Glossary of terms

Explanation of technical terms used in site stories in the Minnesota Groundwater Contamination Atlas.

Active gas system – a landfill treatment process which actively pulls the gas out of the landfill. The gas is burned before it can be released into the atmosphere.

Aeration, soil – a treatment process in which air is pushed through the soil at the contamination site to remove volatile compounds. Examples include soil vapor extraction and air sparging.

Aeration, water – a treatment process in which water is pushed up into the air via a fountain or bubbler to remove volatile compounds from the water. This process can also increase oxygen levels in water.

Air stripping – a treatment process which strips volatile compounds from water by promoting air to water contact, usually inside an enclosed tower.

ArcMap – a GIS (Geographic Information System) program; the primary tool used to produce maps for this project.

Cap, landfill – a series of layers made up of clay, soil, and/or manmade watertight material that form a barrier between the waste and the surface. Landfill caps prevent water from soaking through the waste and carrying contamination away from the site.

CEC (contaminants of emerging concern) – contaminants identified by an MDH initiative that investigates the health and exposure potential of contaminants of emerging concern in water, and informs partners and the public of appropriate actions for pollution prevention and reducing exposures to contaminants that might be unhealthy. These contaminants are identified because improved research methods allow us to look for new chemicals at lower levels than previously possible, industry and individuals are using new chemicals in a variety of products and applications, and old chemicals are being used in new ways.

CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act of 1980) – the federal law that created the federal Superfund program.

Contamination – an impure or hazardous substance.

Detection – a groundwater, soil, or vapor sample that contains contaminants in lower concentrations than the health-based guidance values set by MDH or EPA. (This means that contaminants are present, but at a low enough concentrations to be considered safe for human consumption.)

DNAPL (dense non-aqueous phase liquid) – a groundwater contaminant that is not soluble in water and has higher density than water. This contamination will sink below the water table until stopped by a non-permeable layer (bedrock or clay).

DNR (Department of Natural Resources) – a state agency dedicated to protecting and managing land, water, fish and wildlife – and providing access to outdoor recreation opportunities.

EPA (Environmental Protection Agency) – an agency of the United States federal government dedicated to protecting human and environmental health.

EQuIS (Environmental Quality Information System) – a system used by MPCA to store and manage surface water and sub-surface monitoring data and associated laboratory results from sampling locations across the state.

Exceedance – a groundwater, soil, or vapor sample that contains contaminants in higher concentrations than the health-based guidance values set by MDH or EPA.

GAC filter (granular activated carbon filter) – a treatment system which uses granular activated carbon to adsorb natural organic compounds, taste and odor compounds, and synthetic organic chemicals from drinking water.

Gas flare – a landfill treatment system that burns off harmful gases as they come out of a landfill.

GIS (Geographic Information System) – a system designed to capture, store, manipulate, analyze, manage, and present spatial or geographic data.

HBV (Health-Based Value) – a drinking water standard; the concentration of a groundwater contaminant that can be consumed daily with little or no risk to health (MDH). An HBV is expressed as a concentration in micrograms per liter (µg/L).

HRL (Health Risk Limit) – a drinking water standard; the concentration of a groundwater contaminant, or a mixture of contaminants, that can be consumed with little or no risk to health and which has been promulgated under rule (MDH). A HRL is expressed as a concentration in micrograms per liter (µg/L).

IC (Institutional Controls) – restrictions, conditions, or controls intended to protect the integrity of a response action and help minimize the potential for exposure to contamination.

In-situ chemical oxidation – also known as injection; a treatment process in which chemicals are injected into the soil to make it easier to remove contamination.

ISV (intrusion screening values) – chemical-specific, risk-based inhalation screening criteria for volatile compounds commonly evaluated during vapor intrusion investigations. An ISV is defined as a concentration of a contaminant in indoor air that is unlikely to harm human health.

LCCMR (Legislative-Citizen Commission on Minnesota Resources) – a panel of legislators and citizens that make funding recommendations to the legislature for special environment and natural resource projects, like this one.

