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roller-compacted concrete came to play a much more vital role in meeting the project objective of having a completed FCO Spillway chute by the November 1, 2017, deadline. This paper identifies and discusses specific dam safety risks and the evolution of the key structural design features that were developed to meet the project-specific design and public safety requirements, including critical reviews by state and federal regulatory authorities along with the independent Board of Consultants. 2. BACKGROUND The Oroville Dam Spillway Incident of 2017 was one of the most serious dam safety occurrences in the United States in many years. As the tallest dam in the United States and the keystone of California’s State Water Project, Oroville Dam and Lake Oroville stand as a steadfast monument to water resource development in the 20th Century. The Oroville Dam Spillway Incident has provided a testimony to the dedication of emergency response and dam safety professionals who came together to meet the challenges of a rapidly changing situation to assure the safety of the Oroville Dam and the public living downstream. Starting in Oroville, California, this incident will impact the dam safety profession around the world as the details of the incident, response, and recovery become fully known and realized. The original mission of Oroville Dam and Lake Oroville as part of the California State Water Project (SWP), was originally conceived as the following [1]: Oroville Dam and its appurtenances comprise a multipurpose project encompassing water conservation, power generation, flood control, recreation, and fish and wildlife enhancement. The Lake stores winter and spring runoff which is released into the Feather River as necessary, to supply project needs. The (United States) Federal Government shared in the cost of the Dam, which provides 750,000 acre-feet of flood control storage. The 15,805- acre surface of the Lake with a 167-mile shoreline provides water-oriented recreational opportunities. An incident such as this at the Oroville Dam spillways has many facets from beginning to end, along with many lessons learned. Along with others in this series of papers developed for the U.S. Society on Dams [2, 3, 4, 5, 6], this paper presents important technical details from those directly involved in the groundbreaking Herculean effort to recover from the incident in an expedited manner to protect and serve the people of California. With strong leadership from the Oroville Dam owner, the California Department of Water Resources (DWR), the Oroville Emergency Recovery Spillways Task Force pulled in professional resources from industry, including consultants, independent experts, regulators, and contractors to make the seemingly impossible into a reality of success based on pure determination, hard work, commitment, and dedication to the single mission of recovery. 88