Abstract: A method for stabilizing and repairing whereby components are mixed to form an expandable foam which is injected under pressure in an expanded state behind or into the backfill material of an existing sheetpile seawall. Upon expansion, the foam displaces water and fills and seals cracks in the seawall and fills scoured voids in the backfill material. The method is also applied to rock revetment seawalls whereby the unexpanded foam is injected under pressure into the rock revetment. Upon expansion, the foam displaces water and fills and seals spaces in the rock revetment and interlocks the rock revetment.