Description

Geodynamics was contracted by the USACE Wilmington District to perform a high-resolution survey of the seafloor surface and sub-bottom to better delineate the horizontal and vertical boundary conditions between limestone bedrock and silty-clayey strata that floor the navigation channel within the Charleston Harbor Entrance.

The survey objectives were to delineate the boundary conditions, determine and map the top of bedrock surface elevation, map the distribution of surficial sediment types (consolidated v. unconsolidated), map the occurrence of substantial rock outcropping from the channel floor, and delineate the occurrence of submarine hard grounds.  These goals were met by collecting a combination of multibeam bathymetry (Kongsberg EM2040c), sidescan sonar (Edgetech 4200HD) and seismic sub-bottom sonar (Edgetech 216s) imagery aboard the Geodynamics vessel R/V Benthos.  The Benthos is a 30’ dedicated survey vessel with a fixed-mount dual-head multibeam and A-frame winch for towed array.  Precise positioning was provided by the Applanix POS-MV with post-processed PPK corrections, with DGPS positioning for towed units.  The multibeam bathymetry data was collected in accordance with ISO S-44 and USACE standards for navigation and dredging requirements.  Multibeam backscatter data was used to identify areas of complex seafloor morphology and identify surficial sediment reflectivity.  Hypack software was used to create survey line plans, to record navigation, to modify line plans OTF as necessary, and to log targets of importance.

Every CPARS Rating for this task was Exceptional, with additional comments that “Geodynamics continues to deliver high quality products that support the various missions of the Corps of Engineers.  Their expertise and professionalism is exceptional and it is recommended to use their services for similar requirements in the future.”