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- 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 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: Visible flue gases 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.

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.

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.

Virginia Clean Water Revolving Loan Fund (VCWRLF): This is the Commonwealth of Virginia's State Revolving Loan Fund that was established by the Virginia General Assembly to provide a long term, renewing source of funding for wastewater treatment improvements. The fund is separate, permanent, and perpetual, and was originally dedicated solely to wastewater treatment improvements at publicly owned facilities. In recent years the General Assembly expanded the scope of the fund to allow loans for Brownfield remediation, Land Conservation and Agricultural BMP projects. Several variations of the fund's name are commonly encountered but the preferred version is Virginia Clean Water Revolving Loan Fund. Perhaps the most descriptive variation, it links the state's revolving fund to its origin, the Federal Water Quality Act (also known as the Clean Water Act). Other variations of the funds name you may encounter are: Virginia Revolving Loan Fund, Virginia Water Facilities Revolving Loan Fund, Virginia Revolving Fund and even the generic term State Revolving Fund is used, primarily by federal government agencies.

Virginia Pollutant Discharge Elimination System Permit: The permit that came out of Section 402 of the Clean Water Act which established the National Pollutant Discharge Elimination System to limit pollutant discharges into streams, rivers, and bays. It regulates the management of pollutants carried by storm water runoff.

Virginia Pollution Abatement Permit: The permit issued by DEQ whenever an owner handles waste and wastewater in a manner that does not involve discharging to a sewage treatment work, or to state waters pursuant to a valid Virginia Pollutant Discharge Elimination System permit. The treatment, storage, and land application of industrial waste (sludge and wastewater), sewage sludge, municipal wastewater, and animal waste is a regulated activity in the Commonwealth of Virginia.

Virginia Water Protection Permit: The VWPP Program regulates impacts to state waters, including wetlands. This permit program also serves as Virginia's Section 401 certification program for federal Section 404 permits. Application is made through the Joint Permit Application process for concurrent federal and state project review.

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 EPA 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.

Vulnerable Zone: An area over which the airborne concentration of a chemical accidentally released could reach the level of concern.

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

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