Browse through our glossary of remediation and other industry related terms.

Aboveground Release

Any release to the surface of the land or to surface water. This includes, but is not limited to, releases from the aboveground portion of an UST system and aboveground releases associated with overfills and transfer operations as the regulated substance moves to or from an UST system.

Aboveground Tank

A tank used to store or process used oil that is not an underground storage tank..


Transport of a substance through the outer boundary of a medium, frequently through biological membranes, through active transport, passive diffusion, etc.

Accidental Occurence

An accident, including continuous or repeated exposure to conditions, which results in bodily injury or property damage neither expected nor intended from the standpoint of the insured.

Accidental Release

Any sudden or nonsudden release of petroleum from an underground storage tank that results in a need for corrective action and/or compensation for bodily injury or property damage neither expected nor intended by the tank owner or operator.

Action Memorandum

The internal EPA document that serves as a written record of Regional or HQ approval of Superfund financing of a removal action. The Action Memorandum describes site conditions, including the nature of the release, actual or potential threats, enforcement strategy and proposed costs and actions. An Action Memorandum is also the appropriate format within EPA for requesting and obtaining Superfund ceiling increases, exemptions to the twelve-month and $2 million limits, and redistribution of funds because of changes in the scope of work.

Activated Carbon

Activated carbon, also known as activated charcoal, is a highly porous carbonaceous material characterized by a large surface area and an extensive network of pores.

It is produced by activating carbon-rich substances, such as wood, peat, coconut shells, or sawdust, through processes involving high temperatures and controlled oxidizing gases. The resulting material possesses a unique structure that enhances its adsorption capabilities. Read more on activated carbon here.

Active Maintenance

Any significant remedial activity needed during the period of institutional control to maintain a reasonable assurance that performance objectives are met. Such active maintenance includes ongoing activities such as the pumping and treatment of water from a disposal unlit or one-time measures such as replacement of a disposal unit cover. Active maintenance does not include custodial activities such as repair of fencing, repair or replacement of monitoring equipment, revegetation, minor additions to soil cover, minor repair of disposal unit covers, and general disposal site upkeep such as mowing grass.

Active Portion

That portion of a facility where treatment, storage, or disposal operations are being or have been conducted after the effective date of Part 261 of this chapter and is not a closed portion.

Active Production Facility

Any ongoing operations that manufacture, recycle, handle, store, or transport hazardous materials or waste as a primary ingredient, product or by-product of operations or any location contaminated due to off-site migration of hazardous materials or wastes from such operations.

Active Waste Management Facility

Any ongoing legal or illegal operation or site whose primary purpose is to handle, exchange, transfer, store, treat, or dispose of hazardous materials or wastes or any location contaminated due to off-site migration of hazardous materials or wastes from such a facility or site.

Acutely Hazardous Waste

Certain hazardous wastes subject to the small quantity generator exemption. These wastes include those bearing the prefix "F" distinguished by the hazard code "H " and those wastes bearing the prefix "P". Commonly referred to as the "F-wastes" and the "T-wastes," these terms reflect the first letter of the EPA hazardous waste code for those wastes. - Alternatively- A waste capable of causing injury, illness, or death in the short-term.

Administrative Action

A nonjudicial enforcement action taken by the U.S. EPA Administrator (or designee) or a State.

Administrative Order

A legal document signed by EPA directing an individual, business, or other entity to take corrective action or refrain from an activity. It describes the violations and actions to be taken, and can be enforced in court. Such orders may be issued, for example, as a result of an administrative complaint whereby the respondent is ordered to pay a penalty for violating a statute.


What is Adsorption?

Adsorption is the bonding of a, frequently ionic, substance to soil or other medium. A substance is said to be adsorbed if the concentration in the boundary region of a soil particle is greater than in the interior of the contiguous phase.

Affected Public

The people who live and/or work near hazardous waste sites.


The EPA standard national forms for applying for a permit,,including any additions, revisions or modifications to the forms; or forms approved by EPA for use in approved States, including any approved modifications or revisions. Application also includes the information required by the Director.


A geologic formation, group of formations, or part of a formation capable of yielding a significant amount of ground water to wells or springs.

Area of Attainment

The area of the plume outside the boundary of any waste to be managed in place as part of the final remedy and inside the boundaries of the containment plume. -Alternatively- The area outside the boundary of any waste remaining in place and up to the boundary of the contaminant plume. Generally, the boundary of the waste is defined by the source control remedy. If the source is removed, the entire plume is within the area of attainment. But if waste is managed on site, the ground water directly beneath the waste management area is not within the area of attainment.

