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Dams in a Valley

 
Posts: 7
Location: Washington State
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Quick summary: I have 40 acres in South West Washington. Its all steeply sloped, facing south west, and heavily forested. I've built 6 ponds so far, all in relatively dry spots, then fed with long reaching swales.

Today I attempted to dam up a steep valley/gulch, one where water flows year round. It was a complete failure. I dug out the start to the keyway, which ended up being nearly 10' deep before I found virgin clay (fully saturated with water). Then tapped out my dry clay stores just back filling the maybe 6' of keyway (which needs to be nearly 20') only to find that clay refused to be compacted due to all the water. Mind you, this was out side of the deepest part of the valley where the small stream is flowing.

\--v--/ imagine that is the cross section, and I was a single -  into the keyway.

I also managed to get myself completely stuck trying to move up the valley to harvest more dry clay from the valley walls. (when they send the dozer to snatch me, I'll be sure to build temp log platforms to work from moving forward) but the real question remains.

How do I get the valley dry enough to build dam walls? Should I trench the flowing stream significantly then give the ground a few summer weeks to dry out (not convinced that will even allow it to dry due to the amount of uphill catchment)?
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pioneer
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Jack Powers wrote:Quick summary: I have 40 acres in South West Washington. Its all steeply sloped, facing south west, and heavily forested. I've built 6 ponds so far, all in relatively dry spots, then fed with long reaching swales.

Today I attempted to dam up a steep valley/gulch, one where water flows year round. It was a complete failure. I dug out the start to the keyway, which ended up being nearly 10' deep before I found virgin clay (fully saturated with water). Then tapped out my dry clay stores just back filling the maybe 6' of keyway (which needs to be nearly 20') only to find that clay refused to be compacted due to all the water. Mind you, this was out side of the deepest part of the valley where the small stream is flowing.

\--v--/ imagine that is the cross section, and I was a single -  into the keyway.

I also managed to get myself completely stuck trying to move up the valley to harvest more dry clay from the valley walls. (when they send the dozer to snatch me, I'll be sure to build temp log platforms to work from moving forward) but the real question remains.

How do I get the valley dry enough to build dam walls? Should I trench the flowing stream significantly then give the ground a few summer weeks to dry out (not convinced that will even allow it to dry due to the amount of uphill catchment)?



Holy cow Jack, I don't think I've ever seen anyone get stuck worse than that.  I don't have any advice, but, WOW.
 
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Is there a before picture?
 
Jack Powers
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Location: Washington State
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Of the valley? No, it's extremely difficult to get good pictures of heavily forested areas before I tear things up. I'll take a more zoomed out picture so I can better explain the dam(n) situation.

I sent this pic to the rental company and they had a good laugh.. Sending a bulldozer tomorrow to snatch me out.
 
Jack Powers
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Couldn't get a good angle on the valley, but got another one of the cat trying to swim in the mud...
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pollinator
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Yup . . . that's stuck.  You win.

If you aren't failing at something, you're not trying hard enough.  My hat is off to you for going out there and giving it your best shot!  Believe it or not, that inspires me to try to do more to improve my suburban lot and make it better.

It seems like you need to import some beavers to get busy and do your damming landscape restoration for you.  I'd be curious is there is some sort of state program that relocates beavers.  Let them do the heavy lifting for you.
 
Jack Powers
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They are slowly making their way up the valleys. I imagine another 10 or so years and they will be up this far. I've definitely thought about trapping a few and bringing them up, but that will only get me beaver ponds and I'm after some small lakes up here.

I've been a lurker here for a long time, but hearing that my failures motivates you leads me to believe I should post more here about the broadscale earthworks and overall permaculture practices we have implemented in this land
 
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Hello Jack,

From the description, it seems like you attempted to dam the gully too high up where the ground is super-saturated. It’s unlikely that dewatering the area via a trench, building a dam, then removing the trench, will help.

Once the ground becomes saturated again a dam wall in that circumstance would likely fail AKA a significant safety hazard because it could slip at any time.

