Underwater Sediment Sampling Research

Abstract : The USCG R and D Center sought to develop a bench top system to determine the amount of total petroleum hydrocarbons (TPH) in underwater bottom sediment in situ. As a bench top system, this design would not have meet all of the final requirements needed for a fully deployed system, but the concept allows preliminary evaluation in a laboratory setting. This scenario can occur whenever oil is weathered and mixed with silt or sand. The result is that the oil sticks to the silt and sinks to the bottom. Poles were used to agitate the bottom during the Kalamazoo River spill in 2010 and the detection measure of the oil locations was whether sheening did or did not occur. Currently, the only reliable method to determine the exact concentration is to obtain a full sample and perform an analysis in a laboratory. During the Deepwater Horizon spill response, a large amount of samples were needed because oil only comprised about 10-20 percent of the tar mats and were sometimes very scattered. The approach here is to sample the interstitial water between the grains of sand and attempt to determine the amount of oil in and on thesurrounding particles. This effort focused on locating diluted bitumen (Dilbit), due to limited response experience with Dilbit spills. However, the study sought a system that could also be applied to the other types of crude oil and environments. This report describes the equipment and process followed for the demonstration and includes recommendations for further efforts needed to develop a fieldable system for use in subsequent testing. This system would need to function at depths of up to 100 feet, in currents of up to 0.5 knots, and perform at least five (5) samples per hour during a 12-hour operating window without bringing a sample to the surface. These performance criteria are based on the experiences during the Deepwater Horizon and Kalamazoo River Spills.