Area of Contamination

A continuous (significant) extent of contamination at a Superfund site. For the purposes of ARARs, is used as the equivalent of a RCRA land-based unit to determine whether disposal occurs.


Any material or structure that prevents or substantially delays movement of water or radionuclides.

Baseline Risk Assesment

During the Site Characterization phase of an RI/FS, a baseline risk assessment (RA) is used to evaluate the potential threat to human health and the environment in the absence of any remedial action. That is, the baseline RA describes the risk conditions under the "no action alternative." The baseline RA is extremely important because it provides the basis for determining whether remedial action is necessary. It also determines the extent of cleanup needed to reduce potential risk levels to within EPA's acceptable range.

Below Regulatory Concern

A definable amount of low-level waste that can be deregulated with minimal risk to the public.

Belowground Release

Any release to the subsurface of the land and to ground water. This includes, but is not limited to, releases from the belowground portions of an underground storage tank system and belowground releases associated with overfills and transfer operations as the regulated substance moves to or from an underground storage tank.

Bench-Scale Tests

Laboratory testing of potential cleanup technologies, also known as treatability studies.

Best Available Technology (BAT) or Best Demonstrated Available Technology (BDAT)

Treatment technologies that have been shown through actual use to yield the greatest environmental benefit among competing technologies that are practically available.

Beta Particle

A negatively-charged subatomic particle emitted during decay of certain radioactive elements. A beta particle is identical to an electron.

Beta Radiation

Emitted from a nucleus during fission. Beta radiation can be stopped by an inch of wood or a thin sheet of aluminum.

Biological Additives

Microbiological cultures, enzymes, or nutrient additives that are deliberately introduced into an oil discharge for the specific purpose of encouraging biodegradation to mitigate the effects of the discharge.


Techniques using biological processes to treat contaminated soil or groundwater. Bioremediation can occur either in situ or in bioreactors where contaminated media are placed in contact with organisms to degrade the contaminants in a controlled environment. Generally, the technique involves stimulating organisms by adding materials such as nutrients or oxygen to increase the rate of biodegradation. -Alternatively- The use of living organisms, such as bacteria and fungi, to treat hazardous substances.


The uptake of contaminants by biological organisms (plants and animals) .

Blended System

A drinking water supply system which can or does combine (e.g., via connecting valves) water from more than one well or surface water intake, or from a combination of wells and intakes.


An enclosed device using controlled flame combustion and having the following characteristics: The unit must have physical provisions for recovering and exporting thermal energy in the form of steam, heated fluids, or heated gases; the unit's combustion chamber and primary energy recovery sections must be of integral design. To be of integral design, the combustion chamber and the primary energy recovery sections (such as waterfalls and superheaters) must be physically formed into one manufactured or assembled unit. A unit in which the combustion chamber and the primary energy recovery sections are joined only by ducts or connections carrying flue gas is not integrally designed; however, secondary energy recovery equipment (such as economizers or air preheaters) need not be physically formed into the same unit as the combustion chamber and the primary energy recovery section. The following units are not precluded from being boilers solely because they are not of integral design: process heaters (units that transfer energy directly to a process stream), and fluidized bed combustion units; and while in operation, the unit must maintain a thermal energy recovery efficiency of at least 60 percent, calculated in terms of the recovered energy compared with the thermal value of the fuel; and the unit must export and utilize at least 75 percent of the recovered energy, calculated on an annual basis.

Bottoms Receiver

A container or tank used to receive and collect the heavier bottoms fractions of the distillation feed stream that remain in the liquid phase.

Brine Mud

A waste material, often associated with well drilling or mining, composed of mineral salts and other inorganic compounds.

Buffer Zone

A portion of the disposal site that is controlled by the licensee and that lies under the disposal units and between the disposal units and the boundary of the site.

Bulk Density

The weight of an object or material divided by its volume, including the volume of its pore spaces. Specifically, the weight per unit volume of a soil mass that has b_en oven-dried to a constant weight at 105 degrees C.

Buried Waste

Low-level radioactive waste that has been disposed of by near-surface burial.

Burning Agents

Those additives that, through physical or chemical means, improve the combustibility of the materials to which they are applied.


