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Glossary: U V W
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 Factor:
One of several factors used in calculating the reference dose from experimental
data. UFs are intended to account for (1) the variation in sensitivity among
humans; (2) the uncertainty in extrapolating animal data to humans; (3) the
uncertainty in extrapolating data obtained in a study that covers less than the
full life of the exposed animal or human; and (4) the uncertainty in using LOAEL
data rather than NOAEL data.
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 Injection Control (UIC):
The program under the Safe Drinking Water Act that regulates the use of wells to
pump fluids into the ground.
Underground Injection Wells:
Steel- and concrete-encased shafts into which hazardous waste is deposited by
force and under pressure.
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.
Unreasonable Risk:
Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA),
"unreasonable adverse effects" means any unreasonable risk to man or the
environment, taking into account the medical, economic, social, and
environmental costs and benefits of any pesticide.
Unsaturated Zone:
The area above the water table where soil pores are not fully saturated,
although some water may be present.
Upper Detection Limit:
The largest concentration that an instrument can reliably detect.
Uranium Mill Tailings Piles:
Former uranium ore processing sites that contain leftover radioactive materials
(wastes), including radium and unrecovered uranium.
Uranium Mill-Tailings Waste Piles:
Licensed active mills with tailings piles and evaporation ponds created by acid
or alkaline leaching processes.
Urban Runoff:
Storm water from city streets and adjacent domestic or commercial properties
that carries pollutants of various kinds into the sewer systems and receiving
waters.
Urea-Formaldehyde Foam Insulation:
A material once used to conserve energy by sealing crawl spaces, attics, etc.;
no longer used because emissions were found to be a health hazard.
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).
User Fee:
Fee collected from only those persons who use a particular service, as compared
to one collected from the public in general.
Utility Load:
The total electricity demand for a utility district.
Glossary: V
Vadose Zone:
The zone between land surface and the water table within which the moisture
content is less than saturation (except in the capillary fringe) and pressure is
less than atmospheric. Soil pore space also typically contains air or other
gases. The capillary fringe is included in the vadose zone. (See: Unsaturated
Zone.)
Valued Environmental Attributes/Components:
Those aspects(components/processes/functions) of ecosystems, human health, and
environmental welfare considered to be important and potentially at risk from
human activity or natural hazards. Similar to the term "valued environmental
components" used in environmental impact assessment.
Vapor:
The gas given off by substances that are solids or liquids at ordinary
atmospheric pressure and temperatures.
Vapor Capture System:
Any combination of hoods and ventilation system that captures or contains
organic vapors so they may be directed to an abatement or recovery device.
Vapor Dispersion:
The movement of vapor clouds in air due to wind, thermal action, gravity
spreading, and mixing.
Vapor Plumes:
Flue gases visible because they contain water droplets.
Vapor Pressure:
A measure of a substance's propensity to evaporate, vapor pressure is the force
per unit area exerted by vapor in an equilibrium state with surroundings at a
given pressure. It increases exponentially with an increase in temperature. A
relative measure of chemical volatility, vapor pressure is used to calculate
water partition coefficients and volatilization rate constants.
Vapor Recovery System:
A system by which the volatile gases from gasoline are captured instead of being
released into the atmosphere.
Variance:
Government permission for a delay or exception in the application of a given
law, ordinance, or regulation.
Vector:
1. An organism, often an insect or rodent that carries disease. 2. Plasmids,
viruses, or bacteria used to transport genes into a host cell. A gene is placed
in the vector; the vector then "infects" the bacterium.
Vegetative Controls:
Non-point source pollution control practices that involve vegetative cover to
reduce erosion and minimize loss of pollutants.
Vehicle Miles Travelled (VMT):
A measure of the extent of motor vehicle operation; the total number of vehicle
miles travelled within a specific geographic area over a given period of time.
Ventilation Rate:
The rate at which indoor air enters and leaves a building. Expressed as the
number of changes of outdoor air per unit of time (air changes per hour (ACH),
or the rate at which a volume of outdoor air enters in cubic feet per minute (CFM).
Ventilation/Suction:
The act of admitting fresh air into a space in order to replace stale or
contaminated air; achieved by blowing air into the space. Similarly, suction
represents the admission of fresh air into an interior space by lowering the
pressure outside of the space, thereby drawing the contaminated air outward.
Venturi Scrubbers:
Air pollution control devices that use water to remove particulate matter from
emissions.
Vinyl Chloride:
A chemical compound, used in producing some plastics, that is believed to be
oncogenic.
