[hvacman]

The drought may not be over for much of California, but man, we up here in the North State sure wish the rain would stop for a while.

We've had over 60" of rain here at Shasta Lake since October 1, with 23" of it in the last 30 days. Expecting another 2-3" today and tomorrow. This is getting old, really old.

Shasta Lake is much fuller than the US Bureau of Reclamation engineers are comfortable with for early February, but they can't bleed off much water without flooding both urban and rural areas downstream. If you look at the lake storage level plot at the link below, you'll see that it is currently at 4 million acre-feet. Usually they don't let it get that full until April when the rain stops, allowing the lake to fill by June from from snow-melt. The lake is 100% full at 4.5 million acre feet. Only 500,000 AF of freeboard left and the level is going up at 125,000 AF/day. It could top out in less than a week and then there is zero flood-control capacity left. NOT GOOD....

http://cdec.water.ca.gov/jspplot/jspPlo ... =6000&cook

At least Shasta dam is not falling apart. The dam at Lake Oroville, the state's 2nd largest reservoir and the largest lake owned and managed by the state, is having some spillway issues. They have to bleed off water from the lake to make room for new inflows expected from the current series of storms coming onshore, but the spillway passage downstream of the dam has had some major erosion issues from the last major water dump.

http://www.sacbee.com/news/state/califo ... 79999.html

(I just edited the link to a better link with more detailed information)

To clarify the structural issue, the Oroville spillway is actually a long concrete canal that extends downstream from the dam a distance before it flows back to the original stream-bed. The portion that is having erosion issues is NOT on the dam, so spillway damage does not threaten the dam itself.

It's not just this dam. Roads are falling apart. The main east-west highway linking the North Coast to Redding and I-5 has been closed to most traffic for a couple of months now due to a major landslide. Local roads have failed due to small stream flooding, along with parks, some homes, etc. etc.

From our perspective up here in this corner of California, we could actually use a little more "drought". We are declaring just the opposite sort of "emergency" right now.

[vtsnowedin]

Oroville spillway flows for first time ever.
https://weather.com/news/news/oroville- ... -emergency

[vox_mundi]

Evacuations ordered below Oroville Dam after a hole is found in its emergency spillway

$this->bbcode_second_pass_quote('', ' ')

Tens of thousands of residents in Northern California were ordered to immediately evacuate Sunday afternoon after erosion at the emergency spillway at Lake Oroville threatened to flood downstream towns.

The flood danger emerged suddenly when a hole developed Sunday in the auxiliary spillway that was being used to lower the levels of the full-to-the brim reservoir, the second-largest in California.

The erosion could undermine the concrete top of the spillway, allowing torrents of water to wash downhill into the Feather River and flood Oroville and other towns in Yuba, Sutter and Butte counties.

Sunday night, officials said the threat had diminished because the lake level had dropped and water was no longer washing over the emergency spillway.

But the situation at Oroville remained precarious. The two main avenues for getting water out of the lake – the unpaved emergency spillway and the main concrete spillway – were both damaged.

[Cog]

The dam itself is not in imminent danger of failure. What was in imminent danger of failure was the emergency spillway. When water reached 901 feet in elevation water spilled over it. That was the design elevation at which water will flow over it. The emergency spillway has never been used before. The water starting eroding back towards lake and now the regular spillway(which is damaged) is back up to 100,000 cu feet per second release so they can get the lake level back under 901 feet. Water is no longer flowing over the emergency spillway and increased flow is going down the damaged but functional regular spillway.

The threat of immediate collapse of the emergency spill way has passed for now. Wednesday will bring more rain and they will have to see if the regular spillway can handle the inflow into the lake.

[onlooker]

http://www.cnn.com/2017/02/12/us/califo ... m-failure/
The dam, which is the nation's tallest, remains intact

[hvacman]

By now, most of you probably have heard of the Oroville dam spillway failure. Living only a few miles from Shasta dam and about 80 miles from Oroville dam, and having assisted in some hydroelectric plant designs early in my career prior to taking up HVAC, the engineer in me has habitually followed the blow-by-blow details of each dam's water management strategies and each dam's water control infrastructure over the decades.

The latest shared challenge - of full reservoirs and major on-going inflows - has been a tale of two dams. Shasta dam has created about as much national noise as a typical successfully-developed deep water GOM well - i.e. - none. My wife and I did a bike ride to the dam and rode across to witness the spectacular waterfall going down the 500-foot-high dam spillway face as dam operators vented 70,000 cubic feet/second of excess water. Spectacular, but "not a big deal" from an operational or engineering standpoint. The dam's multi-ported spillway system is designed for handling up to 250,000 cfs.

https://goo.gl/images/NJHM66


Oroville dam? Exhibiting a similar formula for disaster as Deepwater Horizon and Fukushima, as the facts slowly roll out, it increasingly reveals an element of hubris in their emergency-event management plan that collided with unexpectedly challenging natural events beyond their control, some political decisions by management going back decades, engineering weaknesses in the original construction, and catastrophic failures of multiple fundamental safety features.

