bog filter with waterfall construction questions


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Hi,
We're expanding a small duck pond (small pond, the ducks are average sized) into something slightly less small (it's looking like it the pond itself will be about 6.5'x8.5' max depth 3'
The bog, which is partially raised(the bottom 6" or so are below pond level, the rest is above grade), will be about 3.5'x6.5'.
I can't do the math, but eyeballing it, it seems to be at least 30% of the total surface area.

I've been reading a lot but still have a few construction questions. Can I use earth or sandbags to build the retaining wall for the bog? It would be under the liner.
If so, how best to do this? We have piles of stones we can use over the liner, to hold things in place and to hide the liner. I'm hoping the ducks wont kick everything off.
Or - if I use pressure treated 4x4s (the other readily available option)....how best to close the gaps? I would be using short sections to create curves.

Also wondering how to build the waterfall section? We're planning for a maybe 8"drop and I'd like to direct the water over a large flat stone. I assume this needs to be lower than the gravel level. How do you direct the water over the stone?

I've read some things that say keep at least 2" of gravel above water level, but some things I've read say there should be standing water. My instinct tell me that standing water would reduce the effective filtration but maybe not? What's the general consensus on this?

Any other thoughts or suggestions before we get too much farther? Thank you!!
IMG_3556.jpg
 
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Nice project you're doing there!

My bog is also partially in the ground and partially above.

I used stones and packed soil in between them to create the retaining walls.
The liner goes over that, then I placed another layer of stones to hide the liner.

Just create a low spot in the wall for your water to return to the pond.

Some people like some water above the gravel, some don't. I think it's just personal preference. You can create a stream if you like heading toward your waterfall.

If you read on the internet there's supposed to be set rules for many of the parameters in bog building, but many here have broken those "rules" and still have great results. So, feel free to get creative.

Here's a link to my bog build, maybe it will give you some ideas...

https://www.gardenpondforum.com/threads/my-add-on-bog-build.26848/
 
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Nice project you're doing there!
...
Here's a link to my bog build, maybe it will give you some ideas...

https://www.gardenpondforum.com/threads/my-add-on-bog-build.26848/

Thank you! I've actually spent a lot of time studying your build already - it's very inspiring!
I think I just got tired, so I'm making excuses for not finishing. The chickens are happy - they love a good dig - but the
ducks are losing patience, so gotta get moving on this.

I'm still a bit worried because my strong but overzealous assistant just dug straight down, so I've had to build back up for walls and shelves
and I'm not sure I've tamped them down enough, not sure the shelves are big enough.

I'm glad to hear stones and packed soil have worked for you as a retaining wall. Is that between bog and pond as well? I currently have no wall in that area....what will be the bog is basically just a big shelf at the moment. I need to make sure I keep the retaining wall there relatively narrow so I don't lose too much space. But I'd like to think the water from the pond will push against whatever I build one way, countering the push from the bog in the other direction. Wishful thinking?

How did you set up your spillway so water goes over rather than under the big stone?

Thanks for the inspiration and thoughts!
I'm already mentally epxanding my bog to come out under the fence from the pen (basically right where I took the photo from) into the main yard, so frogs and insects can come enjoy but be safe from those ducks and chickens......
I can see how this never ends
 
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I took apart my existing waterfall and folded that liner back toward the pond temporarily.

Then I built the separation wall out of cobblestones I had laying around. I used soil as mortar for the cobblestones.

I left an opening in the center of that wall for the spillway. You just need to create a low spot. I also struggled with how to create the spillway, but it ended up not really being a big deal.

Then folded the old liner up over that wall. Then the new bog liner went in and overlapped the old liner.
I used two liners because the bog was an add-on. If you're starting from scratch, you can use one liner to cover both bog and pond.
 
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Thank you! Sounds like it's all pretty forgiving really, which is good news for me.
I research a lot, but when it comes down to it I like to keep things pretty simple.

I'll make the wall out of whatever I can move or get someone to move, then double up with stones over the liner to hold things in place.
My husband is still pretty worried about leaks under the spillway rock, he keeps talking about the path of least resistance.
Sounds like it should be fine though.
We'll be using two liners because that's what we have. Unless this project gets any bigger.....

I keep going back to your thread, it's great to have so many photos of the process. Thank you!
 
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Addy was the one that inspired most of us when it came to bogs.
If you haven't seen her bog showcase, check it out. Tons of information and input from others too.
 
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Addy was the one that inspired most of us when it came to bogs.
If you haven't seen her bog showcase, check it out. Tons of information and input from others too.

Your thread and hers were the first two I read! And the ones I go back to most
 

addy1

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Your thread and hers were the first two I read! And the ones I go back to most
I built mine before it was acceptable to do, got a lot of grief from filter lovers. But time has proven it works and works well. I really do nothing to my pond but pull excess growth and groom lilies. I love the bog!

This is bog growth from 3/30 to today approx the same view, new net further down, without a huge hole...........

nvr travel_west pond_main_20210330112222_@3.jpg
nvr travel_west pond_main_20210421102738_@3.jpg
nvr travel_east pond_main_20210520121224_@3.jpg
nvr travel_west pond_main_20210520121726_@3.jpg
 
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I MYSELF WOULD HAVE THE BOG ALMOST EQUAL IN SIZE TO THE POND, WITH DUCK THEY are poop machines if you want clear water then lots of circulation lots of flow and a big old bog.
 
