by Bob Walsh
It is November 1 as I write this. That is the self-imposed deadline by DWR to get the initial repair of the Oroville Dam principle and secondary spillways ready. They claim they have been successful. That's good because a significant storm could hit as early as Thursday, though the lake is well below maximum level right now.
DWR officials now assert that the current spillway is able to handle up to 100,000 CFS, twice the amount of water that was pouring out of the damn dam when the old spillway failed.
The current main spillway is about 3,000 feet long. The very top section has only been patched. It is scheduled for a full rebuild next year. One section has been rebuilt with less-durable roller compacted concrete and will have to be further built up and faced with different concrete next year. Two other sections have been fully rebuilt and are now firmly anchored to bedrock with a shitload of erosion resistant concrete. Also next year they will cover the face of the emergency spillway with concrete (rather than the current bare dirt) so it will actually be usable in case of an emergency.
DWR is seriously considering a second spillway at the dam.
So far the repairs have been about $500 million, about 75% of which is supposed to be covered by the feds. The original guesstimate was about $260 million. It seems that the underlying rock was in much worse shape than expected, requiring much more excavation and much more concrete than originally estimated.
A total of 93 other dams around the formerly great state of California are being evaluated and repaired. The state ordered an extensive inspection and review of these dams after the near-catastrophe at Oroville early this year.
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