AuthorTopic: Small Dam & Micro-Hydro Building  (Read 11128 times)

Offline Eddie

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Re: Small Dam & Micro-Hydro Building
« Reply #15 on: March 04, 2017, 03:24:30 PM »
But building dams is FUN. Nothing like damming up a creek. When I was a kid we did it on the Frio, using rocks. After about an hour, your fingertips bleed.



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Offline azozeo

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Re: Small Dam & Micro-Hydro Building
« Reply #16 on: March 04, 2017, 03:32:17 PM »
And a build challenge and a materials sourcing challenge. 

All that stuff adds time and costs. It does sound like a feasible idea, for someone with the right skills and access to good salvage. Not me.

Hard enough to stack 300-400 bags of 80 pound dead weight sacks of concrete. If the creek flow gets low, maybe I can carry most of it in the tractor bucket to right where I need it. I have learned, in my fence building, to try to work smarter with that stuff. I'm sure my back will take weeks to recover from one day of dam building, though.

Now you are thinking like LD, like YOU need to do the back breaking work of construction.  That would be stupid, considering how much you can earn in a given day drilling teeth.

What you need is to have the DESIGN for it done, then on construction day you hire a professional contractor to do the work, while you spend an extra day at the dental office drilling teeth.  You use this money to pay the contractor and his laborers.

I am going to work on a design for this we can build at 1/20th scale or so for a starter.  I already got figured out how it works.  :)

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Offline Eddie

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Re: Small Dam & Micro-Hydro Building
« Reply #17 on: March 04, 2017, 03:35:32 PM »
Very elegant.
What makes the desert beautiful is that somewhere it hides a well.

Offline azozeo

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Re: Small Dam & Micro-Hydro Building
« Reply #18 on: March 04, 2017, 03:35:52 PM »
And a build challenge and a materials sourcing challenge. 

All that stuff adds time and costs. It does sound like a feasible idea, for someone with the right skills and access to good salvage. Not me.

Hard enough to stack 300-400 bags of 80 pound dead weight sacks of concrete. If the creek flow gets low, maybe I can carry most of it in the tractor bucket to right where I need it. I have learned, in my fence building, to try to work smarter with that stuff. I'm sure my back will take weeks to recover from one day of dam building, though.

Now you are thinking like LD, like YOU need to do the back breaking work of construction.  That would be stupid, considering how much you can earn in a given day drilling teeth.

What you need is to have the DESIGN for it done, then on construction day you hire a professional contractor to do the work, while you spend an extra day at the dental office drilling teeth.  You use this money to pay the contractor and his laborers.

I am going to work on a design for this we can build at 1/20th scale or so for a starter.  I already got figured out how it works.  :)

RE



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LD,
Trademark "Bamboo-Jurt"
You'll make a killing bro...  :icon_sunny:
I know exactly what you mean. Let me tell you why youíre here. Youíre here because you know something. What you know you canít explain, but you feel it. Youíve felt it your entire life, that thereís something wrong with the world.
You donít know what it is but its there, like a splinter in your mind

Offline RE

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Re: Small Dam & Micro-Hydro Building
« Reply #19 on: March 04, 2017, 03:43:40 PM »
But building dams is FUN. Nothing like damming up a creek. When I was a kid we did it on the Frio, using rocks. After about an hour, your fingertips bleed.


Small dam on a creek, a few rocks and mud, fun.

Dam on a Big Creek with dozens if not hundreds of bags of concrete to put in place?  Not so much fun.

Besides that is the issue of equipment.  A contractor will have all the right equipment to do the job efficiently.  Back hoe and front end loader, maybe even some Dynamite to quickly get rid of a nasty obstruction.

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Offline Eddie

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Re: Small Dam & Micro-Hydro Building
« Reply #20 on: March 04, 2017, 04:14:08 PM »
I have a backhoe, and two other tractors with loaders, one of which is currently even working.

There are issues here you haven't considered. For one thing, no contractor is going to build a dam without some kind of permit from da gooberment. Plus, bringing in trucks, tractors and crews makes a spectacle, and every neighbor for a mile around is going to trot down the creek from the low water bridge to check out what I''m doing.

When I build it, I want it to be built and there before anybody notices what I'm doing. Eventually it will be known about, but I want it to be a very low profile job. Best way.
What makes the desert beautiful is that somewhere it hides a well.

Offline Farmer McGregor

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Re: Small Dam & Micro-Hydro Building
« Reply #21 on: March 04, 2017, 04:34:35 PM »
I found out Home Depot (the one up by Ft. Hood) will deliver anything for a flat  $79 fee. I am considering ordering three or four pallets of Quikrete readymix to build the dam for my new swimming hole, just using stacked bags (with big nails driven through them for rebar).