http://www.usatoday.com/story/news/nati ... /97844512/

Lake Oroville is the 2nd largest reservoir in California (Shasta Lake is the largest) and is the largest in the state-managed "State Water Project" (Shasta Lake is part of the Federally-managed Central Valley Project).
Even if the emergency spillway does not fail, both it and the main spillway will require complete re-construction, which will take years and $$$$$. These spillway failures will cripple Oroville dam's ability to dynamically manage outflows when near full-pool, which will probably mean dramatically reducing its allowable storage volume. This will wreak havoc on long-range water management plans and dramatically reduce available summer water releases through the State Water Project for years, if not decades.

There is great irony in the flows of one good wet winter creating a situation of even greater water shortages in the future.

I'll keep you all posted as more details are revealed.

[KaiserJeep]

I have faith in the dam. It was designed back in the 1950's and constructed in the 1960's. Engineers used slide rules then, and believed in safety margins and overbuilding to implement those margins. Nowadays they would have used computer modeling, cut the safety margin to the minimum, and the dam might already be failing.

The one fly in the pie is the damaged regular spillway. That might be an indication of poor maintenance, or a lack of necessary repairs during the drought years, as a result of state budget priorities.

[Cog]

They sort of limited their options here. By using the emergency spill way, the have uncovered it won't work for them because it was eroding so badly it will fail if used again. So they are now limited to using the primary spillway only, no matter what damage it does to itself. Maybe they dodge the bullet on this maybe not. Depends on the rain.

[KaiserJeep]

I believe in the dam. It was designed in the 1950's and built in the 1960's, when engineers used slide rules and believed in safety margins. Nowadays they would have used computer modeling of rainfall, then cut the margin to the minimum, and the dam might already be failing.

The one fly in the pie is the damaged regular spillway. It was lined with concrete to prevent erosion, unlike the emergency spillway. The damaged spillway lining may be an indication that the regular maintenance was neglected during the drought years as a result of state budget priorities.

[dohboi]

As I understand it, there is more than 'one fly in the pie.'

The main spillway is damaged near it's base of the concrete portion...a 200 foot wide, 30 foot deep hole.

But now the emergency spillway, used for the first time, is breaking down at the top--a much more worrying prospect.

They seem to have now gotten the water level down below the level that it would further erode the emergency spillway gash, and it isn't supposed to rain for a couple days, so it would seem that the worst is over. But who knows? It doesn't sound as if they are calling back the nearly two hundred thousand evacuees yet. One official described the situation as 'dynamic' and 'could change anytime.'

As mentioned above, it's going to take hundreds of millions of dollars and many years to fix these problems, and in the mean time, water will not be as available as it should be if everything was functioning properly.

http://abcnews.go.com/US/thousands-evac ... d=45450195

[Plantagenet]

$this->bbcode_second_pass_quote('dohboi', '
')They seem to have now gotten the water level down below the level that it would further erode the emergency spillway gash, and it isn't supposed to rain for a couple days, so it would seem that the worst is over. But who knows? It doesn't sound as if they are calling back the nearly two hundred thousand evacuees yet. One official described the situation as 'dynamic' and 'could change anytime.'

As mentioned above, it's going to take hundreds of millions of dollars and many years to fix these problems, and in the mean time, water will not be as available as it should be if everything was functioning properly.

http://abcnews.go.com/US/thousands-evac ... d=45450195

[Cog]

The primary spillway, at 100K cfps release has ceased pealing off concrete slabs and eroding upstream towards the dam. At least for now. Hard to say what is going on underneath those slabs of concrete closer to the outfall. They can't use the emergency spillway, until it is reinforced. It was going to fail quickly if they hadn't lowered the lake level.

At some points during the rainfall last week, the lake was accumulating 200K cfps of water.

[KaiserJeep]

For the record, Pete, I never blamed Obama for this dam, it's a state project, and Moonbeam is responsible for neglecting maintenance. The drought years certainly cracked the earth on the backside of the dam as they did elsewhere in the state. But if the spillway cracked as a result, it should have been repaired while still dry.

The cracks on the hill above my house have all closed up now. The amount of water weight as mud is worrisome, but we do have a gunite-lined drainage canal at the base of the hill. The Water Control District has not done any maintenance on the canal in the 31 years I have lived here, aside from covering the ends of the drain pipes with gratings to exclude skunks.

[hvacman]

Yes this is a DWH type event.

