On Sep 11, 7:33*am, salmobytes wrote:
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.

One way they can address this is to build another dam 50 feet
upstream, then once this dam is isolated and dry, they can repair it.
Common strategy in canyon regions, including digging a hole around the
damaged dam.

A second way is to lower a gate over the opening of the collapsed
tube. Its impossible to put a solid steel plate in front, as the water
pressure jams it against the dam long before it covers the opening.
But a louvered steel gate can be lowered while it is open, allowing
the water to pass through, then once its positioned, the louvers are
shut, sealing the hole. They did this in Maine a few dozen years back
when the ice had frozen the 'in' side of an outlet tube shut, and the
engineer opened the 'out' side. The external air pressure crushed the
30' diameter tube flatter than a toothpaste tube instantly, and they
had to seal the dam to replace it.

In any case, Dam Engineers and the Army Corps are highly skilled in
dealing with such things.

I hope.

--riverman