Very fast build, no forms, the concrete sets right in the bag and the bags exposed to the outside quickly biodegrade.

I've seen nice looking retaining walls built this way here by the highway department. (The added nails to reinforce the wall is my idea).
Eddie, sorry to intrude, but I can't not comment about stacking bags of concrete mix.

For retaining walls, it will work in a relatively dry climate like Texas and Colorado.  The bags absorb moisture and over time some of the concrete sets up.  The static pressure behind the wall is fairly minimal unless a lot of moisture builds up there -- again, okay in the desert.  Notice in the pic how the stack of bags is canted toward the hillside; that helps with the pressure as well.  Actually, they might use bags of concrete because the low-portland fence-post mix is really cheap since it's mostly sand and gravel -- as cheap as concrete block and way cheaper than cut stone  -- and much easier to work with since there is no 'fitting' required.  Pile the bags, they conform to each other nicely, push in and tamp down some backfill, pile more bags.  Gorillas can do it.

The bad news: this will not work as a hydraulic dam; it will fail.

Water pressure is a totally different beast than stacked/rammed earth; it presses outward as much as it presses downward -- earthen fill does not.  Yes, some of the concrete in the bags will set up after getting wetted, but not consistently, and it will be riddled with paper leakage pathways.  Even a little leak eventually becomes a big leak.

I've got some background in (mostly commercial) construction, including working with concrete structures like monolithic storage tanks for thermal solar, or embedding tanks in monolithic pours (a bitch of a job) and a lot of retaining walls.  Trust me, a concrete dam can not have escape paths for water because it will enlarge them over time.  Now if you used the stacked bag thing as the outside stabilizing retainer for a rammed earthen dam with a good bentonite layer on the inside, that might be okay, but all you're really depending on there is mass -- lots and lots of mass.  The concrete in the bags serves little purpose.  This is true for those retaining wall affairs as well.

It's all about the mass, it's all about the mass... (there's a song in there somewhere).

If you've ever had sacks of concrete mix get soaked and allowed to harden, you've seen that you don't end up with bag shaped blocks, you end up with crumbly partially cured crud that doesn't even make good rip-rap.  The moisture does not saturate or distribute into the contents of the bag evenly, and portland needs to be kneaded or churned to get thoroughly wetted (it's somewhat hydrophobic), so they don't set up like you'd imagine.

Use the concrete, but mix it (always spiking with some extra portland since sack-crete is low quality) and place it in properly formed and reinforced structures that you can count on.  Failures really suck.
--Greg
« Last Edit: March 04, 2017, 04:42:06 PM by Farmer McGregor »
For years we have let ourselves believe that as long as we have money we will have food. This is a mistake. The government will bring forth no food by providing hundreds of billions of dollars to the agribusiness industry.  --Wendell Berry after the 2008 crash

Offline Eddie

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Re: Small Dam & Micro-Hydro Building
« Reply #22 on: March 04, 2017, 05:25:35 PM »
Thanks for weighing in. I do appreciate the voice of experience.

If I built it at the right time of year, the creek could be dry. We aren't THAT  dry here in central Texas as far as relative humidity, and the bags of ready mix I don't use eventually set up completely, sitting under dry cover, in less than a year. Trust me on that one. Not partially. Rock solid.

I think that with spikes holding it together, the structural strength would be adequate. What you are saying about leaks makes sense to me completely though. Maybe a layer of poured or troweled concrete on the inner wall? What do you think?

We are talking about a tiny dam. Five feet high at the deepest part. Fifty feet wide.
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Offline RE

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Re: Small Dam & Micro-Hydro Building
« Reply #23 on: March 04, 2017, 09:24:17 PM »
I have to agree with FM here, I can't see it having structural integrity with the separate bags.  You need forms and you need proper rebar, not some spikes.

Your going to need to do it at low water, when you can dig a channel around the main stream to dry it out.  Here's a bunch of guys trying to hold backwater to get a dam built.  Good luck with that.  ::)

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Offline Farmer McGregor

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Re: Small Dam & Micro-Hydro Building
« Reply #24 on: March 04, 2017, 09:53:51 PM »
Thanks for weighing in. I do appreciate the voice of experience.

If I built it at the right time of year, the creek could be dry. We aren't THAT  dry here in central Texas as far as relative humidity, and the bags of ready mix I don't use eventually set up completely, sitting under dry cover, in less than a year. Trust me on that one. Not partially. Rock solid.

I think that with spikes holding it together, the structural strength would be adequate. What you are saying about leaks makes sense to me completely though. Maybe a layer of poured or troweled concrete on the inner wall? What do you think?

