What is being observed is referred to as exfoliation and is expected to occur. The exfoliation that the wall is experiencing is the result of “mill scale” on the sheet piles that is corroding and becoming disbonded from the piles. Mill scale is essentially an extra surface layer of material that is formed/embedded during the rolling (or metal forming) process of the sheet pile. The layer corrodes and flakes off over time when exposed to the environment.
The project’s corrosion expert is testing the sheet piles to determine the corrosion rate and ensure nothing of significance is occurring. This is part of an ongoing monitoring program that will continue throughout the useful life of the levee.
Current consensus is that the rusting of the mill scale is to be expected.