Oroville Dam Crisis Could Affect UP/Ex-WP Line

[C855B]

NOT a news item in itself, just an observation from familiarity with the area. Here's the latest from the local (Oroville) newspaper:

  http://www.orovillemr.com/general-news/20170212/emergency-spillway-could-fail-evacuations-ordered

The UP/ex-WP mainline, a/k/a/ "Feather River Route", is at the base of the dam, on a causeway over the diversion pool. If the erosion of the emergency spillway continues and it gets into an uncontrolled release situation, that bridge and the approaches are going to bear the brunt of it. My concern is whether UP will decide to abandon the line given the cost/effort to rebuild. Abandonment or sale was discussed after the merger in '82.

The Shasta line is in the floodplain as well, in Marysville. If any resulting inundation there proves damaging (and things are already dicey from area flooding), UP has a lot of rerouting to do.

Something I read elsewhere is they averted the partial breach this evening by lowering levels using the eroded main spillway, further damaging it. Concerns now are any more releases there may damage the gates, making them unusable. Not helping is they can't release through the generators now because of concrete from the damaged spillway affecting flows there. It was said that if the weather works against them, the dam structure itself is at risk. Oroville is the highest dam in the U.S.

Next two or three days - more rain forecast for Wednesday - will bear watching.

[Smike]

The main dam structure is far from being at risk, this is the one thing that has been reporting incorrectly ad nauseum.

If the dam’s outflow pipes are shut down, and the operational spillway closed again, the emergency spillway is designed to act as a pressure release valve. While if it happens it will be ugly, the geology is such that water unchecked spilling over the emergency spillway could/would erode the 30' concrete at the top (current concern and reason for evacuations), it would stops eroding once it reaches bedrock. They build the this spillway there at that location specially as it has a natural bedrock depression which would channel all water down and could not erode towards the main dam structure. The main concerns with this, is that water would be released without any control (as it was prior to the dam being built) So the river below would rise and fall naturally based on the weather. So flooding would be a big concern, but thankfully not the biblical sized flood which would result from the main dam structure failing.


If the main structure would be in jeopardy of failing, then they would need to evacuate what could be over several million people. 

[C855B]

Thanks, Mike. 1500 miles away now I have to a certain point rely on what's being published. Yeah, there were a lot of partial reports and conclusion-jumping, but I did read one going into detail about further erosion of the primary spillway versus the gates. It also discussed the state emergency management agency has impact plans for the instance of a full failure, but not a partial with losing the emergency spillway.

[basementcalling]

Big mess. Ma Nature is playing hardball. The access road below the emergency spillway, which CDWR has now been calling the auxiliary spillway - perhaps to chagne the tone from doom and gloom - is already washed away.

I watched some of Channel 3 from Sacremento last night live on Facebook and they were confused as well, but did a pretty good job explaining the impacts. Their weather guy was top notch, though why the weather guy should be an expert on geology and dam construction is beyond me. Hey, he's just a meteorologist. 

Pretty scary stuff even if only the emergency spillway were to break.

Levees can handle up to 210,000 CFS of flow downstream, but the highest flow ever since the dam went in is 160,000 back in 83, and for that they evacuated Oroville and Marysville as a precaution in case a levee failed.
The main gates were discharging 100,000 cfs yesterday plus an estimated 12,500 from the emergency spillway, so the level was within limits, but if the 30 feet of concrete on the emergency spillway went, there would be an uncontrolled and unknown, but significantly larger, volumne of water rushing down the Feather River. One report I saw estimated a 10 meter high wall of water would come down the river.

Yikes.

As far as I know, UP lines upstream of the dam have had a couple washouts and landslides, but are largely in tact.

[wazzou]

I heard a CBS National radio report this AM stating the plan is to lower the level of the lake by another 50' to enact repairs prior to another round of storms late this week.
They mentioned that upward of 200,000 people downstream have been evacuated thus far.

