The process by which substances in gaseous, liquid, or solid form dissolve or mix with
The attraction and adhesion of ions from an aqueous solution to the surface of solids.
The process of injection of air below the water table to strip volatile contaminants from
the saturated zone.
A remediation process for removing VOCs from groundwater by aeration.
Pertaining to, or composed of, alluvium or deposited by a stream or running water.
A general term for clay, silt, sand and gravel, or similar unconsolidated material
deposited by a river as a sorted or semi-sorted sediment in the bed of the river or on its
floodplain or delta.
A mathematical model that provides an exact or approximate solution of a differential
equation (and the associated initial and boundary conditions) for subsurface water
movement or transport.
The conditions under which one or more of the hydraulic properties of an aquifer vary with
direction. (See also isotropy.)
A geologic formation which may contain water (sometimes in appreciable quantities), but is
incapable of transmitting significant quantities under ordinary field conditions.
A geologic formation, group of formations or part of a formation that contains saturated
permeable material that yields sufficient, economical quantities of groundwater.
Two or more permeable units separated at least locally by confining units that impede
groundwater movement but do not greatly affect the regional hydraulic continuity of the
See pumping test.
An impervious formation which neither contains nor transmits water.
A semi-pervious geologic formation which can store water but transmits water at a overflow
rate compared to the aquifer.
area of influence
Area surrounding a pumping or recharging wen within which the water table or
potentiometric surface has been changed due to the well's pumping or recharge. Also called
zone of influence.
Commonly used expression, generally synonymous with (but less favored term than)confined
aquifer. The term "artesian" takes its name from the basin of Artois in France.
A well deriving its water from a confined ("artesian") aquifer.
The process by which water can be injected or added to an aquifer. Dug basins, wells, or
the spread of water across the land surface are all means of artificial recharge.
The process of diminishing contaminant concentrations in groundwater, due to
filtration,biodegradation, dilution, sorption, volatilization, and other processes.
A tool attached to the end of the drill string and pulled through the bore to enlarge the
hole and mix the cuttings with the drilling fluid.
A device used to withdraw a water sample from a small-diameter well or piezometer. It is
typically a piece of pipe having a check valve in the bottom.
A type of slug test performed by using a bailer to remove a volume of water-from a
That part of a stream discharge not attributable to direct runoff from precipitation or
snowmelt, usually sustained by groundwater discharging into the stream.
A general term for the rock formation, usually solid, that underlies soil or other
An absorbent aluminum silicate clay formed from volcanic ash. When thoroughly mixed with
water, bentonite breaks down into small particles called platelets. The platelets plaster
or shingle off the wall of the hole and form a filter cake that cuts off the flow of water
into the surrounding sand or gravel.
Similar to bioremediation, but involving the introduction of organisms to affect cleanup.
A subset of biotransforination, it is the biologically mediated conversion of a compound
to more simple products.
A cleanup method involving the stimulation of naturally occurring organic substances in
A process by which air is injected into the subsurface to stimulate biodegradation by
1. A hole made in the ground by drilling or pushing.
2. The act of making a hole in the ground by drilling or pushing.
A single-sack boring fluid system, which consists of bentonite, polymer, and soda
ash,specially formulated by Baroid Drilling Fluids, Inc., for use in trenchless technology
construction applications. Processed from premium grade Wyoming sodium bentonite with an
extra high yield, enhanced to provide superior hole stabilizing properties and cuttings
support with improved lubrication and torque reduction.
The female thread portion of a drill pipe.
The pressure at which air enters saturated zone (or air entry value or threshold
The potentiometric surface (or the water table) rise in the vicinity of a' recharge wen.
It is the vertical distance between the initial and the new potentiometric surface (or the
water table in the case of an unconfined aquifer) at a given point.
The mass of a soil per unit bulk volume of soil; the mass is measured after all water has
been extracted and the volume includes the volume of the soil itself and the pore volume.
