OROVILLE, Calif? Hope you are OK!

[showbizkid]

Pouring in big rocks doesn't seem like it would work either.

It won't. They tried the same thing at Teton Dam in '76, and it was useless.

[rockne10]

Residents can return now, with the understanding that they may have to leave again on a moments notice with another storm on the way.
The consensus is that corners were cut fifty years ago when the dam was built; and that it must be corrected if habitation of the valley is expected to last; which it is.
Minimal estimates of the correction start at $500 Million and, without federal support, the cost will fall to the farmers in the Imperial Valley and the tap water users in Southern Cal. Expect more increases in produce prices.

[SN-60]

Residents can return now, with the understanding that they may have to leave again on a moments notice with another storm on the way.
The consensus is that corners were cut fifty years ago when the dam was built; and that it must be corrected if habitation of the valley is expected to last; which it is.
Minimal estimates of the correction start at $500 Million and, without federal support, the cost will fall to the farmers in the Imperial Valley and the tap water users in Southern Cal. Expect more increases in produce prices.

I really don't feel this is the time to be thinking about MONEY!

[Lothar]

I really don't feel this is the time to be thinking about MONEY!

The potential (looming?) failure of Oroville Dam is an extremely serious situation. Tom Walgamuth's explanation of the problem and analysis of the situation are very clear and concise from what I know with my limited knowledge of this type of structure. MUCH more accurate than most media accounts. What no one has yet explained to my satisfaction is what is the nature of the emergency spillway material? I assume that its soil over bedrock, but what type of bedrock? If I knew that information (I will look for it online, now that I think about it), I would have a clearer idea of how erodible it is.
Also, I don't think that Brad is in any way downplaying concern about affected people by pointing out that fixing the problem will cost money and we all will need to pay a share of that cost, directly or indirectly.

[t walgamuth]

Thanks John.

The emergency spillway I read today is earth with a concrete lip. This is what they fear might fail, it being 30' high so I suppose that means that after the 30' earth structure there is bedrock....although it seems to me that an earth dam can fail about anyplace as the water can seep through.

Once that starts happening I believe its just a matter of time until the dam fails.

As for money, yes, that is the question. These western dams provide water to CA's enormous agricultural business and the result financially if they fail would be huge.

I heard tonight that there are hundreds of dams around the country that were designed with a 50 year life in mind which now are 50 years old and older.

I know the Hoover dam was constructed by first building diversion tunnels through the bedrock so the river could be completely run past the area where the dam was to be constructed. It seems to me that we must provide such total bypass mechanisms in every dam project so it can be rebuilt safely when it has reached its design life.

[Lothar]

This article in Forbes magazine answered my questions about the geology of the dam spillway. It doesn't look like a good situation. I hope and pray that the dam holds through the spring. If it can, then CA DWR and the feds might have enough time to really fix the spillways before next winter.

http://www.forbes.com/sites/davidbressan/2017/02/14/some-geological-observations-on-the-oroville-dam/#375eb15b1925

This is a very well-written article, if you're interested in this detail of the subject.

[t walgamuth]

Good article. Here is the part which leaps out at me: but the ground of the emergency spillway consists of backfilled soil. This is a cheap and effective method to build dams, but it's also prone to erosion by fast flowing water, especially if the soil becomes soaked with it. Thus, the running water of the spillover is washing away soil, earth and rocks, forming deep gullies. The erosion front is creeping upslope as water flows down the slope.

Building it up to support the spillway with soil instead of proper fill material was foolhardy. Its fine until you actually flow a flood over it...Yikes!

[Commander Eddie]

Its raining buckets here in Oregon. This is the same storm hitting northern California right now. I hope the dam holds.

[t walgamuth]

Yep. Me too. they have lowered the lake level by as much as they can to make room for the storm water coming in. Trouble is you don't know when it will start or stop raining.

[t walgamuth]

I just read that the water is now 30' below the top of the dam. Good!

[rockne10]

I just read that the water is now 30' below the top of the dam. Good!

With the sluices still at full bore the residents below the dam can probably rest easy for the season.
But a correction to this dam MUST be made at GREAT expense. The take-away here eludes no one!
We can relate this to our auto restorations. If we are going to go on the cheap the first time, we are going to exponentially multiply the future expense.
Scrapping a poor auto restoration does not jeopardize the lives threatened by scrapping a poorly financed dam.

[SN-60]

With the sluices still at full bore the residents below the dam can probably rest easy for the season.
But a correction to this dam MUST be made at GREAT expense. The take-away here eludes no one!
We can relate this to our auto restorations. If we are going to go on the cheap the first time, we are going to exponentially multiply the future expense.
Scrapping a poor auto restoration does not jeopardize the lives threatened by scrapping a poorly financed dam.

MONEY again???...Brad, that really isn't the issue right now!!!

[Sdude]

Pat escaped his home in his studebaker and put his 68 Biscayne up on the lift. He lives far enough downstream to not see water that surpasses that. He has returned home and is getting better prepared should he have to evacuate again. We have other members in the area and hope to see them at our meeting this Sunday at the California Auto Museum in Sacramento. Scary situation right in the middle of Karel Staple Chapter's turf. They are working around the clock to shore things up and continue to reduce the level of the lake to handle the rain water expected in the next storm due at any time. Rivers are overflowing all over Northern California. We all appreciate your concern and prayers.

[rockne10]

MONEY again???...Brad, that really isn't the issue right now!!!

Tell that to the people who live below the dam.

[t walgamuth]

Looks like they have to repair the primary spillway first, then rebuild the section which is the backup or secondary earth spillway. I suppose a temporary dam will have to be built to contain that part of the lake so they can rebuild the secondary spillway.

Sounds expensive. I am guessing that taking the dam down is not an option financially because of the need for the water storage.

And it sounds like this is a wake up call to look hard at a whole list of other dams which may be in need of rebuilding.