Social Media Icons DEQ Facebook DEQ Twitter DEQ Instagram DEQ LinkedIn


A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

- U -

Ultra Clean Coal (UCC): Coal that is washed, ground into fine particles, then chemically treated to remove sulfur, ash, silicone, and other substances; usually briquetted and coated with a sealant made from coal.

Ultraviolet Rays: Radiation from the sun that can be useful or potentially harmful. UV rays from one part of the spectrum (UV-A) enhance plant life. UV rays from other parts of the spectrum (UV-B) can cause skin cancer or other tissue damage. The ozone layer in the atmosphere partly shields us from ultraviolet rays reaching the earth's surface.

Uncertainty Analysis: An e valuation of how: 1) definition of the physical setting; 2) model applicability and assumptions; 3) transport, fate and exposure parameter values; and 4) magnification of potential error through the steps of the risk assessment contribute to uncertainty in the results.

Unconfined Aquifer: An aquifer containing water that is not under pressure; the water level in a well is the same as the water table outside the well.

Underground Sources of Drinking Water: Aquifers currently being used as a source of drinking water or those capable of supplying a public water system. They have a total dissolved solids content of 10,000 milligrams per liter or less, and are not "exempted aquifers." (See: exempted aquifer.)

Underground Storage Tank (UST): A tank located at least partially underground and designed to hold gasoline or other petroleum products or chemicals.

Unrestricted Use: The designation of acceptable future use for a site at which the remediation levels, based on either background or standard residential exposure factors, have been attained throughout the site in all media.

Unsaturated Zone: The area above the water table where soil pores are not fully saturated, although some water may be present.

Untreated regulated medical waste: Waste that has not been treated to substantially reduce or eliminate its potential for causing disease. (See: treated medical waste, destroyed medical waste, and regulated medical waste)

Upper Detection Limit: The largest concentration that an instrument can reliably detect.

Use Cluster: A set of competing chemicals, processes, and/or technologies that can substitute for one another in performing a particular function.

Used Oil: Spent motor oil from passenger cars and trucks collected at specified locations for recycling (not included in the category of municipal solid waste).

Utility Load: The total electricity demand for a utility district.

footer divider
footer divider
footer divider
Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000

Some resources on this website require Adobe Reader and Flash Player, Microsoft Word, PowerPoint or Excel. If you wish to receive this content in an accessible format pursuant to Section 508 of the federal Rehabilitation Act of 1973, as amended (29 U.S.C. ยง 794 (d)), please call 800-592-5482. In addition, this website includes hyperlinks to websites neither controlled nor sponsored by DEQ or the Commonwealth of Virginia. Links may open in a new window. If you wish to receive content from a website which is neither controlled nor sponsored by DEQ or the Commonwealth, please contact the host of that website directly.

Privacy Statement | Terms Of Use | WAI Compliance | Contact Us