![[logo] US EPA](http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Terms and Definitions
This page defines in non-technical language several of the terms and acronyms on the Charnock MTBE (Methyl tert Butyl Ether) Project Web Page. It also contains links to additional sites which contain more information on specific topics.
Air
Stripping 
:
A treatment system that removes toxic volatile organic compounds (VOCs)
from contaminated water by forcing an airstream through the water and
causing the compounds to evaporate from the water. Learn more about this
technology by reading The U.S. Army Corps of Engineers Web page on air
stripping .
Carbon
Adsorption :
A treatment system that removes contaminants from water by passing it
through tanks containing activated carbon treated to attract the contaminants.
Capture Zone: The area within an aquifer that drains to and is captured by a pumping well. For example, the 10 year capture zone of a well is the area within which groundwater will reach the well within approximately 10 years. Capture zones for a well can change over time due a number of factors including changes in pumping rates and rainfall patterns.
Depth-Discrete Water Samples: These are samples of groundwater collected from specific limited intervals (~1 foot or less) of an aquifer. Collection of depth-discrete samples allows investigators to observe the vertical profile of contamination and determine if contamination is limited to discrete thin zones and help to locate monitoring wells appropriately to monitor contamination.
Numerical Ground Water Model: A simplified mathematical simulation of a groundwater system that utilizes the computer to predict the rate and direction of groundwater flow. The model can be used as a tool to help make decisions about how to manage a groundwater system. Since models are simplified versions of reality they often contain some degree of uncertainty in their representation and predictions. Models can be useful illustrative and comparative tools for future courses of action.
Parts per billion (ppb) or parts per million (ppm): Units commonly used to express contamination ratios of the amount of a contaminant in water, land, or air. In water, 1 microgram (1 millionth of a gram) of a substance per liter of water is equal to one part per billion, while 1 milligram (1 thousandth of a gram) of a substance per liter of water is equal to one part per million. 1 liter of fresh water weighs approximately 1000 grams.
Potentially Responsible Party (PRP): Any individual or company potentially responsible for or contributing to a spill or other contamination at a site. Whenever possible, through administrative and legal actions, EPA requires PRPs to clean up sites they have contaminated.
Soil Vapor Extraction (SVE): One of the most frequently selected treatment technologies at leaking underground storage tank sites. It is a relatively simple process that physically separates contaminants from soil. As the name suggests, SVE extracts contaminants from the soil in vapor form. Therefore, SVE systems are designed to remove contaminants that have a tendency to volatilize or evaporate easily. SVE removes volatile organic compounds (VOCs) and some semi-volatile organic compounds (SVOCs) from soil beneath the ground surface in the unsaturated zone-that part of the subsurface located above the water table. By applying a vacuum through a system of underground wells, contaminants are pulled to the surface as vapor or gas.
Source Water Assessment Report (SWA): A report required by DHS for certain drinking water sources that determines the extent to which the water source is vulnerable to contaminating activities in the area.
Ultraviolet Oxidation: A water treatment technology which involves generation of powerful chemicals known as oxidants by exposing of substances such as hydrogen peroxide to ultraviolet light generated by mercury vapor lamps. Under the right conditions, these oxidants then react with contaminants such as MTBE to break them down into chemicals that can be broken down further to less toxic chemicals or removed more easily through other treatment processes.