An alternative is not to construct a wall, but simply dig a series of small ponds so water is pooled and can cascade along the natural flow lines. It’ll take a bit of assessment and skill to determine how deep is safe enough, but I’d err on the side of caution and be generous with the downhill ‘wall’ width. Besides, in total capacity, several such ponds would add up to a few big ones without creating a domino landslide event.

P.S. That stuck excavator could make a ‘unique’ but expensive water feature!



 
Jack Powers
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I don't follow. The higher up I go in the gully the less uphill catchment there is, and the less saturated the ground is compared to lower in the gully. I have a dam above this spot (near the top of the hillside) which now holds water year round, and is most likely saturated. In fact, when I build any dam wall that holds back water year round I'm contributing to the saturation of the ground, no?
 
pollinator
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Location: East tn
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Been similarly stuck. A bit nerve wracking.

If you are intent on a big pond, you may have better luck with a bulldozer. Use it to push out the wet clay if possible.

If you dont find dry clay underneath, you'll have the right tool to put stuff back :)
 
pollinator
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I agree with J Davis, you are really do not seem to be using the right machine for the job. You would be way better off with a bulldozer, and get a lot more done. Their deep grousers will help you go through the but, and steel tracks give a lot better floatation than rubber ones.

I do not think there is anything wrong with using an excavator and bulldozer in tandem; that is use the excavator to move the bulk of the material, but then a bulldozer to shape it. You really need that smooth blade on the bulldozer to really slope and shape the pond, which will keep it water tight.

But then I would also recommend you rent a much bigger excavator. I rented the same excavator you did in the photos, and it was a good machine, but nowhere near big enough for what I wanted. They just do not have enough reach. You really cannot do much with them because by the time you pull what you need, you are right on top of yourself, and it is an excavator, it really only works well by digging down, and towards itself. They also have a pretty small bucket. I would suggest a 34.000 pound class machine. I have dug many ponds with that class machine, and with a 1 cubic yard bucket, you can move some dirt by the end of the day. The cost is twice as high, but you get 4 times more done.
 
Jack Powers
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This machine has steel tracks, but I agree. I have a 30k lb machine and a large dozer coming in 3 weeks. I used this little one to prep access in some tight spots for that rental. The plan wasn't to build the dams with this little guy
 
Travis Johnson
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Okay, I understand now.

I rent a lot of equipment too and fully understand how sometimes their equipment is rented out to others. It really sucks, but it sure beats owning heavy equipment. I got some bulldozers and stuff, but if you can get the seat time on the rental equipment, its usually a pretty good deal.

Best wishes on your dam project! :-)
 
pollinator
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Jack Powers wrote:Today I attempted to dam up a steep valley/gulch, one where water flows year round. It was a complete failure. I dug out the start to the keyway, which ended up being nearly 10' deep before I found virgin clay (fully saturated with water). Then tapped out my dry clay stores just back filling the maybe 6' of keyway (which needs to be nearly 20') only to find that clay refused to be compacted due to all the water. Mind you, this was out side of the deepest part of the valley where the small stream is flowing.


Jack,
I wish you well on your clay excavation. Hopefully someone with plenty of heavy duty permaculture earthworking experience will chime in to help you complete your project.

As for heavily wooded areas with highly erosive soils in moist climates without much clay & steep slopes, some friends of mine use bioterracing as a soil-ution. One such project, HAPI, took down a stand of invasive monoculture trees with chainsaws, leaving their stumps in the ground, laid the giant logs down on contour uphill of their own stumps so that the stumps would hold the logs in place. They planted out everything from seed. The rains backfilled the logs with soil & leaf litter. Now they have a syntropic food forest thriving there.
 
Jack Powers
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The rental company sent a guy with a dozer to pull me out. He got the dozer stuck and drove the excavator further into the mud.

I got his dozer unstuck and sent him home, hired a local guy to bring a bigger machine to the rescue.

Didn't flood the little one and even got some more work done with it before they came and picked it up!

Upside, the hole where the excavator was is now functioning as a pond.

Downside, nothing on earth can cross the makeshift dam wall made of basically quicksand (clay).
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J Davis
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Oh man...

Thanks for the update.

Perhaps by the end of the dry season things will firm up.
 
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