A probe or transmitter that operates with a wire attached to the drill rack for locating
calibration of models
Refinement of estimates of the input parameters and boundary conditions of a model until
model results match the field-observed data. Also known as "history matching."
A geological formation often found in the Southwestern United States that can be as hard
as rock but more closely resembles very dry layered clay which becomes sticky when wet.
Interfacial forces between immiscible fluid phases, resulting in pressure differences
between the two phases.
The zone immediately above the water table within which the water is drawn by capillary
forces (fluid is under tension). The capillary fringe is saturated, and it is considered
to be part of the unsaturated zone.
A sediment formed by the organic or inorganic precipitation from aqueous solution of
carbonates of calcium, magnesium, or iron.
A rock consisting chiefly of carbonate minerals, such as limestone and dolomite.
A woven wire device used to pull product back through the bore. It is slipped over the
outside diameter of the product and attached to the drill string. The harder it is pulled,
the tighter it gets.
Pertaining to a rock or sediment composed principally of broken fragments that are derived
from pre-existing rocks or minerals and that have been transported some, distance from
their places of origin.
The term used to denote sand and gravel. The use of bentonite in the drilling fluid is
recommended when boring in this type of soil conditions.
A reamer that enlarges the hole by compressing the soil as it is pulled through the bore.
The change in concentration with distance across a fluid medium.
A clear arnber liquid blend of water soluble anionic surfactant manufactured by Baroid
Drilling Fluids, Inc. It can be used in conjunction with Quik-Gelo« to aid in reducing
the tendency of the hole-boring tools being stuck by adhesive.
cone of depression
A depression in the groundwater table (or potentiometric surface) that has the shape of an
inverted cone and develops around a discharge well.
An aquifer bounded above and below by confining layers of distinctly lower permeability
than the aquifer material and the one containing confined groundwater. When a well is
installed in a confined aquifer, the water level in the well rises above the top of the
A hydro geologic unit of relatively low hydraulic conductivity, bounding one or more
aquifers. (See also aquitard, aquifuge, and aquiclude.)
A non-reactive constituent that does not undergo chemical reaction during substance
Toxic substances found in soils and groundwater.
The degradation of natural water quality as a result of man's activities. There is no
implication of any specific limits, since the degree of permissible contamination depends
upon the intended end use of the water.
The interaction of one or more organic contaminants that may cause them to behave
differently than if they were present alone in their pure form.
Soil particles, also known as drilling spoils, created during the boring process..Use of
the proper drilling fluid will help to suspend the cuttings which reduces the risk of
getting stuck while boring and backreaming.
An empirically derived equation for the flow of fluids through porous media. It is based
on the assumptions that flow is laminar and inertia can be neglected, and states that the
specific discharge, q, is directly proportional to the hydraulic conductivity, K, and the
hydraulic gradient, J.
A unit of intrinsic permeability, k (I darcy = 9.87 x 10-9 cm2). The relationship between
hydraulic conductivity, K, and the permeability, k, is given as K = kpg/u where p is the
fluid density, g is the gravitational constant, and u is the dynamic viscosity.
The amount of flex applied to the drill stem while steering the head.
The mass of a substance per unit volume [ML-3] Units are pounds per cubic foot
(Ib/ft3),kilograms per cubic meter (kg/m3), or grams per cubic centimeter (g/cm3).
Refers to the depth of the drill head during a bore.
See adsorption, which is the reverse process.
See molecular diffusion.
An area in which groundwater is discharged to the land surface, surface water, or
atmosphere. An area in which there are upward components of hydraulic head in the aquifer.
Groundwater is flowing toward the surface in a discharge area and may escape as a spring,
seep, or base flow, or by evaporation and transpiration.
The spreading and mixing of chemical constituents in groundwater caused by diffusion and
mixing (due to microscopic variations in velocities within and between pores).
A measure of the spreading of a flowing substance due to the nature of the porous
medium(and specific substance or fluid properties), with interconnected channels
distributed at random in all directions. Also the sum of the coefficients of mechanical
dispersion and molecular diffusion in porous medium.
