the most harmful effects of DDT is nerve damage. this results in hair loss, muscle atrophy, disorientation, cancer.
Mountains and high places such as cliffs in front of oceans could be good for defense because you have the high ground and an easier to attack ships.
Ground that is very fertile and has enough access to sun could prove very good to plant crops and make farms.
Rivers and lakes could come off of a mountain so being on lower ground could be good to provide water for yourselves and your crops or animals that are used for food.
Idaho had good soil for potatoes and farming. Towns with lakes and hills would be good for water and farming and life with a family in general.
You would want to avoid rocky ground and mountains unless you wanted to protect yourself, so avoiding new england and also high places like colorado.
Well dumping is a method, waste materials are dumped in open low labs away from the city.