We have mitigated homes in Lakeland that had so much radium and uranium in the soil that gamma radiation exposure exceeded the safe level limit unless a person was walking on a “radiation shield” sidewalk or inside a home with a thick “radiation shield” concrete slab.

At one location near Ocala, outdoor radon was not the usual 1.3 – 1.6 picoCuries per liter. It was in the high teens, outdoors. Radon was being emitted from the Bone Valley and Hawthorne formations laid down from south of Naples up toward Jacksonville and west toward and through Tallahassee, passing through Ocala and Gainesville. Both were laid down by dying sea creatures and plants that had accumulated radon in their bodies about 25 million years ago when most of Florida was at the bottom of the Gulf of Mexico. At that time, most of Florida was underwater except for the Lake Wales Ridge which was like an island. And that is why radon is so common in Florida. Plant and animal life were concentrating radium in their bodies, dying and creating radioactive, radon-bearing horizons commonly six to eight feet thick. In some places, those radioactive layers are at the surface of the soil and in direct contact with the bottom of the concrete slab. But careful slab sealing will block radon entry into a finished home.

Curiously, the preferred locations for the construction of a home are the ones most likely to have radon issues.

In south Florida, we learned that when a subdivision was created that included dug lakes, radon-bearing soil from the Bone Valley and Hawthorne formations was commonly excavated and used to build pads upon which floor slabs of new homes were placed. Those homes more often had radon issues despite the fact that we observed that the design and construction of the homes were even better than most other homes.

The highest radon level we ever mitigated in south Florida was in a 23rd-floor penthouse in Naples, nearly 35 picoCuries per liter. It took us nearly two months of sophisticated micro pressure and unintentional airflow, temperature, and relative humidity computer data logging, testing, and toil. But we found the hidden air conditioning installation defect, repaired it and found and sealed the radon entry points. The couple had been at their wit’s end. He advised us that we were the sixth firm that tried to make the radon go away. What a celebration.