Nondestructive testing based on wave propagation methods is used to identify changes in mechanical impedance such as changes in material properties and geometry. In civil engineering, a nondestructive testing program may be performed on new or existing construction. The testing is done on new construction as part of the quality control and quality assurance (QA/QC) process to determine if the construction meets the design requirements. The testing is done on existing construction when concerns about defects or damage are raised, or when the information on the material properties and geometry are required but neither design drawings nor construction records is available. The results presented in this paper are from investigations performed on existing seawalls at three different locations in southeast Michigan. At all three locations, local consultants were asked to determine the load-carrying capacity of the walls but neither design drawings nor construction records was available. One site is located in Algonac, Michigan, and the other sites are located in Detroit, Michigan. The nondestructive testing was performed to determine the geometry of the wall, specifically depths of the toe, i.e., the length of the sheets. The nondestructive test method used was a modification of the existing sonic echo method. The background of the sonic echo method, which was developed for the nondestructive testing of deep foundations, and the modification of the method for the nondestructive testing of steel sheetpile sections is presented. The background on Algonac, Michigan site and the nondestructive testing program are presented in detail. A summary of the testing and results is presented for the two Detroit, Michigan sites.

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