While I was at BEAK, they had the world’s leading Natural Resource Damage Assessment (NRDA) group working on oil spills. They represented insurance clubs for the carrier in the incident, and usually dealt with floating oil. I provided support for three spills involving releases of heavier than water "sinkers" in the Mississippi River (slurry oil) and in the Gulf of Mexico (chlorinated solvent). In the Gulf incident, two ships collided 3 miles off the Mississippi River entrance. A 25-foot gash in a single cargo tank resulted in an 1800 metric ton spill of 1,2-dichloroethane (aka EDC). I did an aquarium test to estimate EDC DNAPL thickness on the Gulf floor.
Using that estimate and simple math, we collected bottom samples at the incident site to define the release area; sampling results agreed with the prediction. I authored transport/fate sections of a report to trustees including half-life estimates for EDC based on observed rates in groundwater. It was necessary to rebut trustee comments that denied the laws of physics by claiming "they believed the release covered a much larger area and was thicker” than what sampling showed. The area was allowed to recover naturally (2nd graphic).
