The U.S. Coast Guard, in cooperation with the maritime industry, is trying to identify promising new methods of cleaning up marine oil spills.
The April 2010 blowout on the Deepwater Horizon oilrig — which sent huge volumes of crude oil spilling into the Gulf of Mexico for many months — focused the nation on the limitations and shortcoming of existing oil recovery technology. But even before the Deepwater Horizon disaster, the Coast Guard was actively looking for better ways to respond to a catastrophic marine spill.
In May 2011, a research team with representatives from the Coast Guard and industry presented a report at the International Oil Spill Conference in Portland, Ore. The report details three new prototypes for underwater and seafloor oil recovery in relatively shallow waters.
A remotely operated vehicle (ROV), manned submersible and a sub-dredge were outlined, and each of these, with advanced prototypes being developed and tested in 2011, have the potential to greatly enhance recovery of oil from an offshore spill.
Kurt Hansen, the spill response program manager from the Coast Guard Research and Development Center in New London, Conn., has conducted a project to identify methods of recovering oil that is sitting on the seafloor. This phase identified three submersible recovery devices that are currently under development.
According to the report, the ROV systems will use a combination of high-powered sonar and 3-D positioning to detect oil, while deploying a remote-controlled recovery device. The manned submersible will operate almost identically as the ROV units, but with a recovery specialist at the helm. Lastly, the sub-dredge will have the capability of remotely dredging for oil in sensitive areas of the seafloor.
Because of pressure to come up with new and original ideas quickly, the Coast Guard R&D team focused on the most vulnerable areas of the oceans. While skimming surface oil is slow and inefficient (only a fraction of what is collected is actually oil), surface oil is still visible and easy to track. Underwater oil, however, can have a greater impact on the environment. Sinking oil can destroy sea life and cause closures of industrial facilities on or near the water. Yet the methods currently in use to locate and recover subsurface oil are not effective for recovering large quantities of oil that have spread out over a large area.
Hansen believes that multiple spills, even prior to Deepwater Horizon, demonstrated the need for this kind of technology. Two that were especially influential happened in shallow waters off Texas and in the Delaware River. Each spill was significant because the oil was submerged in environmentally sensitive areas rich in marine and bird life.
"This project started in 2007 in response to the barge DBL-152 spill in the Gulf of Mexico in 2005. The barge was holed by a platform sunk by Katrina and eventually flipped over," he said. "And the Athos I, which hit a submerged object in Delaware Bay (in 2004)."
Although the Coast Guard is working closely with outside organizations, the project is fully funded by the Coast Guard R&D Center, Hansen said.
Currently, the most common method of recovering oil from the bottom of the sea floor is for a diver to use a suction hose and pump the oil to the surface. For shallow spills the pump is put on a vessel or pier, and funneled into a holding tank, but deeper oil requires submersible pumps. Underwater and seafloor recovery is even more difficult to manage than surface oil because of poor conditions. Visibility and endurance of the diver are key concerns, as well as the amount of sediment that is taken in with the oil.
Hansen's report identified the need to create submersibles capable of overcoming these difficulties. "The main objective," the report states, "is to define a fully integrated system that includes detection, recovery and waste processing. The specifications are designed to overcome the lack of visibility and endurance of divers in addition to handling a large amount of water and sediment along with the oil during the actual recovery."
The impact that these newer systems may have on current recovery methods is unknown. For example, it is not clear if the new equipment under development could be quickly deployed on existing oil recovery vessels.
Hansen suspects that these new systems will not be put into widespread use immediately, but would be used on a case-by-case basis.
The hope is that these systems will be relatively easy to transport and use in a variety of places and situations. Dr. Gregory Johnson, the New London branch manager of Alion Science & Technology, which is developing an oil-recovering ROV, believes that his company's vehicle will meet the new standards described in the report.
"Our design concept has been to develop a lightweight device that can be easily transported, deployed and handled by one to two people," he said.
Johnson hopes that these qualities will set the Alion ROVs apart from existing oil recovery technology by offering the industry a faster, sleeker and more productive way of clearing oil from the seafloor.
The Alion ROV systems use a sled-type vehicle that is connected to a larger survey vessel or barge. While this type of vehicle would require the survey vessel to use sonar, the ROV itself could confirm the oil's presence. The ROV, which can work in depths up to 200 feet, controls the pump, nozzle and hoses that collect the oil and move it to the surface. There, a multistage decanting system filters the water through several holding tanks.
Dr. Johnson stressed that the ROV exhibits the qualities the Coast Guard researchers said are needed. "It is small enough to be carried on a response vessel, inexpensive enough to be purchased in sufficient quantity," he said. "It is designed to be flexible to configure to available equipment and conditions." This system is currently in the second phase of testing.
Also in development is a system based on a manned submersible. While this operates in similar fashion to the ROVs, it will allow recovery professionals to work directly with the oil. "The system safely positions an oil recovery specialist at the site of a submerged oil mass, with a direct view of the work area and with enhanced oil detection sensors (other than visual) and recovery controls at hand," Hansen's report states. A marine umbilical system attached to the sub pumps all materials to the surface.
David Usher, the chairman of Marine Pollution Control, has confidence that his company's two-person sub will represent a big advance over current methods. "We think it's the best approach after working for 14 years with divers that tried to accomplish recovery with minimal return because of having to walk on the sea bottom," he said.
The company's full-scale model has completed two successful tests in rivers, but has yet to be tested in the ocean. "We feel that we would be ready for a sea trial in February or March of 2012," Usher said.
The third system for seafloor recovery is a submersible dredge. Dredging can pose environmental risks, since it can stir up and spread polluted seafloor sediments, but this sub-dredge is designed to work carefully — an impressive achievement considering it is a remote-controlled, self-propelled vehicle.
Leo Guidroz, the sales manager at Oil Stop, a division of American Pollution Control Corp., states that the sub-dredge has advanced capabilities when it comes to sensitive dredging. "It's specialized in sensitive area dredging, removing sediments that may have contaminants that you don't want to redistribute into the water column," Guidroz said. "The way it does that is by being able to minutely adjust its down-pressure into the sediments."
While initially designed by Tornado Motion Technologies, the dredge captured the attention of distributors like Oil Stop. Like the other systems, the sub-dredge is attached to the surface through a complex pump system. Although not fully tested, it may have the ability to work in deeper conditions based on the power of its specialized pump.
In the fall of 2011, representatives from American Pollution Control (sub-dredge), Marine Pollution Control (manned sub), and Alion Science & Technology (ROV) were scheduled to take part in testing their prototypes at the National Oil Spill Response Research & Renewable Energy Test Facility in New Jersey. However, tests in the tank there cannot fully demonstrate how each of these will perform in depths of 200 feet or more. Additional field tests are being planned.
Guidroz stated that all three systems, while being designed for the same purpose, might work better in certain situations. "All three units are very viable solutions to a situation. Some may perform better under certain conditions than others," he said.