Oroville Dam Update

February 16, 2017, 5:42 a.m .PST | self

[keat]

It rained through most of the night in the Oroville area. A storm passed over and is currently dumping rain in the foothills and mountains to the east of the lake. It's a warm storm and can be expected to trigger some snow melt and runoff.

As of 5 a.m. the reservoir level stood at 870 feet, 30 feet below the lip of the emergency berm.

Inflow from the storm should begin late today and max out over the weekend. It remains to be seen whether this will cause the lake to rise dangerously as releases continue at the maximum.

It looks fairly promising and the Pineapple Express doesn't look to have another storm queued up over the Pacific at least for a week.

Temps have risen to 70 degrees in parts of the Central Valley and almond trees are in bloom. It's Spring, albeit a wet one.

[CIB-173RDABN]

Rain is not the only problem.

It is getting warmer. The snow packs will be melting. It is the combination of the two that should have them worried.

[KC Burke]

I have tried to follow this closely but I still haven’t seen a definitive answer on a particular item. The generating plant is flooded and can’t be used to move water through the damn. Volume wise this is not the biggest issue at this point as it only moves about 17% of what the main spillway is discharging even with the main spillway only running at a rate to avoid more catastrophic damage to its out-flow structure.

But here is my question. At what elevation does the main spillway quit being an available drain for the lake? The power generating outlet usually is running so the Lake has protection against repeated Pineapple Express periods as it lowers it when the main spillway can’t. But that is now non-functioning.

It seems to me that the main spillway can only drain the upper XX’ of the lake. Anyone got that number? In that case the lake WILL fill to the emergency spillway again regardless of the first run of storms.

[palmer]

It can drain at least 50 feet. 900 is when the water reaches the emergency spillway. 850 is the level they want before a big rain.

[palmer]

Some facts sprinkled in this article: https://ww2.kqed.org/news/2017/02/07/engineers-assess-spillway-problem-at-oroville-dam/

[mrsmith]

info is at 951: http://www.freerepublic.com/focus/news/3524221/posts?q=1&;page=951#971

Looks like about 100 ft.

[ProtectOurFreedom]

Absolutely right. The roads all over CA are a mess — gigantic potholes and torn-up pavement everywhere. All the money spent on illegals AND on that damned train could have gone to fixing up infrastructure. We pay the highest taxes in the nation and get the lousiest public services. That’s what Dem uniparty control gets you — it’s been proven time and time again.

[ProtectOurFreedom]

The dam was designed and built in the 60s, WAY before we had illegals and stupid notions of high-speed trains. The design decisions were made back then.

[janetjanet998]

I believe the monday-tuesday system will be the wettest of the seaon

inflows may exceed 200.000 cfs for a while

[tomkat]

Caveat: I've not seen blueprints of the innards of this dam, so this only supposition.

Swiped this pic from a link that OMA put up early this morning.

Assume that the egress gates thru the spillway structure are a straight line affair, without some fancy angle to them.
Then visualize a line from the bottom/floor of the gates across to the Espill on the left.

From other pics that have been posted of the backfill/grouting work going on over there, the Espill looks to be about, at most, 50' high.
That line you visualized looks to me to be more/less on the same plane as the bottom of the Espill.

So my guess is that the -50' lake depth they've been aiming for would correspond to the maximum depth the main spillway is capable of releasing.
/.02

             

[henkster]

The Oroville dam is a classic example of what happens when a government becomes so large and bloated that the only thing it accomplishes is its continued existence and ceases to perform its actual function.

Here is a link to a very good summary of the California budget, and proof of how they spend gigantic sums money but accomplish nothing:

https://ballotpedia.org/California_state_budget_and_finances

The best part of the information is how Moonbeam's last budget had 1.5 Billion put into a "rainy day fund." Well Jerry, take a look out the window. It's raining.

[KC Burke]

My point is of course we have already seen inflow at 200k and the lake jump over a hundred feet in short order, so I think we are going to get to see how those emergency repairs to the emergency spillway hold up in the next ten days.

