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
UAC
User Advisory Committee.
UAM
Urban Airshed Model.
UAPSP
Utility Acid Precipitation Study Program.
UAQI
Uniform Air Quality Index.
UARG
Utility Air Regulatory Group.
ubiquitous background levels
concentrations of chemicals that are present in the environment due to anthropogenic sources (e.g., industry, automobiles).
UCC
Ultra Clean Coal.
UDMH
Unsymmetrical Dimethyl Hydrazine.
UEL
See Upper Explosive Limit, Upper Flammable Limit.
UFL
See Upper Explosive Limit, Upper Flammable Limit.
ULF
Upper Flammability Limit.
ultra clean coal (UCC)
coal that has been washed, ground into fine particles, then chemically treated to remove sulfur, ash, silicone, and other substances; usually briquette 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 enhance plant life and are useful in some medical and dental procedures; UV rays from other parts of the spectrum to which humans are exposed (e.g., while getting a sun tan) can cause skin cancer or other tissue damage. The ozone layer in the atmosphere provides a protective shield that limits the amount of ultraviolet rays that reach the Earth's surface.
UMTRCA
Uranium Mill Tailings Radiation Control Act.
UNAMAP
Users' Network for Applied Modeling of Air Pollution.
underbedding
see Support Media.
underground area
means an underground room, such as a basement, cellar, shaft or vault, providing enough space for physical inspection of the exterior of the tank situated on or above the surface of the floor.
underground release
means any belowground release.
underground storage tank (or "UST")
means any one or combination of tanks (including underground pipes connected thereto) that is used to contain an accumulation of regulated substances, and the volume of which (including the volume of underground pipes connected thereto) is 10 percent or more beneath the surface of the ground. This term does not include any: (a) Farm or residential tank of 1,100 gallons or less capacity used for storing motor fuel for noncommercial purposes; (b) Tank used for storing heating oil for consumptive use on the premises where stored; (c) Septic tank; (d) Pipeline facility (including gathering lines) regulated under:(1) The Natural Gas Pipeline Safety Act of 1968 (49 U.S.C. App. 1671, et seq.), or(2) The Hazardous Liquid Pipeline Safety Act of 1979 (49 U.S.C. App. 2001, et seq.), or(3) Which is an intrastate pipeline facility regulated under state laws comparable to the provisions of the law referred to in paragraph (d)(1) or (d)(2) of this definition; (e) Surface impoundment, pit, pond, or lagoon; (f) Storm-water or wastewater collection system; (g) Flow-through process tank; (h) Liquid trap or associated gathering lines directly related to oil or gas production and gathering operations; or (i) Storage tank situated in an underground area (such as a basement, cellar, mineworking, drift, shaft, or tunnel) if the storage tank is situated upon or above the surface of the floor. term "underground storage tank (or "UST") does not include any pipes connected to any tank which is described in paragraphs (a) through (i) of this definition.
underground sources of drinking water
as defined in the UIC program, this term refers to aquifers that are currently being used as a source of drinking water, and those that are 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).
unit operation
a single, discrete process as part of an overall sequence, e.g., precipitation, settling or filtration.
UN Number
See DOT Identification Numbers; PIN.
United States
when used in relation to section 311(a)(5) of the CWA, means the states, the District of Columbia, the Commonwealth of Puerto Rico, the Northern Mariana Islands, Guam, American Samoa, the United States Virgin Islands, and the Pacific Island Governments. United States, when used in relation to section 101(27) of CERCLA, includes the several states of the United States, the District of Columbia, the Commonwealth of Puerto Rico, Guam, American Samoa, the United States Virgin Islands, the Commonwealth of the Northern Marianas, and any other territory or possession over which the United States has jurisdiction.
unsaturated zone
the area above the water table where the soil pores are not fully saturated, although some water may be present.
unstable
tending toward decomposition or other unwanted chemical change during normal handling or storage. An unstable chemical in its pure state, or as commonly produced or transported, polymerizes vigorously, decomposes, condenses, or becomes self-reactive under conditions of shock, pressure, or temperature. See Stability. See Stability, Reactive.
upgrade
means the addition or retrofit of some systems such as cathodic protection, lining, or spill and overfill controls to improve the ability of an underground storage tank system to prevent the release of product.
Upper Explosive Limit, Upper Flammable Limit
UEL, UFL. The highest concentration of a material in air that produces an explosion in fire or ignites when it contacts an ignition source (high heat, electric arc, spark, or flame). A higher concentration of the material in a smaller percentage of concentration of air may be too rich to be ignited. See Flammable Limits.
uranium
a radioactive heavy metal element used in nuclear reactors and the production of nuclear weapons. Term refers usually to U 238, the most abundant radium isotope, although a small percentage of naturally occurring uranium is U 235.
urban runoff
storm water from city streets, usually carrying litter and organic wastes.
urticaria
nettle rash; hives; elevated, itching, white patches.
USA
United States Army.
USAF
United States Air Force.
USAO
United States Attorney's Office.
USATHAMA
United States Army Toxic and Hazardous Materials Agency.
USBM
United States Bureau of Mines.
USBS
United States Bureau of Standards.
USC
United States Code.
USCA
United States Code Annotated.
USCG
United States Coast Guard.
USCS
United Soil Classification System.
USDA
United States Department of Agriculture.
USDOI
United States Department of the Interior.
USDW
Underground Sources of Drinking Water.
USEPA
United States Environmental Protection Agency.
USFS
United States Forest Service.
USGS
United States Geological Survey, Department of the Interior.
USMC
United States Marine Corps.
USN
United States Navy.
USNRC
United States Nuclear Regulatory Commission.
USPHS
United States Public Health Service.
USPS
United States Postal Service.
UST
underground storage tank; regulated by RCRA; tank with 10 or more percent of its volume underground with connected piping; used to store petroleum products or CERCLA regulated hazardous chemicals.
UST system or "Tank system"
means an underground storage tank, connected underground piping, underground ancillary equipment, and containment system, if any.
UV
ultraviolet (light)
USWAG
Utility Solid Waste Activities Group.
UTM
Universal Transverse Mercator.
UV
Ultraviolet.
UZM
Unsaturated Zone Monitoring.