We are talking about a tiny dam. Five feet high at the deepest part. Fifty feet wide.

Quote
Not partially. Rock solid.
Have you ever busted one up?  Apparently you have the humidity to saturate it.  Out here they last pretty well under cover but the ones that get hard it's only the outer inch or so.  If you bust it open its nowhere near solid like you would want it to be for structural purposes.  Crumbly in the middle.

Quote
Maybe a layer of poured or troweled concrete on the inner wall?
Definitely something like that, though I'm pretty sure you'll want rammed earth.  You have to have a fairly impervious membrane because seepage will only get worse and will eventually break through catastrophically.  Water is aggressively erosive.  That's where bentonite or another expansive clay comes in.  Poured concrete would need to be thick enough to not crack up easily, so it would need rebar.  I suspect that packed earth over a solid structure is your best bet.  Dirt (clay) is far more inclined to self-seal than concrete.

One of my brothers has a smallish earthen dam that gets perforated by pocket gophers and salamanders.  By spreading bentonite on the surface of the water so that it settle down onto the dam you can seal the holes.  The outflow of water carries the clay into the perforations where it clings and expands and clogs them.

Dam construction is way more complex than first meets the eye: pile up dirt to stop water.  Seems easy but keeping it in place is a be-otch.  I wish we were neighbors so I could get right in there with you.

up.www.fao.org/docrep/012/i1531e/i1531e.pdf
For years we have let ourselves believe that as long as we have money we will have food. This is a mistake. The government will bring forth no food by providing hundreds of billions of dollars to the agribusiness industry.  --Wendell Berry after the 2008 crash

Offline Farmer McGregor

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Re: Small Dam & Micro-Hydro Building
« Reply #25 on: March 04, 2017, 10:03:11 PM »
Eddie,
Have you looked into geomembrane material?

http://www.coloradolining.com/applications/dam1.htm

For your shallow dam, I bet there's a reasonable-costing material you could use that would give you a fundamentally impervious barrier that would hold up well as long as you didn't somehow puncture it.  Should work well with just shaped earth structures, no need for concrete, except perhaps at the spillway.
For years we have let ourselves believe that as long as we have money we will have food. This is a mistake. The government will bring forth no food by providing hundreds of billions of dollars to the agribusiness industry.  --Wendell Berry after the 2008 crash

Offline RE

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Re: Small Dam & Micro-Hydro Building
« Reply #26 on: March 05, 2017, 02:45:00 AM »
If you are just using the bags of cement for mass, and it will have cracks through it, why use cement at all?  Sandbags would perform the same function and would be a lot cheaper.  Then you mud and clay seal the back side to keep water from leaking through.  You could also Shotcrete the front side to make it more solid.  Hang rebar off the sandbags then blow the shotcrete over that,just like in Monolithic Dome construction.

You can order a dump truck full of sand and the sandbags, and have a party filling them up.


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Offline luciddreams

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Re: Small Dam & Micro-Hydro Building
« Reply #27 on: March 05, 2017, 08:48:51 AM »
What about doing what kids do and just using rock?  You've got a shit load of rock Eddie.  Pile enough rock up and you'll have a damn of sorts.  At least you could make a swimming/fishing hole that way couldn't you? 

Offline RE

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Re: Small Dam & Micro-Hydro Building
« Reply #28 on: March 05, 2017, 09:05:09 AM »
What about doing what kids do and just using rock?  You've got a shit load of rock Eddie.  Pile enough rock up and you'll have a damn of sorts.  At least you could make a swimming/fishing hole that way couldn't you?

He couldn't build a big enough one that way to get his plan for a Micro Hydro generating system going.

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Offline Farmer McGregor

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Re: Small Dam & Micro-Hydro Building
« Reply #29 on: March 05, 2017, 09:09:16 AM »
What about doing what kids do and just using rock?  You've got a shit load of rock Eddie.  Pile enough rock up and you'll have a damn of sorts.  At least you could make a swimming/fishing hole that way couldn't you?
The trouble here is that, yes, you can slow down and hold back some water with a pile of rocks, but it leaks. BADLY!

If water can flow through it, it will, over time, tear it apart.  Have you ever gone back later to where you had piled rocks in a river to create a little pond only to discover that your dam was mostly dismantled?  Dams must hold back all of the water, releasing only under controlled conditions, or nature will un-dam it for you.  All dams require some maintenance to keep them in place because any seepage will escalate toward collapse.
For years we have let ourselves believe that as long as we have money we will have food. This is a mistake. The government will bring forth no food by providing hundreds of billions of dollars to the agribusiness industry.  --Wendell Berry after the 2008 crash

 

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