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North Pole Refinery Glossary

Removal of a pollutant from air or water by collecting the pollutant on the surface of a solid material; e.g., an advanced method of treating waste in which activated carbon removes organic matter from wastewater.1
Air Sparging
A technique to treat contaminated groundwater. Compressed air is injected into the groundwater through specially designed wells. The air moves upward through the groundwater and soil, releasing the contaminant as vapor which may be extracted and treated using a soil vapor extraction system.2
An underground geologic formation composed of materials such as rock, sand, soil or gravel that can store and supply groundwater to wells and springs. Aquifers in Alaska can be as little as a few feet below ground surface to more than 200 feet below ground surface. A groundwater supply is usually considered an aquifer if it contains enough water to supply the water needs for a community. An unconfined aquifer is open to receive water from the surface, and whose water table surface is free to fluctuate up and down, depending on the recharge/discharge rate. There are no overlying confining beds of low permeability to physically isolate the groundwater system.
The acronym stands for the Agency for Toxic Substances and Disease Registry, which is in the U.S. Department of Health and Human Services. It’s a sister agency to the Centers for Disease Control. DEC’s interim cleanup level for sulfolane at Flint Hills is 25 parts per billion, which is based on ATSDR’s lowest recommended action level for sulfolane in drinking water.
The process by which a compound is reduced in concentration over time, through absorption, adsorption, degradation, dilution, and/or transformation. Can also be the decrease with distance of sight caused by attenuation of light by particulate pollution.1
A cancer-causing chemical associated with fuels, such as gasoline. Benzene evaporates quickly and dissolves easily in water.2
A technique that uses bacteria or other organisms to clean up contamination. Bacteria generally break down the contamination into less harmful components, such as carbon dioxide and water. Bioremediation can be used to clean up soil or water. Water and nutrients, such as fertilizer and oxygen, may be added to the contaminated soils to speed up the breakdown process. Some chemicals, such as gasoline, are easily bioremediated while others, such as pesticides, cannot be effectively treated using bioremediation. The contamination can be treated in place (in situ) or the material can be excavated and treated above ground in a different location (ex situ). Types of soil bioremediation methods include landfarming, composting, land spreading, biotreatment and biopiles. Types of water bioremediation include natural attenuation and engineered wetlands.2
Passive sampling tools that collect microbes over time for the purpose of better understanding biodegradation potential. When a Bio-Trap® sampler is deployed in a monitoring well, internal beads absorb contaminants and nutrients present in the aquifer essentially becoming an in situ microcosm which is colonized by subsurface microorganisms. Once the Bio-Trap® is recovered from a monitoring well (ranging from, 30-60 days after deployment), DNA, RNA, or phospholipid fatty acids (PLFA) can be extracted from the beads to evaluate the microbial community.
Carbon adsorption/carbon filtration
A treatment system for contaminated water or air, where the contaminated media is forced through tanks containing activated carbon. Activated carbon attracts, or adsorbs, the contaminants. This treatment is usually combined with other forms of treatment such as air stripping or an oil/water separator. Spent carbon must be treated or properly disposed of.2
Efforts to mitigate environmental damages or threat to human health, safety or welfare from hazardous substances or oil. It may include removal of a hazardous substance from the environment, including restoration, remediation and other measures that are necessary to mitigate or avoid further threat to public health, safety and welfare, or the environment. Cleanup is often used interchangeably with terms such as corrective action, remedial action, removal action or response action. It is often used broadly to describe various actions or phases of an action, such as the remedial investigation/feasibility study in the Superfund process.2
Conceptual Site Model
A summary of conditions at a site that identifies the type and location of all potential sources of contamination and how and where people, plants or animals may be exposed to the contamination.2
Corrective Action Plan
Action/ or plan put in place to stop the migration, determine the extent, and undertake recovery of petroleum after its unpermitted release; clean up affected soil and groundwater, and stabilize the site of the release to prevent or remove hazards to the public health or the environment.
Exposure Pathway
An exposure pathway refers to the way in which a person (or plants or animals) may come into contact with a hazardous substance. An exposure pathway has five parts: a source of contamination (such as an abandoned business); an environmental media and transport mechanism (such as movement through groundwater); a point of exposure (such as a private well); a route of exposure (eating, drinking, breathing or touching); and a receptor population (people, or plants or animals, potentially or actually exposed). When all five parts are present, the exposure pathway is termed a completed exposure pathway.3
Feasibility Study (FS)
[Federal] A study undertaken by the lead agency to develop and evaluate options for remedial action using data from the Remedial Investigation.2
Free product/ free phase
A petroleum product in the liquid phase. Free phase contamination implies an advanced stage of petroleum fuel hydrocarbon contamination. Product recovery wells and remediation wells are usually placed in areas of maximum free and residual phase contamination to remove as much liquid product as possible from the environment.2
Granular activated carbon
A water treatment technique in which contaminated water is pumped through a bed of activated carbon to remove organic compounds. Granulated carbons are used for water treatment, deodorization and separation of components of flow system.
Water found beneath the earth's surface that fills pores between sand, soil particles or gravel creating a saturated zone. In aquifers, groundwater is in sufficient quantities that it can be used for drinking water, irrigation or other purposes.2
Hazard Ranking System
The principal screening tool used by EPA to evaluate risks to public health and the environment associated with abandoned or uncontrolled hazardous waste sites. The HRS calculates a score based on the potential of hazardous substances spreading from the site through the air, surface water or groundwater, and on other factors such as density and proximity of human population. This score is the primary factor in deciding if the site should be on the National Priorities List and, if so, what ranking it should have compared to other sites on the list.1
