OK : So if you don’t know about these things? here is a crash chat…take a bathtub fill in the plug hole ans seal it then lift the tub above the ground and toss in some 100mm ag pipe cover this and up all the sides with geo-textile or weed mat (my case)drill a hole 5in ( 125mm) up the side and another 6in (150mm0 for heavy drainage (like in Heavy downpours of rain) then cover the ag pipe with loose weed mat and fill to 5in 125mm with corse sand now cover the sand with a 2nd layer of geo-textile or weed mat up over the sides.This is now topped off with a good topsoil mix.
So 1 bathtub with 2 holes for water fill and flood relief.
Now the start of these are 100mm (4in) agg pipe laid in a large ring around the bottom of the tub, mine I joined the ring with joiners as they were on hand and as I cut 2 I had another section that just took up space in the bottom these are used as a clear run of water within the sand layer,
the weed mat is laid over so the sand will not seap down and fill the 100mm ag pipe
Now this next step is not mandated but I laid down 50mm grass clipping left a week in a plastic drum and then 50mm of hay that I had run over with the catcher mower to make it fine. now my soil mix was 10 shovelfulls of a cow and lake mud that mixed with lawn clippings was about 4 years old this was added to 1 x 55 kg bag of good potting mix
the whole bet was then milched with mowen straw.
That was #1 test bed will load up test bed #2 tomorrow.