The ability to remotely track wave conditions when skimming oil could enhance understanding of the environment in real time and improve the effectiveness of recovery operations
Conditions encountered during oil spill response operations can have a significant effect on the rate of recovery and on the overall effectiveness of recovery operations. Bad weather, high winds and waves make recovery more difficult, but what if you could assess conditions in real time and track where equipment is and where and how it might best be deployed?
Scientists at the Ohmsett Oil Spill Response Research & Renewable Energy Test Facility in the US recently described work carried out by Aecom in Gaithersburg, Maryland, that led to the development of a system that combines a geo-referencing identification (GRID) tagging system capable of characterising wave conditions whilst tracking oil spill response equipment. At the heart of the system is a wave characterisation module (WCM). When mounted on a skimmer, the tagging system characterises the motion of waves, tracks the location of skimmers and transmits the information to operators and to other personnel at remote locations.
An Aecom team recently spent time at Ohmsett evaluating the GRID system, which was mounted on a skimmer in wave conditions in the test basin at the facility. Aecom and its subcontractors, Midstream and Envigia, also developed a free-floating WCM buoy to calculate local wave conditions.
During the evaluation, the WCM/GRID tagging system was attached to a commercially available skimmer and two WCM buoys to identify wave height, length and period whilst subjected to varying wave conditions.
In order to collect comparative wave data, the WCM buoys were operated separately in the same area as the skimmer. In addition, the team used a wave height reference pole with indices positioned near the skimmer for visual comparison of wave height for each test. Through a mesh network over wifi, AECOM was able to communicate the skimmer position and wave information to a tablet with a custom-made user interface and via satellite to a web-based GIS interface platform.
“We wanted to determine if the algorithms in the GRID units were accurately measuring wave conditions. Ohmsett has a pretty good sense of the exact wave height, length and period, so we could compare the GRID units to reality,” said Bureau of Safety and Environmental Enforcement (BSEE) oil spill response engineer Karen Stone. “The project has enhanced the latest generation of GRID technology and will allow local oil spill responders to measure wave characteristics to finesse their skimming operations. It will also transmit data to incident commanders during spill operations to allow for real-time operational awareness.”
Funded by the BSEE, the technology that Aecom worked on advanced to a technical readiness level that could lead to it being used in real-world scenarios.
Effect of dispersants on containment and recovery addressed
Dispersants are widely used to tackle oil spills on the surface and – potentially – under water, but questions have been raised about the effect that their use might have on the ability to mechanically contain and recover oil treated with dispersants. Dispersants are used to reduce surface tension, allow oil to be broken up into smaller droplets and make it available for biodegradation processes. Sometimes treated oil does not fully disperse because of underdosing or a lack of sufficient surface energy, so it may need to be recovered mechanically.
Recent work undertaken at the BSEE at Ohmsett suggests that the use of dispersants is compatible with mechanical containment and recovery but that it does have an effect. The work undertaken at Ohmsett demonstrated that a skimmer’s rate of recovery was not significantly affected by the presence of dispersants, although the percentage of water held by recovered oil increased significantly with the presence of dispersants. Containment during towing operations was also affected by the presence of dispersants, and with certain types of oil, it was more difficult to contain treated oil.