Glossary
A
Advection/Advective flow
Bulk motion of fluid in the environment defined by direction and velocity
Aerobic
Pertaining to or characterized by the presence of oxygen
Aquifer
A body of permeable rock that can contain or transmit groundwater
Air dispersion modeling
The use of mathematical formulations to characterize pollutant dispersion processes
Anaerobic
Pertaining to or characterized by the absence of oxygen
ANSI/AARST standards
National consensus practices utilized by federal and state agencies
Attenuation factor
A ratio of the indoor air concentration to soil gas or groundwater concentration; sometimes used to estimate the indoor air concentration from soil gas or groundwater concentration
B
Back drafting
The reverse flow of gas in the flues of fuel-fired appliances that results in the intrusion of combustion byproducts into the living space
Biodegradation
The breakdown of chemicals by microorganisms
Building envelope
The physical boundary between the conditioned and unconditioned environment of a building, including the resistance to air and water transmission
Building pressurization
The air pressure within a building relative to the air pressure outside
C
Capillary fringe/Capillary zone
The pore spaces in soil just above the water table that may contain water above the static level from interactive forces between the water and soil
Chemicals of concern
Compounds derived from hazardous substances that are subject to evaluation for purposes of applying risk-based corrective action decision making
Community engagement
The process of communicating with local residents and other stakeholders to provide information throughout the investigation and clean-up of a contaminated site; provide opportunities for offering input about site investigation/cleanup plans; and to facilitate the resolution of community issues related to a contaminated site
Concentration gradient
The change of concentration over a certain distance
Conceptual site model
A three-dimensional visualization of site conditions that allows for evaluation of contaminant sources and affected media, migration pathways, and potential receptors
Confining unit
A layer of rock or soil of very low hydraulic conductivity that hampers the movement of groundwater in and out of an aquifer
Coupon testing
A specimen of an installed material collected for testing or verification
D
Dense nonaqueous phase liquid (DNAPL)
A liquid that is not soluble in and has a higher density than water
Depressurization
To remove the air pressure from
Diffusion
Movement of vapors away from areas of higher concentration
Discharge criteria
Generic term used to describe emission regulatory limits
E
Emission controls
Means employed to limit the discharge of gases
Expansion joints
An assembly designed to hold parts together while safely absorbing expansion and contraction
F
Floor drain
A plumbing fixture that is installed in the floor of a structure, mainly designed to remove any standing water near it
Flow velocity
Vector field that is used to describe fluid motion in a mathematical manner
French drain
A trench filled with gravel or rock or containing a perforated pipe that redirects surface water
Flux
Flow per unit area
H
Heating, ventilation, and air conditioning (HVAC)
The technology of indoor and vehicular environmental comfort, including heating, cooling, and air movement
Human exposure pathway
Refers to the way a person can come into contact with a hazardous substance
I
Inorganic compounds
Substance in which two or more chemical elements (usually other than carbon) are combined
L
Laser screed
A self-leveling head that is mounted on a telescopic boom used to smooth and level concrete
Light nonaqueous phase liquid (LNAPL)
A liquid that is not soluble in and has a lower density than water
Long-term stewardship
Activities implemented for the management of contaminated environmental media that are necessary to protect human health and the environment over time
M
Mitigation strategy
An approach used to reduce the severity of something, such as vapor intrusion
N
Natural draft
The use of natural atmospheric pressure to force gases of combustion out through a ventilation system
O
Operation, maintenance, and monitoring (OM&M) plan
Refers to the routine inspection, servicing, and repairing or replacing of necessary equipment of an operating system
P
Perched aquifer
A water-saturated zone that is above or not directly connected to the regional aquifer; may develop when saturated conditions are present above a low-permeability layer
Phreatic (saturated) zone
The part of an aquifer, below the water table, in which all pores and fractures are essentially saturated with water
Plenum
Continuous void space under the slab that can facilitate air circulation
Petroleum vapor intrusion
The process by which volatile hydrocarbons partition from petroleum-contaminated soils and/or groundwater and migrate through the vadose zone in gaseous form to receptors
Phase partitioning
Separation of fuel into solid, liquid, and gas phases
Post-installation verification
A testing procedure used to show that something is functioning properly after an initial installation or an upgrade
Preferential pathway
A high-permeability conduit for vapor migration, such as a utility penetration, line, or drain; building sump or drainage pit; elevator shaft; fracture in bedrock; or gravel
Pressure field extension
An area beneath a concrete slab or foundation where a sufficient amount of negative pressure (vacuum) has been obtained
R
Redox potential
Chemical reduction-oxidation processes and conditions that can result in the alteration of a chemical compound
Risk communication
Actions, words, and other messages, responsive to the concerns and values of the information recipients, intended to help people make more informed decisions about threats to their health and safety
S
Smoke pen
A hand-held device that creates a puff or a trail of white smoke used to identify leaks or air flow direction
Smoke and tracer gas testing
A nondestructive testing method that detects leaks
Surrogates
Variables with a quantitative relationship to the target compound for a study sufficient to be useful as a substitute for directly measuring the target compounds
T
Telemetry
Process of recording and transmitting the readings of an instrument
Tracer
Substances that migrate similarly to the volatile organic compounds (VOCs) of interest for VI
U
Utilidor/Utility tunnel/Utility corridor
A passage used for routing utility lines, such as electric lines, water supply pipes, sewer pipes, and communications lines
V
Vadose zone
The unsaturated zone of soil in which the pore space is filled with both air and water
Vapor control technologies
Technologies employed to mitigate real or potential impacts from vapor intrusion
Vapor intrusion
The process by which volatile vapors partition from contaminated groundwater or other subsurface sources and migrate upward through vadose zone soils and into overlying buildings
Vent stack
A pipe placed vertically or nearly vertical for ventilation
Volatile organic compounds
A variety of chemicals, some of which may have short- and long-term adverse health effects, that are prone to evaporation at ambient temperatures
