The California Department of Water Resources (DWR) has issued an evacuation order downstream of Oroville dam. According to an alert by KRCTV.com,
A hazardous situation has developed with the Oroville Dam auxiliary spillway. Officials say that operation of the auxiliary spillway has lead to severe erosion that could lead to a fa
Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville.
In response to this developing situation, DWR is increasing water releases to 100,000 cubic feet per second. Immediate evacuation from the low levels of Oroville and areas downstream has been ordered.
The Department of Water Resources is now anticipating failure of the auxiliary spillway within the hour.
This is a tragic development, even more so because the possibility of failure of the Oroville auxiliary spillway due to severe erosion was raised repeatedly by environmental groups and local agencies during relicensing of Oroville Dam by the Federal Energy Regulatory Commission.
California Water Research examined a 2005 legal filing in the FERC relicensing by Friends of the River and Sierra Club California which clearly described the risks of the unarmored spillway:
A single operational use or multiple operational uses (with failure to repair any preceding or cumulative damage) of the ungated spillway could result in a loss of crest control of Oroville Dam. A loss of crest control could not only cause additional damage to project lands and facilities but also cause damages and threaten lives in the protected floodplain downstream. An unarmored spillway is not in conformance with current FERC engineering regulations. (emphasis added.)
In response, the Department of Water Resources reportedly denied there was a risk of loss of crest control if the auxiliary spillway was used, but did not provide any geotechnical information for the environmental groups to examine. The Department of Water Resources also argued that a feasibility study of armoring the auxiliary spillway with concrete should be financed as a flood control project by the US Army Corps of Engineers. DWR never requested a feasibility study by the Corps for armoring the spillway. The armoring project was also likely ineligible for funding as an Army Corps of Engineers flood control project because DWR has the obligation of controlling releases from the dam.
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Sondi has some good replys to your interesting and valid reports on Oroville Dam failure possiblities, and repairs that have taken place. These show that DWR has been open to that degree, and we need more reports like this. I have hopes that the dam failure options for leaving downstream areas in reports to the people (in case this happens) are available. This is important, possibly not reproduced here, but are sure to be there when communicating to them in the future.