A property of a porous medium (and the specific substance of fluid) that determines the
dispersion characteristics of the contaminant in that medium by relating the components of
pore velocity to the dispersion coefficient.
distribution (partitioning) coefficient
Relates the quantity of a solute sorbed per unit weight of the solid phase and the
quantity of the solute dissolved in water per unit volume of water.
Dense Non Aqueous Phase Liquid. A liquid consisting of a solution of organic compounds
(e.g., chlorinated hydrocarbons) and which is denser than water.
The land area from which surface runoff drains into a stream.
A lowering of the water table of an unconfined aquifer or the potentiometric surface of a
confined aquifer caused by pumping of groundwater from wells. The vertical distance
between the original water level and the new water level.
If not enough drilling fluid is used, a dry hole occurs and the product becomes lodged in
The drilling bit that attaches to the front of the boring head. It mounts to the head at
an angle and also is bent. This angle is what provides the steering capability while
pushing the drill pipe.
effective grain size
The grain size corresponding to the 10% finer by weight on the grain-size distribution
The interconnected pore space through which fluids can pass, expressed as a percent of
bulk volume. Part of the total porosity will be occupied by static fluid being held to
mineral surface by surface tension, so effective porosity will be less than total
See gaining stream.
The area where the drill pipe enters the ground after the drill machine is set up.
The angle at which the drill head enters the ground or the degree that the rack is set at.
The Environmental Protection Agency. The federal authority responsible for enforcing the
various laws dealing with environmental standards.
A line in a two-dimensional groundwater flow field along which the total hydraulic
head(the groundwater potential) is constant.
The evaporation that actually occurred under given climatic and soil-moisture conditions.
The evaporation that would occur under given conditions if there were unlimited soil
The area where the drill pipe exits the ground and the service lines are pulled back in.
A discharge well used to remove groundwater or air.
A premium grade, high molecular weight PUPA polymer manufactured by Baroid Company. When
this is added to bentonite in the drilling fluid, it provides extended high viscosity and
gel strength. It also lowers the filtration rate and increases lubrication. It is an
excellent shale/clay stabilizer which minimizes swelling.
The mass flux due to the molecular diffusion is proportional to the concentration gradient
and the diffusion coefficient.
The amount of moisture remaining in the soil after an extended period of gravity drainage
without additional supply of water at the soil surface.
The zone where the bentonite platelets plaster or shingle off the wall of the hole.
The water portion of the drilling fluid that seeps through the filter cake.
Term used to denote clay and shale soils. The use of polymer is recommended in these soil
conditions to reduce swelling while at the same time improving lubrication and torque
When the drilling fluid moves or runs smoothly with unbroken continuity through the entire
length of the bore.
flowline or pathline
The general path that a particle of water follows under laminar flow conditions., Flow
lines are perpendicular to equipotential lines in an isotropic aquifer.
A digital computer model that calculates a hydraulic head field for the modeling domain
using numerical methods to arrive at an approximate solution to the differential equation
of groundwater flow.
A characteristic of a flow system, where the magnitude and direction of specific discharge
are constant in time at any point. If the specific discharge has the same magnitude and
direction at any point, the flow is uniform.
flow, unsteady (transient)
A characteristic of a flow system where the magnitude and/or direction of the
specific discharge changes with time.
The area at each end of a FIRESTICK drill stem where it tapers to a larger diameter. This
larger diameter is achieved by heating the ends of the rod to temperatures in excess of
2000║ F and striking it with tremendous force in a die set. To achieve this, the metal
has to start out 3' longer than the desired finished length of the drill stem.
In certain conditions, the drilling fluid can build tremendous pressure in the bore. If
the pressure becomes great enough, the ground will fracture to the surface. The drilling
fluid escapes the bore through this rupture, and the pressure is relieved.
A general term for any break in a rock, which includes cracks, joints and faults.
