NEED HELP WITH "TURTLE-BOG" CONVERSION

[Mmathis]

Some background info for those who don't know about my set-up. You can skip this part if you already know.
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I have box turtles, and have put a lot of work & planning into their habitats over the past few years. One MAJOR issue was their access to fresh water. Boxies are "land" turtles -- they only need a few inches of water to fulfill their needs. They can swim, to some degree, but they aren't made for an aquatic life, so anything deeper than a few inches can be fatal for them.

The problem was this: turtles are messy critters. They primarily use their water for soaking and as a potty. The usual method of providing water is to have something like a plant saucer filled with water that they can climb into. HOWEVER.....do you know how OFTEN you have to clean and refill a plant saucer when you have a caboodle of turtles using it several times a day? And how much of a pain this gets to be? If I went on vacation during the "turtle months," [when they're not "hibernating"], there's NO WAY my babies would have fresh, clean water -- MAJOR HEALTH CONCERNS!

So that's what lead me to the decision to build a pond. We've always wanted a pond, so it wasn't a difficult decision to make. Originally, it was just going to be something around a hundred or so gallons, but after research, I realized that the larger the water volume, the "easier" it would be to maintain a better water quality. Plus, more water meant that we could have fish! Yea!! [the pond is around 3000 gals]

But the BIGGEST problem was coming up with a way to have a pond that was 100% "TURTLE-SAFE!"
The solution was to make a "false bottom" for the section that was incorporated into their habitat. I won't go into the constructions details, but just to say that I used PVC pipe as a frame and support. I attached cedar fence planks to tie it into the walls of their enclosure, and to provide a PHYSICAL [boxies are escape artists] and VISUAL [if they can see the other side, they want to go there] barrier.
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It has worked out very well over the past year, but there are issues, and I'm now looking at a more permanent solution. Hopefully the pictures will help you understand.

LIST OF ISSUES:
1. Need to ditch the cedar -- looks nice, but EVERY time we get a good rain, tannins from the wood leech into the water, and I have cola-water. It was costing a fortune to have enough activated charcoal on hand to clear the tannins.
2. Not confident in the overall integrity of the PVC structure -- has been fine, so far, but since that area is a "bog," I end up walking on it. Plus it's heavy with pea gravel. Afraid that one of these days it's going to give out, and/or eventually that the weight is going to puncture the liner.
3. The area underneath the "false-floor" is open, so the fish have access there. That's good and bad. It gives them a nice hiding place, but essentially, I have no way of knowing what's going on under there. There is water circulating [since it's a "bog," I have water going from the pump via a PVC set-up], and the bottom is sloped so sediment will flow out. But what's REALLY going on? Do fish get trapped; go there to die....?
4. It's not really an efficient "bog," though the turtles LOVE it. For one thing, the gravel bed isn't that deep -- maybe 6 inches -- so not a lot of support for the plants.
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SOLUTION: I want to convert the area where the turtles live into a real bog! My thoughts were to remove all of the PVC support structures [after confining the turtles, of course]. Pull up the cement ramping I made [it's what bridges the gap between their "land" and the water/bog]. Do a little more excavating and sculpting. Then build a berm or wall that would define the boundary of the NEW bog. If necessary, seam in some additional liner -- which may not be an issue, since the NEW bog will actually take up a more shallow footprint.
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AND THIS IS WHERE I NEED HELP.........

QUESTIONS / ISSUES / CONCERNS: I guess, during the "construction" phase, I could let down some water, then pull the liner back to have access after removing the PVC. I have decided that I want the LINER TO GO OVER the berm/wall rather than build something on top of the liner.
1. Would building a dirt berm to the height needed work? Then pull the liner over it to complete the bog...
2. Would it work any better to use cement block and/or decking wood to build the wall?
-- naturally, I want the wall to be secure and not collapse -- but I'm "construction" challenged about things like this --

3. But my biggest issue is how to add a "turtle fence" [NOT made of wood, this time!] to go on top of the berm, to confine the turtles. It has to be around 16" tall and escape proof -- nothing that can be climbed and something the turtles can't see through [along the lines of what's there now].
-- how to DO it; what to use......

So, now for the pictures:

A "visual" of what's there now, and where I want to go. Not to scale, but the following pics will give you an idea of what it REALLY looks like


First pic is pond, full. Second pic is after a draw-down -- you can sorta see how the "false floor" looks.


I just realized that an iOS upgrade gave me the ability to take panoramic pics! Yea! The areas circled in "red," are where the "turtle bogs" are now. The habitats are separated for boy turtles and girl turtle, each having a separate area. I plan to keep that same "floor plan" with the renovation. You can see the water distribution for the "bog."


Side-views, from both ends. First pic is the "boy" side, and second pic is the "girl" side.

 

[Mmathis]

Was just reading a "Waterbug" comment in another post which made me think this might be an easier way to explain what I'm wanting to do. Basically, what I'd be doing is building another, yet smaller and more shallow pond [the bog] next to the big pond.

