If the radon level is above the EPA action level of 4.0 picocuries per liter (Pc/l), the remedy is a Radon Mitigation System. This usually involves sealing the sump pit and installing a ventilation system that uses a concept called “sub-slab depressurization”, with a special exhaust fan that creates negative pressure under the foundation. This system pulls radon out of the soil below the house and vents it outside. 

Protech Environmental is who ValueCheck recommends to install these systems. You can reach them at (888) 677-2366 or https://www.protechenvironmental.com/