Underground storage tanks, liquids

Three of five men, who lost consciousness within a few minutes of entering a partially drained underground liquid manure storage tank, died before reaching the hospital autopsy showed that two had massive liquid manure pulmonary aspiration, while the third had fulminant pulmonary edema without manure aspiration (Osbem and Crapo 1981). Markedly elevated heart-blood sulfide-ion levels indicated significant hydrogen sulfide exposure. Air samples analyzed about a week after the accident detected only 76 ppm of hydrogen sulfide, but the study authors noted that the environmental conditions were probably different (e g., warmer weather, less-concentrated manure). 

Hydrocarbons are hydrophobic and lipophilic compounds. As free liquid, gas, or solid phases, they are quite immiscible in water primarily because of their low polarity. In a competition between aqueous solution, air and solids, HMW hydrocarbons tend to partition heavily into the solid phases, and hence they are also sometimes referred to as particle-associated compounds. This is true in both the atmospheric reservoir, where they associate with atmospheric particulates, and surface and groundwater systems, where they exhibit affinity for suspended particles and aquifer solids. In the case of nonhalogenated NAPL, the separate liquid phase is generally lighter than the aqueous phase, and hence they tend to physically float on the aqueous surface. Such is the case for oil spills either in surface water (e.g., ocean, streams, and lake) or in groundwater (e.g., underground storage tanks). 

Cylindrical storage tanks for inflammable liquids above and underground at or near atmospheric pressure are subject to standards and codes of Underwriter Laboratory (www.ul.com), or the American Petroleum Institute (www.api.org), or regulations of the EPA. The Underwriter Laboratory covers small tanks up to 25,000 gals. Both sets of standards are restricted to steel construction for noncorrosive service. Manufacturers often fabricate and supply Underwriter or API tanks as a matter of course. The latest standards can be obtained by visiting the above web sites. 

U adioactive wastes have accumulated at Hanford since 1944 when the first reactor fuel was processed for plutonium recovery. High-level liquid wastes generated by the Purex, Redox, and BiP04 processes have been stored as neutralized slurries in 151 underground storage tanks. 

Transport in unsaturated porous media is sufficiently complex when only two fluid phases, air and water, are present flow becomes even more complicated when a third fluid phase, such as an immiscible organic fluid, is involved. This third fluid phase (NAPL) arises when liquid hydrocarbon fuels or solvents are spilled accidentally on the ground surface or when they leak from underground storage tanks. The resulting subsurface flow problem then involves three fluids, air, water, and NAPL, each having different interfacial tensions with each other, different viscosities, and different capillary interactions with the soil. The adequate description of three-phase flow is still a topic of active research, but a few qualitative generalizations can be drawn. 

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