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This glossary defines in non-technical language the terms appearing in the AEG Area of Practice pages. These terms are intended to help the reader understand the practices of Engineering Geology, Environmental Geology and Hydrogeology and may not reflect how regulatory agencies use these terms and phrases. Legal definitions of terminology may be found in county, state and federal regulations and laws. 

Definitions were taken from published lists such as the US EPA and USGS, and specific suggestions made by AEG members. Where definitions were taken directly from the EPA or USGS, these initials are listed after the definitions. Links to other glossaries are provided at the bottom of this page. 

Glossary of Terms


Acid Mine Drainage -- Drainage of water from areas that have been mined for coal or other mineral ores. The water has a low pH because of its contact with sulfur-bearing material and is harmful to aquatic organisms. (USEPA)

Aquifer – A body of sediment or rock capable of storing and transmitting appreciable quantities of water. Aquifers are sources of water for wells and springs.

Brownfields -- Abandoned, idled, or under used industrial and commercial facilities/sites where expansion or redevelopment is complicated by real or perceived environmental contamination. They can be in urban, suburban, or rural areas. EPA's Brownfields initiative helps communities mitigate potential health risks and restore the economic viability of such areas or properties. (USEPA)

Cleanup – Actions taken to deal with a release or threat of release of a hazardous substance that could affect humans and/or the environment. The term "cleanup" is sometimes used interchangeably with the terms remedial action, removal action, response action, or corrective action.

Contaminant -- Any physical, chemical, biological, or radiological substance or matter that has an adverse effect on air, water, or soil. (USEPA)

Contamination- Introduction into water, air, and soil of microorganisms, chemicals, toxic substances, wastes, or wastewater in a concentration that makes the medium unfit for its next intended use. (USEPA)

Debris Flow- Rapid downslope movement of loose rock, soil and surface debris caused by heavy rain or rapidly melting snow.

Detention Basin- An excavated depression intended to halt the downslope movement of debris by letting it accumulate in the depression. The debris is subsequently removed for disposal elsewhere.

Earthquake –A sudden ground motion or vibration of the Earth, produced by a rapid release of stored-up energy along an active fault.

Fault -- fracture in the Earth along which one side has moved relative to the other. Sudden movements on faults cause earthquakes. (USGS)

Groundwater – water found beneath the surface of the Earth.

Hazard -- A condition that endangers the health and safety of the public or threatens the destruction of property. A Geologic Hazard is such a condition that occurs naturally.

Hydrogeologist – A person trained in the study of hydrogeology.

Hydrogeology – the science of the occurrence, movement, abundance, distribution, and quality of water in the Earth’s soils and rocks and related surface waters as well as interactions between water and geological materials.

Landfill -- Sanitary landfills are disposal sites for non-hazardous solid wastes spread in layers, compacted to the smallest practical volume, and covered by material applied at the end of each operating day.. Secure chemical landfills are disposal sites for hazardous waste, selected and designed to minimize the chance of release of hazardous substances into the environment. (USEPA)

Landslide -- Downslope movement of rock, soil, and mud. (USGS)

Love Canal --Love Canal is a 16-acre landfill in the southeast corner of the City of Niagara Falls, New York, about 0.3 mile north of the Niagara River. In the 1890s, a canal was excavated to provide hydroelectric power. Instead, it was later used by Hooker Electrochemical for disposal of over 21,000 tons of various chemical wastes. Dumping ceased in 1952, and in 1953 the disposal area was covered and deeded to the Niagara Falls Board of Education. Extensive development occurred near the site, including construction of an elementary school and numerous homes. Problems with odors and residues, first reported at the site during the 1960s, increased in the 1970s as the water table rose, bringing contaminated ground water to the surface. Studies indicate that numerous toxic chemicals have migrated into surrounding areas. Run-off drains into the Niagara River at a point 2.8 miles upstream of the intake tunnels for Niagara Falls' water treatment plant, which serves about 77,000 people. At this discharge point, the river sediment has also become contaminated. After years of remediation activities, Love Canal was “de-listed” as a Superfund site in 2004. (USEPA)

Migration – The movement of chemicals or elements in soil or groundwater, usually influenced by gravity and the porosity and permeability of soil and rock.

Mine Shafts- Vertical or steeply inclined excavations used to access underground mines.

Minerals - Inorganic elements and compounds which can be dissolved in and transported by ground water.

Polluted – used to describe an area or material which has been contaminated with pollution. See also contamination.

Pollution – Substances which threaten the health and safety of humans or the environment. See also contaminant.

Permeability -- The rate at which liquids pass through soil or other materials in a specified direction. (USEPA)

Pores – small openings between grains in rocks.

Porosity – A property of rocks describing the volume of pore space relative to the total rock volume. Degree to which soil, gravel, sediment, or rock is permeated with pores or cavities through which water or air can move.

Pump – A device used to lift water from the bottom of a well to the surface.

Remediation -- Action undertaken to clean up or restore a contaminated site.

Risk -- A measure of the probability that damage to life, health, property, and/or the environment will occur as a result of a given hazard. The USGS Hawaiian Volcano Observatory provides this discussion: “People commonly think in terms of hazard reduction when they actually mean risk reduction. Hazards are the natural events that can occur in a given area and the likelihood that they will occur in a given time period. Risk is a measure of the financial and human costs associated with the occurrence of such events. There is nothing that we, as a society, can presently do to reduce hazards, but we can reduce risk through proper risk management. There are many ways in which we can reduce risk from natural disasters. The single most important, and the one least used, is land-use planning. After identifying high-hazard areas, we can dramatically reduce risk by not building or living in these areas or, more reasonably, by limiting the density and type of development that can occur in these high-hazard areas. Land-use planning is particularly effective for floods and tsunami, which affect only limited areas along rivers and coastlines.” (USGS, 1995)

Rockfall -- Falling, bouncing, and rolling of rocks and rock debris down slope.

Seepage -- Migration of ground water towards an interface located at the ground surface or percolation of water through the soil from unlined canals, ditches, laterals, watercourses, or water storage facilities.

Superfund -- The program operated under the legislative authority of federal laws (CERCLA and SARA) that funds and carries out Environmental Protection Agency (EPA) solid waste emergency and long-term removal and remedial activities. These activities include establishing the National Priorities List, investigating sites for inclusion on the list, determining their priority, and conducting and/or supervising cleanup and other remedial actions.

Subsidence -- Vertical lowering of the ground surface due to the withdrawal of subsurface fluids such as ground water or oil & gas. 

Well – A hole drilled in the ground designed to intersect an aquifer and to deliver water to the surface. Wetland -- An area that is saturated by surface or ground water with vegetation adapted for life under those soil conditions, such as swamps, bogs, fens, marshes, and estuaries. (USEPA) 

Other Glossary Resources: 

This US EPA website provides terms of environment: glossary, abbreviations, and acronyms. 

This USGS website provides simple definitions of geology and engineering geology terms. 

This Groundwater Foundation website provides definitions of commonly used groundwater and water supply terms. 

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