But again, it's the "how-to-construct-the-berm" to separate the two that I'm focused on..... We still have A TON OF DIRT left over from the pond excavation [advertised on Craigslist, but no takers] that will be useful as fill-in to decrease the depth of the bog.

 

[fishin4cars]

Ms. Maggie, What if you took the turtle bog out, made two small bogs toward the back of the enclosures. (One for each side) then ran a small stream through each enclosure back to the pond? This would give you some bog area for filtration and plants and the stream would provide fresh water all the time for the turtles. Then you could landscape the side of the pond to close them in. Although I doubt they would get in the pond if they have a area that they can get to fresh water Boxies usually don't venture out in water that their feet can touch.
Honestly I worried about the PVC shelf from the beginning of your build. If you look at Todds bog he has a stream that really looks nice from a small bog. If you did something like that you could have the stream enter the pond under a deck/bridge along the side and hide a barrier under it so the turtles would still be in the enclosure. I like the over hang for the fish to hide under, Also along the deck (If you did something like that) you could put planters with holes drilled in the bottom and flow water through them and make little aquapontic filters for veggies, and or aquatic plants.

 

[Mmathis]

Ms. Maggie, What if you took the turtle bog out, made two small bogs toward the back of the enclosures. (One for each side) then ran a small stream through each enclosure back to the pond? This would give you some bog area for filtration and plants and the stream would provide fresh water all the time for the turtles. Then you could landscape the side of the pond to close them in. Although I doubt they would get in the pond if they have a area that they can get to fresh water Boxies usually don't venture out in water that their feet can touch.
Honestly I worried about the PVC shelf from the beginning of your build. If you look at Todds bog he has a stream that really looks nice from a small bog. If you did something like that you could have the stream enter the pond under a deck/bridge along the side and hide a barrier under it so the turtles would still be in the enclosure. I like the over hang for the fish to hide under, Also along the deck (If you did something like that) you could put planters with holes drilled in the bottom and flow water through them and make little aquapontic filters for veggies, and or aquatic plants.

Larkin, thanks for a different perspective! If I completely did away with the "turtle bog" part, and move the fence BACK, I would actually reclaim that same amt. of water for the fish. I absolutely will have to have fencing to enclose the habitats, though -- not an option! But even taking out the "bogs" will not reduce the space in their habitats, though it looks like it would (per my scribbles). The extra space was added to accommodate their habitat when we dug for the pond. Then, if I'm understanding what you're saying, we could construct a small "deck" over the part of the pond that's currently part of the habitat. I like that idea! A place for us to stand or sit, but the fish would still have their covered area! And best of all, NO MESSING WITH THE LINER . HAPPY DANCE!

Then dig a couple of holes elsewhere and connect them via a stream with a return to the pond. I suppose the water TO the first "bog" could "waterfall" in from the pump, pretty much as It does now. Would have to line everything, but otherwise doesn't sound too painfully. Most of the soil back there has been worked enough that digging shouldn't be bad.

Please correct me if I'm wrong, but hey, even if I have misinterpreted, still sounds like a good idea!


What it basically looks like now (brown blobs are trees).


What it COULD look like.

 

[fishin4cars]

exactly what I was thinking. For the return I would go with a PVC grid under 8-12" of gravel like my bog and Addys and Todd's bog. This would serve as a filter and it would hide the piping as well. Lot easier to hide a pipe that just goes over the edging than one that is releasing water such as a fall etc. The stream would be used by the turtles so make sure they can get in and out of it safely. But if they have a stream I don't think they would use the ponds edge as much. Less chance of them getting trapped where they can't get back to safety as easy.

 

[Waterbug]

I never saw pictures of the finished structure before...way cool looking. Seems like an exhibit I'd expect to see in a zoo. You have me thinking of adding turtles now. Could work for a desert landscape, I know a fair number of people here have tortoises.

Yeah, I can't believe the PVC pipe structure held. Amazing.

The dirt berm wouldn't really work, even if you got into rammed earth or adobe type deals. Just isn't strong enough for retaining type stress like you'd have for both the bog and the soil under the bog. Plus I'm not sure how you'd build it. Could fall over when you set the liner.

A concrete block wall requires zero skill, just larbor, $$$ and following a few simple details.

Footer:

Here in Phoenix, for this type of structure, no footer at all is needed. The block itself, being 8" wide, is plenty. But that's a call you'd have to make. When building a house building code and structural engineers tell us exactly how to build. With DIY ponds you have a complete range of options...even PVC pipe as a foundation. So there's no right or wrong way, just what you want.

The footer should be below max freeze depth...not a problem for you. The width and thickness of the footer depends on soil conditions, weight on the footer and if you would be OK with some movement and cracking. You wouldn't have much weight here and some movement and cracking isn't a problem imo as the wall is completely hidden. The rebar in the blocks hold the wall together, so some cracking isn't the end of the world. That leaves soil conditions for your area. A kind of rule of thumb is to make the footer 16" wide by 2" thick. But I'd shoot for 3" thick so if there's some high spots in the dirt no big problem.

