Page - 65 - in Book of Full Papers - Symposium Hydro Engineering

The 2016-2017 Winter Storms brought record breaking precipitation to the Northern California Sierra mountains including the Feather River watershed. On February 7, 2017, the Oroville Dam’s 54.5 m (179-ft) wide Flood Control Outlet (FCO) Spillway chute (Fig. 1) was releasing water to control the Lake Oroville reservoir level in accordance with the prescribed operations plan. During this operation, the FCO spillway suffered a catastrophic failure of the lower chute area eventually resulting in the loss of approximately 427 m (1400 ft) of the lower chute, including the scour of more than 1.2 million m3 (1.6 million yd3 of soil and rock materials. On February 11, 2017, the Emergency Spillway (Fig. 1) was used for the first time since the project was completed in 1968. During this operation, significant erosion and scour caused by the Emergency Spillway overflow led authorities to fear for the safety of the spillway structures, resulting in the activation of the Emergency Action Plan and evacuation of about 188,000 persons from downstream communities. Fig. 1 Flood Control Outlet (FCO) Structure and Emergency Spillway, March 2011 This paper is part of a series developed by the State of California, Department of Water Resources (DWR) to describe the Oroville Spillway Incident Emergency Response and Recovery. This paper focuses on the design and construction processes employed in 2017 to safely allow the dam to pass 65