Dutch Harbor UXO
A multi sensor geophysical survey was completed in Dutch Harbor, AK as part of a contract for the USACE Alaska District. The project had two main objectives 1) to understand the geomorphology of a shallow bar that runs across the entrance to the harbor and 2) to detect potential unexploded ordinances (UXO) across a designated survey area around the bar feature. A vessel of opportunity was mobilized with a full geophysical spread that included a high resolution multibeam with ultra high density upgrade, an EdgeTech Chirp sub-bottom, a geometrics G-882 gradiometer and a boomer sub-bottom system. Objects on the seafloor as small as 1x1ft were detected down to depths of 200ft within the high resolution multibeam. Several ferrous objects were identified lying on the seafloor with the geometry of the object as seen in the multibeam data considered to be a potential UXO target. The Chirp system was towed along survey lines making up a tight grid search pattern to detect buried objects as small as 5ft. Several sub-bottom contacts were noted, with some producing a ferrous return. The combination of higher resolution Chirp and deeper penetrating boomer sub-bottom systems allowed strata to be identified through the bar and to a bedrock system below the feature.