For this size job I think 3/8" rebar is fine, called #3. There are 2 strands of horizontal rebar in the footer and ends pf rebar must overlap 16" and be tied together. Bunch of Youtube videos on how to tie rebar together, very easy.

You want some vertical pieces of rebar, every other void, every fourth, whatever. I don't think the verticals are very important for this type of application so I wouldn't put very many. Just want to tie the blocks to the footer.

I put a single strand of horizontal rebar in every course. That's probably overkill and every other would be fine. Overlap 16" and tie. The horizontals can be tied to the verticals so the horizontal is kind of in the center of the channel that will be filled with concrete.


Top in detail:

I think it's really important to consider the top. Many people get in a hurry, build the wall, and then have to do a lot of extra work to finish.

I like to attach a pressure treated 2x4 to the top so I can nail the liner to that or whatever. Gives me lots of options. They make anchor bolts specifically for this and you can use those. I find them too big for this type of application, we're not holding down a house. I use 1/4" threaded rod used for electrical conduit. Like 50 cent a foot, bolt cutters cut it easy (just put the nut on first because cutting messes up the threads). You only need 2 anchors per piece of 2x4, but more is fine.

To attach: Make your life easy...build the wall and fill with concrete but not all the way to the top. Level the top course like 3-6" empty. Then you aren't rushed trying to set the 2x4. You can do it the same day if you want, or the next day or next week.

Cut the 2x4s so you have what you want and set them in place. Now you can see were each 2x4 falls on voids. Drill a 1/4" hole for the rod so it will be in a void. Put a 6-8" length of rod thru with a washer and nut on top. Once all the anchors are set you can place the 2x4 and fill the voids with concrete. After the concrete are set for a couple of weeks you can tighten the nuts. You can snug down the nuts after a day, enough to lay the liner, but don't go ape.

I hammer the rod end in the concrete over a bit but that is optional.

Cutting rod messes up the threads. Makes getting a nut started a pain. Put the nuts on first and then cut.

Fence. If you don't want wood you could use Hardie board, or any fiber cement board. They make it with a wood grain if you like. That's what I show in the pictures. But you could just continue the block up to the height you wanted and apply whatever covering you wanted. Stone veneer, stucco, wood, Hardie board, paint.

Setting the block. I think this is where people think skill is needed, doing the mortar joints. Not needed. Just dry stack the blocks, no mortar joints. You'll be filling the blocks, that's the strength. Do your best to get them level and vertically plumb but for this size wall, doesn't have to be perfect.

Filling voids with concrete. I fill voids every couple of courses. You can build a little wood funnel type deal to help get the concrete into the void. But I prefer using a scoop like this one. I used to use a garden scoop but these old scoops are lighter, easier to clean and feel better in hand. Plus they're cheaper. I have a few sizes, the big ones can fill a block in 3-4 scoops.

No reason to mix the concrete into a soup. Just enough water to make like thick mashed potatoes is just. Scoop some into a void and then use a length of wood, like a 1x1 or 2x2 to tamp down the concrete like you would dirt. That sets the concrete very fast. This is like they make concrete pavers, pressure instead of lots of water. Results in stronger concrete too. Makes it way less messy and much easier. You don't have to go crazy with the mixing.

Easier and cheaper option. You could skip the footer, all the rebar and concrete. Instead dry stack the block and fill voids with soil. Tamp down as you go, like every 2" of soil, with a piece of wood. Called rammed earth. It is surprisingly strong but you should expect problems long term, maybe even short term. May hold well enough, may not. But compared to just plain dirt as you said this would be many many times better.

You can also do something in between. Fill with soil for say a course and a half, then fill with 6" of concrete and a horizontal strand of rebar. Then soil, and keep alternating. I'd expect this to perform very well.

 

[Mmathis]

Thanks, WB!

 

[Mmathis]

I've been surveying the layout, considering possible construction sites within the habitat. I have some "landscape" software [that Hubby still needs to install for me] that I'm hoping I can use to visualize the finished deal. It's one that you can import your own photos, and it has a "water feature" function so you can add simple ponds, pools, etc.

Two issues that I'm going to need help with: the "deck" or "bridge" that I want to put across [see drawing in my original post].

1 -- The area it will span is about 11 feet, and maybe 2-3 feet wide. Hubby asked, "how will it be supported?" I don't know..... It will be supported, of course, on either end, and partially by that side of the pond, but is that OK? I have NO IDEA about things like this.

2 -- I'll need to use a material that isn't wood [see the original post = tannins]. Did a brief "search," and there is PVC decking. Is it easy to work with? How expensive? Do y'all know of other options for a "non-tannin" building material?

And guess I should continue to ask for more input regarding this whole project.