A material that is not one of the primary products of a production process and is not solely or separately produced by the production process. Examples are process residues such as slags or distillation column bottoms. The term does not include a co-product that is produced for the general public's use and is ordinarily used in the form in which it is produced by the process.


A chemical substance produced without separate commercial intent during the manufacturing or processing of another chemical substance(s) or mixture(s).


The process of making unconsolidated powder or granules by thermal evaporation and partial decomposition of high-level waste.

California List Wastes

To be classified as a California list waste, three conditions must be met: 1) The waste must be a RCRA listed or characteristic waste; 2) The waste must be a liquid (i.e., it fails method 9095 Paint Filter Liquids Test [PFLT]), except for Halogenated Organic Compounds (HOCs), which may be liquid or non-liquid; and 3) The waste must exceed statutory prohibition levels for specified constituents. The types of wastes that may be California list wastes are: free cyanides, certain metals, corrosive wastes, PCBs, and HOCs. The Agency has limited the restricted HOCs to approximately 100 HOCs. These restricted HOCs include solvents, pesticides, PCBs, and dioxins. These hazardous wastes are referred to as California list wastes because the State of California developed regulations to restrict the land disposal of wastes containing these constituents, and Congress subsequently incorporated these provisions into the 1984 HSWA amendments to RCRA. Even if LDR treatment standards have not been promulgated for certain RCRA wastes (e.g., Third wastes), these wastes may be subject to California list restrictions.

Candidate Area

A geologic and hydrologic system within which a geologic repository may be located.

Carbon Adsorption

A treatment system where contaminants are removed from ground water or surface water when the water is forced through tanks containing activated carbon, a specially treated material that attracts the contaminants.

Carbon Regeneration Unit

Any enclosed thermal treatment device used to regenerate spent activated carbon.

Carbon Tetrachloride

A colorless liquid used in refrigerants, metal degreasers, agricultural fumigants, and as a dry-cleaning agent. Exposure to it can cause damage to the central nervous system, liver, and kidneys.

Case Closed

A removal action is considered closed when on-site activities have been completed and all administrative work has been completed. This includes final OSC reports and payment for contract services. The Regional Coordinator is responsible for designating an action to be "closed." Unlike "completion date," dates for "case closed" are not tracked in the RTS/SCAP system.

Case Management System

A data base that contains general information on all enforcement activities, with information on cost recovery and settlements.

Categorical Pretreatment Standards

National technology-based effluent limitations developed by EPA for certain industrial categories. Currently, no national standards exist for CERCLA discharges.

Cathodic Protection

A technique to prevent corrosion of a metal surface by making that surface the cathode of an electrochemical cell. For example, a tank system can be cathodically protected through the application of either galvanic anodes or impressed current.


Comprehensive Environmental Response Compensation and Liability Act

CERCLA Baseline Risk Assessment

Under CERCLA, the U.S. Environmental Protection Agency (EPA) is required to assess the risks to human health posed by uncontrolled hazardous waste sites on the National Priority List (NPL). That assessment is conducted in the remedial investigation/feasibility study (RI/FS) phase of the site cleanup process. When applied to the evaluation of the human health impacts caused by uncontrolled CERCLA sites (i.e., if no remedial action is taken), this process is termed the "baseline risk assessment."

Certificate of Compliance

Certificate granted by the Nuclear Regulatory Commission certifying that a prototype of DOE's TRUPAC-H radioactive waste transport containers has passed its review and testing for "normal" and "hypothetical" accident conditions.

Characteristic Waste

A solid waste defined as hazardous because it exhibits one of the following four characteristics: ignitability, corrosivity, reactivity, or toxicity.


Facility or site sampling, monitoring, and analysis activities to determine the extent and nature of the release. Characterization provides the basis for acquiring the necessary technical information to develop, screen, analyze, and select appropriate cleanup techniques. -Alternatively- Site sampling, monitoring, and analysis to determine the extent and nature of releases. Characterization provides the basis for acquiring the necessary technical information to develop, screen, analyze, and select appropriate cleanup techniques.

Chelating Agent

Amine polycarboxylic acids (e.g., EDTA, DTPA), hydroxy-carboxylic acids, and polycarboxylic acids (e.g., citric acid, carbolic acid, and glucinic acid).

Chemical Agents

Those elements, compounds, or mixtures that coagulate, disperse, dissolve, emulsify, foam, neutralize, precipitate, reduce, solubilize, oxidize, concentrate, congeal, entrap, fix, make the pollutant mass more rigid or viscous, or otherwise facilitate the mitigation of deleterious effects or the removal of the pollutant from the water.