LNAPL (light non-aqueous phase liquid) – a groundwater contaminant that is not soluble in water and has lower density than water. This contamination will float to the top of the water table.

MCL (Maximum Contaminant Level) – a drinking water standard; the legal threshold limit on the amount of a substance that is allowed in public water systems under the Safe Drinking Water Act (SWDA).

MDA (Minnesota Department of Agriculture) – a state agency dedicated to enhancing Minnesotans’ quality of life by ensuring the integrity of our food supply, the health of our environment, and the strength of our agricultural economy.

MDD (Minnesota Decision Document) – a public document that explains the remediation plan for the cleanup of a state Superfund site.

MDH (Minnesota Department of Health) – a state agency dedicated to protecting, maintaining and improving the health of all Minnesotans.

MERLA (Minnesota Environmental Response and Liability Act) – the state law that created the state Superfund program.

MPCA (Minnesota Pollution Control Agency) – a state agency dedicated to protecting and improving the environment and human health.

Non-detection – a groundwater, soil, or vapor sample that contains contaminants in lower concentrations than what can be detected by the lab running the sample. Concentrations of contaminants in the sample at this location may not be zero, but concentrations are low enough to be considered negligible.

NPL (National Priorities List) – the list of sites of national priority among the known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout the United States and its territories.

Passive gas system – a landfill treatment process which allows landfill gas to passively vent from the landfill. The gas is burned before it can be released into the atmosphere.

PFAS (Per- and polyfluoroalkyl substances) – a group of widely used synthetic chemicals found in many products, including non-stick cookware, commercial household products, cosmetics, food packaging, firefighting foam, and waterproof clothing, carpeting, and furniture. PFAS never break down in the environment and are harmful to human health.

PLP (Permanent List of Priorities) – Minnesota’s list of state Superfund sites.

RAA (Risk Assessment Advice) – technical guidance concerning exposures and risks to human health (MDH). RAA may be quantitative (e.g., a concentration of a chemical that is likely to pose little or no health risk to humans) or qualitative (e.g., a written description of how toxic a chemical is in comparison to a similar chemical). Generally, RAA contains greater uncertainty than HRLs and HBVs because the available information is more limited. Sometimes MDH derives guidance as RAA because new risk assessment methodology was applied to develop the value.

ROD (Record of Decision) – a public document that explains the remediation plan for the cleanup of a federal Superfund site.

Sparging, air – also known as in-situ air stripping; a cleanup process which removes volatile compounds by injecting air directly into contaminated groundwater.

Superfund – programs at both the state and federal level that focus on investigating and cleaning up waste sites where contamination poses a threat or potential threat to public health and the environment.

SWDA (Safe Water Drinking Act) – the principal federal law in the United States intended to ensure safe drinking water for the public.

Vapor intrusion – when chemical vapors, such as VOCs, migrate from a source of contamination through the soil into the basements or foundations of buildings. These chemical vapors can sometimes pose risks to human health.

VOC (volatile organic compound) – a large group of chemicals that are found in many products we use to build and maintain our homes. They easily vaporize or “off-gas” into the air we breathe. VOCs may pose risks to human health if inhaled at unsafe levels.

Volatile – see also VOC; used to describe a substance that vaporizes easily at normal temperatures.

Water table – the level below which water saturates the subsurface.

Well – any drilled hole used to extract or sample underground water and gas. Wells consist of a borehole with a PVC or metal casing grouted inside. A screen at the bottom of the well allows water or gas to enter the casing. A pump or a fan may be used to push water or gas to the surface, where there may be a well cap or seal.

Well, barrier – an extraction well that is used to remove contaminated groundwater near to the source of the contamination.

Well, buffer – an extraction well that is used to remove contaminated groundwater which has migrated past the barrier wells at a site.

Well, extraction – a well where water or gas is pumped out so it can be treated at the surface.