[Smike]

One thing that is lost in the news cycles, is that there are two reason how the level got to the point of spilling over the emergency spillway. (causing all of the panic)

• Recent rains and snow melt increasing inflow very rapidly
• The damage to the normal operational spillway, which made using it further more costly as it increases the future repair costs, but has little effect to safety regarding the main dam

So they took a gamble last week to shut down the damaged spillway to prevent further increasing repair costs.  They hoped the outflow tunnels in the dam itself could release enough water to keep up with the inflow.  Obviously to anyone seeing the rain forecast and inflow /outflow rates could tell this was going to backfire.  Now that they have made the decision to screw worrying about further repair costs, they are using the damaged spillway to lower the lake and will be able to do so. While nothing is 100% they should have this under control.  The only thing that could cause them to shut down damage spillway and hence having the lake rise up to crest the emergency spillway again, would be to find that bedrock under the spillway is somehow transporting water underground towards the main dam structure (thus weakening it)  Highly unlikely given the geological make up of the ground here.  (That's kind of why they built the dam here instead of any old place with ah bunch of dirt and rocks piled up to make a wall.)

True test and display of the engineering work that when into accounting for the worst case scenario when they built it.

[Scottl]

Free the sediment!

This reminds me of Fulsom dam on the American River.  They filled the reservoir in a few weeks in the 1950s- showed design storms were undersized and they got lucky that time.  We use it as an example teaching hydrology.

[C855B]

Something else I read was concern over undermining the transmission tower closest to the spillway. If they were to lose that, it creates another problem forcing the generator penstocks closed, losing that outflow as well. I think they're shut at the moment because of broken spillway debris. The inference was they couldn't turn the turbines without the generators connected, but I don't know how accurate or complete this particular report was.

[Scottl]

The rainy season is not over yet.  If the spillway is out of action and the turbines are inoperable, they only can watch and pray.

[Smike]

Something else I read was concern over undermining the transmission tower closest to the spillway. If they were to lose that, it creates another problem forcing the generator penstocks closed, losing that outflow as well. I think they're shut at the moment because of broken spillway debris. The inference was they couldn't turn the turbines without the generators connected, but I don't know how accurate or complete this particular report was.

Good question, I think they must have a way to let water flow regardless of the up time of the electric generators.   Until very recently the only way water was flowing through the dam was through those pipes over the last couple of years. With the drought the water was far below the spillway to use it.  The Spillway only has the ability to adjust water flows down to 60 or so feet below the lake level drops and its no longer usable.

[C855B]

This reminds me of Fulsom dam on the American River.  They filled the reservoir in a few weeks in the 1950s- showed design storms were undersized and they got lucky that time.  We use it as an example teaching hydrology.

At the other end of the spectrum, do you also use Optima Lake as what not to do? $46+M down the drain... so to speak.

[Scottl]

LOL, I have a list somewhere of the top 10 worst wastes of water resource money by the BRec and Army Corps.  Lots of politics feeds the decisions to build these things.

[coldriver]

The UP/ex-WP mainline, a/k/a/ "Feather River Route", is at the base of the dam, on a causeway over the diversion pool. If the erosion of the emergency spillway continues and it gets into an uncontrolled release situation, that bridge and the approaches are going to bear the brunt of it. My concern is whether UP will decide to abandon the line given the cost/effort to rebuild. Abandonment or sale was discussed after the merger in '82.

UP's use of the Feather River Route has declined over the last several years, but the line also hosts 4-6 BNSF trains per day coming down the Oregon Trunk/Inside Gateway lines, so it is still a heavily used mainline, at least west of Keddie.  Any thought of abandoning the Feather River Canyon would require UP to host BNSF I-5 corridor trains on the Shasta Route. 

[jagged ben]

It's official at this point.

http://www.latimes.com/local/california/la-live-updates-oroville-dam-20170212-htmlstory.html

I have a feeling we're highly likely to see BNSF on the Shasta line to Klamath.  Also UP sure is happy they enlarged the Donner tunnels for double stacks a few years ago.

What intrigues me is whether the former SP East Valley lines are also shut down.  That article was not clear.  Is it possible we'll see diversions to the Cal Northern's former West Valley lines?  The Brooklyn trailers going that way would be kinda neat.

[Smike]

You can clearly see the reason for the evacuations just on the issue of this emergency spillway only.  While the concrete lip is 30' and it looks like its sitting on at least another 10-20' of fill on top of the bedrock (at least just down stream of it from this angle)

Why on earth would anyone build a crest and not connect it to the bedrock? This is serious as you can see what only 1.5' of water coming over the crest did in terms of erosion. Look at the gouges going almost to the base of the crest.