How do you grow things in tainted soil?

You probably only have one choice. Remove the soil in that area. That is the only way to assure that you get rid of whatever was put on the soil.

You would have to replace the soil . We had a lot of construction junk in our yard and would have to dig a much bigger hole than needed and replace that soil with new to plant shrubs because if not they would die.

I agree, Unless you are trying to garden (veggies etc) which has other possibilities like raised bed gardens. if bit you have to remove the tainted soil

You need to replace the soil in that area - or water the heck out of it, till, add new soil and take your chances next spring.

Its best to replace the soil instead of growing things in it. good luck!