Virgin Materials:
Resources extracted from nature in their raw form, such as timber or metal ore.
Viscosity:
The molecular friction within a fluid that produces flow resistance.
Volatile:
Any substance that evaporates readily.
Volatile Liquids:
Liquids which easily vaporize or evaporate at room temperature.
Volatile Organic Compound (VOC):
Any organic compound that participates in atmospheric photochemical reactions
except those designated by USEPA as having negligible photochemical reactivity.
Volatile Solids:
Those solids in water or other liquids that are lost on ignition of the dry
solids at 550° centigrade.
Volatile Synthetic Organic Chemicals:
Chemicals that tend to volatilize or evaporate.
Volume Reduction:
Processing waste materials to decrease the amount of space they occupy, usually
by compacting, shredding, incineration, or composting.
Volumetric Tank Test:
One of several tests to determine the physical integrity of a storage tank; the
volume of fluid in the tank is measured directly or calculated from
product-level changes. A marked drop in volume indicates a leak.
Vulnerability Analysis:
Assessment of elements in the community that are susceptible to damage if
hazardous materials are released.
Vulnerable Zone:
An area over which the airborne concentration of a chemical accidentally
released could reach the level of concern.
Glossary: W
Waste:
1. Unwanted materials left over from a manufacturing process. 2. Refuse from
places of human or animal habitation.
Waste Characterization:
Identification of chemical and microbiological constituents of a waste material.
Waste Exchange:
Arrangement in which companies exchange their wastes for the benefit of both
parties.
Waste Generation:
The weight or volume of materials and products that enter the waste stream
before recycling, composting, landfilling, or combustion takes place. Also can
represent the amount of waste generated by a given source or category of
sources.
Waste Load Allocation:
1. The maximum load of pollutants each discharger of waste is allowed to release
into a particular waterway. Discharge limits are usually required for each
specific water quality criterion being, or expected to be, violated. 2. The
portion of a stream's total assimilative capacity assigned to an individual
discharge.
Waste Minimization:
Measures or techniques that reduce the amount of wastes generated during
industrial production processes; term is also applied to recycling and other
efforts to reduce the amount of waste going into the waste stream.
Waste Piles:
Non-containerized, lined or unlined accumulations of solid, nonflowing waste.
Waste Reduction:
Using source reduction, recycling, or composting to prevent or reduce waste
generation.
Waste Stream:
The total flow of solid waste from homes, businesses, institutions, and
manufacturing plants that is recycled, burned, or disposed of in landfills, or
segments thereof such as the "residential waste stream" or the "recyclable waste
stream."
Waste Treatment Lagoon:
Impoundment made by excavation or earth fill for biological treatment of
wastewater.
Waste Treatment Plant:
A facility containing a series of tanks, screens, filters and other processes by
which pollutants are removed from water.
Waste Treatment Stream:
The continuous movement of waste from generator to treater and disposer.
Waste-Heat Recovery:
Recovering heat discharged as a byproduct of one process to provide heat needed
by a second process.
Waste-to-Energy Facility/Municipal-Waste Combustor:
Facility where recovered municipal solid waste is converted into a usable form
of energy, usually via combustion.
Wastewater:
The spent or used water from a home, community, farm, or industry that contains
dissolved or suspended matter. Water Pollution: The presence in water of enough
harmful or objectionable material to damage the water's quality.
Wastewater Infrastructure:
The plan or network for the collection, treatment, and disposal of sewage in a
community. The level of treatment will depend on the size of the community, the
type of discharge, and/or the designated use of the receiving water.
Wastewater Operations and Maintenance:
Actions taken after construction to ensure that facilities constructed to treat
wastewater will be operated, maintained, and managed to reach prescribed
effluent levels in an optimum manner.
Wastewater Treatment Plan:
A facility containing a series of tanks, screens, filters, and other processes
by which pollutants are removed from water. Most treatments include chlorination
to attain safe drinking water standards.
Water Purveyor:
A public utility, mutual water company, county water district, or municipality
that delivers drinking water to customers.
Water Quality Criteria:
Levels of water quality expected to render a body of water suitable for its
designated use. Criteria are based on specific levels of pollutants that would
make the water harmful if used for drinking, swimming, farming, fish production,
or industrial processes.
Water Quality Standards:
State-adopted and USEPA-approved ambient standards for water bodies. The
standards prescribe the use of the water body and establish the water quality
criteria that must be met to protect designated uses.
Water Quality-Based Limitations:
Effluent limitations applied to dischargers when mere technology-based
limitations would cause violations of water quality standards. Usually applied
to discharges into small streams.
