ENGINEMAN 1 & CThe Navy preferred containment equip-ment/procedures are piston film chemicals andsolid, floating booms.Piston Film Chemicals.—Piston filmchemicals have high surface activity and spreadrapidly over the water surface. The spreadingforce of the chemical is sufficient to overcome thespreading forces of the slick. These chemicals pushthe oil layer back until it reaches a limiting slickthickness, which the piston film cannot exceed.The oil may be moved ahead of the spreading filmtoward a collecting or containment device asshown in figure 8-2A, or the piston film may bequickly spread around the periphery of the spillas is shown in figure 8-2B. This technique simplyslows down the spreading rate.Containment Booms.—Containment boomsare solid (floating barrier) booms. They are solid,continuous obstructions to the spread or migra-tion of oil spills. Because they are the mosteffective containment device, they are preferredfor use with Navy related spills.1. Booms are available in various sizes (in50-foot lengths) which are joined to form a con-tinuous barrier to the oil. Their freeboard mustbe sufficiently high to prevent the oil from beingwashed over the boom, and the skirt long enoughto prevent oil from being swept under it. Boomsare purchased in several height/depth sizes to meettheir use requirements under various wind and seaconditions.2. Booms may be used in either a dynamic(towed) mode or in fixed position. Figure 8-3.Ishows a boom being towed in a “vee” configura-tion in conjunction with a skimming device. Theboom directs the oil to the skimming device whereit is collected.3. Booms are also being used to prevent oilfrom going under the pier and to direct the oilto the skimmer (figure 8-3.II). The slick ismoved to the skimmer under the influence of windand current, or it could be pushed toward theskimmer by hose spray, air jet, or piston film, ifnecessary.4. Booms may be anchored in a position thatwill entrap the oil but leave a channel open fornavigation if necessary (figure 8-3.III). The angleat which the boom must be set is important inorder to avoid loss of collected oil due to entrap-ment in the current or from being carried underboom skirts.5. Figure 8-3 .IV depicts typical use of a boomstretched across a stream. This alinement is feasi-ble in small streams, mild currents, or tidalFigure 8-2.—Use of Piston Film Chemicals.8-6
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