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EarthBag reinforced pond/cistern/resevoir  RSS feed

 
Posts: 24
Location: Portland, OR
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I'm considering building a deep, straight cylinder pond that might be best considered a cistern for garden irrigation.  Its a strait cylinder to minimize surface area and evaporation, and also just use less of my precious high area.  A cylinder requires structure...

The cylinder is about 30' in diameter, and 5'-10' deep with a 3' berm constructed from the removed dirt.  If 6' deep with a 3' berm it should hold about 45,000 gallons.  I was considering using concrete (blocks or poured), but of course earthbags make a lot of sense. Water law means that I'll need to use a liner.  

While earthbags have been used for basements and in some wet areas, I haven't seen them used in just this way.  My concerns are:

  • resisting the compression of the surrounding dirt, especially when empty of water.
  • need to plaster/coat the pond liner side of the earthbags
  • width of the earthbags, and should they be tapered
  • considerations for packing material ( I have good clay, not sand or gravel)

  • Any thoughts or experience using earthbags in this way would be greatly appreciated.
    earthbag-pond-small.jpg
    [Thumbnail for earthbag-pond-small.jpg]
    Cross section of pond with earthbags
     
    pollinator
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    When I think of earthbags, actually the first thing I think of is how they are used for water retention. It seems every time I watch TV where there is flooding, it is almost a media law that they show people desperately trying to shovel sand into sand bags to keep their homes from being flooded. I know it works because a company was able to save itself from a flood back in 1987 here where its employees, desperate for their jobs, built a sand bag wall to stop a river nearby from flooding their factory. Surely if sand bags can keep OUT water, it can also keep it in.


    I see nothing wrong with your plan at all. If you were concerned about slumping when the cistern was empty, you could put in geofabric every foot of so of backfill to give you engineered soil that would resist slumping.
     
    pollinator
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    Intriguing.
    Must you plaster the bags at all?
     
    Eliot Mason
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    Thanks Travis!

    Yes, of course sand bags!  A single course of those would just be a few feet tall ...

    Excuse me if I'm missing the definition of "earth bag" , but would rammed earth be sufficient or should it be more of a mixture of cement and gravel?  I'm not worried about the vertical load, but the compression load from the side... I'd think that a "soft" ring doesn't have much compression strength/tension (ok, my engineer skills are maxed out here...) and could be pushed in by slumping soil.

    And sure, geofabric! I'd need to make the initial hole larger in order to have space to make a consistent backfill, but that would certainly help.

    Of course, the whole slumping discussion might be moot.  Since the point is to store rain water, this will fill with water as the soil softens.  The ground will be pretty hard when this is drained down for irrigation.  The berm on top will keep rainwater away from the earthbag wall, so the risk of the top-ring collpasing in early rains is minimized.

    I'm liking this idea!
     
    Eliot Mason
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    William:

    I'm not sure about plastering.  Obviously in this instance I don't have to protect the bags from the elements.  I do wonder if a cementitious skin would provide enough rigidity to make the rings "hard".  If it doesn't matter/isn't needed then I could just use my clay to make a smooth surface on the bags.

    The other purpose of a plaster is to smooth the surface of the wall, so the liner doesn't get stretched into the cracks and develop a weak spot.  That might be more of a question for the manufacturer - but their answer is predictable.

    Of course now I'm wondering if the plaster could be made truly watertight and spare me from wondering "Just what is that liner leaching into the water?" for twenty years.  I bet Ludwig has something to say about that...
     
    Travis Johnson
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    I am just a dumb sheep farmer so please do not go by my limited engineering, but I think you would be fine with your design. I would include geotextile as insurance for slumping, but compression of the wall MAY not be as a huge of an issue as you think. You are not pressing against a flat wall after all, but an arched wall, which obviously has one of the most strongest aspects to it. Think of the Hoover Dam pressing back all that water in a nice arch!

    Here in Maine we have hand dug wells that are many feet deep. They are not as big in diameter as your plan, but 24 to 30 feet deep. They are made up of hand placed rock in a circle around the well and have been in place for hundreds of years. The thing is, water does not often come to the top, yet here in Maine frost action really pushes on the top portion. In this case this is just rock atop of rock with no mortar, so that has less adhesion I would think then geotextile/engineered earth backfill against earth bags.


    Sounds like a neat, low cost, doable project.


     
    author
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    Eliot Mason wrote:I'm considering building a deep, straight cylinder pond that might be best considered a cistern for garden irrigation.  Its a strait cylinder to minimize surface area and evaporation, and also just use less of my precious high area.  A cylinder requires structure...

    The cylinder is about 30' in diameter, and 5'-10' deep with a 3' berm constructed from the removed dirt.  If 6' deep with a 3' berm it should hold about 45,000 gallons.  I was considering using concrete (blocks or poured), but of course earthbags make a lot of sense. Water law means that I'll need to use a liner.  

    While earthbags have been used for basements and in some wet areas, I haven't seen them used in just this way.  My concerns are:

  • resisting the compression of the surrounding dirt, especially when empty of water.
  • need to plaster/coat the pond liner side of the earthbags
  • width of the earthbags, and should they be tapered
  • considerations for packing material ( I have good clay, not sand or gravel)

  • Any thoughts or experience using earthbags in this way would be greatly appreciated.


    There have been many cisterns constructed with earthbags, both above and below ground. We have posted several articles about this: http://www.naturalbuildingblog.com/earthbag-cisterns/, http://www.naturalbuildingblog.com/earthbag-rainwater-cistern/

    Earthbags in a circular configuration with naturally resist compression when empty if they are well tamped.

    A pond liner of some sort is the most secure way to assure that water does not leak out. If the bags are kept from sunlight penetrating them with the liner they do not need any further plaster.

    I would suggest bags at least as big as is standard for the construction of buildings: measuring about 18" wide when flat. Long tubing would be even better at providing tensile strength.

    Solid clay is not advisable as fill because of its potential to expand and contract with moisture content. About 30% clay is the most that should be considered; the rest should be sandy soil.
     
    Eliot Mason
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    Travis Johnson wrote:I am just a dumb clever sheep farmer



    There, fixed it!

    Thanks for the reassuring words.  Since I've never built with earthbags, its just hard to know if I'm building that arch out of a flaccid spaghetti noodle or something more rigid.  Sounds like it will be ok.

    I'll start with a smaller project ... a duck pond.
     
    Eliot Mason
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    Kelly Hart wrote:[
    There have been many cisterns constructed with earthbags, both above and below ground. We have posted several articles about this: http://www.naturalbuildingblog.com/earthbag-cisterns/, http://www.naturalbuildingblog.com/earthbag-rainwater-cistern/



    Doh!  Of course, I remember seeing the Owen Geiger video a while ago... I'd forgotten about it.

    Its great to know that I'm not coloring out of the lines, and that there are others to follow so I don't have to re-invent this particular wheel!  The size might be 10x what others have done, but

    Thanks for clarifying the other details.  Voice of experience is most welcome!
     
    William Bronson
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    Elliot, if you want to avoid a liner, surface bonded cement is a possible solution.
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