Visible on aerial photographs, fracture traces are natural linear-drainage, soil-tonal,
and topographic alignments that are probably the surface manifestation of underlying zones
front locate point
The point in front of the drill head where the DIGITRAKTM locator goes from + to -. This
point is also referred to as the front negative locate point.
A stream or reach of a stream, the flow of which is being increased by inflow of
groundwater. Also known as an effluent stream.
The ability of the drilling fluid to support and suspend the cuttings. The use of
bentonite in the drilling fluid greatly increases these characteristics.
A methodology for the analysis of spatially correlated data. The characteristic feature is
in the use of variograms or related techniques to quantify and model the spatial
correlation structure. Also includes various techniques such as kriging, which utilize
spatial correlation models.
False signals received by the locator.
A general term for unconsolidated sediment transported by glaciers and deposited directly
on land or in the sea.
Well-sorted sand, or sand and gravel, deposited by the meltdown from a glacier.
A glacial deposit composed of mostly unsorted sand, silt, clay, and boulders and laid down
directly by the melting ice.
Component of total hydraulic head related to the vertical position of a given mass of
water relative to an arbitrary datum.
Water that moves into, through, or out of a soil or rock mass under the influence of
A long copper rod with a T handle and auger bit that is screwed into the ground and
attached to the boring machine to provide an additional path for electricity to flow in
the event of an electrical strike.
The water contained in interconnected pores below the water table in an unconfined aquifer
or in a confined aquifer.
Rock or artificial material with a relatively low permeability that occurs (or is placed)
below ground surface, where it impedes the movement of groundwater and thus causes a
pronounced difference in the heads on opposite sides of the barrier.
General term used to define a groundwater flow system that has defined boundaries and may
include more than one aquifer underlain by permeable materials that are capable of storing
or furnishing a significant water supply. The basin includes both the surface area and the
permeable materials beneath it.
Ridge in the water table, or potentiometric surface, from which groundwater moves away at
right angles in both directions. Line of highest hydraulic head in the water table or
The movement of water through openings in sediment and rock that occurs in the zone of
A simplified conceptual or mathematical image of a groundwater system, describing the
feature essential to the purpose for which the model was developed and including various
assumptions pertinent to the system. Mathematical groundwater models can include numerical
and analytical models.
Raised area in a water table or other potentiometric surface, created by groundwater
Process of water addition to the saturated zone, or the volume of water added by this
A term used in the environmental industry to identify materials classified as hazardous by
To treat metal by alternate heating and cooling in order to produce desired
characteristics,such as increased hardness; temper.
The relationship between the partial pressure of a compound and its equilibrium
concentration in a dilute aqueous solution through a constant of proportionality known as
the Henry's Law Constant.
Characteristic of a medium in which material properties vary from point to point.
Characteristic of a medium in which material properties are identical throughout. Though
heterogeneity or nonunifonnity is the characteristic of most aquifers, assumed
homogeneity, with some other additional assumptions, allows use of analytical models as a
valuable tool for approximate analyses of groundwater movement.
A situation that has been known to occur while pulling product through the bore. In this
condition, the bore acts as a huge hydraulic cylinder with the product string acting as a
large hydraulic ram. The drilling fluid stops flowing in the bore and pressure begins to
build. The pressure continues to build to the point where the boring machine can no longer
pull the product string and you have a stuck situation. Increased pullback pressure with
decreased rotational pressure is an indication that hydra-lock is occurring. This most
often occurs in very tight soil conditions such as dry clay and can sometimes be cured by
digging a burp hole to relieve the pressure or by letting everything set for a period of
time while the pressure seeps past the product string.
