Posted on 02/14/2017 6:09:46 AM PST by Mariner
While more than 180,000 residents remain evacuated from their homes in Butte, Sutter and Yuba counties, there is no timetable as to when people can return home as water officials and engineers assess the damage and situation at the two damaged Oroville Dam spillways, the Butte County sheriff said Monday.
As tensions remain high around the area, some good news came early Monday morning when water levels at Lake Oroville dropped below capacity, stopping water from spilling over the potentially hazardous emergency spillway.
However, officials are still looking to lower the lake another 50 feet to less than 850 feet elevation to allow space in the lake for the upcoming storm, projected to arrive Thursday. Dropping the lake levels that much without increasing outflows could take several more days, KCRA meteorologist Dirk Verdoorn said.
(Excerpt) Read more at kcra.com ...
Oh Oh :-)
The sad part is to save Sacramento, they may have to deliberately breach the levees west of the Sutter and Yolo Bypasses to relieve the pressure. In short, the towns of Knights Landing, Woodland, Davis and possibly even Dixon may have to be sacrificed to save the much bigger Sacramento.
The second problem is that the emergency spillway has cut a path higher up and across the spillway itself which you can see when you run videos of the last hours of high water flow down the emergency spillway. It is about to cut a path under the concrete spillway, which will cause another tear on the spillway high up at a weaker point in the dam if that emergency spillway runs hard again.
The third problem before even getting to the point of reaching the top of the main dam is damage points to the left of the dam where that both spillway areas cover that might have leaks. The least of their worries is the earthen dam itself overflowing but the undercutting of it on its side.
Earthen dams are risky to begin with but this one has some huge danger point now even before the main part of the dam overflows which is usually a horrible thing for an earthen dam. I am not saying that this dam will break, just that it has some very dangerous points that are visible at the moment and major concerns that are not visible at the moment before you even worry about overtopping the earthen dam which is never good.
True true - There are definitely “lesser” scenarios that will be nearly as devastating as the failure of the dam itself. We will just have to watch, see, and most importantly: pray!
Consider this: if the primary spillway began to cut back too close near the dam, they would by necessity have to shut the gates. That means the emergency spillway would become the fail point. In that case, would you allow chance to take place to determine the outflow point, our would you dynamite the section nearest the parking lot in an attempt to have the outflow carve a huge canyon, but still stay 200-300 yards away from the primary spillway complex and main dam?
Ok, the damaged spillways are separate from the dam itself. the dam itself is not experiencing problems - the spillways are.
the main spillway was severly damaged but has been demonstrated the ability to still allow 100,000 cfs and they could push it higher as good bedrock has been encountered.
The emergency / auxillary spillway is what cause the evacuation. erosion of the hill side was approaching the concrete weir of the spillway crest. had it reached it, it could have resulted in tunneling under the concrete and making direct connection to the lake. the weir is about 30 feet high. this is the catastrophic failure that concerned everyone.
Please the dam itself is not in trouble.
It is a book that everybody should read at least once in their lifetime.
I've read it three times and it's on my list to read a fourth time. Fountainhead well worth checking out too.
California and dam maintenance are the criminals in this situation as none of this was unexpected if water rose to danger levels for this dam.
My friends who are in the danger zone: wife has evacuated with valuables. husband knows what will happen if they leave the ranch/farm completely uninhabited. He has stayed behind, armed.
There are a lot of folks there who will NOT leave their property completely unprotected. I pity the fools who think they’ll take advantage of supposed unoccupied homes.
I hope he has a boat.
I agree, except that the dam is leveraged to the wall that the spillway and emergency spillway are on. It is the spillway areas weakening that are the concern.
He does! and also (I find funny) he used to be a professional undersea welder, so he’s got scuba gear :) not that it would help much.
Study of Feather River Basin runoff processes
https://pubs.usgs.gov/sir/2004/5202/sir2004-5202.pdf
http://www.sacriver.org/aboutwatershed/roadmap/watersheds/feather/upper-feather-river-watershed
Knowing him, he’s smart enough... just hope he’s quick enough! Saw a map showing the time-to-flood from the time-of-failure... he is in the 45 minute area... and he knows back-roads through the ranches and farms. He has a very good chance.
OK - Prudence is always the best idea. I’ll keep him (and everyone else over there) in my prayers!
I have no clue after that what their options would be dealing with a breach. I can just tell you what I see happening and what I have been told in the past about the dangers of dams.
Once you have erosion at the top, it always makes it way down to the river bed.
Eventually.
And cuts a wider, deeper path as it escapes.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.