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Contaminated and Hazardous Waste Site Management

Glossary C


Calibration: The process of matching a model simulation with observed data. Typically, one or more model parameters are varied within reasonable limits until a suitable match is obtained.

Calibration Blank: A volume of acidified deionized/distilled water.

Calibration Standards: A series of known standard solutions used by the analyst for calibration of the instrument (i.e., preparation of the analytical curve).

Cap: A layer (or layers) of material, such as clay or a synthetic material, used to prevent precipitation from penetrating and spreading contaminated materials. The surface of the cap generally is mounded or sloped so water will drain off.

Capillary Forces: Interfacial forces between immiscible fluid phases, resulting in pressure differences between the two phases.

Capillary Fringe: The zone immediately above the water table, in which water is drawn upward by capillary action, and the pores are filled with water under pressure less than atmospheric.

Capillary Suction: The process whereby water rises above the water table into the void spaces of a soil due to tension between the water and soil particles.

Capture Zone: That portion of the groundwater flow system where the action of a pumping well causes the groundwater to flow to or be captured by that well.

Case: A finite, usually predetermined number of samples collected over a given time period from a particular site. Case numbers are assigned by the Sample Management Office. A Case consists of one or more Sample Delivery Groups.

Carcinogen: A substance that causes cancer.

Carbon Adsorption: A treatment system in which contaminants are removed by forcing water or air through tanks containing activated carbon, a specially treated material that attracts and holds or retains contaminants.

Catalytic Oxidizer: An off-gas post-treatment unit for control of organic compounds. Gas enters the unit and passes over a support material coated with a catalyst (commonly a noble metal such as platinum or rhodium) that promotes oxidation of the organics. Catalytic oxidizers can also be very effective in controlling odors. High moisture content and the presence of chlorine or sulfur compounds can adversely affect the performance of the catalytic oxidizer.

Cation: A positively charged atom or radical.

Cation Exchange Capacity (CEC): A measure of the availability of cations that can be displaced from a solid surface and exchanged for other cations. For geologic materials, the cation exchange capacity is the number of milliequivalents of cations that can be exchanged per 100 grams of dry sample.

Centrifugation: Process using centrifugal force to separate liquids of different specific gravities or suspended colloidal particles, according to particle-size fractions.

Characteristic Curve: a) A curve to show the relation between two changing values b) Refers to one of a pair of conjugate curves in a surface, which has the property that the directions of the tangents through any point of the curve are the characteristic directions of the surface.

Characterization: A determination of the approximate concentration range of compounds of interest used to choose the appropriate analytical protocol.

Chargeability: The normalized (using the primary voltage) area under an induced polarization (IP) decay curve, between two times, after the transmitted current is stopped in a time domain survey. Usually expressed in millivolt-seconds per volt.

Charge Balance: A calculation in which the total number of positive charges in cations are compared to the number of negative charges in anions. Since groundwater is electrically neutral, the charges should be balanced.

Chemical Fixation: The use of chemicals to bind contaminants, thereby reducing the potential for leaching or other movement.

Chemical and Microbiological Transformation: The conversion of a chemical to other chemicals by either chemical or microbial processes.

Chemotrophs: Organisms that obtain energy from oxidation or reduction of inorganic or organic matter.

Chromated Copper Arsenate: An insecticide/herbicide formed from salts of three toxic metals: copper, chromium, and arsenic. This salt is used extensively as a wood preservative in pressure-treating operations. It is highly toxic and water-soluble, making it a relatively mobile contaminant in the environment.

Chromatogram: Graph produced during a gas chromatograph analysis and showing the constituents present and their relative concentration.

Cirque: A large size amphitheatre shaped hollow which has been excavated by ice action in mountainous regions.

Clastic Rock - (Detrital Rock): A sedimentary rock composed of fragments ofpre-existing rocks or organic structures.

Cleanup: Actions taken to deal with a release or threatened release of hazardous substances that could affect public health or the environment. The term is often used broadly to describe various response actions or phases of remedial responses, such as the RI/FS.