Chemical Substance

Any organic or inorganic substance of a particular molecular identity, including: Any combination of such substances occurring in whole or part as a result of a chemical reaction or occurring in nature, and any element or uncombined radical. Such term does not include: Any mixture; any pesticide (as defined in the Federal Insecticide, Fungicide, and Rodenticide Act) when manufactured, processed, or distributed in commerce for use as a pesticide; tobacco or any tobacco product; any source material, special nuclear material, or byproduct material (as such terms are defined in the Atomic Energy Act of 1954 and regulations issued under such Act); any article the sale of which is subject to the tax imposed by Section 4181 of the Internal Revenue Code of 1954 (determined without regard to any exemptions from such tax provided by Section 4182 or Section 4221 or any provisions of such Code); and any food, food additive, drug, cosmetic, or device (as such terms are defined in Section 201 of the Federal Food, Drug, and Cosmetic Act) when manufactured, processed, or distributed in commerce for use as a food, food additive, drug, cosmetic, or device.

Chemical Waste Landfill

A landfill at which protection against risk of injury to health or the environment from migration of PCBs to land, water, or the atmosphere is provided from PCBs and PCB Items deposited therein by locating, engineering, and operating the landfill.


The act of separating waste materials manually, by screening, or by air classification into categories of size, weight, and/or color.

Clean Closure

Removal and/or decontamination of all wastes from a disposal facility. Clean closure is an option for certain types of HWMUs, including surface impoundments and waste piles. To clean close a HWMU, DOE facilities must remove or render nonhazardous all hazardous and mixed waste associated with the unit, including contaminated equipment, structures, and soils. If a unit can be clean closed, no post-closure care is required.

Clean Water Act

A statute under which EPA promulgates Water Quality Criteria and administers the National Pollutant Discharge Elimination System (NPDES) permit program, as well as regulates discharges to or dredging of wetlands.


Actions undertaken during a removal or remedial response to physically remove or treat a hazardous substance that poses a threat or potential threat to human health and welfare and the environment and/or real and personal property. Sites are considered cleaned up when EPA removal or remedial programs have no further expectation or intention of returning to the site and threats have been mitigated or do not require further action.

Cleanup Level

The containment concentration goal of the remedial action, i.e., the concentration of a ground-water contaminant to be achieved through remedial action.


The ignition of oxygen with an organic substance that results in the production of energy.

Commercial Solid Wastes

Solid wastes generated by wholesale, retail or service businesses, and multi-unit residential structures. Some communities define institutional solid wastes as commercial solid wastes. Commercial solid wastes are one form of municipal solid wastes.


The ability of materials to exist together without adverse environmental effects or health risks. Primarily applied to waste fluid combinations and liner materials.


The ability of two or more substances to maintain their respective physical and chemical properties upon contact with one another for the design life of the tank system under conditions likely to be encountered in the UST.

Completion Date

The actual date that the cleanup contractor or the OSC has demobilized, completing the scope of work in the Action Memorandum and the disposal of waste is completed as set forth in the Action Memorandum or subsequent modifications. If the Action Memorandum's scope of work includes the ultimate disposal of wastes, then the date the site's wastes are received for final disposal would be the completion date. However, if the Action Memorandum's scope of work does not include off-site disposal, then the completion date would be the date the contractor left the site. Temporary demobilization and on-site temporary storage are not considered completions unless temporary storage was the only action identified in the Action Memorandum. Likewise, temporary off-site storage of hazardous substances at a storage, treatment and disposal (TSD) facility other than the facility of ultimate disposal is a continuation of the removal action, not a completion.

Compliance Order or Compliance Action

An order or action issued by RCRA that requires any person who is not complying with a requirement of RCRA to take steps to come into compliance.


Either the tank or ancillary equipment of a tank system. Any constituent part of a unit or any group of constituent parts of a unit which are assembled to perform a specific function (e.g., a pump seal, pump, kiln liner, kiln, thermocouple).


Description of the components of solid waste, with the amount of each component expressed as a percentage of the total waste.

Comprehensive Environmental Response Compensation and Liability Act

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986. A federal law passed in 1980 and modified in 1986 by SARA. The Acts created a special tax that goes into a Trust Fund, commonly known as Superfund, to investigate and clean up abandoned or uncontrolled hazardous waste sites. Under the program, EPA can either: 1) Pay for site cleanup when parties responsible for the contamination cannot be located or are unwilling or unable to perform the work; or 2) Take legal action to force parties responsible for site contamination to clean up the site or pay back the Federal government for the cost of the cleanup.


