I'm extremely new to gardening I'm in coastal north carolina, lots of rain. For my eagle scout project, I'm planning on converting a large 15x5x3 feet Brick fountain into a flower/vegetable garden in my local retirement home. There's no drainage holes except for a large concrete overflow pipe that sits about a foot off of the bottom.The bottom of the fountain is solid concrete. After a heavy rain, water seems to puddle up to about 6 inches off of the bottom of the fountain.
Plan one: Fill the first 6 inches of the fountain with Large rocks, then fill the rest with a few truckloads of compost/soil mixture. my idea is that since the water already puddles that high, it'll keep the soil from becoming oversaturated. (I'm talking big jagged 6 inch in diameter rocks) Instead of the water staying saturated in the soil, it'll fall through and make a pseudo-water-table in the bottom. However, someone on reddit commented there would be issues with the "perched water table" being too high, and the rocks not helping.
Plan two: Just fill the whole thing with the compost/soil mixture.
(edit) I'm planting things in the outer, bottom section. the middle is to be filled with smooth stones and a neat statue that's being provided by the establishment. :P
A sub irrigated planter sounds awesome! but i'm not sure how i'd go about getting a layer of air down there, i guess maybe putting a layer of mesh over the rocks could possibly work, but i'm not sure how to go about that without ripping the mesh, that's about 2 feet of dirt that'd be piled on top of it. also when it comes to the other plan of just drilling a drainage hole in the bottom, the inside of the fountain sits about 3 inches lower than the outside, so i'd have issues with puddling.
Idea 3? Fill it with dirt and place pots on top. any input is appreciated, i've never grown more than a cactus before