Hebgen dam

I haven't posted anything in a long time because....I didn't
have much to say. But here's an interesting story:

Sarah Palin is a space alien, oops, no, that's the wrong story.
What is interesting is Hebgen dam right now.
About a week ago a vertical square tube of reinforced concrete,
that forms the output flow for the dam, imploded insward, suddenly
allowing 3500cfs flow out the tube.

Montana Power made a press release saying they appologized, but they
would have it all under control soon. There was no danger, they said.
But in the mean time all campgrounds downstream of the dam are closed,
and the fishing sucks. This is peak late June flow level.

I started thinking about it, and I suspected this was a lot worse than
they were letting on. The collapsed outflow tube is a good thing for
the fishery. I sucks the water off the bottom of the lake, so the
outflow stays cool in summer. Without the tube, the damn would
have to flow out over the top, using emergency overlow channels.
But any over-the-top flow in summer would be a fishing disaster, because
it would turn the Madison into a smallmouth bass fishery.

Mt Power said not to worry. They would lower a heavy steel
somethingorother down around or into the tube to restrict the flow.
Today they announced they'd given up on that idea: it was too dangerous.
Trying to manipulate equipment and heavy metal plates in deep turbulent
water just wasn't working out the way they wanted it to.

So what happens next? They'd better figure something out fast.
If 3500cfs goes over the damn all winter, ice jams will wash out
every bridge between Quake Lake and the dam at McAllister.
Uncontrolled ice dams might knock the willy off that damn dam too.

I worked a winter on an oil rig once, when I was young. At one point
we did a "work over rig" where we cut off a crumpled casing 2500 feet
down, rethreaded the casing and re-cased it, all with natural gas
leaking around us the whole time. No smoking within a mile of the rig
and they had special spark arresters on the big V-12 diesels that ran
the rig. That was bad, but possible. But if you add huge swirling
currents and water pressure into that mix, then you begin to understand
how difficult it would be to fix an outflow tube deep down at the bottom
of a lake. They could plug it in various ways. But then the water will
go over the top, which would be summer time fisheries disaster.

To fix the tube, they might have to drain the lake. They didn't say
that. But I did.

So what happens next? *They'd better figure something out fast.
If 3500cfs goes over the damn all winter, ice jams will wash out
every bridge between Quake Lake and the dam at McAllister.
Uncontrolled ice dams might knock the willy off that damn dam too.

Okay, wouldn't Quake Lake take the brunt of this? Quake is right
below Hebgen. I'm trying to figure out the dynamics here.
Frank Reid

Frank Reid © 2008 wrote:
So what happens next? They'd better figure something out fast.
If 3500cfs goes over the damn all winter, ice jams will wash out
every bridge between Quake Lake and the dam at McAllister.
Uncontrolled ice dams might knock the willy off that damn dam too.

Okay, wouldn't Quake Lake take the brunt of this? Quake is right
below Hebgen. I'm trying to figure out the dynamics here.
Frank Reid

This isn't a dam collapse story. It's all about flow levels.
What ever flows into quake lake will also flow (at that rate)
out of quake lake. The Madison is currently high and muddy and not
fishing at all.

3500cfs has never happened in winter. The riverbed isn't big enough
to handle it in cold weather. 3500cfs in February would build up
ice jambs 50 feet high.

They need to figure out a way to restrict the uncontrolled flow (now
feeding out off the bottom of the lake). They probably will figure out
how to plug that tube, temporarily. But they will have to fix it
eventually. To do that--without draining the lake--would be an
engineering miracle, the way I see it.

Just my .02 slide a huge metal plate down the lake side of the dam
blocking the hole.........Open up the side gate so water flows around
and not over build a new tube on the river side slide into hole secure
problem solved...........Tell them to send me the check...........

Mike wrote:
Just my .02 slide a huge metal plate down the lake side of the dam
blocking the hole.........Open up the side gate so water flows around
and not over build a new tube on the river side slide into hole secure
problem solved...........Tell them to send me the check...........

That might be what they have to do.
The radio had a few more details an hour ago.
They tried to poke a metal rod down the inside of the output
tube. That rod was supposed to guide a metal plate down the
inside of the tube, down to the rupture. That would restrict flow.
But the rod started shaking so violently (because of deep, powerful
turbulence at the bottom of the tube) it threatened to collapse
the crane that was lowering the rod.

Now they're back to head scratching.
They did mention the lake is dropping by 5" per day.
That's 150" or 12.5' per month.
Or roughly 50' drop in four months.
In other words, if they don't get it plugged, the lake
will drain by winter's end.

I assume they WILL get it plugged, one way or another.
And then (as you suggested) the best approach might well
be to build an new outflow tube, rather than fixing the old one.
That will take at least a season.

That would probably mean a lot of 75 degree water going over the top
of the damn dam next summer. Better hope they get it fixed in one season.

salmobytes wrote:
Mike wrote:
Just my .02

I drove down there today, jumped the fence when nobody was looking
and shot a bunch of photos. It's quite a sight. There is a huge amount
of water geysering out of the 75 year old (Hebgen Dam) syphon tube.
At the current rate, the lake will be empty (or at least down
to the bottom of the outflow tube) by the first of the year.
That seems to what they're waiting for now.....in other words,
hurry up and wait. Fix it next year. So we might have to buy
some pitch forks, for all those big browns in the soon-to-be-empty
lake. Actually I don't the think the bottom of the syphon tube actually
drains the lake. But there will be some very long steep and muddy banks
to Hebgen Lake next summer......I think.

Here are some photos I took yesterday.....

http://montana-riverboats.com/Robopa...es/Hebgen-Damn

On Sep 11, 8:44*am, salmobytes wrote:
Here are some photos I took yesterday.....

http://montana-riverboats.com/Robopa...Robopages/Hebg....

Great pics and thanks for reminding me of the best stocked (fly wise)
fly shop I've ever been to. The Beartooth is spectacular.
Frank Reid
(my favorite fishing hat is from there)

salmobytes wrote:

I'm not sure what the following means. But it does sound like good news.
http://www.montanasnewsstation.com/G...0435,menu227_7

===========
Engineers think they have found a way to stop the flow of water from the
Hebgen Lake dam.

PPL engineers discovered that giant timbers in front of the stuck head
gates have deteriorated.

Thursday afternoon, crews were preparing to replace those timbers in
hopes of controlling the flow of water and easing turbulence so the
gates could be closed on their own.

The waters rushing through the gates could be stemmed as soon as this
weekend, according to Mark Lambrecht, PPL public information officer.

Workers are using a special sonar equipped boat brought in from Seattle.

salmobytes wrote:

......now some good news, afterall.

http://www.montanasnewsstation.com/G...0435,menu227_7