Sometimes defects in either steel or timber piles are not evident above water (refer to photos – courtesy of Polaris Marine).  Underwater inspection of piles is therefore an important part of routine maintenance of marine structures. 

Marine piles should be periodically inspected and measured by an experienced team of commercial divers.  Timber piles are typically measured using calipers (refer to photo).  Steel piles are typically measured using NDT (non-destructive testing) techniques, for example ultra-sonic thickness testing, or pulsed eddy current testing.