In seven communities surrounding Hill AFB, chemicals from historical practices at the base have contaminated areas of shallow groundwater. Since the groundwater is not used for drinking or other household uses, the only way for the public to be exposed to the chemicals in the groundwater is through a process known as vapor intrusion. Vapor intrusion occurs when chemicals from the groundwater evaporate and move into homes or businesses within the affected area. (Click here to see how vapors may move into homes or businesses.)
Vapor intrusion doesn’t happen in every home or business within the affected area. Hill AFB's Indoor Air Sampling Program focuses on testing locations most likely to have vapor intrusion—those above or close to areas of shallow groundwater contamination. In cooperation with state and federal regulators, the Air Force has established contaminant levels at which it will recommend taking action to prevent vapors from the groundwater from entering the home or business. These levels are called Risk-Based Action Levels, or RBALs. (Click here for more information about RBALs.) All sampling and mitigation actions will be done at no cost to the resident.
Since 2001, Hill has tested the air in more than 3,100 locations in communities surrounding the base affected by groundwater contamination. Less than 10 percent of homes and businesses tested have had vapor levels above an action level. A vast majority of those locations, however, were tested using a 24-hour method that could have missed vapor intrusion. Testing is now done with a 24- to 26-day sampler to ensure more accurate results. (Click here for more information about how testing methods have changed to more accurately determine if vapor intrusion is occurring.)