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

S0300-A6-MAN-060rips and other phenomena that dampen waves. SLAR is effective up to twenty miles and is largelyunaffected by cloud cover and moisture. SLAR cannot be used to determine oil thickness.IRLS determines the presence of oil by measuring natural radiation emitted from the sea surfacein the thermal infrared region and detecting the difference between sea temperature and the temperatureof substances floating on the sea surface. IRLS has a much shorter effective range thanSLAR. Because IRLS operates on a temperature differential principal, it may indicate the presenceof substances other than oil. As an oil slick absorbs heat from the sun, the thicker portions ofthe slick will become warmest, enabling IRLS to determine slick thickness. IRLS cannot seethrough fog and cloud cover. UVLS, useful only during daylight, detects differences in UV lightreflected from the sea surface. UVLS can detect very thin films of oil. Like IRLS however, it doesnot discriminate between oil and other substances.These sensing devices display their outputs on video screens in aircraft. The information thenmust be interpreted by an equipment operator and later by personnel at the oil spill response commandpost. Because all three remote sensors can return contacts that may not be oil, the presenceof oil detected by remote sensors should be confirmed visually. Relay of the information gainedby the remote sensing devices can take an inordinate amount of time, so plans should be made tocommunicate this information quickly. The most common method of information transmission atthis writing is videotape, however, other means of electromagnetic data transmission are beingdeveloped.The Coast Guard AIREYE remote sensing system is a composite package incorporating SLAR,IRLS and UVLS. AIREYE is installed in several aircraft and is scheduled for upgrading. TheMarine Spill Response Corporation (MSRC) is presently designing a remote sensing system tosupport around-the-clock spill response operations. SUPSALV does not have a remote sensingsystem in its inventory, but is examining site-specific systems, such as remote cameras to supportskimmer operations.Free oil is not distributed uniformly throughout an oil slick. Influenced by wind, current and theoil source, free oil will consist of oil, water-in-oil emulsion and oil sheen. Estimates of the volumeof floating oil must be made by adding the contribution of each form of oil. Such an estimate maybe done by estimating the percentage of the total spill area consisting of each form of oil with thetotal equal to 100 percent. An example using Table 2-3 follows:2-17