The original subgrade conditions generally consisted of loose, liquefiable sands, expected to significantly lose strength during the design earthquake and soft, compressible clays. To mitigate the risk of liquefaction-induced instability and to mitigate the risk of long term settlements in clays, ground improvement using vibro-replacement of the embankment subgrade was incorporated into the design plans. The results indicate that the vibro-replacement increases the spectral acceleration for embankments commonly constructed in coastal South Carolina. The influence of vibro-replacement is more dramatic in the characteristic clay profile as compared to the characteristic sand profile