Groundwater classification, general

Two of the larger LNAPL hydrocarbon occurrences, site No. 1 and 4 (see Ligure 12.23), formerly reinjected coproduced groundwater into generally the same hydros-tratigraphic zone from which it is withdrawn site No. 1 reinjected without treatment into the Gage aquifer, whereas site No. 4 reinjected into the Old Dune Sand aquifer. Because of the presence of dissolved hydrocarbons, notably benzene, in the coproduced water that is typically returned to the aquifer during LNAPL recovery operations, immediate application of the EPA toxicity characteristic rule may result in classification of the reinjected water as disposal of a hazardous waste. This, in turn, would terminate use of UIC Class V wells (which many of these operations currently... 

Mining is the process by which ores or related materials are extracted from the Earth. Ore is defined as a rock or mineral, generally metallic, which can be mined, processed, transported, and sold at a profit. Therefore, the classification of an Earth material as ore depends as much on economics and technology as geology. Non-metallic substances that are commonly mined but not considered to be ores include coal, phosphate, and sand and gravel. The term groundwater mining is sometimes... 

For a better comprehension of the chemistry of a groundwater system the redox status needs to be well-defined. Until recently, most efforts have relied solely upon Ej.j or pE, intensity factors, as the master variable. However, it is apparent that these intensity factors do not truly represent the redox status of a system because some pertinent redox couples are not electroactive and redox reactions are generally slow and are not at equilibrium. In this paper, the oxidative capacity, a capacity factor, is operationally defined and shown to be a better descriptive parameter of the redox status. Determination of the OXC of an aqueous system allows investigators to cla.ssify the system in terms of well-defined geochemical and microbial parameters. This classification combined with other predictive tools, such as a redox titration, allows one to predict the identity and assess the role of chemical reactions and microbial populations within a specific groundwater system. As such, the capacity factor OXC should be determined in water quality assessment. 

FIGURE 5.2 Classification of subsurface environment and characterization. (From USGS Circular 1186, General facts and concepts about groundwater in snstainability of ground water— Water resources, pubs.usgs. gov/circ/circll86/html/gen facts.html.)... 

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