A method and apparatus are disclosed for building a reinforced sea wall or levee. The reinforced structure is designed particularly for use in areas of soft sub-soil such as those sub-soils found near the Gulf of Mexico which are capable of bearing loads of less than 5 pounds per square inch of weight. The structure includes first and second rows of soil-cement columns formed on opposite sides of the centerline of the structure. Soil-cement columns are formed by mechanically cutting the soft sub-soil and simultaneously hydraulically mixing the cut soft soil with a cement slurry injected at velocities of 200 feet per second or more. Reinforcing structural elements, preferably H-beams, are embedded in at least some of the soil-cement columns in each of the two rows. Tensile load bearing members, such as cables or beams, are interconnected between some of the reinforcing structural elements in the first row of soil-cement columns with some of the structural elements in the second row of soil-cement columns. Lagging walls are installed between upstanding H-beams. Fill materials, such as sand, silt or sediment, are then deposited between the two rows of soil-cement columns. Optionally, a third row of soil-cement columns is placed between the first and second rows and longitudinal beams are placed at ground level, extending between the outer rows of soil-cement columns and being placed on top of the center row of columns. An optional semi-permeable mat is placed on top of these beams to bear the weight of the sandy fill material and to transfer that weight to the three rows of soil-cement columns.