Last winter was one of the wettest winters in California in nearly a century. The record rains caused significant damage to the spillway at Oroville Dam, leading to the mass ordered evacuation of nearly 200,000 people from communities downstream from the dam. The damage to the dam prompted the first-ever use of an emergency spillway to release water from Lake Oroville.
As the start of the rainy season in California looms, here is an update on the present status of the Oroville Dam situation.
The Department of Water Resources has announced the spillway is ready for winter. Total costs of repair ended up exceeding half a billion dollars, nearly double the original estimate. This figure only includes work done by the main contractor, Kiewit Corp., to repair the spillways. It does not include the costs of other contractors, nor the costs of the emergency response, including the evacuation. Furthermore, farms and residents living downstream from the Dam have filed over $1 billion in claims for damages that they blame on the deliberate releases of water to deal with the crisis.
A team of forensic experts has concluded that water entering through cracks or repair seams in the main spillway may have triggered crumbling of the spillway. However, they have also concluded that there were a number of problems in the original construction of the dam, including thin concrete, poorly placed drains and inadequate foundations. Their report faulted dam inspectors for relying too heavily on visual inspections of the dam, ignoring other evidence that could have warned them that the damage to the spillway was imminent.
[The leader of the forensic panel said that] Oroville was a wakeup call for dam inspectors everywhere, and urged them to go beyond the visual inspections that are typical for the industry.