So since we are as high as we still are, take a look at this chart as of today and see what happens if we jump like we did at the end of January and first of February.

[KC Burke]

see todays chart at #31,

[Ancesthntr]

“The dam was designed and built in the 60s, WAY before we had illegals and stupid notions of high-speed trains. The design decisions were made back then.”

---

The dam could have been retrofitted with better equipment.

Besides, “Operation Wetback” dealt with a couple million illegals along the southern border, who were deemed to be a big problem, commencing in June of 1954.

[KC Burke]

Found it.

813.6 feet in elevation. So, from the 901 where it is going over the emergency spillway, they can only take the lake down 87.4 feet. After that only usage by the water districts draws down the elevation (we can only assume that is on-going). The generator outflow can’t run again until that whole area is restored from flood damage.

[Rik0Shay]

A little Dam Info.

A typical dam has several ways to release water.

Outlet Works is one. It is a vertical pipe installed from the base of the river bed. It has several openings, as it rises, with plugs that can be opened and closed. Is purpose is to maintain stream flow, at a predetermined level, so the river below the dam does not go dry.

Main Gates is another. This releases water onto the main spillway to control the lake level when you have to either stop the lake from rising or lower the lake level. It is only used when needed. The bottom of the gates determine how low you can lower the lake. They can be very tall gates.

Emergency Spillway. This is installed to prevent topping of the dam during an emergency. Topping of the dam can cause dam failure. (this would be catastrophic). Failure of the emergency spillway would be bad but not near as catastrophic as a dam failure. It is designed primarily as a buttress against the pressure of the water. In this case 30 feet or so. Whether to include a reinforced spillway for the emergency spillway is a design decision.

Power turbines are used in some dams to generate power. This releases water to generate power and is not part of the designed water release.

This lake developed problems when its main spillway started breaking down. Because of this breakdown the gates were partial raised to slow the controlled release to prevent further damage. This slowing down of the water release caused the topping of the emergency spillway and the possibility of failure.

There are two problems here. First, the design decision to construct the emergency spillway with out reinforcing it and the later decision to continue that way and not reinforce it in 2005 or so. Second, the failure of the main spillway. Any routine competent inspection would have uncovered this problem and allow it to be repaired.

[mrsmith]

That bump was caused by the operation of the flood gates.

Entertaining graph: shows them trying to get the level up to “par”, then shutting down the floodgates when the spillway broke.
Looks like the best time to repair the spillway will be late winter. IF they can wait.
Such a stupid failure, probably caused simply by not caulking expansion joints in the spillway.

[KC Burke]

Thanks Rik0Shay,

The Outlet Works flow is 5400 CFS which is about 5.5% of what the spillway is running now, so it will continue to go down at a slight rate even when the spillway minimum elevation is reached, but at a very slow rate and only if there is no inflow, No inflow won’t occur again until late summer.

[morphing libertarian]

Yes, billions of dollars a year.

[tomkat]

Perhaps I misunderstood, but what I was trying to get at is that 50' x # acres in the reservoir would be the # of acre/feet of new water that the Mspill would have to discharge to avoid overtopping the Espill.
This of course assumes there's no internal damage (??) to the Espill embankment that would cause it to fail from the lateral pressure of any further sub-topping rise in reservoir level.

If my guesstimate of 50' for the floor of the Mspill gates relative to the bottom of the Espill embankment is close to correct, then the distance from the floor of the Mspill gates to the top of the Espill weir would seem to be the volume range in question.
Once the reservoir drains to the level of the Mspill gate floors, and absent functional generator gates, no further drainage via the dam would be possible.
I'd also imagine that that's where the 'magic number' of DWR's 50' target has come from.

Apart from that, it's almost lunchtime here in PA, so I'll leave it to the engineers to figger out   ;-)

[tomkat]

Oops, was typing and just saw your #34.

Oh well, I was in the neighborhood .. prolly not too bad for an old carpenter eyeballing it from PA   ;-)