In California, crews are rushing to repair the Oroville Dam’s dangerously eroded emergency spillway. If the damaged area of the dam were to collapse, it would release a 30-foot wall of water into the Feather River. The precariousness of the situation led authorities to evacuate nearly 200,000 people downstream.
According to the Los Angeles Times, helicopters are depositing sacks of rocks into the hole created by the erosion, helped by dump trucks that are also patching up spots with rocks, and creating a slurry — a cementlike mixture — to plug everything in place. The urgent construction is a stopgap measure, one attempt to head off potential disaster in advance of another round of rainstorms expected Wednesday.
The crisis peaked Sunday, when engineers found the pocket of erosion under the emergency spillway — a concrete wall built to permit overflow when Lake Oroville hits capacity. The dam — the nation’s tallest — was built in 1968; and until this year, operators have never once relied on the spillway.
The emergency spillway came into use for the first time because of heavy rainstorms and snow, and the discovery of a large hole last week in the dam’s main spillway. But concerns about that problem have been set aside for the time being:
The goal is to lower the lake by about 50 feet below the top of the 770-foot dam, as more rain is expected later this week — potentially up to four inches. The main spillway is holding, but the release of such high volumes of water has flooded parts of the area — though not even close to the catastrophic inundation that could happen if the emergency spillway collapsed. Evacuation orders have not yet been lifted, and flash-flood warnings are in effect until at least Tuesday afternoon, local time, as emergency crews rush to beat the next impending storm.