The amount of any resource or energy used in a given time by a given number of people.


The confinement of waste within a designated boundary.


To make impure, unclean, or unfit for use through contact or addition of something; pollute.

Contaminated Soil

Soil onto which available evidence indicates that a hazardous substance was spilled, spread, disposed, or deposited.

Contingency Plan

A document setting out an organized, planned, and coordinated course of action to be followed in case of fire, explosion, or release of hazardous waste or hazardous waste constituents which could threaten human health or the environment.


Any remedial action intended to stabilize, inhibit future misuse of, or reduce emissions or effluents from residual contaminants.

Conventional Pollutants

The pollutants classified as biochemical oxygen demand (BOD), total suspended solids (TSS), fecal coliform, oil and grease, and pH pursuant to the CWA.

Corrective Action Order

An order issued by EPA that requires corrective action at a facility where a release of hazardous waste or constituents into the environment has occurred. Corrective action may be required beyond the facility boundary, and it can be required regardless of when the waste was placed at the facility. Actions under RCRA that require a permitted facility to correct the release(s) of hazardous waste or constituents from a hazardous waste management unit. A Corrective Action Order can suspend or revoke the authority to operate a treatment, storage, or disposal facility, or seek appropriate relief (including an injunction) from a U.S. district court.

Corrective Measures Implementation

The stage of corrective action where actual cleanup of a facility takes place.

Corrective Measures Study

The portion of a RCRA corrective action that is generally equivalent to a feasibility study (FS) taken under Superfund.


A waste with a pH less than or equal to 2.0 or greater than or equal to 12.5, or capable of corroding steel at a rate of more than 0.25 inches per year.


Clean Water Act


Process of removing a facility from operation.


The act of removing a chemical, biological, or radiologic contaminant from, or neutralizing its potential effect on, a person, object or environment by washing, chemical action, mechanical cleaning, or other techniques.

Deep-Well Injection

The subsurface emplacement of fluids through a bored, drilled or driven well, or through a dug well whose depth is greater than the largest surface dimension.

Degradation Rate

The rate at which a chemical is broken down in the environment by hydrolysis, photodegradation, or soil metabolism; the length of time that a parent chemical persists in the environment.

Detection Level

The minimum concentration of a substance that can be measured with a 99% confidence that the analytical concentration is greater than zero.


The spreading out of molecules, atoms, or ions into a vacuum, fluid, or porous medium in a direction tending to equalize concentrations in all parts of the system.


Thinning down or weakening a compound by mixing with water or other solvents.


A synthetic organic compound made up of chlorinated hydrocarbons known to cause birth defects, skin disorders, liver damage, immune system suppression, and cancer in laboratory animals at extremely low doses. Dioxin is produced in the combustion of solid waste and in the manufacturing of certain herbicides and wood preservatives. It has become a widespread environmental pollutant.


The discharge, deposit, injection, dumping, spilling, leaking, or placing of any solid waste or hazardous waste into or on any land or water so that such solid waste or hazardous waste or any constituent thereof may enter the environment or be emitted into the air or discharged into any waters, including ground waters.


Department of Defense


Department of Energy


The general physical characteristics of a rock or the rocks in a particular area.


No Further Action

Petroleum Hydrocarbons

Petroleum hydrocarbons are a group of organic compounds composed primarily of carbon and hydrogen derived from crude oil.

These compounds are classified into various categories based on their molecular structure. Environmental contamination by petroleum hydrocarbons occurs through accidental spills, leaks, or improper disposal of petroleum-based products. The release of these hydrocarbons into soil, water, or air can have detrimental effects on ecosystems. Petroleum hydrocarbons can disrupt microbial activity in the soil, impede plant growth, and alter the overall soil structure. In aquatic environments, such as rivers and oceans, they can form oil slicks, impacting marine life by coating and smothering organisms. Additionally, hydrocarbons can dissolve in water, posing a threat to aquatic species through direct exposure and the accumulation of contaminants in the food chain. Efforts to mitigate the environmental impact of petroleum hydrocarbons involve implementing stringent regulations, employing advanced remediation technologies, and promoting sustainable practices in the extraction, transportation, and use of fossil fuels.


Permeable Reactive Barrier