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  1. CRM114

    Pre-Failure Oroville Dam Spillway Historical Images

    Great find. There is minute flow at the lip of the energy dissipator at the bottom of the spillway. I'd guess flow had just been shut off. The conditions are seemingly perfect for identifying these features, and from other closer up photos, they do seem to be cracks at least in the damaged...
  2. CRM114

    Pre-Failure Oroville Dam Spillway Historical Images

    I colorized the photo above at: http://demos.algorithmia.com/colorize-photos/ Then compared to Google Earth for a then vs now. They are quite badly misaligned, but some of the roads on either side are the same and can be used for orientation:
  3. CRM114

    Pre-Failure Oroville Dam Spillway Historical Images

    From: https://www.reddit.com/r/orovilledam/comments/5vzgoi/photo_spillway_construction_1965/
  4. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    Cracks are herringbone pattern, and spaced about 20 feet apart. (slab panels are 50 long in flow direction per Google Earth). I'm not saying it's underdrains, but....
  5. CRM114

    Oroville Dam Main Spillway Waterfall Erosion Watch

    I see what you mean. It's tough to tell. I added some lines for reference. I tried the same on your google pic, but it's sketchy to pick the top of wall.
  6. CRM114

    Oroville Dam Main Spillway Waterfall Erosion Watch

    It is. The right spillway wall looks to be leaning towards the flow. If so, there could be slab separation. I don't recall seeing that in previous photos, but it could just be the perspective. It is certainly not evident in this photo, but that was a long time ago...
  7. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    I missed this when posted, but note that the pipes are likely at different grades (slopes), giving them different carrying capacity. From all the evidence, the collector pipe is at the slope of the spillway.
  8. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    I think the spillway was running at 55,000 CFS when the hole developed, but yes, it's still a lot of water. From all the photo evidence, it's apparent to me flow in the drains goes up with more flow in the spillway. There is some evidence that flow in the drains has gone up over time, imo...
  9. CRM114

    Oroville Watershed Weather Forecast, Lake Level and Inflow Calculations

    There are physical reasons as well. Some reservoirs seep to deep groundwater, and there is some evaporation. 5000 cfs is a lot of that, though. To rule out evaporation: For Oroville, it's around 40 mm in Feb...
  10. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    A zoom of a pic by dierdre on the historical pics thread: https://www.metabunk.org/pre-failure-oroville-dam-spillway-historical-images.t8410/page-2#post-202175 Shows relatively low flow, but drains appear mostly dry or just trickling. But it's useful to compare to recent pics where much...
  11. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    It's good to compare these details with the photos compiled by wrorke: Oroville Dam Spillway Failure It looks like they may have added dowels to the longitudinal expansion joints between this study and final construction, but a lot of those photos seem to match these details.
  12. CRM114

    Oroville Dam Spillway Failure

    Based on what I have seen, most of the main spillway is not worth salvaging - too much seepage and too many cracks. As you point out it's risky to rebuild the main, as they really only have from May to January to do it. Other months are at risks of spills They could spend money on an...
  13. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    From deep in, Drawing A-389-4: https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/HYD/HYD-510.pdf This doesn't mean this is the way it ended up, but this is what they were thinking at one point. It sure does match the photo evidence, and the text descriptions, right down to the...
  14. CRM114

    Oroville Watershed Weather Forecast, Lake Level and Inflow Calculations

    Nice work. I had to use a fudge factor as well when looking at inflows vs. outflows. Any chance that fudge factor was about 5000 cfs leaving the reservoir unaccounted for?
  15. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    I think you may be right. FWIW, here is a photo from the other day for comparison, zoomed: http://pixel-ca-dwr.photoshelter.com/galleries/C0000OxvlgXg3yfg/G00003YCcmDTx48Y/I0000sA1kRFkUp6g/FL-Oroville-4173-jpg
  16. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    A French Drain is the general idea, yes. Dimensions on the gravel for the Oroville spillway drains would be bigger, I would guess.
  17. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    From: http://pixel-ca-dwr.photoshelter.com/galleries/C0000OxvlgXg3yfg/G00003YCcmDTx48Y/I00000Kzkg4IDq7U/KG-oroville-damage-12949-02-20-2017-jpg Zoomed and edited to saturate color. The drain on the left looks like it's running a little dirty.
  18. CRM114

    Oroville Dam Spillway Failure

    No. Dams in the US, at least where I've worked, are designed to handle the PMF. Depending on the state, smaller dams can get away with less than the PMF in many cases. Oroville's emergency spillway was specifically designed to handle the PMF, as it should be. See: Oroville Watershed...
  19. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    I think they still would have had gravel over the pipe allowing water to reach all perforations. The trench would be designed for the gravel and the pipe. I have designed these before and specify a minimum clearance of gravel around the pipe. The contractor is allowed to overexcavate rock up...
  20. CRM114

    Oroville Dam Drains in The Spillway Walls - How Do They Work?

    Yet there they are in the photo. There is always a gap between design and constructed versions. Engineers draw neat lines and contractors try to cut rock to a neat line, and an inspector splits the difference. A trench for a 6 inch pipe is mighty hard to cut in some rock without making it...
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