Modifications to a groundwater flow system that restrict or impede movement of
hydraulic conductivity (K)
Proportionality constant relating hydraulic gradient to specific discharge,
which, for an isotropic medium and homogeneous fluid, equals the volume of water at the
existing kinematic viscosity that will move in unit time under a unit hydraulic gradient
through a unit area measured at right angles to the direction flow. The rate of flow of
water in gallons per day through a cross section of one square foot under a unit hydraulic
gradient, at the prevailing temperature (gpd/ft2). In the standard International System,
the units are m3/day/m2 or m/day. A coefficient of proportionality describing the rate at
which water can move through a permeable medium. The density and kinematic viscosity of
the water must be considered in determining hydraulic conductivity.
hydraulic conductivity, effective
Rate of water flow through a porous medium that contains more than one fluid (such as
water and air in the unsaturated zone), which should be specified in terms of the fluid
type,content and the existing pressure.
hydraulic gradient (J)
Slope of a water table or potentiometric surface. More specifically, change in
the hydraulic head per unit of distance in the direction of the maximum rate of decrease.
The difference in hydraulic heads (hl-h2), divided by the distance
(L) along the flowpath: J= (hl-h2)/L.
hydraulic head (h)
Height above a datum plane (such as mean sea level) of the column of water that
can be supported by the hydraulic pressure at a given point in a groundwater system. Equal
to the distance between the water level in a well and the datum plane.
Spreading (at the macroscopic level) of the solute front during transport resulting from
both mechanical dispersion and molecular diffusion. The process by which groundwater
containing a solute is diluted with uncontaminated groundwater as it moves through an
aquifer (see dispersion coefficient).
Those factors that deal with subsurface waters and related geologic aspects of surface
Numerical parameters that describe the hydro geologic characteristics of an aquifer such
as porosity, permeability, and transmissivity.
Pressure exerted by the weight of water at any given point in a body of water at rest.
Any soil or rock unit or zone that has a distinct influence on the storage or movement of
groundwater because of its hydraulic properties.
The chemical property where two or more liquids or phases do not readily dissolve in one
another, such as soil and water.
Characteristic of geologic materials that limits their ability to transmit significant
quantities of water under the pressure gradients normally found in the subsurface
An area in the subsurface that has zero air flow. Limits the range of influence of
extraction wells in SVE systems.
The downward entry of water into soil or rock.
Rate at which soil or rock under specified conditions absorbs falling rain, melting snow,
or surface water; expressed in depth of water per unit time. Also, the maximum rate at
which water can enter soil or rock under specific conditions, including the presence of an
excess of water; expressed in units of velocity.
See losing stream.
Latin term for "in the site," used in environmental industry to describe the
treatment of contaminants without removal from their immediate location.
Pertaining to the relative ease with which a porous medium can transmit a liquid under a
hydraulic or potential gradient. It is a property of the porous medium and is independent
of the nature of the liquid or the potential field.
A line connecting all points having the same time of travel for contaminant particles to
move through the saturated zone and reach a well.
The condition in which the properties of interest (generally hydraulic properties of the
aquifer) are the same in all directions.
Where the male and female threads of the drill stem come together.
The ratio of dynamic viscosity to mass density. It is obtained by dividing dynamic
viscosity by the fluid density. Units of kinematic viscosity are square meters per second
Gas slippage along pore walls. Darcy's Law assumes that the velocity of a fluid at the
pore wall surface is zero.
A weight-moving-average interpolation method where the set of weights assigned to samples
minimizes the estimation variance, which is computed as a function of the variogram model
and locations of the samples relative to each other, and to the point or block being
Fluid flow in which the head loss is proportional to the first power of the
velocity;synonymous with streamline flow and viscous flow. Type of flow in which the fluid
particles follow paths that are smooth, straight, and parallel to the channel wars. In
laminar flow, the viscosity of the fluid dampens out turbulent motion.
Removal of materials in solution from rock, soil, or waste; dissolving out of soluble
constituents from a porous medium by percolation of water.
Flow of water from one hydrogeologic unit to another. This may be natural, as through a
somewhat permeable confining layer, or anthropogenic, as through an uncased well. It may
also be the natural loss of water from artificial structures, as a result of hydrostatic
The rate of flow across a unit (horizontal) area of a semi-pervious layer into (or out of)
an aquifer under one unit of head difference across this layer.