Closure: The process by which a landfill stops accepting wastes and is closed under Federal and/or State guidelines to ensure the long-term protection of the public and the environment.

Coefficient of Storage: See Storage Coefficient.

Coefficient of Variation (CV): The standard deviation as a percent of the arithmetic mean.

Coefficient of Permeability: See Hydraulic Conductivity.

Cohesion: The tendency of similar parts of a body to hold together, due to intermolecular forces.

Cohesionless Materials: Such as sand on a beach, lack this tendency.

Collector Well: Constructed with horizontal lengths of screened collector pipe radiating out from a central vertical well.

Colloids: Fine-grained material in suspension. Specifically refers to a particle-size range of less than 0.00024 mm.

Colluvial Deposits: Weathered, unconsolidated materials transported and deposited by gravity.

Cometabolism: The simultaneous metabolism of two compounds, in which the degradation of the second compound (the secondary substrate) depends on the presence of the first compound (the primary substrate). For example, in the process of degrading methane, some bacteria can degrade hazardous chlorinated solvents that they would otherwise be unable to attack.

Complexation: A reaction in which a metal ion and one or more anionic ligands chemically bond. Complexes often prevent the precipitation of metals.

Complex Number: Comprised of a real and imaginary part.

Complex Resistivity (CR): A geophysical effect, also the basis of the CR method, in which polarization within the medium results in the voltage and applied current being out of phase - that is, their ratio is complex. Also known as spectral IP. Induced polarization (IP) is one form of complex resistivity.

Compositing: The combining and homogenizing of samples (e.g., soils) prior to preforming an analysis of the composite sample.

Compressibility: The relative volume reduction that geological material can undergo when a force is applied or water is removed from the vicinity by pumping.

Computational Algorithm: That part of the computer code containing the step-by-step solution procedure for the mathematical equations of the hydrogeological model.

Computer Code: The complete set of computer-language instructions which contain the input data statements, computational algorithm, and output statements. Common computer languages include BASIC, FORTRAN and PASCAL.

Concentration Gradient: The change in concentration from one point to another. This is the "force" driving diffusion.

Concentration Level (low or medium): Characterization of soil samples or sample fractions as low concentration or medium concentration is made on the basis of the laboratory's preliminary screen, not on the basis of information entered on the Traffic Report by the sampler. High concentration samples may be multi-phase, and are considered to be those collected directly from drums, pits, ponds, lagoons or areas where no dilution of waste is evident.

Conceptual Model: Our idealization of a hydrogeological system on which we can base a mathematical model. The conceptual model includes assumptions on the hydrostratigraphy, material properties, dimensionality and governing processes.

Condensate: The liquid that separates from a vapor during condensation.

Conductance: The product of conductivity and thickness [Siemens].

Conduction Currents: Electrical current resulting from the movement of free charges (contrast with displacement current).

Conductivity: A coefficient of proportionality describing the rate at which a fluid (e.g., water or gas) can move through a permeable medium. Conductivity is a function of both the intrinsic permeability of the porous medium and the kinematic viscosity of the fluid which flows through it.

Cone of Depression: The area around a discharging well where the hydraulic head (potentiometric surface) in the aquifer has been lowered by pumping. In an unconfined aquifer, the cone of depression is a cone-shaped depression in the water table where the media has actually been dewatered.

Confined Aquifer: A fully saturated aquifer overlain by a confining layer. The potentiometric
surface (hydraulic head) of the water in a confined aquifer is at an elevation that is equal to or
higher than the base of the overlying confining layer. Discharging wells in a confined aquifer
lower the potentiometric surface which forms a cone of depression, but the saturated media is not

Confining Bed: -A bed of impermeable material stratigraphically adjacent to one or more aquifers. Confining bed is now used to replace terms such as "aquiclude", "aquitard" and "aquifuge".

Confining Layer: A geologic body of low hydraulic conductivity above or below one or more aquifers. Also called an aquiclude.

Connectivity: The degree to which a fracture network is connected. When defined statistically, fracture connectivity can be used to generate many different fracture network realizations for use in groundwater flow and mass transport models.

