A question about silted lakes.

[Bubba1235]

In the mid-west we have been having horrible problems with controling flood waters and one of the biggest reasons is that many of the man made lakes are getting old and are full of silt. (No capacity to hold the water.)

When they talk about it they say its unbelievably expensive to dredge them so I was wondering,,, why not drain them as low as possible in the late summer/fall and when the ground begins to freeze go in with bull dozers and scrappers and remove the silt?

By no means am I any sort of expert at this but I have done work like that on a few farm ponds and it seems to work well. Any thoughts on why it would not work on a larger scale? (Our ground freezes pretty solid in December, January and Feburary)

 

[Bifflefan]

Re: A question about silted lakes.

Maybe you should take your idea to the city councel and propose it. Id talk to the city engineer and see what he says.
It sounds like a good plan to me, but with my luck we would have the warmest winter ever recorded that same year.

 

[rbh]

Re: A question about silted lakes.

Find one big sludge pump and have at it, it could work.

 

[JB]

Re: A question about silted lakes.

Five years ago Hideout Pond was 4 feet of water on top of about 20 feet of silt. The local gas drilling company agreed to clean it out if I would agree to sell them water from it.

The contractor didn't believe me that there was 20' of silt. He wouldn't get a dragline and tried to do it with a track loader and a D-8. He had to get a tank recovery vehicle to rescue the D-8.
After making a really awful mess he abandoned the project.

JB was pretty sore.

A second contractor was hired. They recommended filling it in and leveling it. JB said okay, but only if you build me a similar pond downstream. The state said, can't do that. . .something about interrupting watershed drainage.

Discussions on that issue are not suitable for iboats.

The state agreed to moving the dam downhill 50' and raising the elevation 4'.

The new Hideout Pond is gorgeous and holds about 2.4 million gallons.

That sounds like a happy ending except that it cost the gas drilling company a little over $50K.

What do you suppose it would cost the taxpayers to rehab a 40 billion gallon reservoir??

 

[bassman284]

Re: A question about silted lakes.

After the 2008 flood here in Iowa there was a lot of demand that the Coralville reservoir be dredged or otherwise de-silted so that water could NEVER EVER AGAIN go over the spillway.

Ball park estimates to dredge were $150 to 200 million with a maximum capacity gain of 4 or 5%. This would have delayed water going over the spillway by 12 to 18 hours in 2008. Water ran over the spillway at a level 5 feet above said spillway for 14 days.

Even that capacity gain would be fairly meaningless to flood control since it would all be below the normal pool level.

Problem was that, due to record snow falls followed by a very wet spring topped off with some 6-8 inch rains in June 2008, water was coming in at more than 2.5 times the rate that the gates could let it out.

 

[SS MAYFLOAT]

Re: A question about silted lakes.

The main problem with silt is what to do with it once it is removed. It can't be stacked/piled up. It retains the water for years to come. Somehow it will have to be processed into something useful to make it profitable. If not, it will be a continuing problem.

I know the Corp has tried using a flushing technique, but all it does is wash it downstream only to cause further problems. If someone could engineer a way to seperate the water from the silt, they will be finding a fortune in their bank account. The left over dirt no doubt would be fertile for fields.

 

[marlboro180]

Re: A question about silted lakes.

Yeah I know dredging is ungodly expensive, that was why I wondered if digging it out during the winter would work better. Like I said, we do that on farm ponds without many problems once its frozen.

Yeah, I understand what you are saying. But , you go down 1 cut below frost, at say, minus 4 feet, then you get muck again. Ever try that on a multi- acre site? Ugggggg....
Then you gotta wait for it to freeze again. Sounds like a good idea until you are the operator, or the owner of the equipment in there and you get a sudden thaw.....

 

[j_martin]

Re: A question about silted lakes.

Find one big sludge pump and have at it, it could work.

That's what a dredge is.

 

[TilliamWe]

Re: A question about silted lakes.

I was told that here in Illinois (although it would seem to be a Federal thing) that if you remove ANY silt from the Illinois River, you have to have an EPA permit and LOTS of other hoops to go through. However, Chicago gets some dredged silt from our river to build playgrounds and parks, and I haven't heard of them needing EPA approval. Of course, in 10 years when kids start getting sick and they test the soil (formerly located on the bottom of the Illinois River) and it comes back LOADED with heavy metals, and fertilizers, well...

 

[TilliamWe]

Re: A question about silted lakes.

Sounds like it should go back to the farm fields it came from.

They don't want or need it!

 

[rbh]

Re: A question about silted lakes.

Like most rivers, erosion is a major concern as well as run off from farmers fields.
So to combat the silt, fecal matter, phosphates in some areas, they have started demanding a treed zone on the waters edge as well as a catch ditch along the inside of the treedline.
One other thing I have heard is that fertilizing should only be done late spring after the majority of the field has dried up, this way the fertilizer will not float away in the event of heavy rains.

 

[rbh]

Re: A question about silted lakes.

And just to add that on some rivers that have oxbows there is thinking that these should be filled in as they present a swamp for much of the year.
In my mind this is wrong as they are a flood plain during high water as well are critical habitat for fish, fowl and many animals.
conserve your wetlands.

 

[sfy]

Re: A question about silted lakes.

silt removal is going to become a very big issue in the west in the next few decades, specifically at two massive Colorado River impoundments, Lake Powell and Lake Mead. with such huge dams in place imagine the amount of silt that has built up behind them. and with Powell being basically a type of filter for Mead it is pretty safe to assume it has a much larger amount of silt.

i have heard "experts" claim that one day soon the Glen Canyon Dam will literally be so backed up that the water will just flow over the top. of course, these "experts" are usually paid for their testimony by groups that want all dams removed, so they may be a tiny bit biased.

but as much as i want to dismiss them, they could be right. the silt bed is growing larger every day, and considering the depth of the water dredging boats may have a hard time being effective. giant cranes have been mentioned by some in the past as a possible fix, but the problem is still the depth of the water. by the time they get the bucket topside they have lost a large amount of silt back into the water.

so basically, this is the literal 64 Billion dollar question....how do we clean up the messes that we created by installing these dams in the first place?
you solve the riddle, you get the 64 Billion dollar prize.

 

[rbh]

Re: A question about silted lakes.

SFY-
Dredging is some times not the best answer. In my best opinion you have to drop a stem pipe to the bottom of the muck and slowly aggitate it so you are pulling the crud out from the bottom, just a big vaccuum removing silt, not water.