Bog Retaining/Dividing Wall Question

[KDubU]

I have a bit of a conundrum about how to secure the dividing wall between my bog and pond. Below is a pic looking from the bog towards the pond. The bog is about 9’L x 7’W x 14”D at it’s largest. It will be filled with pea gravel on top of liner that will be a separate piece to the one in the pond itself. It will hang over into the pond by about 12” or so. Now from my understanding, I need to build some form of retaining/dividing wall on top of the liner, my question is with what materials and how to keep it in place without part or all of it falling into the pond? I have read some have used concrete blocks but are the mortared together? Even if they are, couldn’t the whole section collapse into the the pond with the weight of the pea gravel and water in the bog? I also thought of a treated wood dam of some type but again how to secure? I am not a fan of treated wood in the water anyways but just thinking of options. I can’t rebar the wall into the soil as the liner is underneath or does the liner need to fold up and over the wall? That does not seem right to me but I’m a newbie. Thoughts? Opinions?

 

[Lisak1]

Construction is not my jam, but let me pose a question - why do you want this to overhang the pond? I think that's going to cause engineering issues that you could avoid if you eliminate that from the equation.

 

[KDubU]

I was looking to have the water from the bog to flow into the pond so like a small waterfall. Nothing extreme in drop but there has to be some form of overflow to the pond and as it’s gravity fed from bog so a wall of some form is required.

 

[mrsclem]

You can put a row of block under the liner at the edge of the bog. That will form the wall where the water can flow to the pond.

 

[addy1]

Mine has a landscape wood wall, used rebar to secure and concrete on the ends. The liner goes up and over the wall, one piece of liner for the pond and bog. The wall is higher than the pond surface, therefore a nice waterfall into the pond, not tall but still nice. The waterfall is where the cut in the timbers is.

 

[Blueeyes]

I used large rocks and smaller rocks to fit in between to create small crevices creating a partial wall where the water will fill and then seep back into the pond you can use waterfall foam 2 tighten things up at the bottom. I like this concept that way if the pump goes down you're active bog can remain a passive bog even though water is not being pumped up and in by the pump it also acts as a passive bog in the winter once you shut down your pump as well. I actually had things growing in the Bog before the pump was ever connected in the spring. Water is able to flow back and forth freely the back Edge has to be higher to prevent overflowing the back side. My overflow point is on the backside of the bog this way when it rains and things get too full the water will push his way through the bog and out the back side.

 

[Rex]

@KDubU. I built something similar to what you are explaining, but I built an entire cinder block rectangle area for my bog. Each of the walls of the four sides give the other wall lateral support (i.e. meaning they wouldn't easily be pushed over). My liner is also under my cinder block wall. I didn't want my liner going up and over my bog wall because I'm going to put a rock veneer on the cinder block wall to make it look prettier than a liner showing. I used mortar for my cinder block wall. On the waterfall side, I filled the voids of the cinder block up with concrete to make it sturdier.

If you just built a dividing wall, you are going to struggle with lateral support. Free standing walls are more unstable. Of course, the higher and longer the wall is, the more unstable it will be. You might consider enclosing the entire bog in a cinder block wall, that way you have the support from the other walls. I used some thin strap material at the corners of my walls to add additional corner support plus the bricks are overlapped/staggered. If you do go with a freestanding wall, you will have to extend the wall past the pond on both sides of the pond and add lateral support there. Or, you could add tiebacks somehow towards the bog side.

If your block wall inside the pond, is say two cinder blocks high, you don't have to dig down and make it two blocks high when it extends outside of your pond. It could only be one block high there. This will provide the lateral support you need.

If I had my pond to do over, I would have poured a concrete footing for my cinder block wall to sit on...at a minimum just under the waterfall side. I'm kind of concerned the ground will settle over time, crack my concrete wall, crack the veneer I'm going to add, and also mess up the flow of my waterfall. The following video is a footer the Pond Digger is building

. He isn't using it for a bog, but the same idea.

Good luck!

 

[KDubU]

Thanks everyone for the ideas. @Rex, yes you kind of nailed my concerns and had thought yesterday I may have to line the whole bog with concrete block mortared together. As you say though, without a solid base it likely will crack one day in the future due to the cold so would have to plan to avoid this. I had thought of going a similar route as @addy1 with the concrete blocks running longer than the bog opening embedded in earth with surrounding earth not disturbed (basically a trench wide enough for the blocks and no more). I would then nail in rebar about 2-3’ down inside the block holes, 2 per block. That would hold up for a while but then I am definitely running the liner up over the blocks. Just not sure yet and it sucks this is holding me back from moving forward as I like to have all my details mapped out.

 

[Lisak1]

How wide is the side that faces the pond? If I'm looking at the photo right, it looks like you have the short side toward the pond, so 7 feet? At only 14 inches deep I don't know why you couldn't just retain it with a well packed berm. The liner goes over the berm and you build a waterfall on the other side. What's the drop from the bog to the pond?

Caution: I am not an engineer. I don't even play one on TV. I've just watched lots of professionals on YouTube and no one is using cement or blocks or rebar, especially when the bog outlet feeds a waterfall.

 

[GBBUDD]

Considering this is almost a month old i'd assume you have come to a design and have started building but here is my two cent. i absolutely would not build a pond without a waterfall, all of mine are a little more then a foot tall. They are stress relievers for sure and they remove any road noise in the area "VERY SOOTHING" You are right cement will need to get below the frost line if you want it to last and not shift ,lift and crack. but when your done it's done for 20 years or more. but with your shallow plan for the bog a concrete retaining wall that's very popular today could be an option as could a simple wood box weather it be with landscape ties or with 2x12. i myself would never add pressure treated in the pond. but as a frame that works but it will rot out in time probably no more then ten years if it's laying in the dirt place stone all around it so it can dry out and you could extend it's life a little. looking at your area i would lean toward the bog mimicking the planted area on the other side. and if the bog was raised it would be similar to the planted but distinctly different. the big thing to try and achieve is to have the pond and the bog have sides that will keep water run off from storms out of the pond.

 

[KDubU]

@Lisak1, yes it’s around 6’ at the opening to the pond and then is about 9-10’ long. Yes earthen berm is another idea as it can last if one packs the earth well. Something to consider definitely, Tks.

@GBBUDD, nope still have the issue. I agree about waterfalls and that is why I am planning one from the bog into the pond. It will not be a big drop but around 12”-15”. I also have a Big Bahama waterfall unit that I had thought of installing beside the bog or close by and split the pump feed between the bog and waterfall. Pump is rated for 4500 gph so I believe it could handle the two.

 

[GBBUDD]

@Lisak1, yes it’s around 6’ at the opening to the pond and then is about 9-10’ long. Yes earthen berm is another idea as it can last if one packs the earth well. Something to consider definitely, Tks.

@GBBUDD, nope still have the issue. I agree about waterfalls and that is why I am planning one from the bog into the pond. It will not be a big drop but around 12”-15”. I also have a Big Bahama waterfall unit that I had thought of installing beside the bog or close by and split the pump feed between the bog and waterfall. Pump is rated for 4500 gph so I believe it could handle the two.

You may be disappointed when you see how small a water fall 4500 gallons makes. it sounds like a ton of water but it really isn't