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I built mine before it was acceptable to do, got a lot of grief from filter lovers. But time has proven it works and works well. I really do nothing to my pond but pull excess growth and groom lilies. I love the bog!

This is bog growth from 3/30 to today approx the same view, new net further down, without a huge hole...........

View attachment 139146View attachment 139147View attachment 139149View attachment 139150

really lovely! well done for going with your gut! it's brilliant!
 
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I MYSELF WOULD HAVE THE BOG ALMOST EQUAL IN SIZE TO THE POND, WITH DUCK THEY are poop machines if you want clear water then lots of circulation lots of flow and a big old bog.
that was my goal, but the kid kept making the pond section bigger and we've just about run out of room for bog expansion.
i'll go back out and see where i can stretch it. or if i can reasonably back fill some of the pond section (although that feels wrong)
 
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addy1

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Make the bog deeper! That would help also. At least imho. Mine is 2.5 feet deep.
 
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Make the bog deeper! That would help also. At least imho. Mine is 2.5 feet deep.

thanks! hadn't thought of that - most of what i've read said no more than 12'"...
same size gravel all the way down?
 

addy1

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thanks! hadn't thought of that - most of what i've read said no more than 12'"...
same size gravel all the way down?
mine is just pea gravel, others have used different sized stones, other have added aqua blocks, snorkels etc. Mine is simple, liner, pvc, gravel , plants oh and water.........................
 

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mine is just pea gravel, others have used different sized stones, other have added aqua blocks, snorkels etc. Mine is simple, liner, pvc, gravel , plants oh and water.........................
@addy1 ,nice views. I'm not sure I've ever seen the dimensions of your big pond; would you fill in the blanks? Including any various depths.
 
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mine is just pea gravel, others have used different sized stones, other have added aqua blocks, snorkels etc. Mine is simple, liner, pvc, gravel , plants oh and water.........................
sounds like the way to go - especially since i'm expecting a big load of pea gravel this weekend!
thanks for the feedback...
 
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addy1

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@addy1 ,nice views. I'm not sure I've ever seen the dimensions of your big pond; would you fill in the blanks? Including any various depths.
Approximately, 26 feet long, biggest width is about 20, angles down to around 12-15 feet wide, depth from 5.5 feet going up to 2 feet, right at the crawl out is about a foot. Notice all the approximates. I bought a 26x30 foot net to cover the pond, hung high dropping down 3ish feet and it just covered it.

I was bound (up slope side) by our septic tank found while digging, the septic line found while digging up slope side and west end. A wall of solid rock on the west end, east end the interior fence line, shale, our slope, dug down the uphill side by 4ish feet build up the down slope side by 7ish feet to make a flat spot.

Some liner shows here and there, not perfect, but I love it.
 

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Approximately, 26 feet long, biggest width is about 20, angles down to around 12-15 feet wide, depth from 5.5 feet going up to 2 feet, right at the crawl out is about a foot. Notice all the approximates. I bought a 26x30 foot net to cover the pond, hung high dropping down 3ish feet and it just covered it.

I was bound (up slope side) by our septic tank found while digging, the septic line found while digging up slope side and west end. A wall of solid rock on the west end, east end the interior fence line, shale, our slope, dug down the uphill side by 4ish feet build up the down slope side by 7ish feet to make a flat spot.

Some liner shows here and there, not perfect, but I love it.
Thanks! I knew it was larger, just didn't hit me from any earlier pics until I saw those you just posted! Guess when you dug, you didn't really have a plan, hey? Just sort of dug until you hit something? ha! :)

Did you also dig steps to make it easier to get in and out? I never did, not even with the expansion as I never figured I'd need them.
 

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Just sort of dug until you hit something? ha!
Sort of, put also sort of had a plan. Laid a garden hose down there sort of drew it out. Dug the stream first, went from a straight down to a swtichback stream, slope too steep for straight down. About a 25 degree slope near the house.

Then dug the pond. The septic tank for sure was a blockage, the line was a stop point that wall of solid rock was a stop point The fence and huge maple was a stop point

Did you also dig steps to make it easier to get in and out? I
No I just have the low spot, it drops down sort of fast but sloped enough you can get out. I sloped it for me and for the critters ie deer , that seem to fall in. The liner was huge, don't recall the size exactly, something like 50 x 45 the stream was 85 x 10
 
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Did you also dig steps to make it easier to get in and out?

"Steps" don't need to be STEPS exactly, but every pond should have a way for any creature that needs a way out to get out. A low end like @addy1 built is one way, especially if you have a big pond and don't mind losing the depth. We built ours with a "steps" that are actually big boulders - the first "step" is 12 inches down, the second another 12 and then step down to pond depth. From the outside it appears to drop straight down at that point. It's also our feeding spot for the fish where they can come right up to the edge.

One other thing I've noticed - early on those boulders were rather slippery with algae and biofilm and I had to take my time getting in and out. Now, ten years later, they're covered with carpet algae which gives you great traction. Much easier to navigate!
 

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