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   From: morons@sfchronicle.com   
      
   Why the Oroville Dam Won’t Fail   
   February 12th, 2017 by Roy W. Spencer, Ph. D.   
      
   While it is said, “never say never”, after researching this   
   issue I’m pretty convinced that it would be nearly impossible   
   for the Oroville Dam to fail.   
      
   Even though it is an earthfill embankment dam, which can be   
   destroyed if the dam is topped, the following Metabunk graphic   
   demonstrates why the Oroville design is virtually fullproof:   
      
   The emergency spillway (which is now in use) drains excess water   
   along its 1,700 ft length when the lake level exceeds 901 ft. At   
   this writing the lake level is 902.5 ft, which is 1.5 ft. above   
   the lip of the spillway.   
      
   The water level would have to rise another 18.5 feet (!) in   
   order to reach the top of the dam itself, which would never   
   happen because the emergency spillway flow (which occurs over a   
   natural ridge made of bedrock) would handle the excess flow long   
   before the lake level ever reached that point.   
      
   Now, is there any scenario in which this might happen? I’m not a   
   hydrologist, so I can’t answer that. But if there was a sudden   
   warm spell in the next few weeks with say, 10-20 inches of rain   
   over the watershed melting most of the mountain snowpack, adding   
   tremendously to the inflow into the lake, I’m sure we would see   
   a much greater flow over the emergency spillway. But I suspect   
   it would never reach the top of the dam itself. Nevertheless,   
   there would be a massive flooding event downstream in the   
   Feather and Sacramento Rivers.   
      
   79 Responses to “Why the Oroville Dam Won’t Fail”   
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   Curious George says:   
   February 12, 2017 at 10:22 AM   
   Fullproof?   
      
   Reply   
   Eric Barnes says:   
   February 12, 2017 at 10:49 AM   
   A play on words.   
      
   Reply   
   Curious George says:   
   February 13, 2017 at 9:12 AM   
   Nothing is foolproof because fools are so ingenious.   
      
   Reply   
   Donna says:   
   February 13, 2017 at 11:53 AM   
   Isn’t that what they said about the Titanic..   
   For that matter isn’t that what they told Noah…   
   Interesting that this sanctuary state who hopes to secede has   
   already asked for 200 million in federal funds. I say let God   
   deal with them.   
      
   Reply   
   ren says:   
   February 12, 2017 at 10:26 AM   
   2017 WY Precipitation Summary   
   provided by the California Cooperative Snow Surveys   
      
   For the period Oct 1, 2016 to Jan 31, 2017   
   Report generated: 02/09/2017 10:52   
   https://cdec.water.ca.gov/cgi-progs/precip/PRECIPSUM   
      
   Reply   
   Ric Werme says:   
   February 12, 2017 at 11:06 AM   
   Oh, WY is Water Year, not Wyoming. Mutter, mutter, mutter.   
      
   I usually spell out New Hampshire because NH could refer to   
   Northern Hemisphere.   
      
   Reply   
   ren says:   
   February 12, 2017 at 10:35 AM   
   Daily Precipitation Summary   
   February 11, 2017   
   24-hours ending at midnight   
   for selected automatic-reporting rain gages   
   (Provisional data, subject to change)   
   Report generated: 02/12/2017 08:09   
   https://cdec.water.ca.gov/cgi-progs/precip/DLYPCP   
      
   Reply   
   ren says:   
   February 12, 2017 at 10:46 AM   
   Daily Snow Sensor Report   
   February 10, 2017   
   Provided by the California Cooperative Snow Surveys for selected   
   automatic reporting snow gage sensors   
   Report generated: 02/10/2017 08:46   
   https://cdec.water.ca.gov/cgi-progs/snowsurvey_sno/PAGE6   
      
   Reply   
   Ric Werme says:   
   February 12, 2017 at 11:03 AM   
   That’s pretty much my thinking. There could be problems if   
   erosion of the main spillway climbs all the way uphill, but it   
   looks like if it reaches the low slope portion, there’s likely   
   bedrock under it. If it gets above that, the water will have a   
   lot less erosive force.   
      
   What may be a problem is that the reservoir has pretty much lost   
   its flood control utility for a while. However, while the   
   outflow is impressive, it needs to double before the immediate   
   down stream towns would be imperiled.   
      
   It might still be a good week to leave town.   
      
   It’ll be impressive to see what it all looks like when the   
   spillways are no longer in use.   
      
   Reply   
   ren says:   
   February 12, 2017 at 11:19 AM   
   Forecast.   
   https://accuweather.brightspotcdn.com/dims4/default/a6e0e70/2147   
   483647/resize/590x/quality/90/?url=http%3A%2F%2Faccuweather-   
   bsp.s3.amazonaws.com%2F86%2F43%2F8fb0686a47b6b2c19077ea06838   
   1%2Fstatic-west-us-mid-pattern-m-to-w.jpg   
   https://accuweather.brightspotcdn.com/dims4/default/6c460d2/2147   
   483647/resize/590x/quality/90/?url=http%3A%2F%2Faccuweather-   
   bsp.s3.amazonaws.com%2Fb9%2F2e%2F7bbba33649bb9f77a28eacb5f0c   
   3%2Fstatic-west-storms-return.jpg   
      
   Reply   
   Pete Mack says:   
   February 12, 2017 at 12:00 PM   
   The dam could never fail directly, it’s true. But the hillside   
   next to it could fail–water with that kind of energy can easily   
   erode rock, via ‘hydraulic mining’, and rock in the Sierra is   
   not good quality–mostly shale.   
   If the rock were to erode back to the spillway, the spillway   
   superstructure would collapse, leading to an uncontrolled   
   breakaway; in that case, the entire hillside would eventually   
   wear away. It’s happened before. It wouldn’t be quite as   
   catastrophic as a dam collapse–there’d be plenty of time to   
   evacuate. But it still would do massive damage downstream.   
      
   Presumably the emergency spillway has been judged adequate to a   
   sustained load. But with continuous use, it would eventually go   
   down. It’s how natural water gaps open in the first place.   
      
   Reply   
   Beyond Concerned says:   
   February 12, 2017 at 3:32 PM   
   If hillside erodes enough then the spot where the dam is   
   attached to it would be compromised. First it would cutback up   
   the spillway and then the whole thing would go.   
      
   Reply   
   Pete Mack says:   
   February 12, 2017 at 7:37 PM   
   Well, that didn’t take long. So much for ‘judged adequate for a   
   sustained load.’   
      
   --   
   More than a decade ago, federal and state officials and some of   
   California’s largest water agencies rejected concerns that the   
   massive earthen spillway at Oroville Dam — at risk of collapse   
   Sunday night and prompting the evacuation of 185,000 people —   
   could erode during heavy winter rains and cause a catastrophe.   
      
   Those agencies included the Metropolitan Water District of   
   Southern California, which provides water to 19 million people   
   in Los Angeles, San Diego and other areas, along with the State   
   Water Contractors, an association of 27 agencies that buy water   
   from the state of California through the State Water Project.   
   The association includes the Metropolitan Water District, Kern   
   County Water Agency, the Santa Clara Valley Water District and   
   the Alameda County Water District.   
        
      
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