Do I need a concrete collar for my in-ground pond?

[CreatureBlackLagoon]

Hello! I've been lurking for some time around here learning everything I can while I prepare to build a pond. Thanks so much already for your expertise. I have most everything figured out but am still torn about whether I should pour a concrete collar. I've read places that it's a good idea to dig a ditch and pour a concrete ring of footing and stack it with a couple of bricks. (I think the edges of the liner can be rolled in these bricks, with lots of padding of course!) Of course I'd like to do what's best, but it is pretty labor intensive, and if it's unnecessary...Here are the details about my pond-to-be.

The pond will be in-ground, about 8x10 feet and 2 feet deep, kidney-shaped. We live in Tennessee zone 7a. Our soil is very dense and claylike. We plan to dig in three shelves. We haven't decided about fish yet but will probably hold off at least until we get things complete and the ecosystem begins to flourish. We'll be building a small waterfall (18"). We have a skimmer and submersible pump and will be using a 45 mil EPDM liner. We will be setting flat rocks along the edge and want to be sure that when it rains hard (the area did flood badly several years ago), the walls maintain. I know the water in the pond does a lot of this work, but some books and websites really push for the concrete collar. We also plan to put smooth river rocks in the pond. (Have read TONS in the forum about the pros and cons of rocks. Thanks for that!)

The pic is of our pond site with a barely perceptible form painted with blue spray paint.

I'd love to hear from you. Thanks so very much!

 

[Mmathis]

Hello and welcome!

You really hear more about collars on the koi forums, where they go pretty deep and need the extra support. That being said, my pond is around 3000 gal and about 3' at the deepest (I have goldfish, BTW). Our soil is clay and we have a high water table. After 2 years there were problems with wall collapses, even though the walls were slanted and not vertical. We did a re-build and added a concrete & cinder block collar. It's been great! No issues at all. I also wanted the sides raised about a foot above ground level so that there would be a greater amount of pressure from the water in order to keep the liner from bubbling due to the high water table.

 

[mgmine]

I wouldn't bother with any concrete, concrete is permanent and without a footer can heave and shift and cause all sorts of headaches . Bring the liner to the top and leave plenty of extra in case its ever needed. with the liner on the ground (fold if necessary) then cover it with dirt. Stones are optional but they do look nice if done right and provide a pace to plant things like sedum.

 

[Meyer Jordan]

If excavation in done properly a concrete collar is an option, not a necessity. Personally I think that one detracts from the aesthetics. I feel that a pond should appear natural.

 

[sissy]

Welcome and all you really need is a top border of rocks to hide the liner

 

[Mmathis]

I wouldn't bother with any concrete, concrete is permanent and without a footer can heave and shift and cause all sorts of headaches .

Not for a collar! Not saying the OP needs a collar, but it's not the same as doing a concrete wall.

 

[CreatureBlackLagoon]

Thanks so much, everyone! I was thinking a collar that is covered with some soil. I specifically read about it in a book called The Pond Specialist by A.&G. Bridgewater. (image attached)

@tadpole Could you elaborate a bit about "if excavation is done properly"? I know you have loads of expertise. We were thinking of hand digging with 2-3 shelves. Thank you!

 

[sissy]

Do you want shelves for plants .Reason I ask if you have predators it could give them easy access to your fish

 

[CreatureBlackLagoon]

Do you want shelves for plants .Reason I ask if you have predators it could give them easy access to your fish

Hi sissy,
Thanks for your question. Yes, I do want shelves for plants. I've felt deterred from fish for this reason... am really excited about the planting possibilities! Am leaning against fish for this reason and a couple others... I've heard that without fish, it encourages other creatures to join the habitat and I'd be really interested to see what shows up! It seems like fish might add to the maintenance because "what goes in what must come out."

 

[Meyer Jordan]

@tadpole Could you elaborate a bit about "if excavation is done properly"? I know you have loads of expertise. We were thinking of hand digging with 2-3 shelves. Thank you!

Unless you have extremely sandy soil, if the walls of the pond are sloped no less than 17 degrees from the vertical there should be no instance of collapse. A collar becomes an option.

 

[sissy]

I have stock tanks with ony plants and they do need fertilized more often ,but can understand the no fish .You could go pondless with a waterfall with planting areas in it with a shallow water area at the bottom for birds and critters and plants .Alll up and down the waterfall would be great for plants and pondless gives a place for birds and butterflies and frogs to frolic in .

 

[Usman]

Thanks so much, everyone! I was thinking a collar that is covered with some soil. I specifically read about it in a book called The Pond Specialist by A.&G. Bridgewater. (image attached)

Hi welcome . what is the depth given in that book for this pond ? they have added alot of extra layers which is not usual practice now days , if u have very loose soil or clay , u can add a layer of rocks at the border which will act like ring to stablise the border but normaly its not needed , just have shelf and place liner then cover the edges with rocks to hide it , concrete ring is recommended when ur going over 4 ft steep without shelves with loss soil .

river rocks are fine in some environments and circumstances , some times not suitable , depends , but i wud recommend having them in the shelf rather then at the bottom , can b problems cleaning and they will discolor turn black at the bottom so u cant even see them .

 

[mgmine]

Not for a collar! Not saying the OP needs a collar, but it's not the same as doing a concrete wall.

Any large area of concrete can shift and crack if the ground below it freezes . Since a collar is thin I personally wouldn't risk it

 

[CreatureBlackLagoon]

Hi welcome . what is the depth given in that book for this pond ? they have added alot of extra layers which is not usual practice now days , if u have very loose soil or clay , u can add a layer of rocks at the border which will act like ring to stablise the border but normaly its not needed , just have shelf and place liner then cover the edges with rocks to hide it , concrete ring is recommended when ur going over 4 ft steep without shelves with loss soil .

river rocks are fine in some environments and circumstances , some times not suitable , depends , but i wud recommend having them in the shelf rather then at the bottom , can b problems cleaning and they will discolor turn black at the bottom so u cant even see them .

Thanks so much! We decided to skip the collar based on all this feedback.