The following are definitions for some of the words used on this Web site or in other project related documents.

A - C - D - E - F - G - H - I - M - P - R - S - T - U - V - W

-A-

Ambient air: Refers to the surrounding air. Generally, ambient air refers to air outside and surrounding an air pollution source location. Often used interchangeably with "outdoor air."

Aquifer: A water-bearing layer of rock or sediment that is capable of yielding useable amounts of water. Drinking water and irrigation wells draw water from underlying aquifers.

-C-

Cleanup process: A comprehensive program for the cleanup (remediation) of a contaminated site. It involves investigation, analysis, and development of a cleanup plan and implementation of that plan under Washington State Department of Ecology oversight.

Containment: Enclosing or containing hazardous substances in a structure to prevent the migration of contaminants into the environment.

-D-

DOH: Washington State Department of Health

Downgradient: The direction in which groundwater or air flows.

-E-

EPA (U.S. EPA): United States Environmental Protection Agency

Ecology: Washington State Department of Ecology

Exposure pathways: Existing or possible ways by which humans, animals, or plants can come into contact with chemicals in soil, water, or other media.

-F-

Feasibility study: An evaluation of the alternatives for cleaning up soil or groundwater contamination and selection of a preferred alternative.

-G-

Groundwater: Water beneath the earth's surface that flows through soil and rock openings in an aquifer.

-H-

Hazardous substance: Chemicals that can pose a substantial or potential risk to human health and/or the environment when improperly managed.

Hydrogeology: The study of the occurrence, movement, and quality of water found beneath the earth’s surface.

-I-

Interim measures: Cleanup actions taken to protect public health and the environment while long-term solutions are being developed.

-M-

MTCA: Model Toxics Control Act: Implemented by the Department of Ecology, MTCA began as a grass-roots citizen initiative in 1988, and started the process of cleaning up contaminated sites in Washington State. Under MTCA, a current or past owner or operator may be held responsible for the cleanup of contamination to standards that are safe for both human health and the environment. Ecology was mandated with implementing MTCA and overseeing cleanups through the state, and has issued regulations and guidance governing those cleanups. Ecology investigates any report of property contamination, and if it presents a significant threat to human health or the environment, the site is placed on the Hazardous Sites List, and the cleanup process begins.

Micrograms per liter (ug/L): A measuring unit for substances in water. Substances in water are often measured in very small units. One microgram per liter equals one part per billion.

Milligrams per liter (mg/L): A measuring unit for substances in water. Substances in water are often measured in very small units. One milligram per liter equals one part per million.

Micrograms per cubic meter (ug/m3): A measurement unit for substances in air. Substances in air are often measured in very small units.

Migration: The movement of chemical contaminants through soils, groundwater, or air.

Mitigation: Actions taken to improve site conditions by eliminating, limiting, reducing, or controlling hazards and contamination sources.

Monitoring wells: Specially constructed wells are used exclusively for obtaining samples for testing water and/or soil gas quality, and for monitoring water levels. Monitoring wells are not used for drinking water or for industrial uses.

-P-

Parts per million (ppm): A measuring unit for the concentration of one material in another. When looking at contamination of water and soil, the substances are often measured in parts per million. One part per million is equal to one gram of substance in one million grams of material.

Parts per billion (ppb): A measuring unit for the concentration of one material in another. When looking at contamination of water and soil, the substances are often measured in parts per billion. One part per billion is equal to one gram of substance in one billion grams of material.

Plume: An area of contaminated groundwater or air, such as a cloud of smoke or vapor.

Public participation plan: A document approved by Ecology or U.S. EPA that is designed to determine a community's informational needs and to provide a program for public involvement during facility permitting, site investigation and cleanup, or other similar activities.

-R-

Remedial Investigation/Feasibility Study (RI/FS): A series of investigations and studies to identify the types and extent of contaminants of potential concern at the site, determine possible health risks, determine cleanup criteria (Remedial Investigation), and to provide an evaluation of the alternatives for remediating any identified soil or groundwater problems (Feasibility Study).

Remediation: Cleanup of a site to levels determined to be health-protective for its intended use.

Risk assessment: A risk assessment looks at the contaminants detected at a site, the frequency and concentration of the contaminants, the toxicity of the contaminants, and evaluates if it is possible that human and/or the ecological health may be affected by exposure to the contaminants. Routes of exposure for humans are generally through ingestion (such as eating), dermal (contact with the skin), or inhalation. The risk assessment does not predict health effects; it only describes the increased possibility of adverse health effects, based on the best scientific information available.

-S-

Soil gas: Soil gas (or soil vapor) is air existing in spaces in the soil between the groundwater table and the ground surface.

Solvent: A liquid capable of dissolving another substance to form a solution. Water is sometimes called “the universal solvent” because it dissolves so many things, although often to only a very small extent. Organic solvents are used in paints, varnishes, lacquers, industrial cleaners, and printing inks, for example. The use of such solvents in coatings and cleaners has declined over the last several years.

-T-

Trichloroethylene (TCE): A volatile organic compound that is often used as an industrial degreasing solvent.

-U-

Upgradient: The direction from which water flows in an aquifer, or where outdoor air blows from.

-V-

Vadose Zone: The zone in soil between the ground surface and the water table where the soil pores are only partially filled with water.

Volatile: Describes a substance that readily evaporates into vapor at normal temperatures and pressures.

Volatile organic compounds (VOCs): Organic liquids, including many common solvents, that readily evaporate.

-W-

Water table: In a shallow aquifer, a water table is the depth at which groundwater is first encountered in the subsurface.

Work plan: The site work plan describes the technical activities to be conducted during the various phases of a project.