EK80 Water Column Sonar Data Collected During NOAA MC20 Survey

In 2018, NOAA and its partners conducted a comprehensive assessment of the MC20 site. This data compilation contains ship-based surface echosounder surveys characterizing the spatial structure of the plumes. Data were collected using three frequency Simrad EK80 splibeam echosounders and Kongsberg M3 multibeam echosounder from a ship. Inspection of the acoustic backscatter indicates multiple plume components emitting from separate origins on the seafloor within an erosional pit at the northwest corner of the downed jacket. Broad-band acoustic frequency backscatter intensity suggests indicators of oil and gas plumes within the water column. Closer inspection using ROV-integrated three frequency Simrad EK80 splitbeam echosounders and Kongsberg M3 multibeam sonars confirm the presence of at least four plume sources emitting from the seafloor with acoustic signatures indicating oil separating from gas as well as oil and gas mixtures. In subsequent chapters, the separation of oil from gas from each of the seep sources was verified using in situ optical and direct capture methods. The assessment provides further evidence of an oil and gas leak that has likely occurred since the original toppling of the MC20 platform.