Big Manufactured Mountain

I'm designing the primary living structure on Plott World, and I'm thinking it will be about the size of the Bay Area, but a single giant structure reaching kilometers into the sky. Then I considered the sheer meterological impact of such a structure, and decided that I didn't want a pollution planet on my hands. So I figure the whole thing can be a manufactured mountain, complete with greenery on the surface.

That solves the impact on the planet's economy, but doesn't solve how the people get fed. I'm going to have to look into some different urban populations and how they get their food and clothing. Then there's other importation of goods- media, drugs, and labor. I imagine there will have to be vast polyagriculture fields nearby, designed to recycle topsoil into a viable food product for the masses, which I will call mana. Then, depending on your economic status in the hive, you can afford flavoring and texturizing for the mana, or even afford some of the fruits and animals grow naturally in the polyagriculture.

I suppose enough technology and attention to the planet as a system could contain all of its waste within itself. So the waste will be pushed deeper and deeper into the system of the underhive, where the unfortunates have to deal with it.