Conservative: A dissolved substance which moves as fast as water in the groundwater system, and is not prone to attenuation beyond that occurring by diffusion and/or dispersion.

Consolidated: Naturally occurring geologic material that has been lithified and so has strength and resists disintegration.

Consolidation Test: A test in which a sample is confined laterally in a ring and compressed between porous plates which are saturated with water.

Constituent: An essential part or component of a system or group (e.g., an ingredient of a chemical mixture). For instance, benzene is one constituent of gasoline.

Containment: The process of enclosing or containing hazardous substances in a structure, typically in a pond or lagoon, to prevent the migration of contaminants into the environment.

Contaminant: Any physical, chemical, biological, or radiological substance in air, soil or water that has an adverse effect.

Contaminant Plume: Contaminants which encroach into a groundwater system are moved down gradient. The area of the aquifer containing the degraded water which resulted from the migration of a pollutant is called a contaminant plume.

Contamination: The introduction into soil, air or water of a chemical, organic or radioactive material or live organism that will adversely affect the medium's quality.

Contamination Concept: The model which considers the source(s), migration, fate and impact of subsurface contaminants. Its precision should improve as site assessment progresses.

Contingency Plan: A document setting out an organized, planned, and coordinated course of action to be followed in case of fire, explosion or other accidents that release toxic chemicals, hazardous wastes or radioactive materials into the environment.

Continuing Calibration: Analytical standard run every 10 analytical samples or every 2 hours, whichever is more frequent, to verify the calibration of the analytical system.

Continuous Liquid-Liquid Extraction: Synonymous with the terms continuous extraction, continuous liquid extraction, and liquid extraction. This extraction technique involves boiling the extraction solvent in a flask and condensing the solvent above the aqueous sample. The condensed solvent drips through the sample, extracting compounds of interest from the aqueous phase.

Contoured Map: A map with contour lines drawn at regular intervals to show surface configuration (elevation), geophysical and geochemical data distributions.

Contract Required Detection Limit (CRDL): Minimum level of detection acceptable under the contract Statement of Work.

Control Limits: A range within which specified measurement results must fall to be compliant. Control limits may be mandatory, requiring corrective action if exceeded, or advisory, requiring that non-compliant data be flagged.

Core: A continuous columnar sample of subsurface material extracted from a borehole. Such a sample preserves the features of the sampled material.

Correlation Coefficient: A number (denoted "r") which indicates the degree of dependence between two variables (e.g., concentration and absorbance). The more dependent they are the closer the value of r is to 1.0. Determined on the basis of the least squares line.

Cost Recovery: A legal process where PRPs can be required to pay back the Federal government for money spent on cleanup actions.

Cross-hole: Geophysical methods carried out between boreholes (see also Tomography).

Creosotes: Chemicals used in wood preserving operations and produced by distillation of tar, including polycyclic aromatic hydrocarbons and polynuclear aromatic hydrocarbons. Contaminating sediments, soils, and surface water. Creosotes may cause skin ulcerations and cancer through prolonged exposure.

Cultural Noise: Geophysical noise caused by anthropogenic sources (cars, pumps, etc) as well as wind, moving tree roots, etc..

Cultural Environment: The part of the environment which represents man-made features (e.g. roads, buildings, canals, bridges) as opposed to natural features.

Current Density: A measure of current flow through a given (oriented) area [Amperes/ m2].

Current Channelling/Gathering: Channelling is a restriction of current flow due to an insulating barrier or narrowing of a conductor. Current gathering is a concentration of current in a locally, more conductive zone. The disproportionate influence of lakes and swamps on VLF surveys is a well known example.

Cuttings: Fragments of soil or rock created by the drilling process (with or without free water). Also called drill cuttings.

Cyclone: A type of separator for removal of larger particles from an exhaust gas stream. Gas laden with particulates enters the cyclone and is directed to flow in a spiral causing the entrained particulates to fall out and collect at the bottom. The gas exits near the top of the cyclone.


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