DMSO is a pretty common solvent. It's still nasty stuff, but easy to clean from a sample.

Take a bunch of contaminated soil, wash with DMSO, filter out soil, wash again, take all of that and electrolyze it.

Take the soil, dilute with lots of water and boil in a chamber with a fractionating column / distillation setup to reclaim the last of the DMSO.

I'd be surprised if this was in any way economical, but it's the cheapest way to permanently get rid of DDT, and the production of benzene and other hydrocarbons is a nice side benefit to reclaim some of the cost.