Frop Bog 2.0 - looking at concrete even though we have Michigan winters

I’ll keep the preamble here short, but a quick synopsis is last July I felt very good and wanted to make a new Frop bog that is 3x the size of our infamous Frop Bog and nearly 3x as deep. But I got critically ill last year after I’d ripped out 20% of the old bog. I was devastated that my lungs and heart were failing so quick and wondered if I could possibly fight back against my Cystic Fibrosis… a battle I’ve losing. Fast forward to late winter. We know something is very wrong and the accelerated decline of the lung tissue is not something I can accept. Entered pulmonary rehab and have been working hard for months. This week I had my first victory in a long time. I got the remaining pebbles and rocks out of the old bog and was able to rip out the old hardshell liner. I am now “go” for Frop Bog 2.0 digging.

So I’ve got a lot of digging to do, but even though that will be very hard… that’s the easiest part of what we have to do. The new bog will look like a 3 leaf clover, with each clover being a species of bog plant. Pond water from our koi pond will be pumped into each clover from underneathe to nourish the plants, the water will then cascade back into the pond off a 1 foot waterfall. The hard part will be deciding how to construct the watertight barrier. Rubber liner is a pain to work with and with a lot of bog plants slated to grow, the rubber epdm is at risk of puncture. Making a clover shape with rubber liner will also not look good with giant folds all over. So a concrete shell seems like the best route to go, but we live in Michigan and have a lot of freeze/that’s cycles plus a deep freeze. Also…the only concrete work I’ve ever done is concreting posts into the ground.

Right now I’m looking at options on the internet and I’m worried I won’t be able to complete this the way I want. We cannot afford to hire someone to help so it’s up to us to find some way to do this on our own.

If anyone has any ideas to help, videos, books, anything - we could sure use the reference material as my google-fu isn’t great. Or if you have an idea, no matter how weird please post.

Each bog clover will be ~ 4 feet in diameter and 3.5 feet deep. The sides will be nearly vertical straight down to maximize water volume in a limited area. The stem of the clover is where the waterfall will cascade into the koi pond.

Well, I wouldn’t entirely discount a plastic liner, but if you want to do it right you’ll need to cut it into sections to better fit the shape of the hole, and then use a plastic welder to seal the joins. We use this technique for our crocodile pool, and it’s housed a 16 ft saltwater crocodile for the past eight years without too many problems. Well, except that one time when he went a bit nuts and bit several large holes into the lin… well, we don’t talk about that. To encourage plant growth we then put a geomesh / shade-cloth sandwich (filled with mulch, sand and soil) over the top of the liner, and eventually roots begin to infiltrate it and things will grow. If you put a lot of work into it, you can get it to look 100% natural like a mossy bank, and it helps not having a 500 kg crocodile trampling everything too.

Concrete is fine, but if you want to prevent it from cracking you’ll need to put a wire frame into place that you concrete over. Chicken mesh would be fine for what you’re doing. I’ve always found concrete to be a pain, and here at least it’s ridiculously expensive (the plastic and welding was much cheaper) although it’s probably less work overall (although those vertical sides will need some thought). Bear in mind that plants won’t grow into it either, to state the blindingly obvious, but you can use the same technique of laying a growth-encouraging material over the top.

You could also fiberglass it as well I suppose, although it’s nasty stuff to work with. Not necessarily something I would encourage you to be using in fact! Worth a thought though.

Here are two, never-before-seen work in progress shots when we built it.

The plastic liner (1mm in our case, overkill for a Frop Bog though)

The liner sandwich for plant growth visible on the edge.

What it looks like today. The edge liner still isn’t completely hidden but again, 500 kg crocodile. ;)

I’m with Krok: doing almost vertical sides with concrete is going to be a massive pain–you are going to have to build plywood box containers to hold it in place while it cures. Most vertical walls of concrete these days are pre-form that is hauled to the site and set in place for that reason: it is just a LOT less work to have preforms at the factory and hauls the finished wall than it is to build the forms on site.

Get a good solid bottom of the hole packed down, to avoid too much settling and then line the whole thing with plastic. Yes, it will look ugly at first, but as he noted, you can put a mesh matrix of growth material down, and in a year you won’t see the plastic any more. Or just dig the hole a bit deeper and use sand at the bottom to cover the plastic. The mesh will work better, though, imo. Add some sandy beaches along the edges to cover the overlap and you should have a great look in a year or two.

This is the kind of advice I was hoping to get. Thank you so much for putting your thoughts here as I am/was very scared about working with concrete.

Krazykrok - there are some weird impressions in the liner. Was it cut and then heat glued back together? If so maybe that’s the answer to my giant folds issue?

Exactly. You need what’s called a “plastic welder” which is basically a glue gun for plastic. Smaller ones can be bought or hired (we’ve used them in the past to seal PVC pipe joins), although for the 1mm plastic we needed to hire guys in specifically to do it. It still turned out a fair bit cheaper than concrete, and looks better too. So you cut large plastic sheets into roughly the right shape, and cut appropriately to get rid of folds and fill in holes, then glue the seams back together.

We lined the bottom of the pool with sand and stone, added plants, added the growth matrix, and away it went. We also stocked the whole thing with native daphnia, snails, fish, crustaceans, and of course a couple of crocodiles. It’s now entirely self-sustaining except for the crocodiles.

In between being sick I’ve had some wonderful friends and family helping carve out the new bog. I’m extremely happy with the direction we’re going but am remiss to post photos since my own parents can’t figure out why it looks like a round Suez canal. The latest evolution adds a mini-island (actually a peninsula) and a little bridge that will span part of it. The middle island area will be like a Frog resort.

Old Bog area (plastic insert torn out):

Excavating and remarking the slope (the water for the bog will be 18" higher than the level of the pond to create a nice waterfall off one end)

A few posts are now cemented in which will provide a stable base for a frame and plywood boards to keep the walls from caving in. The frame will follow the contour and I’ll attach the liner right to the frame like I did for our pond. Violent storms in-bound so we had to tarp the middle area so the dirt won’t fill back in. It’s hard to tell depth, but its all about 4-5 feet deep and 4 feet wide.

Blood vessels in my left lung have ruptured 7 times since I started this in June. It’s been rough.

7 times? Fuck, Jeff. That’s terrible.

Dang JP you must love you some Frops. Muck love man.

Jeff, I have no health issues, and looking at the scale of what you’re doing I find myself intimidated. You are truly amazing. Those frops have no idea how good they have it.

Thanks for the compliments. Some of our work got washed away today. We got 2.7" of rain in just 12 hours so the sides of 2 zones caved. I knew this could happen… just hoped it wouldn’t and I’d have time to reinforce the sides before we had major storms. I had one post ready to be cemented (it was leaning in the hole), and so much mud flooded in I can’t just pull the post out.