Page 4 of 21 FirstFirst 1234567814 ... LastLast
Results 46 to 60 of 301

Thread: OT: Oroville Dam queries.

  1. #46
    Golden Bear oskirules's Avatar
    Join Date
    Aug 2010
    Location
    outside the matrix
    Posts
    5,443
    Quote Originally Posted by Phantomfan View Post
    I cant imagine how.

    This is the cycle for California and why our water system is designed like this. It is more apparent now with somewhat more severe weather, but this isnt the first time in the last 25 years.
    Five year cycles, yes, but the overflow has never been used in the dam's history.

  2. #47
    [QUOTE=concordtom;842808076]Without looking at it, I suspect this is the account of the SJ Merc article linked previously. I heard the following on the radio this morning.

    12 years ago there was an attempt to sue (so as to force) for construction of the overflow emergency spillway to be given a concrete path rather than the current dirt path, which is now degrading RAPIDLY. Instead, the water agencies that would have had to pay for this backup concrete path, which would only be used if the actual spillway failed (which is what has happened), argued that it was not necessary.

    Well, now the main spillway has failed, and water was sent over the emergency spillway, but the water degraded the path so fast that the entire hill is in jeopardy.

    The main concrete dam will not fail. But the rapid erosion occurring at the spillway and emergency spillway does mean that the water could all be let out of the lake above. Erosion is just pulling the hill down. Hopefully we can make it past this winter without catastrophe.

    Had the nervous nellies 12 years ago been heeded, none of this would be happening. I'm sure the people who argued against it are feeling like a pile of crap, because not only have 200,000 evacuated their homes, but the price tag involved is going to be tremendous.

    To repair the main spillway was said to be $200M.
    But now they are going to have to also repair the emergency spillway area.

    Here are pictures of what happened.



    This is the main spillway. Water started shooting at irregular angles, so they shut it down to inspect. This photo was taken at that time.
    Concerned that this would damage things worse, they decided to let the water rise and I suppose test the Emergency Spillway path.




    Below is the dam on the Right. You can see the extent of the damaged spillway on the middle, it's carved a path to the right, eroding the dirt hill. And on the left is the emergency spillway, as of this photo it was unused and so mostly naturalized in appearance (red dirt area).




    And below is the water as it began to flow over the Concrete Lip of the Emergency Spillway



    And below is the result of what happened to the earth (erosion) after all that water flowed over the Emergency Spillway.




    So now I guess they are back to running water back down the main Spillway, and dealing with whatever damage they suffer there.

    The threat is that either the hill below the main Concrete Spillway or the non-concrete Emergency Spillway erodes to the extent that either lip or the entire top of the restraint gives way, causing a huge rush of water downhill. This would flood or destroy towns, and wipe out levees and flood a huge massive area.

    My guess is it will play out until the rainy season ends in another 1-2 months, and then we'll have a huge repair effort and bill this summer.[/QUOTE. Excellent info. Thanks

  3. #48
    So is any of this water slated for Socal, or is it a fungible thing where more goes to Norcal, therefore Socal can take more through the aqueduct?

  4. #49
    True Blue Golden Bear Phantomfan's Avatar
    Join Date
    Jul 2008
    Location
    California
    Posts
    15,074
    Quote Originally Posted by okaydo View Post
    I agree. Both sides are to blame. My problem was the "social causes" thing. Has the California government really spent so much time on social causes?

    Frankly, it's all the fault of the Hoover Dam.

    The Hoover Dam gets all the attention. And yes, it's well deserved. But it takes the spotlight away from the Oroville Dam, which is the tallest dam in the United States. (Hoover is #2).

    Honestly, I never even heard of the Oroville Dam before this past week. And now I'm concerned because I hear it's in Butte County, and one of my favorite quarterbacks used to play for Butte College.
    haha

    I have known about Oroville and the lake for some time (my dads friend has a houseboat on the lake), and still had no idea how big it was.

    I agree on the "social issues." Maybe it does have an impact on the funding, but I suspect without any social programs, the budget for "spillway maintenance" would have been exactly the same.

  5. #50
    Quote Originally Posted by Phantomfan View Post
    haha

    I have known about Oroville and the lake for some time (my dads friend has a houseboat on the lake), and still had no idea how big it was.

    I agree on the "social issues." Maybe it does have an impact on the funding, but I suspect without any social programs, the budget for "spillway maintenance" would have been exactly the same.
    Social issues probably had as much of an impact on the Oroville Dam issues as the costs of Iraq War part deux and tax cuts for the rich did.