Health consultation
A review of available information or collection of new data to respond to a specific health question or request for information about a potential environmental hazard. Health consultations are focused on a specific exposure issue. Health consultations are therefore more limited than a public health assessment, which reviews the exposure potential of each pathway and chemical.3
Hot spots
The definition of hot spots depends upon the medium that is contaminated. Generally, for water, a hot spot exists if contamination results in a significant adverse effect on the beneficial use of that resource and if restoration or protection of the beneficial use can occur within a reasonable amount of time. For media other than water, a hot spot exists if the site presents an unacceptable risk and if the contamination is highly concentrated, highly mobile or cannot be reliably contained.3
Interim Remedial Action
An interim measure to remove or isolate contamination. This action can be taken any time during the process and is usually taken to protect people and the environment from high levels of contamination until the final remedial action can be taken.2
Light Non-Aqueous Phase Liquid (LNAPL)
LNAPLs are undissolved chemicals, typically petroleum products, which float on the surface of groundwater rather than mix with it. A good analogy would be oil and vinegar salad dressing.2
Limit of detection (LOD)
An estimate of the minimum amount of a substance that an analytical process can reliably detect. An LOD is analyte- and matrix-specific and may be laboratory-dependent.
Limit of quantitation (LOQ)
Limits of Quantitation (LOQ): The minimum levels, concentrations, or quantities of a target variable (e.g., target analyte) that can be reported with a specified degree of confidence.
Monitoring Wells
Wells drilled at specific locations where groundwater parameters (depth, flow direction, chemical nature and so forth) can be sampled to determine the types and amounts of contaminants present.2
National Priorities List (NPL)
[Federal] A list maintained by EPA of the most serious uncontrolled or abandoned hazardous waste sites identified for possible long-term cleanup using money from the Superfund trust fund. EPA is required to update the NPL at least once a year.2
Natural attenuation, or intrinsic remediation
The natural breakdown of hazardous substances in the environment. Many hazardous substances will slowly degrade or break down into non-hazardous substances through natural processes in the environment. Natural attenuation may be approved as a remedy for contamination, particularly if other efforts have been exhausted without achieving the applicable cleanup levels, and as long as there is little chance that the contamination will pose a threat to people, plants or animals. Regular monitoring of soil and groundwater may be required to ensure that natural attenuation is occurring.2
Non-aqueous phase liquid (NAPL)
Contaminants that remain undiluted as the original bulk liquid in the subsurface and do not readily dissolve in water, e.g. spilled oil.2
Parts per billion
For both soil and water, one part per billion (ppb) is when a microgram, or 1/1,000,000th of a gram, of a contaminant is present in one liter of water or one kilogram of soil. Here are some analogies to visualize one part per billion: One part per billion is one drop of water in an Olympic-size swimming pool, which holds about 130,000 gallons. One part per billion is 1/32 of a second of one year. One part per billion is one minute of 1,903 years. Download the Contaminant Concentrations fact sheet (PDF)
Soil or other earth material with a temperature that remains below 32 degrees Fahrenheit for two or more years.2
Pilot Test
A small-scale version of a larger system that is being tested to anticipate the performance of the larger system. Pilot test results are typically used to design and optimize the larger system.2
A visible or measurable discharge or release of a contaminant as it moves water or air from a given point of origin. The plume of a contaminant in groundwater is the area of water which, as it moves underground, carries the contaminant with it. The shape is often like that of a skinny balloon. The portions of the plume close to the source will have higher concentrations than the portions further away from the source. Natural physical, chemical, and biological processes diminish the concentration levels as the water carries the contaminant away from the source.
Public health assessment
An ATSDR document that examines hazardous substances, health outcomes and community concerns at a hazardous waste site to determine whether people could be harmed from coming into contact with those substances. The public health assessment also lists actions that need to be taken to protect public health.3
Pump and Treat
A groundwater treatment technique that includes removal of the groundwater by pumping it to the surface and treating in it by various methods, such as by air stripping or carbon absorption. Extraction wells are drilled into the contaminated groundwater plume to collect the water, bringing it to the surface for treatment. A non-domestic wastewater discharge permit may be required for operation of the treatment system.2
Resource Conservation and Recovery Act (RCRA)
[Federal] A federal law that established a regulatory system to track hazardous and solid wastes from their generation to disposal. The law requires safe and secure procedures to be used in treating, transporting, storing, and disposing of hazardous wastes. It also provides a framework for management of non-hazardous solid wastes. RCRA is designed to prevent the creation of new, uncontrolled hazardous waste sites.2
Risk Assessment
The scientific process used to evaluate the toxic properties of compounds and the conditions of human and ecological exposure to determine the likelihood that an exposed population or ecosystem will be adversely affected.2
A person, group or community who has an interest in activities at a hazardous waste site.2
Is a solvent developed by Shell Oil Company in the early 1960s and is used at the North Pole Refinery for the extraction of aromatic components from petroleum. Gasoline is the only produced fuel at the North Pole Refinery which currently undergoes and requires the sulfolane extraction process. Also referred to as, tetrahydrothiophene 1, 1-dioxide.
The study of the harmful effects of substances on humans or animals.2
Work plan
A written plan that describes the planned actions, such as sampling and analysis, site investigation, site assessment or risk assessment. It includes the justification and instructions for conducting these activities. It also includes health and safety plans for the workers conducting these tasks.2

1 From the U.S. Environmental Protection Agency's Terms of Environment: Glossary, Abbreviations and Acronyms at

2From the Alaska Department of Environmental Conservation’s Spill Prevention and Response Division Glossary of Terms and Acronyms

3From the Agency for Toxic Substances and Disease Registry's Glossary of Terms at


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