Water Quality-Based Permit:
A permit with an effluent limit more stringent than one based on technology
performance. Such limits may be necessary to protect the designated use of
receiving waters (e.g. recreation, irrigation, industry or water supply).
Water Solubility:
The maximum possible concentration of a chemical compound dissolved in water. If
a substance is water soluble it can very readily disperse through the
environment.
Water Storage Pond:
An impound for liquid wastes designed to accomplish some degree of biochemical
treatment.
Water Supplier:
One who owns or operates a public water system.
Water Supply System:
The collection, treatment, storage, and distribution of potable water from
source to consumer.
Water Table:
The level of groundwater.
Water Treatment Lagoon:
An impound for liquid wastes designed to accomplish some degree of biochemical
treatment.
Water Well:
An excavation where the intended use is for location, acquisition, development,
or artificial recharge of groundwater.
Water-Soluble Packaging:
Packaging that dissolves in water; used to reduce exposure risks to pesticide
mixers and loaders.
Water-Source Heat Pump:
Heat pump that uses wells or heat exchangers to transfer heat from water to the
inside of a building. Most such units use groundwater.
Waterborne Disease Outbreak:
The significant occurrence of acute illness associated with drinking water from
a public water system that is deficient in treatment, as determined by
appropriate local or state agencies.
Watershed:
The land area that drains into a stream; the watershed for a major river may
encompass a number of smaller watersheds that ultimately combine at a common
point.
Watershed Approach:
A coordinated framework for environmental management that focuses public and
private efforts on the highest priority problems within hydrologically-defined
geographic areas taking into consideration both ground and surface water flow.
Watershed Area:
A topographic area within a line drawn connecting the highest point’s uphill of
a drinking water intake into which overland flow drains.
Weight of Scientific Evidence:
Considerations in assessing the interpretation of published information about
toxicity--quality of testing methods, size and power of study design,
consistency of results across studies, and biological plausibility of
exposure-response relationships and statistical associations.
Weir:
1. A wall or plate placed in an open channel to measure the flow of water. 2. A
wall or obstruction used to control flow from settling tanks and clarifiers to
ensure a uniform flow rate and avoid short-circuiting. (See: short-circuiting.)
Well:
A bored, drilled, or driven shaft, or a dug hole whose depth is greater than the
largest surface dimension and whose purpose is to reach underground water
supplies or oil, or to store or bury fluids below ground.
Well Field:
Area containing one or more wells that produce usable amounts of water or oil.
Well Injection:
The subsurface emplacement of fluids into a well.
Well Monitoring:
Measurement by on-site instruments or laboratory methods of well water quality.
Well Plug:
A watertight, gastight seal installed in a bore hole or well to prevent movement
of fluids.
Well Point:
A hollow vertical tube, rod, or pipe terminating in a perforated pointed shoe
and fitted with a fine-mesh screen.
Wellhead Protection Area:
A protected surface and subsurface zone surrounding a well or well field
supplying a public water system to keep contaminants from reaching the well
water.
Wetlands:
An area that is saturated by surface or groundwater with vegetation adapted for
life under those soil conditions, as swamps, bogs, fens, marshes, and estuaries.
Wettability:
The relative degree to which a fluid will spread into or coat a solid surface in
the presence of other immiscible fluids.
Wettable Powder:
Dry formulation that must be mixed with water or other liquid before it is
applied.
Wheeling:
The transmission of electricity owned by one entity through the facilities owned
by another (usually a utility).
Whole-Effluent-Toxicity Tests:
Tests to determine the toxicity levels of the total effluent from a single
source as opposed to a series of tests for individual contaminants.
Wildlife Refuge:
An area designated for the protection of wild animals, within which hunting and
fishing are either prohibited or strictly controlled.
Wire-to-Wire Efficiency:
The efficiency of a pump and motor together.
Wood Packaging:
Wood products such as pallets, crates, and barrels.
Wood Treatment Facility:
An industrial facility that treats lumber and other wood products for outdoor
use. The process employs chromated copper arsenate, which is regulated as a
hazardous material.
Wood-Burning-Stove Pollution:
Air pollution caused by emissions of particulate matter, carbon monoxide, total
suspended particulates, and polycyclic organic matter from wood-burning stoves.
Working Level (WL):
A unit of measure for documenting exposure to radon decay products, the
so-called "daughters." One working level is equal to approximately 200
picocuries per liter.
Working Level Month (WLM):
A unit of measure used to determine cumulative exposure to radon.
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