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In this situation, retention at the drain is a workable <br /> alternative. . This technique is an effective measure only for <br /> materials lighter than water or for materials that are insoluble <br /> in water. The solubilities of specific materials can be obtained <br /> from material safety data sheets, chemical texts, or computerized <br /> sources. <br /> Response personnel should consider volatile liquids and protect <br /> against air hazards that may occur when using any confinement <br /> method. For example, if volatile liquids are spilled onto the <br /> ground, an air hazard may be created. <br /> If the spill is small, response personnel need only cover the <br /> material with a salvage cover or tarp to contain the material. If <br /> the spill is large, response personnel may have to spray the <br /> material with foam in order to prevent the formation of hazardous <br /> vapors . <br /> In some cases, it may be more appropriate to retain hazardous <br /> materials in an excavated pit, pond or basin. Constructing a <br /> retention pit, pond or basin could mean simply placing a five- <br /> gallon bucket under a dripping valve or excavating a retaining <br /> structure using construction equipment. <br /> Like diversion barriers and dikes, whether a retaining structure <br /> may be constructed depends primarily upon the time and the <br /> resources (i.e. , personnel and equipment) available for <br /> construction, and the amount of construction needed. In an <br /> emergency, portable water tanks and "kiddy" swimming pools are <br /> alternatives that provide for a quick solution for blocking <br /> materials from entering storm drains, or for holding materials. <br /> Generally, any above ground structure offers a quicker solution <br /> than a below grade structure that must be built. <br /> C. Releases into Water <br /> Releases of materials into water may be controlled using several <br /> different measures. For example, if the material in water is insoluble <br /> or slightly soluble in water, and its specific gravity is greater than <br /> that of water causing the material to sink, a method for confinement <br /> might be an overflow dam. <br /> An overflow dam is used to trap heavier than water material by causing <br /> the material to sink to the bottom of the stream behind the dam. When <br /> the material is trapped, relatively uncontaminated water flows over the <br /> barrier. <br /> 59 <br /> Site Safety G Health Plan Rev./1.0 <br /> October 20, 1997 <br />