Crews Race to Stabilize Vulnerable Oroville Dam Spillway
Crews dumping "super" sand bags, filling four gouges in the hillside as storm expected tonight
Work crews repairing Oroville Dam’s damaged emergency spillway are dumping 1,200 tons of rock each hour and using shotcrete to stabilize the hillside slope, an official with the Department of Water Resources told the California Water Commission today.
The pace of work is “round the clock,” said Kasey Schimke, assistant director of DWR’s legislative affairs office.
The Oroville Dam crisis began Feb. 7 when a crater appeared in the main concrete spillway. DWR temporarily halted releases from the reservoir in order to inspect the damage. Officials subsequently ramped-up releases again but also decided to use the emergency spillway to help release water from the rapidly rising reservoir.
Water poured over the emergency spillway Sunday for the first time in the dam’s history, eroding the dirt hillside. Fearing a catastrophe, officials ordered that people evacuate from the city of Oroville and surrounding environs as a precautionary measure. Releases from the main spillway were increased to 100,000 cubic feet per second (cfs) to help bring the lake’s level down below the emergency spillway. By 11 a.m. today, the lake stood at 877 feet, 23 feet below the crest of the emergency spillway, Schimke said. Meanwhile, 100,000 cfs of water continues to plunge down the main spillway. The inflow into the lake ranges between 15,000 cfs and 30,000 cfs.
The repair work, some of it being done by helicopter, aims to fill four gouges in the hillside below the emergency spillway. Crews are dumping “super” sandbags to help stabilize the ground, Schimke said. The Hyatt Power Plant at the base of the dam is not operating because of the build-up of sediment.
There is a bit of a race against the next storm system. The system could arrive as early as tonight and is expected to dump seven inches of rain during the next nine days. Some reprieve is expected because of a lowering of the snow level, Schimke said.