  6. #51
    Quote Originally Posted by burritos View Post
    Social issues probably had as much of an impact on the Oroville Dam issues as the costs of Iraq War part deux and tax cuts for the rich did.
    Iraq War and Tax Cuts for the rich >>>> Federal government

    Responsibility for maintaining Oroville Dam and tax increases for the rich >>>> California state government

    Nice try though.

  7. #52
    Quote Originally Posted by oskidunker View Post
    Excellent info. Thanks
    I should have made it more simple.

    There are 3 ways for water to exit the lake behind the dam:

    1. Bottom of dam, where electric power is generated. All is working fine here. It just can't process the amount of water coming into the lake above.

    2. Main Spillway, concrete runway handles excess amounts. You don't get to collect electricity on this, but you maintain the lake level properly this way by opening or closing the gates.

    3. Emergency spillway. It's the backup if there is any problem with the Main Spillway (as happened here). Never been used before this event. Only can be used if water runs over the top lip, like a bathtub too full. Has no gates. Has a concrete lip, but then water runs over dirt/rock/trees. Problem is, the backup design sucks, because it just erodes itself. See photos in prior post.

    Thus, after flipping back and forth between erosion on both of the spillways to get rid of excess, they have gone back to the Main Spillway. That will hopefully erode safer than the backup.

    Wait until rains are over in 1-2 months to see if the mountain held.
    Last edited by concordtom; 02-13-2017 at 03:18 PM.

  8. #53
    Quote Originally Posted by RioDelMarBear View Post
    Closer to home, the Anderson Dam/Reservoir above Morgan Hill has too much water in it; a few days ago it was 91% full. It's not supposed to be more than 68% full because it could fail in the event of a major earthquake, and the dam itself is very close to the Calaveras Fault. $400M retrofit scheduled for 2020. They're releasing as much water as they can, but it'll be a few weeks before they get it down to an acceptable level. And more rain is on the way later this week.
    I owned a lot at the other end that was supposed to be "lakefront property" but the water never got close and i have to go around the corner just to see the lake. I guess this would be a good time to see if I actually had "lakefront property". i bought it because I knew there were going to actually make 101 a freeway there (you had to go through the town of Morgan Hill before), but as soon as they built the freeway, they put a moratorium on the sewer hookups. I ended up selling it to 14X what I paid for it but it took 25 years.

  9. #54
    Quote Originally Posted by BearGoggles View Post
    Iraq War and Tax Cuts for the rich >>>> Federal government

    Responsibility for maintaining Oroville Dam and tax increases for the rich >>>> California state government

    Nice try though.
    Thanks.

  10. #55
    Hey, if you are reading this "parentswerebears", you live up that way, no?
    Are you evacuated or are you not in the direct path?
    Hope you're okay.

  11. #56
    Unless the lake is full, the only way for water to exit is from the penstocks at the bottom of the dam, whether or not the water is used for generation.

    Spillways can only be used if the lake is full, although some concrete dams have internal spillways that can be used even if the lake is not full.

    Emergency spillways are a feature of an earth filled dam. Concrete dams like Hoover and Shasta do not have emergency spillways. Instead water flows over the top of the concrete
    dam with no danger of erosion. Also concrete dams typically have the main spillway built into the dam; however due to the danger of erosion, earth fill dams will have their spillways
    physically separated from the dam to protect the dam from erosion by the spillway.

    Dam operators can open the penstocks and release extra water in excess of the needs for power generation
    to lower the dam level in anticipation of spring runoff. However increased water releases at higher pressures due to higher lake
    levels can create major erosion and water flow damage downstream. Dam operators may try and maintain
    mandated release rates until the water goes over the spillway. Although much newer, the spillways for the
    Oroville Dam look much smaller than those on the concrete Shasta Dam. It may have been determined that due
    to the dam's height the spillway volume was reduced to protect structures in the bottom of the canyon. Or
    it could be that Shasta Dam was planned to be 200 feet taller and need a more robust spillway. Even though
    the design change lowering Shasta 200 feet is quoted on the internet; I think it is an alternative fact.

    The main north south railroad and hiway on the West Coast goes through the Upper Sacramento River Canyon.
    Over 50 miles of Hiway and railroad had to be relocated, the new Pit River hiway and railroad bridge was among the
    world's highest bridges when built. A dam 200 feet higher would have required possibly hundreds of miles of new
    railroad and hiway right of way. I think the so-called 200 foot higher dam plan was an early concept quickly discarded.
    I don't think the lake formed by the higher dam would have ever been filled.


    Quote Originally Posted by concordtom View Post
    I should have made it more simple.

