Oroville Dam Spillway Incident Report

Oroville Dam Spillway Incident Report

Jan 17th, 2018

The Oroville Dam Spillway Incident Report became public in January 2018. The story it tells is remarkably similar to the one we assumed, based on publicly available information in the aftermath of the accident. As risk advisers and managers we discuss below the various statements in the Oroville Dam Spillway Incident Report. We aim at highlighting risk biases and potential management changes to avoid similar developments.

Author: Dale Kolke / California Department of Water Resources

Oroville Dam Spillway Incident Report Conclusions Commented

The Independent Forensic Team Report made a number of conclusions as follows, with our comments:

Incident causes and responsibilities

  • The cause of the Oroville Dam spillway incident was a long-term systemic failure of the California Department of Water Resources (DWR), regulatory, and general industry practices to recognize and address inherent spillway design and construction weaknesses. In addition, poor bedrock quality, and deteriorated service spillway chute conditions caused the incident.

Indeed, this was a case of normalization of deviance over service life during which no one evaluated how the multi-hazard risk landscape of the system had evolved. Quantitative multi-hazard convergent, scalable and drillable risk assessments are paramount. Monitoring, near-misses and inspections should feed their updates.

  • The incident cannot reasonably be “blamed” mainly on any one individual, group, or organization…

Failures does not happen overnight and the “common practice” siloed management structure is certainly to blame, rather than any individual, group or organization. Abolishing the silo culture is paramount.

  • There was no single root cause of the Oroville Dam spillway incident, nor was there a simple chain of events …

Interdependencies and common cause failures need to be accounted for in the risk register (i.e. complex failure modes, domino effects, long chains of events).

The inclusion of complex failures modes would deliver to management a good perception of reality.

Crisis time risk tradeoffs

  • Responding to the damage to the service spillway chute necessitated difficult risk tradeoffs in times of crisis…

Yes, certainly, and risk tradeoffs may be extremely difficult when on top of actual uncertainties one finds a layer of “soft uncertainties” due to the lack of robust and uniform glossary, poor risk assessments, misleading conclusions. That becomes especially important in infrastructures with a long term service life. Foster clarity and transparency ensuring the use of robust and uniform glossary, train people to recognize hazards from risks, understand well made risk assessment, which are not using risk matrix based approaches.

  • …resulting decisions, made without a full understanding of relative uncertainties and consequences, allowed the reservoir level to rise above the emergency spillway weir for the first time in the project’s history, leading to severe and rapid erosion downstream of the weir and, ultimately, the evacuation order.”

Decisions made under stress, in fear and under poor information are indeed oftentimes ill-guided and tend to look to the short term and forgetting the longer term. Risk assessment should describe the multi-hazard risk landscape, and deliver understanding of uncertainties and multi-dimensional consequences.

  • Following the unexpected chute slab failure and erosion, and subsequent closure of the service spillway gates to examine the damage, delicate and difficult risk tradeoffs, involving myriad considerations, were necessary over the next few days in order to manage the incident.

Risk informed decision making (RIDM) aka, although not exactly a synonym, risk based decision making (RBDM) allow specifically to manage those considerations. RIDM and RBDM are preparatory processes, not crisis-time reactions. Indeed, they should rely on adaptive hazards and risk registers that can easily update.

Inspections and monitoring

  • More frequent physical inspections are not always sufficient to identify risks and manage safety.

The inclusion of the quantification of mitigation efficiency in the risk landscape is paramount. That means performing residual risk assessments. The goal is to define a rational risk reduction roadmap.

  • Periodic comprehensive reviews of original design and construction and subsequent performance are imperative. These reviews should be based on complete records and need to be more in-depth than periodic general reviews (needs for risk repository), such as the current FERC-mandated five-year reviews.

As soon as conditions change the risk landscape should reflect those changes.

  • Qualified individuals must give attention to appurtenant structures associated with dams, such as spillways, outlet works, power plants, etc.. This attention should be commensurate with the risks that the facilities pose to the public, the environment. Efforts should include risks associated with high consequence events which may not result in uncontrolled release of reservoirs.

Properly defining the system should be the 2nd step when preparing a risk assessment, (after defining the system). Third step is to define performance and failure criteria .

Geoethics and risks, compliance with codes

  • Compliance with regulatory requirements is not sufficient to manage risk and meet dam owners’ legal and ethical responsibilities. Some of these general lessons are self-evident. Others noted them before the IFT’s investigation of this incident.

To maintain SLO and a good CSR, mere following regulatory compliance criteria is inadequate. Fostering continuous communication and consultation including explanations of necessary risk tradeoff is paramount.

Closing remark

If you are in charge of a dam, or any other hydraulic, energy, geo infrastructure contact us. We will support your program to deploy a full risk and crisis management approach setup using ORE, our proprietary methodology. It is not a matter of complying with obviously already existing codes. It is the matter of fostering a strong and defensible geoethical stance, sustainable operation and a valuable operation.

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Category: Consequences, Crisis management, Hazard, Mitigations, Probabilities, Risk analysis, Risk management

One response to “Oroville Dam Spillway Incident Report”

  1. Don Colson says:

    This report fails on two accounts. The IFT actually found the root cause of the failure, but the did not follow though. This Spillway was not built as intended, DWR’s Construction Inspectors changes the requirements for the foundation. The second issue was not wanting to say anything that would hold those accountable for the decision to allow the lake level to rise above the Emergency Spillway.
    In addition they included at false story about a young design engineer. This is totally false. All I
    need to say is please read the USBR Hyd-510 Model Study. Among other things the Hydraulic Study by the IFT does not accunt for the poorly designed Headworks. This failure has always been just a matter of time. Yes, the IFT has a lot of good information, they could find this because they were not restricted like others by the misapplication of the CEII Regulation for DWR.

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