|Shoreline cleanup following the 1989 Exxon Valdez Oil Spill. Credit: Alaska DEC|
Thirty-three surface washing agents are currently listed on the National Contingency Plan Product Schedule, an EPA list of products that have met basic requirements for being considered for use in an oil spill response. Approval from the Regional Response Team is needed before a surface washing agent can be used in a manner that would cause it to be released to the environment.
When Surface Washing Agents are Used
Surface washing agents are used to soften and lift oil off of surfaces or structures that have been oiled, such as beach rocks, rock platforms, artificial structures, and riprap. Typically, conventional cleanup methods are used first to the extent of their utility (e.g., removal of gross oiling).
|Cleanup workers performing final polishing of the rocky Lebanese shoreline with pressure washers. Credit: USAID|
Surface washing agents also are used to clean and decontaminate response equipment and, less often, vessels that have been oiled. For example, in 2001, the M/V Genmar Hector was cleaned with surface washing agents after its hull and superstructure were oiled.
Surface washing agents typically act relatively quickly and can be used on all types of oil. The application methods vary but the agents are typically sprayed on the oiled surface, allowed to soak 5 to 15 minutes, followed by a warm water/high pressure wash.
How They Work
Surface washing agents contain surfactants, solvents, and/or other additives that soften and lift oil off the surface. There are two main types. “Lift and float” products lift oil from the surface so it floats on the water as a slick and can be recovered. Booms, sorbents, and vacuum pumps are often used with these products to collect and recover the oil. “Lift and disperse” products act like detergents to lift oil off surfaces, emulsify it (break it into fine droplets), and disperse it into the water.
Because it’s not possible to recover the oil directly when using this type of product, responders must contain and recover the washwater.
Example Surface Washing Agents
Corexit 9580 and PES-51are both “lift and float” surface washing agents. PES-51 is composed mainly of surfactants and d-limonene, a chemical with a lemon-like odor produced naturally by citrus plants and some coniferous trees. PES-51 has been used or tested at many oil spills.
|Located over 40 miles north of Beirut and almost 10 miles south of Tripoli, the peninsula of Anfeh is home to the Citadel of Anfeh, also known as "Raas Anfeh," which dates back to the Crusaders of the 12th Century. The citadel is characterized by a rock-cut trench that was built for the eastside defense of the structure. USAID removed up to two feet of oil from the trench using oil releasing agents and powerwashing. Credit: USAID|