In February 2017, Oroville Dam‘s main and emergency spillways were damaged, prompting the evacuation of more than 180,000 people living downstream along the Feather River.
Heavy rainfall during the 2017 California floods damaged the main spillway on February 7, so the California Department of Water Resources stopped the spillway flow to assess the damage and contemplate its next steps. The rain eventually raised the lake level until it flowed over the emergency spillway, even after the damaged main spillway was reopened. As water flowed over the emergency spillway, headward threatened to undermine and collapse the concrete weir, which could have sent a 30-foot (10 m) wall of water into the Feather River below and flooded communities downstream. No collapse occurred, but the water further damaged the main spillway and eroded the bare slope of the emergency spillway.
- Evaluate the location and distribution of the drainage gallery beneath the undamaged portion of the spillway.
- Provide estimates of concrete thickness within the undamaged spillway
- Identify any potential voids at the base of concrete within the undamaged spillway
- Measure concrete velocities every 100 ft to evaluate variability
- If possible, identify the distribution of any rock discontinuities beneath the undamaged spillway