S/V Blake The S/V Blake is a new 82-foot hydrographic survey vessel, custom-built for DEA’s Marine Services Division. Operating out of Gulfport, Mississippi, the new vessel will complement the firm’s national operations and expand DEA’s hydrographic and geophysical survey capabilities in the Gulf of Mexico and beyond. The Blake is an aluminum catamaran designed to be a stable, efficient, and cost-effective survey platform with wave-piercing bows, Tier-3 diesel engines, twin 55-kilowatt generators, and a full suite of state-of-the-art survey instrumentation. She will start her career in the Gulf of Mexico with a crew of 10, performing charting surveys of Gulfport Channel and Chandeleur Sound with 24-hour survey operations and port calls every 10 days.
Sediment Transport Monitoring DEA conducted a series of high resolution multibeam bathymetric surveys and Acoustic Doppler Current Profiling (ADCP) surveys in support of the Remedial Investigation/Feasibility Study to evaluate the transport of contaminated sediments in the Willamette River. Areas of deposition and erosion were clearly defined by running a difference analysis between subsequent surveys. Data was also used for input, calibration and verification into a hydrodynamic sedimentation model which was created to better understand surface sediment transport within the system after major flooding events.
Current and Water Level Modernization DEA was contracted by NOAA’s Center for Operational Oceanographic Products and Services (CO-OPS) to support the NOAA mission to modernize current and water level monitoring throughout Alaska. The contract included: installation of new water level stations to expand the water level monitoring footprint and support the tsunami warning system; annual and emergency maintenance of the existing National Water Level Observation Network (NWLON) stations throughout Alaska; and deployment of bottom mount Acoustic Doppler Current Profilers to measure tidal currents over a 30 day period to improve current modeling throughout Cook Inlet and SE Alaska.
Oregon Coast Nautical Charting DEA was contracted by NOAA’s Office of Coast Survey to update nautical charts of the Oregon Coast based on pre-1940’s partial coverage surveys. This work also supported marine spatial planning and furthered NOAA’s mission to integrate ocean and coastal mapping efforts for the greatest public benefit. Requirements included 196 square nautical miles of object detection multibeam surveys with associated backscatter and bottom sampling. The multi-use data acquired from this survey employed the latest technologies and was used to: update nautical charts with current soundings and previously uncharted navigational hazards; provide data for tsunami inundation modeling; and map offshore seafloor geology and document features of coastal seabeds for delineation of Marine Protected Areas.
Howard Hanson Dam Monitoring DEA conducted a series of surveys under increasing hydrostatic loads to monitor deformation of the Howard Hanson earthen dam. The surveys consisted of upland high definition laser scanning, vessel based laser scanning and multibeam bathymetric surveys. The primary goal of the surveys was to develop an accurate 1-foot grid of elevation data of the earthen dam and surrounding areas, and compute movement analysis after each subsequent survey as part of the monitoring program to detect changes as the forebay elevation was raised.
USACE Dam Monitoring DEA Marine Services has been identified as a premier provider of high resolution mapping as part of the USACE dam monitoring program. These services include: high resolution multibeam bathymetric sonar mapping to develop a one-half foot grid for comparison to concrete stilling basins relative to prior surveys; bottom deployed scanning sonar surveys to map areas of potential undercut; 3-D modeling of structures to be used for design upgrades; terrestrial laser scanning surveys of fish bypass structures and tainter gates to support design changes; Remotely Operated Vehicle (ROV) operations for underwater video inspections; and Acoustic Doppler Current Profiling (ADCP), wind measurements, and time lapsed video to map river current velocity and direction for fish bypass facilities.
David Evans and Associates, Inc.’s Marine Services Division is a leader in hydrographic, bathymetric, and marine geophysical surveying.