The above photo was the state of play 3 days prior to this morning. It has been a bit wet since then,
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The water table has risen 18" in those 3 days

Are you going to use this bog as part of the filtration for your pond or just for plants on the side?

Just plants, it will 'dispose' of the overflow from the pond.

So then it's not going to be peat right? Just rocks and dirt?. Because the pond water will be high PH and if it runs into the acidic peat it will keep the PH fluctuating in the bog. I don't know how that will effect the plants of they are true acid eaters.
Hopefully the acid bog expert will drop in and comment on that.

It will be peat, the overflow from the pond to the bog will be one way flow and the overflow from the bog to the outside world will be 1/8" lower than that, so the bog shouldnt be able to contaminate the pond.

Today. The risky bit, the wall between pond and bog, RHS done, the far end is a stream wall. It's still raining. Not all the water is rainwater.
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This shows the other 'long' side, because of the pipe at the bottom this wall will be sloped soil. the pipe connects the settlement-tank/pump-chamber with the filter tank
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The bags are stone to hold the bottom of the flagstones in place whilst the backfill behind the flagstones drains. The bottom of the bog is in a marine sand layer which partially collpases when soaking wet so I was left with large voids under the soil crust behind the flagstones. I washed sand in to fill these voids, hence "drains" and some of the water in the last two photos.

Looks like you are enjoying your workout. Can't wait to see what it looks like in full greenery or whatever dominant colr the plants happen to be.

I lined and filled the bog with water yesterday to prevent any more side slips, hopefully sometime soon we will get back to summer weather.
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As I have 2 garden paddling/swimming pools (cheap holding tanks for pond water) which is where this water came from I can empty this 'pond' quite easily when I want to do more work. It may yet grow 6" to the left.

I enlarged the hole, widened it, yesterday to just under 9'x6' and lined all the walls with 3'x2'x2" flagstones, sand on the floor. It hadnt rained in 24 hours, WWWWOOOOWWWWWW, so I was able to keep ahead of the ground water. My forearms a b******d after trying to get enough grip over the edges of those flagstones to manipulate them. The liner is in the background.
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I put the peat in on top of the water, MISTAKE.
It actually quite a scarey entity and as I said in the other thread it forms a crust. The crust is quite thick, in the photo below that thing on/in the crust is a hozelock titan pump and I had to push it into and through the crust to get to the water underneath to get some water out. The pump sat like that for 5 minutes without moving before I gave up and pushed it through.
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The wall was not as stable as I had hoped for so I have had to add a concrete collar around the outside.
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Well I finally have everything levelled off, the edging screwed in place and the liner fitted, trimmed and stuck in place AND A SLIGHT LEAK, I think. That shouldnt be too bad to repair, assuming I can find the b****r, as I can now lift the liner and replace it with out having to repositon it, hopefully positioning will be more or less automatic. Photo to follow.

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