Contaminated and Hazardous
Waste Site Management
Draft Tube: A narrow tube lowered into an extraction well through which a strong
vacuum is pulled via a suction pump at ground surface. Fluids (gas, water, and/or
free product) are drawn into the draft tube and conveyed to the surface for treatment
or disposal. Depending upon the configuration of the extraction system, the inlet
of the draft tube may be either above or below the static level of the liquid
in the well.
Extraction: A technology used to remove VOCs from soils. Vacuum pumps are connected
to a series of wells drilled to just above the water table. The wells are sealed
tightly at the soil surface, and the vacuum established in the soil draws VOC-contaminated
air from the soil pores into the well, as fresh air is drawn down from the surface
of the soil.
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 spaces also typically contain air or other
gases. The capillary fringe is included in the vadose zone.
Time of Sample Receipt (VTSR): The date on which a sample is received at the Contractor's
facility, as recorded on the shipper's delivery receipt and Sample Traffic Report.
Before a mathematical model can be accepted for use, it must be validated, or
proven to realistically simulate the processes for which it was designed. Validation
is usually completed by comparing model results against a controlled laboratory
or field scale experiment.
Density: The amount of mass of a vapor per unit volume of the vapor.
Pressure: The partial pressure exerted by the vapor (gas) of a liquid or solid
substance under equilibrium conditions. A relative measure of chemical volatility,
vapor pressure is used to calculate air-water partition coefficients (i.e., Henry's
Law constants) and volatilization rate constants.
Laminated clays and fine grained sediments of glacial origin deposited in lakes
during the retreat of glacial ice. Each lamina or varve has a thicker coarser
layer and a finer layer which represent a years seasonal cycle of deposition.
Varve is the Swedish word for cycle.
A short tube with a constricted throat for determining fluid pressures and velocities
by measuring differential pressures generated at the throat as a fluid traverses
A mathematical model is verified by comparing the results to a known exact solution,
often obtained using an analytical model.
A measure of the internal friction of a fluid that provides resistance to shear
within the fluid. The greater the forces of internal friction (i.e. the greater
the viscosity), the less easily the fluid will flow.
Fingering: The formation of finger-shaped irregularities at the leading edge of
a displacing fluid in a porous medium which moves out ahead of the main body of
The process of electrically melting wastes and soil sludges to bind the waste
in a glassy, solid material more durable than granite or marble and resistant
Organic Compounds (VOCs): VOCs are manufactured as secondary petrochemicals. They
include light alcohol's, acetone, trichloroethylene, perchloroethylene, dichloroethylene,
benzene, vinyl chloride, toluene and methylene chloride. These potentially toxic
chemicals are used as solvents, degreasers, paints, thinners and fuels. Because
of their volatile nature, they readily evaporate into the air, increasing the
potential exposure to humans. Due to their low water solubility, environmental
persistence and widespread industrial use, they are commonly found in soil and
The process of transfer of a chemical from the aqueous or liquid phase to the
gas phase. Solubility, molecular weight, and vapor pressure of the liquid and
the nature of the gas-liquid interface affect the rate of volatilization.