This being the rural United States, burn barrels for household waste were a thing for most of a century and spewed dioxin and a lot of other stuff all over the place. You can find lots of studies for background levels of dioxin.
It isn't a binary "Is there dioxin?" There certainly is. The question is, is it elevated above background? Is it elevated about established safe levels? If you run it through that nearby incinerator, will the dispersed plume raise land above acceptable levels?
The EPA has experience with dioxin sites and incineration. They bought a town of 800 people, demolished everything, hauled all the surface dirt to a site-built incinerator and over the course of a year incinerated everything and built a mound out of it. The locals were vocally aggrieved that the incineration was done near them. Its now a nice park for bicycle riding on flat land by a river.