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

S0300-A6-MAN-0602-4.12 Archeological Sites. Archeological or historical sites can be irretrievably harmed whensites are damaged to the extent that material to be excavated or examined is lost due to oil contamination-eitherdirectly or because of response measures. For this reason, archeological sites shouldbe noted in contingency plans and be protected in the same manner as environmentally sensitiveareas.2-5 OIL SLICK MONITORINGKnowledge of the quantity and movement of spilled oil helps responders to select and deployappropriate response resources to be used. Chapter 5 discusses selection of response resources indetail.2-5.1. Visual Quantification. The volume of oil spilled from ships or handling facilities may bedetermined by comparing oil container levels before and after the spill. When soundings are notavailable, the amount of spilled oil may be determined by visual observation of the oil slick. Estimatesof quantities of spilled oil can be made with the information in Table 2-3. Although theoreticalestimates can be made, experience has shown field estimates of spilled oil quantities to behighly inaccurate.Table 2-3. Relationship Between Appearance, Oil Thickness and Volume of Free Oil.APPEARANCE APPROXIMATE THICKNESS (MM)* APPROXIMATE VOLUME (GAL/SQ MI)Barely discernible --- 25.0Silvery sheen --- 50.0Faint colors --- 100.0Bright bands of Color --- 200.0Iridescent 0.0003 265.0Dull brown --- 600.0Dark Brown --- 1,300.0Black/dark brown 0.1 88,500.0Brown/orange, frothy (mousse) >1 885,000.0+* 1/10 mm = approximately 0.004”2-5.2 Remote Sensing. Sensors deployed from aircraft enable oil slicks to be identified duringhours of darkness and during periods of reduced visibility. This technology makes spill detectionpossible around-the-clock rather than being limited to daylight hours.Three sensors, used separately or in combination, comprise present remote sensing technology:Side-Looking Airborne Radar (SLAR), Infrared Line Scanners (IRLS) and Ultraviolet Line Scanners(UVLS).SLAR can define the extent of an oil spill. With microwave radiation, SLAR detects differencesin signal energy between returns from prevailing sea waves and waves dampened by oil. As aconsequence, SLAR is least effective during periods of calm weather and is influenced by tide2-16