Findings of the Oroville Dam Spillway Forensic Investigation: On-Demand

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At a height of 770 feet, Oroville Dam is the tallest dam in the United States. On February 7, 2017, a section of the concrete chute slab of the service spillway at Oroville Dam failed during spillway discharge. Several days later, as the California Department of Water Resources was evaluating and managing discharges through the damaged service spillway during a large rainfall event, the emergency spillway activated for the first time in the project’s history. The emergency spillway flow resulted in significant erosion of the hillside below the crest structure, leading to concern for the integrity of the emergency spillway and the evacuation of nearly 190,000 downstream residents. The Federal Energy Regulatory Commission mandated a forensic evaluation of the failure of the service spillway chute and the damage to emergency spillway. This webinar will present the findings of the six-person Independent Forensic Team, including discussions of physical factors, human / organization factors, and lessons to be learned from the incident.

John W. France, P.E., D.GE, D.WRE

President, JWF Consulting, LLC

JWF Consulting, LLC.

Mr. France has more than 45 years of consulting engineering experience. Most of his technical work for the past 37 years has focused on dams and water retention structures. He has been responsible for the analysis, design, and construction of embankment and roller compacted concrete dams and their appurtenant structures. He has served on numerous senior technical review boards and panels for dam safety projects for the U.S. Department of the Interior, Bureau of Reclamation, U.S. Army Corps of Engineers, BC Hydro, and Brookfield Renewable Energy. Mr. France was the team leader for the Independent Forensic Teams tasked with investigating the 2017 Oroville Dam, CA spillway incident and the 2020 failures of Edenville and Sanford Dams, MI.

OUTLINE

FINDINGS OF THE OROVILLE DAM SPILLWAY FORENSIC INVESTIGATION

Introduction
1. Purpose of the Investigation
2. Investigation Team
3. Investigation Methodology
Background Information
1. Oroville Facility Description
2. Regulatory Setting
  - i. Federal Energy Regulatory Commission (FERC)
  - ii. California Division of Safety of Dams (DSOD)
3. Spillway Descriptions
  - i. Service Spillway
  - ii. Emergency Spillway
4. Chronology of the February 2017 Incident
5. Service Spillway Chute Design and Construction
6. History of Service Spillway Chute Repairs
7. History of Service Spillway Drain Flows
Question Period #1
The Physics of What Happened
1. Service Spillway
2. Emergency Spillway
Question Period #2
Why Was This Performance Unexpected
1. History of Inspections and Regulatory Setting
2. Geological Evaluations
3. Chute Slab Repairs
4. Potential Failure Mode Analyses (PFMAs)
5. Activation of the Emergency Spillway
6. Conclusions
Lessons to be Learned