and additional data which we are in the process of including in our failure narrative.

The panel  specifically agrees that the design of the TSF itself was a major never corrected contributor to the failure. The panel only cites its steepness and the type of construction   (upstream)  and its poor hydrology without applying what existed as widely recognized standards e.g.  Vick’s that upstream should not be used if the tailings to be deposited are not 40% to 60% sand. or Davies et. al. on the cardinal rules for safe upstream construction ( size, slope, rate of raise etc.)  The report adds a fact that  had not been brought out in previous analysis associated with the dam’s initial design and history:  that the starter dam blocked a creek that had been draining up stream groundwater resulting in a recurring and continuous back up of groundwater  within the structure ( in addition to the inflow we note from the higher draining elevations to which the structure attaches.

The panel adds that a centerline setback undertaken  pre -Vale early in the life of structure contributed to failure in that future  raises built up from a foundation of finer less strong tailings.

It would be useful and fruitful to commission this exact panel to address all our other questions about whether Vale and its consultants executed a standard of care that met or exceeded prevailing practice.   Vale seems to have exceeded prevailing practice. They at least had an in house geotechnical staff and that staff put considerable store in mandated reporting and standards under  Brazilian Law .  Overall and on tailings Vale is right in the middle of the global pack on the various elements of the Responsible Mining Index 2018.

It would greatly contribute to the ongoing Global Tailings Review to have this same panel offer a civil society/best practices perspective on this same data.

(1) in mergers and acquisitions what tailings review should acquiring investors/owners  do of the tailings facilities that come with the deal. (Vale undertook none nor is it customary in most mergers and acquisitions to undertake such a review).
(2) after acquiring and before actually using a previously owned and built TSF’s, what is the appropriate due diligence? Prevailing practice seems to be to just continue to approved maximum  without a fundamental  re review of whether it affords suitable capacity for planned depositions.
(3) at the point where Vale acquired this facility were any corrections possible that would have allowed safe use for ultimate depositions up to approved maximum height and capacity?
(4) could the facility have been de watered to safe levels for decommissioning or re mining given the continuing influx of ground and surface waters, the expected annual rain fall and the inherent deficiencies and inadequacies of the dams hydraulics?
(5) are the aberrant characteristics of these tailngs present in other irons tailings depositions and are they an issue only where undrained conditions can form and prevail?
(6) how should tailings of these characteristics be managed?  would they have been safe in a centerline or downstream or do they need to be in a lined engineered  in ground facility?
(7) what measures to de risk are available once a TSF attains the state this facility was in 2013.

