SHORELINES AND MARINAS
In the absence of significant native plant or animal life in these environments, economic and aesthetic factors generally drive spill response decisions. Clean-up is usually a top priority, especially given that these developments are often constructed in areas where wave activity is minimal, meaning there is less natural dispersion of any spills.
Booms and skimmers are used to contain and remove spilled oil from the water, while relatively aggressive clean-up activities are used to address landed oil. These might include flushing, use of shoreline cleaning agents and bioremediation. Sorbents also may be used for smaller-volume spills, or to "polish up" after other steps are taken.
Booms
These temporary floating barriers are used to contain floating spills. A boom usually includes a containment component that floats on - and extends above - the water's surface, plus an underwater "skirt" or "curtain." Booms may be deployed in various configurations, depending on current and wind conditions:
- to divert spills away from sensitive habitats and/or into collection locations;
- to contain spills for on-site recovery and/or treatment; or
- to completely surround spills for in-situ burning. (Booms used in burning must be either water-cooled or made of fire-resistant material.)
Skimmers
A variety of mechanical equipment is used to physically remove floating spills from the water's surface. Many designs use a kind of conveyor belt placed at the water line to carry the spilled oil into a reservoir, where it is collected for processing and recovery. (Inevitably, a skimmer is going to collect some water mixed in with the oil.) Other skimmer technologies use suction to remove spilled material, while weir skimmers harness gravity to gather skimmed oil into underwater storage tanks. Skimmers generally are effective only in calm waters; suction skimmers are also subject to clogging by floating debris.
Manual recovery / Cleanup
Manual recovery is the most common method of shoreline cleanup, involving teams of workers using rakes, shovels and the like to pick up oil and debris. The oily materials are collected in buckets and drums for transfer to a processing station. Workers may also use suction hoses, pumps and vacuum trucks to recover spilled oil. While manual cleanup is a slow, painstaking process, it generates less waste than other techniques.
Bioremediation
Certain portions of oil are biodegradable. Proper application of certain fertilizers can speed up the biodegradation process as much as tenfold, depending on the type of oil spilled. Certain plants (and their associated microorganisms) have also shown promise in speeding the breakdown of oil. Still, even a speeded-up biodegradation process takes weeks - even years - so bioremediation is used in conjunction with other clean-up activities.
Monitor Only
Spill clean-up operations inevitably have their own environmental impacts. For example, heavy equipment can damage sensitive plants and disrupt wildlife habitats. When the potential harm caused by a spill is less than the potential harm caused by attempts to remove it, spilled petroleum products are allowed to degrade naturally. Technicians periodically monitor the breakdown of the spill to be sure there is no unforeseen threat to sensitive ecosystems and/or groundwater supplies.
Wildlife Cleanup
Oiled fish, birds and animals may absorb potentially lethal toxins through their skin. Following spills, birds, otters, seals and walruses may be collected for cleaning and treatment, then returned to the environment. This is an expensive, time-consuming undertaking and, although techniques have improved greatly in the past few years, recovery rates are often poor. Many other species cannot be rehabilitated because they are either too difficult to capture, or the stress of captivity is likely to have more negative effect than the oiling.
Sorbents
Sorbents are materials used to absorb oil, including peat moss, vermiculate and clay. Synthetic varieties - usually plastic foams or fibers - come in sheets, rolls or booms. Because oil-filled sorbents must be collected and treated, they are most often used on small spills, or as "polishers" after other recovery methods have been used.