fluctuations. As depicted, diagonal deployment,in lieu of perpendicular, has been generally foundmore effective in flowing streams.Procedures to contain spills on land vary withthe amount and type of oil spilled, the type of soiland the terrain. Less viscous oil and more poroussoil allow greater and more rapid penetration andlateral migration in the soil. Where feasible, ab-sorbent materials should be applied as soon aspossible. Larger spills may require containmentdevices such as interceptor trenches or collectingpools from which the oil may be pumped.Spill containment by the use of hose spray canbe an effective method in confined areas. Thistechnique is immediately available to ships’ forcesand provides the earliest form of containment.Phase IV—Recovery, Mitigation,and DisposalThis phase of an oil spill involves those ac-tions taken to recover spilled oil from the affectedenvironment as well as the monitoring activityassociated with determination of the effectivenessof the cleanup operation. It includes those actionstaken to mitigate damage cause by the spilled oil,and to dispose of the recovered oil in an en-vironmentally acceptable manner.REMOVAL.—Removal of spilled oil and oilderivatives may be accomplished several ways,including:1. Allowing evaporation to take place(gasoline and JP-4).2. Use of physical removal methods such asmanual collection or collection by mechanicalequipment, such as skimmers.3. Removal by fostering biodegradation.4. Removal by burning.5. Removal by dispersion (emulsification).6. Pumping of oil in land spills.Because of effects which are detrimental to theenvironment, method 4 is not recommended, orpracticed, by the Navy unless there is a directthreat to human life and property. Because of thelengthy reaction time involved, and because of thepossibility of toxic by products, method 3 is notpracticed nor recommended as a desirable Navypractice. However, it may occur, and can con-stitute a final polishing action if all the oil is notremoved by physical means.In addition, gelling agents (chemicals whichconvert the spill to a semisolid mass) or sorbentmaterials such as straw, polyester plastic shavings,or polyurethane foam may be used to help thesubsequent manual or mechanical removal of aspill.PHYSICAL REMOVAL METHODS.—TheNavy prefers physical-mechanical methods ofremoval, and has designated the types of skim-mers for use with Navy spills in various locations.1. Small Skimmers. The small unit which isdesigned for use in congested harbor areas is basedon the weir principle. The weir depth of theseskimmers is controlled by adjusting the flow rateof the attached pump. As the flow rate isincreased, the fluid is removed from the rearbuoyancy chamber, tipping the unit clockwise,and thereby increasing the weir depth. Decreas-ing the flow rate allows the buoyancy chamberto fill, tipping the unit counterclockwise, andthereby reducing the weir depth. This unit is mosteffective in a stationary mode where it is posi-tioned and the oil directed to it.2. Medium Skimmers. The medium skimmerselected by the Navy is an “endless” belt unit.It is operable from a pier via handheld controls.The principle of operation is shown in figure 8-4.The rotating belt submerges the oil and directs itto the collection well where it concentrates andfrom which it eventually is pumped to a temporarystorage. This principle is entitled the dynamic in-clined plane (DIPt m).3. Large Skimmers. The large skimmerselected for use by the Navy is a larger versionof the medium skimmer (DIPtm). This unit isvessel-mounted for use in protected open waters,and is quite effective even in choppy water in thatit overruns and submerges the oil layer before col-lecting it. A rotating belt directs the oil to the col-lection well.4. Suction Based Skimmers. Other commer-cially available units for oil removal are based onsuction, either taken directly off the surface ofthe water or by the development of a submergedvortex. Since these units are highly susceptible towave action and clogging, they work best in calm,ENGINEMAN 1 & C8-8
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