ABSTRACT PAPER239s1
Sunken oil spills create unique response challenges due to a lack of visibility of the oil and a limited understanding of subsurface fate and transport behavior. Flume studies are being conducted at the Coastal Response Research Center (CRRC) to better predict the movement of sunken oil, and define and quantify the thresholds of oil transport for very low sulfur heavy fuel oil (VLSHFO) (mixed with kaolinite clay 40% by mass) and No. 6 HFO (mixed with kaolinite clay 24% by mass). Flume conditions represent the Lower Mississippi River near Baton Rouge, LA, which experiences a significant amount of shipping traffic, making it a likely location for a spill. A previous flume study provided the critical shear stress (CSS) and critical velocity for sunken No. 6 HFO (mixed with kaolinite clay 24% by weight) on static, flat substrates made of sand, fine pebbles, and medium pebbles. Oil movement can be: (1) ripple formation, (2) break apart/re-suspension, (3) gravity dispersion, or (4) rope formation. The current flume experiments provide CSS and critical velocity for sunken No. 6 HFO and VLSHFO on flat, static sand substrates. The flume operated at water temperatures of 5 °C and 30 °C and at water velocities between 0 – 2.02 knots (1.04 m/s). The current project found critical velocities on flat sand substrates at 5 °C (No. 6 HFO: 0.27 +/- 0.07 m/s; VLSHFO: 0.36 +/- 0.07 m/s) to be larger than at 30 °C (No. 6 HFO: 0.17 +/- 0.04 m/s; VLSHFO: 0.11 +/- 0.03 m/s). CSS results from this research can be used in oil spill models to improve prediction of sunken oil trajectories along sand bedded rivers. The results can be used in the future in the Sunken Oil Transport Tool (SOTT), previously developed at CRRC to predict movement of sunken oils. Inputs to the SOTT include in-situ environmental conditions and oil properties for a spill. A summary table produced by the tool predicts if and how the sunken oil will move.