Oroville Emergency Recovery – Spillways
Oroville Dam is one of the largest dams in the United States and a key feature of the California State Water Project, which supplies water to more than 27 million Californians.
During heavy winter rains in February 2017, the flood control outlet (FCO), spillway chute, and the emergency spillway at the Oroville Dam were severely damaged. Despite this damage, continuing heavy rains throughout that winter and spring meant the FCO had to keep operating. DWR immediately activated its Emergency Action Plan and continually informed the public and various agencies of the situation. The situation developed rapidly. At one point, the local sheriff evacuated more than 180,000 people when it appeared the emergency spillway would fail and cause a partial release of the reservoir.
DWR’s director immediately reached out to GEI to provide executive level support during the immediate emergency. Later, DWR asked GEI to provide engineering leadership for temporary, and then permanent, repairs to both the FCO and emergency spillway.
Temporary repairs to the FCO had to be completed in time to provide an operationally viable spillway by the following winter. Our teams had eight months. This tight schedule meant that construction had to begin before design completion, which required close coordination between designers and contractors.
GEI was instrumental throughout the entire project. Our integrated team conducted geotechnical, civil, and hydraulic analysis, and we developed alternatives, plans, and specifications. The final design included using roller-compacted concrete (RCC) and structural concrete to reconstruct the emergency and FCO spillways. GEI also assisted DWR by prequalifying contractors, estimating project quantities, and conducting constructability reviews.
Once construction began, GEI then provided construction services, including project management support, inspections, civil, hydraulic, and geotechnical engineering services.
The emergency repairs to the Oroville Dam spillway exceeded expectations. All temporary repairs were complete by November 1, which made the spillway operational during the next winter. All permanent repairs were completed the following year. Today, the Oroville Dam and spillway safely provide flood control, recreation, power generation, and water supply to the local community and the entire State of California.
Key Challenges
This billion-dollar mega-project had to be completed within one construction season to provide a functional FCO spillway before the subsequent winter. This unforgiving timeline meant that the integrated teams had to work through issues as they came up in construction without losing momentum. GEI engaged and collaborated with contractors to problem solve and re-sequence activities. Together, we developed alternative design details or approaches during construction.