Hey mate, i had a situation where i reclaimed a city someone had abandoned obviously because it was contaminated, so i took it over trying to find a way to decontaminate the affected area it wasn't a short process, i had to build up money and i did that by building a manufacturing industry and then i had to research at the Academy but eventually i found the solution Ground Scrubbers, just plant them in multiples of about 3 or 4 in the affected area and give it time it will clear the radiation and ground pollution into air pollution. Definitely wise to make sure you have an effective hospital to take care of any sick sims but if you do that then it should work be wary, that this will require a decent amount of money depending on how big the affected area is