This is not an event that is all "due to overwhelming natural forces". It is an engineering/maintenance/political failure. The primary spillway failed at a very moderate release rate - 50,000 cfs. The dam's specs say the primary spillway was designed to handle up to 150,000 cfs. Something disastrous happened (either due to a hidden materials failure or due cumulative damage that went undetected due to poor inspection practice) to cause the initial hole in the primary spillway at that moderate discharge rate. If the hole had not formed, as inflows continued to increase, they dam operators would have just continued to release more through the primary spillway and kept lake levels low. This was not due to "unprecedented" inflows. Inflow briefly surged to 150,000 cfs, but they could have easily just ramped releases to 100,000 cfs and quickly bled off most of the surge. I think that was their original plan. But the hole formed, so they backed off on the primary spillway to 60,000 cfs. Actually, they completely shut off the spillway for a while so they could inspect the hole and figure out what to do. That made the water behind the dam back up even more.

Compounding the operators' problems, the debris and confused flow also affected hydro power plant discharge. They had to completely shut down the hydro plant, which normally would be diverting 18,000 cfs through it. So that added even more water backing up....

Feb. 11, the operators "hoped" that they could minimize primary spillway damage by keeping the spillway flows at 50,000 cfs and letting the reservoir back up until it started spilling over the "emergency" spillway, which also was "rated" for up to 150,000 cfs. But as the water started cascading over, at just over 12,000 cfs, the base of the emergency spillway began to erode. This was as serious "Oh, S#$t" moment for the engineers. They gambled on something that had never been tested before to save their bacon on the primary spillway screwup and lost that bet...

The political failure? First, the whole state management plan for balancing water storage for summer use vs flood control, especially with the drought situation, calls for playing the odds and letting the dam fill up a little more in mid-winter than might be technically prudent for effective and safe flood-control.
Second, the never-tested emergency spillway that just dumps the water on raw dirt was really only considered "safe" to do because it was expected when it was originally built that it would never actually have to be used. Another storage flood/control-dam - Marysville dam - would be constructed later that could give Oroville operators more flexibility about how they regulate lake levels. It was never built, making it more likely that the emergency spillway might have to be actually used someday. The "emergency" spillway then becomes classified as an "auxiliary" spillway, which standard dam design protocols say should have a concrete apron and channel down to the streambed. Because, guess what...it is pretty clearly understood that dirt erodes. Not rocket science. Just like in well-drilling, gravity always works and a mud column heavy enough to create a down-hole pressure higher than the oil at the bottom usually stops blow-outs.

When the dust (or mud) settles, I know that it will be found that the Oroville dam spillway failure was not a natural disaster. It was preventable and man-made. Just like many other modern disasters. At least they had the sense to decide to give up on the failed attempt of using the emergency spillway in-time to (hopefully) prevent a massive spillway face failure that would have flooded the whole valley.

Heads will roll with this debacle....

[jedrider]

Oroville Dam: Feds and state officials ignored warnings 12 years ago

http://www.mercurynews.com/2017/02/12/oroville-dam-feds-and-state-officials-ignored-warnings-12-years-ago/

$this->bbcode_second_pass_quote('', 'M')ore 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.

Three environmental groups — the Friends of the River, the Sierra Club and the South Yuba Citizens League — filed a motion with the federal government on Oct. 17, 2005, as part of Oroville Dam’s relicensing process, urging federal officials to require that the dam’s emergency spillway be armored with concrete, rather than remain as an earthen hillside.

[ROCKMAN]

H-man - You seem to be very familiar withe subject so I have some questions. Might sound like criticism but not...just curiosity.

A) Given the arid nature of the rergion did they delay an earlier release in order to save resources?

B) Not that I've read more about the deterioration/lack of maintence wss the evacuation called much later then it should have been? Evacuations themselves can be deadly but was the late call PR driven?

C) Some comments seem to indicate it would have been a prudent safety policy to have been holding a much lower reservoir long before the rains hit.

The situation reminds on the huge mudslide a few years ago that took out a whole community. Afterwards a geologist showed maps of numerous massive mudslides that happened in the same valley for thousands of years. IOW even though it was inevitable the homes were still built.

[Plantagenet]

$this->bbcode_second_pass_quote('KaiserJeep', '
')The one fly in the pie is the damaged regular spillway. That might be an indication of poor maintenance, or a lack of necessary repairs during the drought years, as a result of state budget priorities.

[Outcast_Searcher]

To me, this is a perfect example of why the US needs to get SERIOUS about actively maintaining the infrastructure ASAP, instead of playing partisan politics or whining about the budget (for the projects that might get lots of people killed if they're not pursued in a timely manner).

Now, I predict that just like for collapsing bridges, dangerous bridges, a terrible water infrastructure problem, an aging energy transportation infrastructure, serious electrical grid issues, etc. etc. -- once this situation has calmed down for a few weeks (assuming no one gets killed), then it will be back to BAU, nothing to see here. (Yeah, minimal local repairs on this particular set of spillways will be done, but this won't, for example, spur the democrats to support Trump in fixing the US infrastructure. To allow credit to that to go to a GOP administration would be unacceptable, no matter how many constituents get killed. (OTOH, if a bunch of people DO get killed because the democrats refuse to support infrastructure spending under a GOP administration, you can be 100% sure they'll blame the GOP)).