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

S0300-A6-MAN-060stone and artificial structures, such as concrete or steel piers. Washing should begin at the top ofthe surface to be cleaned and proceed towards the bottom. Berms, trenches or boom should beused to concentrate the resulting oil and water mixture for collection and to prevent it from contaminatingclean areas. Misdirected high-pressure or high-temperature water jets can cause severeinjury, so personnel must be trained in their operation and equipped with protective clothing.High-pressure water blasting and steam cleaning destroy most marine life in addition to removingoil contamination from rocks and boulders, creating an environmental trade-off. This phenomenonwas reaffirmed during studies conducted following the EXXON VALDEZ spill. As a consequence,these methods should be utilized only when recommended by the scientific supportcoordinator or similarly qualified person.7-5.3.11 Sand or Grit Blasting. Grit blasting can clean hard, smooth surfaces, such as rock orconcrete, by removing stains and moderate contamination. This method is appropriate where allevidence of oil contamination must be removed. The blasting grit will be become oil-contaminatedand should be collected for disposal. Collection of blasting grit on a rocky shore or pebblebeach is very difficult. Grit blasting poses some occupational hazards, including the risk of silicosisand can damage structures, so operators must be trained and equipped with proper protectivegear. Like high-pressure water washing, grit blasting will destroy marine life on the surfaces cleanand should be utilized only when recommended by the scientific support coordinator or similarlyqualified authority.7-5.4 Removal of Contamination. The type of shoreline determines cleanup methods. In general,shorelines are classified as large rocks and boulders, cobbles and pebbles, sand and mud.• Large rock and boulder surfaces can be cleaned by hand or by water or steam wash.Rocks and boulders that have cracks and crevices that hold oil and must be cleaned byvacuum hoses or by hand with buckets. Wave action removes some oil, particularlyduring storms when wave action is most severe. In protected areas, wave action has nosignificant effect.• A sand and pebble beach is the most difficult to clean. Cracks and crevices betweenstones provide a path for oil that is difficult to penetrate with cleaning equipment. Passageon beaches is difficult for tracked vehicles and heavy equipment. A rising tide liftslow-viscosity oils to the surface and cleanses surface stones, but buried oil remains forsome time.• All other conditions being equal, coarse sand beaches are typically steeper thanbeaches of fine sand. Water moves through and drains coarse sand quickly, leaving itdry much of the time. Oil penetrates dry sand more readily than wet sand. Waterretained on wet fine sand beaches keeps oil at the surface so that the oil runs off withthe tide. Storms drive oil into sand so oil contaminates sand beaches more deeply infoul weather. Figure 7-1 illustrates the behavior of oil on sand beaches.Fine sand supports heavy machinery better than coarse sand, but heavy vehicles increase thedepth of contamination in sand by driving the oil into the substrata. Therefore, the benefits of7-7