About lindsaynewlandbowker

Bowker Associates, Science & Research In The Public Interest, is an independent non profit providing self initiated pro bono analysis on key issues with a potential for massive adverse environmental impact . Bowker Associates has been an internationally recognized and cited voice in analysis of the Samarco failure, its consequence, and the possibilties for recovery. In 2017 we partnered with Daveid M. Chambers, a world leader in responsible mining, in our third joint work on the economics of tailings failures. Bowker, L.N.; Chambers, D.M. In the Dark Shadow of the Supercycle Tailings Failure Risk & Public Liability Reach All Time Highs. Environments 2017, 4, 75. A peer reviewed journal published investigation of the cowboy economics of the supercycle and the resulting escalation on the number and magnitude of catastrophic failures. In 2016 we parnered with Dave Chambers in our 2nd joint work together looking at root causes of failures at a conference . Bowker, L.N.; Chambers, D.M. Root Causes of Tailings Management Failures: The Severity of Consequence of Failures Attributed to Overtopping 1915–2015. In Proceedings of the Protections 2016, Fort Collins, CO, USA, 14 June 2016. [Google Scholar] In 2015 Bowker Associates collaborated with geophysicist David M. Chambers to recompile global authoritative accounts of significant TSF failures in recorded history and to analyze these data in the context of global mining economics 1910-2010 ( Risk, Economics and Public Liability of TSF Failures, Bowker/Chambers July 2015) The third annual update of this globally referenced and used compilation was just released at Researchgate. ( In 2014 Bowker Associates commissioned globally respected geophysicist and hydrogeologist Dr. David Chambers to undertake two technical works: (1) development of technical go no go criteria for vetting mine applications tp:// and (2) a case study of Maine's Bald Mountain, an un mined low grade high risk VMS deposit demonstrating the efficacy and accuracy of two risk assessment tools in vetting mine proposals In Maine, Bowker Associates has deeply engaged and been a public voice in the Searsport DCP LPG Tank, The Cianbro proposal for a Private East West Toll Road, JD Irvings rolling pipeline of Bakken crude to its plant in St. John and review of Phase II plans at The Callahan Superfund site in Brooksville, Maine, and Maine's revisitation of mining in statute and regulation... Our only “client”: is always “the pubic interest”. Our model is to focus on only one or two issues at a time so that we have a substantive command of the relevant field as our foundation for ongoing engagement. Our core work is in envirommental risk management, science and technology as well as bringing any available “best practices” models to the fore. The legal and regulatory history/best models are also a major thrust of our work in building and evaluating public policy. Director/Principal Lindsay Newland Bowker, CPCU, ARM is a recognized expert in Environmental Risk Management., Heavy Construction Risk Management and Marine and Transit Risks and has more than 3 decades of engagement in buiding public policy. Appointed by Governor Mario Cuomo to New York State Banking Board (served 1986-1996); President New York Chapter Chartered Property and Casualty Insurers; Environmental Committee, Risk and Insurance Management Society; Director, Convenor/Co-Chair Bermuda Market Briefing "From Captive to Cats" Hamilton Bermuda. Published Articles of Significance The Risk Economics and Public Liability of Tailings Facility Failures, co-authored with David M. Chambers, July 2015 Beyond. Polarization: Superfund Reform in Perspective, Risk & Insurance Managing Risk For Loss Prevention & Cost Control (Jan. 24, 1997). Lead Hazards and Abatement Technologies in Construction: A Risk Management Approach CPCU Journal 1997 Employee Leasing: Liability in Limbo Risk Management June 1 1997 Environmental Audit Privilege and the Public interest Risk & Insurance Managing Risk For Loss Prevention & Cost Control, April 1997 Asbestos:Holes In Abatement Policies Need To Be Plugged, Lloyd’s Environmental Risk International, May 1993 Editor Published Letters Evironmental Risk Management Beware of Facile Policies Like Fetal Protection Business Insurance 1995(?) High Court Review May Increase Sale of Bank Annuities Business Insurances August 8, 1995 Professional Profiles Protecting the Big Apple’s Core Managing Risk For Loss Prevention & Control December 1996 Major Career Highlights First rigorous analysis showing Relationship Between declining ore grades and TSF Failures of increasing consequence ( July 2015) FIrst Documentation that Gentrification Has Same Impacts as Unassisted Displacement from Urban Renewal Sites Direted Court Ordered EIS of FHA Mortgage Scandal Created Nation's First Homeownership Program for Low Income People (SHIP) Created Earliest Geographic Information Systems Using Defense Technology Developed By IBM Designed and Conducted Parallel Census Count to Show Systematic undercount in minority neighborhoods Documented Bias in ISO Territory Rating Plans for Private Passenger Auto Insurance Using ISO's own Rating Techniques Demonstrated Inherent Bias in Mortgage Policies of Banks With Inner City Branches Demonstrated that NY Telephones Plan for Area Code Split To accommodate anticipated cell phone demand was not efficient and would exhaust in 5 years ( which it did) Undertook First Systematic Evaluation of Child Protective Services Caseload Using Multi Variate Analyic Techniques Developed Child Protective Caseload Management and Tracking System (CANTS) and directed implementation in 4 client states including Illinois, Florida and New York Created and Ran Office of Risk Management for NYC DEP the Nations largest Water & Sewer Authority . Designed, Created and Administered Nation's First Owner Controlled Insurance Program (OCIP)for High Risk Tunneling Education Masters NYU Graduate School of Public Administration BSC New School For Social Research Maine Public Schools Deering High School
This entry was posted in Brumadinho Expert Panel Failure Report, Brumahindo Dam Failure, Catastrophic Tailings Failures, Causes Of Catastrophic Tailings Dam Failures, Creep Rupture, Flow Failure, Global Tailings Review, Lindsay Newland Bowker, Rate of Raise for Upstream Tailings Dams, Responsible Mining Foundation, Responsible Mining Index 2018, static liquefaction, Tailings Dam Risk Management, Tailings Hydrology, Tailings Storage Facility Failures, TSF Risk Management, Uncategorized, Upstream Tailings Dam Safety, Vale Indictments, World Mine Tailings Failures. Bookmark the permalink.

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