    There are 3 ways for water to exit the lake behind the dam:

    1. Bottom of dam, where electric power is generated. All is working fine here. It just can't process the amount of water coming into the lake above.

    2. Main Spillway, concrete runway handles excess amounts. You don't get to collect electricity on this, but you maintain the lake level properly this way by opening or closing the gates.

    3. Emergency spillway. It's the backup if there is any problem with the Main Spillway (as happened here). Never been used before this event. Only can be used if water runs over the top lip, like a bathtub too full. Has no gates. Has a concrete lip, but then water runs over dirt/rock/trees. Problem is, the backup design sucks, because it just erodes itself. See photos in prior post.

    Thus, after flipping back and forth between erosion on both of the spillways to get rid of excess, they have gone back to the Main Spillway. That will hopefully erode safer than the backup.

    Wait until rains are over in 1-2 months to see if the mountain held.

  12. #57
    True Blue Golden Bear NYCGOBEARS's Avatar
    Join Date
    Jan 2012
    Location
    The Island of Manhattan
    Posts
    24,263
    Quote Originally Posted by oskirules View Post
    Five year cycles, yes, but the overflow has never been used in the dam's history.
    Thus the lack of urgency in an expensive repair.

  13. #58
    Quote Originally Posted by oskidunker View Post
    How could the guy in charge of the dam say he was not aware of the 2005 report that said the emergency overflow should be reinforced with concrete? Was he hired yesterday? Would it have been prudent to be aware if the history of the dam?

    Maybe a better reply would have been,"I knew about that but we were not given the money to do it". Likely truth
    You get paid to not be a problem

  14. #59
    Quote Originally Posted by sp4149 View Post
    Unless the lake is full, the only way for water to exit is from the penstocks at the bottom of the dam, whether or not the water is used for generation.

    Spillways can only be used if the lake is full, although some concrete dams have internal spillways that can be used even if the lake is not full.

    Emergency spillways are a feature of an earth filled dam. Concrete dams like Hoover and Shasta do not have emergency spillways. Instead water flows over the top of the concrete
    dam with no danger of erosion. Also concrete dams typically have the main spillway built into the dam; however due to the danger of erosion, earth fill dams will have their spillways
    physically separated from the dam to protect the dam from erosion by the spillway.

    Dam operators can open the penstocks and release extra water in excess of the needs for power generation
    to lower the dam level in anticipation of spring runoff. However increased water releases at higher pressures due to higher lake
    levels can create major erosion and water flow damage downstream. Dam operators may try and maintain
    mandated release rates until the water goes over the spillway. Although much newer, the spillways for the
    Oroville Dam look much smaller than those on the concrete Shasta Dam. It may have been determined that due
    to the dam's height the spillway volume was reduced to protect structures in the bottom of the canyon. Or
    it could be that Shasta Dam was planned to be 200 feet taller and need a more robust spillway. Even though
    the design change lowering Shasta 200 feet is quoted on the internet; I think it is an alternative fact.

    The main north south railroad and hiway on the West Coast goes through the Upper Sacramento River Canyon.
    Over 50 miles of Hiway and railroad had to be relocated, the new Pit River hiway and railroad bridge was among the
    world's highest bridges when built. A dam 200 feet higher would have required possibly hundreds of miles of new
    railroad and hiway right of way. I think the so-called 200 foot higher dam plan was an early concept quickly discarded.
    I don't think the lake formed by the higher dam would have ever been filled.
    okay, you know more than me.
    So let me ask you this...

    If they've been able to lower the lake 50' today (or before the next rain, can't recall what I heard), how have they lowered it the last 24 hours? Thru the main spillway or thru the penstocks? And if thru the penstocks, why didn't they do that faster sooner?

    I guess it all has to do with how much was running into the lake from the most recent storm(s) and if they restricted penstocks flow per requirements (and if they are ignoring that and running more thru the bottom now).

    Thanks.
    It's interesting, I have never paid attention to dams before (like most). I'm sure dams across the nation will now be getting lots of funding. Works projects, if not safety issues.

  15. #60
    This is not a R or D thing-- it's an American thing. States everywhere, and the feds, run by both parties, have neglected crucial infrastructure maintenance and upgrades. That's human nature: if you can't see it, or the consequences aren't staring you in the face, the inclination is to ignore the problem.

    The water agencies in 2005 probably opposed reinforcing the emergency spillway because they knew they didn't have the money and the had no good way to raise it. The same can be said for any number of structures in both conservative and liberal states. The only thing we can all agree on is that decades of neglect will begin to catch up to us and the next several years should see more potential catastrophes like this.




Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •