| capillary fringe | The zone immediately above the water table, where rocks and soil are saturated, but at pressure that is less than atmospheric. Water is held in this zone by capillary forces and cannot be removed by a well. |
| carbon adsorption | A treatment system that removes contaminants from groundwater or vapor as the fluid is forced through tanks containing activated carbon. See technology descriptions of Liquid-phase GAC and Vapor-phase Activated Carbon. |
| cation | Ions with a positive charge. |
| CERCLA | The Comprehensive Environmental Response, Compensation and Liability Act of |
| chemical dehalogenation | A chemical process that removes halogens (usually chlorine) from a chemical contaminant, rendering the contaminant less hazardous. See technology description of Dehalogenation. |
| Ci | An abbreviation for Curie, a measure of radioactivity. A Curie is defined as the amount of radiation emitted in one second by one gram of pure radium. It is 3.7x1010 disintegrations per second. |
| cleanup | Actions taken to control a release or threat of release of hazardous substance that could affect public health or the environment. |
| coagulation | Coagulation refers to aggregation of smaller particles. This process is enhanced by the addition of chemical coagulants. |
| cometabolite | An enzyme produced by microbiological metabolism that aids degradation of a contaminant. See technology description of Cometabolism. |
| Commercially available technology | A technology for which cost and performance information is readily available. Only after a technology has been used at many different sites and the results fully documented is that technology considered established. |
| compost | Biological reduction of organic waste to humus. See technology description of Composting. |
| cone of depression | A depression in the surface of groundwater table that develops around a well from which water is being withdrawn. |
| confining layer | A geologic formation characterized by low permeability that inhibits the flow of water. |
| congener | A member of the same kind, class, or group. For example, PCBs have many cogeners because they are chemicals with similar characteristics but may have a different order or number of chlorine atoms. |
| contaminant | A chemical that degrades the natural quality of substance or media. |
| corrosive wastes | Wastes that are so acidic or alkaline that they are capable of corroding metal such as tanks, containers, drums, and barrels. Corrosiveness is one of four characteristics that define a waste as hazardous under RCRA. |
| creosote | An oily liquid obtained by the distillation of wood that is used as a wood preservative and often is found at wood preserving sites. |
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