U.S. Navy Ship Salvage Manual Volume 6 - Oil Spill Response

S0300-A6-MAN-060bent boom can be fabricated by binding straw or other sorbent materials to fiber line with floats ofsome type attached at intervals. In shallow waters such as marshes or tidal flats, sorbent barrierscan be constructed by staking straw bales to the ground or fastening them to poles. Although containmentor sorbent boom can be improvised in the field, the fabrication is so slow that purposebuiltboom can be flown in and deployed before an improvised boom can be completed in mostlocations.Ship hulls, quay walls, etc., can function as opportune barriers. Smaller spills can be contained ormoved by water sprays or propwash, alone or in conjunction with booms. Chemical herdingagents applied around an oil spill may consolidate the spill, but use of chemical agents is subjectto strict controls by various authorities. Spill response chemicals are discussed in Chapter 6.Spill containment is a temporary measure, not a final solution. In the presence of any wind or current,oil will build up along the boom, extending downward until at some point, oil will beentrained in the current passing under the boom. Contained oil must be recovered and disposed ofproperly. Containment methods and equipment and their integration with recovery systems arediscussed in Chapter 4.3-5.1.4 Recovery and Cleanup. Oil spill recovery and cleanup either removes oil from the wateror shore or enhances natural processes such as evaporation, oxidation and photochemical and biologicaldeterioration.Oil is recovered by picking it up from the water surface with skimmers or sorbent materials. Oilsorbents range from sawdust to expensive sorbent mats. Sorbents are usually deployed and recoveredby hand. Some can be re-used after squeezing or wringing the oil from them.Skimmers are available in assorted sizes, some small enough to be used in large cargo tanks.Skimmers are generally used in sheltered waters, although a few types are effective in seas up toabout six feet. Skimmer efficiency (ratio of oil recovered to total volume of oil-water mixturerecovered) depends on several parameters:• Oil slick thickness and degree of containment• Oil viscosity and degree of emulsification• Sea stateThe basic types of skimmers and their relative strengths and weaknesses are discussed in Chapter5. No skimmer is completely effective and all skimmers recover a mixture of oil and water. Oilwaterseparators are desirable to conserve storage capacity. Chapter 5 addresses mechanicalrecovery of free oil from the water surface. Chapter 7 describes methods for cleaning oil-fouledshoreline.Most oil is recovered during the first days of a response, before it has spread and weathered somuch that retrieval is difficult. Skimmers and containment boom fill very quickly in the initialperiod. An ideal skimming operation continues nonstop. Nonstop operation requires pumping oil3-16