Page - 53 - in Book of Full Papers - Symposium Hydro Engineering

actions, all threats and risks, contingency plans, and mitigation measures. Due to the complexity of the organization, it was critical to remind the team that decisions needed to be made within the organizational structure. Due to the size of the emergency, limited data, competing priorities and/or regional impacts, conflicting recommendations were occasionally passed along to decision makers. These more difficult decisions were elevated up to the POC, DOC, and the Acting Director of DWR. The following sections provide some examples of competing priorities and reasoning for some of the difficult decisions that had to be addressed. 5.1.2 FCO Spillway Chute Condition The concrete within the FCO Spillway chute was being damaged and displaced with increasing flows and time. Water flowing down the FCO Spillway chute lifted large slabs of concrete, sending them down to the Feather River channel below. Weathered rock and adverse foundation conditions near the original spillway chute failure site were factors in the significant erosion of the underlying foundation rock. As the rock eroded, additional concrete was damaged and displaced. The failure propagated at a rapid pace, both in the upstream and downstream directions. The integrity of the FCO structure at the top of the spillway was critical to the safety of the dam and the potential for an uncontrolled release of the reservoir. Decision makers were also guarding against additional eroded rock in the tailrace, causing backwater affects to the Hyatt Powerplant, and the loss of the transmission line, resulting in the loss of the ability to release water from the reservoir through Hyatt Powerplant. 5.1.3 Emergency Spillway The Emergency Spillway was intended to protect the dam from overtopping and was not intended to be used during normal flood operations. If ever engaged, the hillside downstream of the control section was expected to experience significant erosion. In addition to surficial soil, further debris such as the trees that covered most of the hillside, would wash into the river channel and would compound issues with downstream structures. Therefore, the use of the Emergency Spillway during this emergency needed to be avoided if possible. 5.1.4 Weather, Forecasts and Modeling One of the most important aspects of the incident was the long collaborative working relationship DWR has with its mission critical partners. The National Weather Service in Sacramento and the California Nevada River Forecast Center are co-located with DWR at a Joint State Federal Operations Center (JOC) in Sacramento. This is the only location in the nation from which both Federal and State agencies provide weather forecasting, river and reservoir modeling, reservoir operations management, and management of flood emergencies. Working side-by- side 24/7 lays the foundation for a “One Mission, One Message” approach.. During this incident, DWR and its Federal partners at JOC were responsible for monitoring and for analyzing weather forecasts, river and reservoir flood routings, 53