As part of improvements to a roadway in coastal South Carolina, a portion of the road crossing reclaimed marshland was widened. The new lanes were constructed on a column supported embankment consisting of sand fill reinforced by geogrid and supported by vibro-concrete columns that penetrate through the underlying very soft clays and into the local basement stratum. Shortly after construction, the roadway on the column-supported embankment began to experience distress characterized by an irregular surface with humps at the column locations and depressions in the areas between column locations.