EK80 Water Column Sonar Data Collected During BordelonMC20

One overnight survey of the seep was performed in order to determine the flow rate of hydrocarbons in the watercolumn using a vessel mounted broadband echo sounder and ADCP. The echo sounder and ADCP were mounted on a pole on the port side of the Gerry Bordelon. ADCP surveys were performed in order to determine the magnitude and direction of flow in the area and then broadband acoustic surveys were performed. The broadband acoustic suverys were performed in two parts: the across seep surveys and the along seep surveys. The across seep surveys were performed first and were used to determine the position of the seep as it transitted downstream of the source. That position was then used to inform the location of along seep surveys in which the entire seep, from source to surface was visualized.

All times UTC

0120-0136 Preliminary ADCP survey. Track lines are run perpendicular to the nomial direction of flow to the southwest of the seep source (downstream of the seep) and northeast of the source (upstream of the seep). Flow is nominally to the northeast.

0227 - 0652 Across-seep echo sounder surveys. Track lines are run perpendicular to the nomial direction of the flow starting from downstream of the downed platform and moving downstream. Lines were approximately 1 km long with spacing approximately 50 m. Once the seep was no longer detected in the across seep survey lines, the survey was repeated moving back from upstream to downstream.

0704-0838 Along-seep echo sounder surveys. The position of the seep determined in the across-seep survey lines was used to inform the survey lines run in the direction of flow. These lines were used to ensonify the entire seep in a single pass from origin to the surface.

0848-0921 Second ADCP survey.