Environmental tests over the past three years show high levels of contamination still exist in groundwater at the former Myrtle Beach Air Force Base.
The findings come more than 15 years after the military left the site.
The chemicals in groundwater are at levels far above what the Environmental Protection Agency considers safe for drinking water.
Regulators require the military to reduce pollution on the site so that the groundwater is safe for drinking, even though the water hasn't been used for consumption since 1999.
Tests show the contamination is largely contained and government agencies say the toxicity likely does not pose a threat to people who live in the area.
