53 replies to this topic

[Chris]

Teton dam, see that spillway to the left....?   Interesting......   Chris

 

 

[4thgenFolsomite]

Teton dam, see that spillway to the left....?   Interesting......   Chris

 

 

looks like they couldn't get the water out fast enough!  that is what they are trying to avoid at Oroville and what is always the big concern at Folsom (or any other concrete dam)

[2 Aces]

Just saw on Channel 3. There is some serious erosion going on, including washing out a frontage road. But no worries, "everything is fine".

[nomad]

What a cluster. These DWR guys have no clue even thought the spokesman the other day said " we have a lot of dam experts here on the job."

 

Evacuations? Who needs those? Let's wait until maybe 1 hour before the emergency spillway fails to call for that. 

 

Typical state mentality which is why that thing is in such poor condition to start with. 

[4thgenFolsomite]

its a big deal to call for the evacuation of 10s of thousands of people.  that kind of evacuation probably means you know some people will be killed just because of the evacuation order.  massive call-out of law enforcement and resources for CalFire, etc.  That's a big deal.  They were watching carefully and then noted the erosion on the back of the emergency spillway and then started the discussions for evacuation.  Its a joint decision on who calls it.  DWR can't call it on their own. They knew the water into the reservoir was decreasing and that the overtopping would stop soon, and it has.  I would rather they were safe than sorry.  

[4thgenFolsomite]

and now

 

confirmed fighting and looting in Oroville.  I guess not everyone was evacuating.

[caligirlz]

 

 

confirmed fighting and looting in Oroville.  I guess not everyone was evacuating.

Are you seeing that on twitter?

A couple of friends reported that as well, but I only could find 1 report on a twitter feed.

 

Just checked the Mercury News were I saw the twitter feed, and now I see this article. They knew about this issue 12 years ago. (incredible pictures in the article)

 

http://www.mercuryne...s-12-years-ago/

[nomad]

and now

 

confirmed fighting and looting in Oroville.  I guess not everyone was evacuating.

 

Fake news. Not happening. 

[Who_Do_You_Trust]

The rating system used to qualify structures like dams, spillways, levees, bridges, etc, drives the design of such structures to be able to withstand some extreme natural event that would occur only once in a particular time span.  

 

For example, the Folsom Dam, when originally built, was designed to be a "100 year" dam.   This doesn't mean it was designed to last 100 years.  It means the dam was designed to withstand some extreme natural event that might occur only once every 100 years.  The recent upgrades around Folsom Lake (new spillway, reinforcement of the Mormon Island dam) have qualified the entire facility to now be a 200 year dam.  Ratings like this are used by insurance companies as part of the insurance rate setting formulas, and once the upgrades are completed, flood insurance rates downstream of Folsom Dam should decrease a bit.  Knowing how insurance companies operate however, the decreases won't be large, and may not happen at all unless downstream residents raise hell with the insurance companies.

 

I'm new to Folsom, but have noticed the results of the Folsom Dam upgrades while driving on the Dam Road to Folsom Auburn Road, and it looks like it was a massive project.  A quick check online shows the costs were nearly $1B, a lotta money.  But when you look at the Oroville situation on TV, you may stop and think, "Gee, maybe it was worth it."  A lot of people around here will get a full night's sleep tonight.   

[The Average Joe]

Yeah, Folsom (like all infrastructure) needs maintenance. Since you are new here, you probably missed when flood gate 3 failed on Folsom Dam. Video starts 26 seconds in  https://youtu.be/dU9BkPxITOg

[Who_Do_You_Trust]

Interesting.  I believe these are called Tainter gates.  I did an article many years ago about agricultural irrigation dams in CO and WY and most use this type of gate.  they are considered extremely reliable and safe.  Or were when I wrote the article.  I read a bit about the Folsom failure and appears someone forgot to oil the pivot pin on the gate.  Oooops...

[4thgenFolsomite]

Fake news. Not happening.

I was tricked on Reddit where it was reported as confirmed by Butte County. I guess some guy was breaking into a store in Oroville and the story grew from there. Glad it's not true.

[tony]

Interesting.  I believe these are called Tainter gates.  I did an article many years ago about agricultural irrigation dams in CO and WY and most use this type of gate.  they are considered extremely reliable and safe.  Or were when I wrote the article.  I read a bit about the Folsom failure and appears someone forgot to oil the pivot pin on the gate.  Oooops...

Uh, it was a little more complicated than that. But, yes the trunnion (the pivot pin) grease was the ultimate cause of the gate failure, but not because they forgot to grease it, but because they changed the type of grease (replaced the lead-based grease they had been using). The replacement grease turned out to be less effective at reducing friction during operation. The real cause of the failure was actually a design problem: they had not adequately considered the forces associated with trunnion friction (it just wasn't routinely considered in the design of tainter gates at the time). On top of that, they had designed with (clearly) not a large enough factor of safety; this was a time of relative hubris in the engineering world as analysis tools and understanding of structural behavior were both improving at a rapid pace. Bottom line is they designed the gates to be a little too efficient, and consequently, not capable of absorbing some unintended loads.

 

The remaining gates have all been strengthened. 

 

As is often the case in our business, disasters end up being good for business. I spent most of the next several years ((with a former employer) inspecting, analyzing and occasionally recommending repairs to tainter gates at dams across the country (never did Oroville; DWR did their own inspections).  Started many a morning walking backwards off the edge of a dam (rappelling); no coffee required! 

[Chris]

Tony, I can only guess the reason that the "lead based grease" was replaced.....?  Like a lot of tragic failures and accidents it starts with one small change or minor event, then add a few more events on top of that, and there you have it.  A series of small changes or events leads to one big, tragic event.  And rappelling and jumping out of perfectly good airplanes are on my "no fly" list....!   Chris

[Carl G]

I was tricked on Reddit where it was reported as confirmed by Butte County. I guess some guy was breaking into a store in Oroville and the story grew from there. Glad it's not true.

 

I'm not so sure about the looting issue.  Fox40 was interviewing an evacuee this morning and I believe I heard her say she saw someone breaking into a business as she was leaving town.  Is it the same incident the sheriff reported last night?  I don't know.  I wouldn't be surprised if some knuckleheads decided to take advantage of the situation to help themselves.