An artesian or water table aquifer that loses or gains water through adjacent
semipermeable confining units.
Lighter-than-water non aqueous phase liquid.
The unit which picks up the signal from the drill head where the transmitter is housed.
A stream or reach of a stream that is losing water by seepage into the ground. Also known
as an influent stream.
Slick or slippery as in lubricate. Polymer in the drilling fluid will increase
"lubricity" in the bore.
Relatively large pores in porous medium that allow the enhanced movement of liquid and
The fitting together of the pin and box sections of the drill stem.
Stainless steel wire mesh that is part of the strike alert and grounding system. The
function of the mats is to equalize the voltage around the machine in the event of an
Solid framework of a porous material or system.
Process whereby solutes are mechanically mixed during advective transport, caused by the
velocity variations at the microscopic level; synonymous with hydraulic dispersion. The
coefficient of mechanical dispersion is the component of mass transport flux of solutes
caused by velocity variations at the microscopic level.
See water content.
Process in which solutes are transported at the microscopic level due to variations in the
solute concentrations within the fluid phases.
A tube or pipe, open to the atmosphere at the top and to water at the bottom, usually
along an interval of slotted screen, used for taking groundwater samples.
Non aqueous phase liquids.
One of two points where a Digitrak locator reading goes from + to -.
A source discharging pollutants into the environment that is not a single point.
Located on the drill head to spray drilling fluid into the bore.
A well drilled in a selected location for the purpose of observing parameters such as
waterl evels and pressure changes. A non-pumping well used to observe the elevation of the
water table or the potentiometric surface. An observation well is generally of larger
diameter than a piezometer and typically is screened or slotted throughout the thickness
of the aquifer.
organic carbon content
The amount of the organic carbon present in a soil. Organic chemicals in soil adsorb to
soil organic carbon and the amount of adsorption can be related to the soil organic carbon
When the intake portion of the well is less than the full thickness of the aquifer. A well
constructed in such a way that it draws water directly from a fractional part of the total
thickness of the aquifer. The fractional part may be located at the top, the bottom, or
anywhere else in the aquifer.
Chemical equilibrium condition where a chemical's concentration is apportioned between two
different phases according to the partition coefficient, which is the ratio of a
chemical's concentration in one phase to its concentration in the other phase.
Relationship between the advective and diffusive components of solute transport;
expressed as the ratio of the product of the average interstitial velocity and the
characteristic length, divided by the coefficient of molecular diffusion. Small values
indicate diffusion dominates; large values indicate advection dominates.
A special case of phreatic aquifer which occurs wherever an impervious (or
semi-pervious)layer of limited aerial extent is located between the water table of a
phreatic aquifer and the ground surface.
Unconfined groundwater separated from an underlying main body of groundwater by an
Downward movement of water through the unsaturated zone; also defined as the downward flow
of water in saturated or nearly saturated porous media at hydraulic gradients of 1.0 or
less. The act of water seeping or filtering through the soil without a definite channel.
Rate of flow of water through a unit cross-sectional area under a unit hydraulic gradient
at the prevailing temperature (field permeability coefficient), or adjusted to 15 degrees
Observed permeability of a porous medium to one fluid phase, under conditions of physical
interaction between the phase and other fluid phases present.
Relative ease with which a porous medium can transmit a fluid under a potential
gradient,as a property of the medium itself. Property of a medium expressing the relative
ease with which fluids can pass through it.
See water table aquifer.
A tube or pipe, open to the atmosphere at the top and to water at the bottom, and sealed
along its length, used to measure the hydraulic head in a geologic unit.
See potentiometric surface.
The male threads on the drill stem.
Measurement for the deviation from horizontal of the drill head.
A minute, disklike cytoplasmic body found in bentonite that plasters or shingles off the
wall of the hole to form a filter cake that cuts off the flow of water into the
surrounding sand or gravel. When broken down to its smallest dimension, there are enough
platelets in a cubic inch of high-quality sodium bentonite to cover 66 football fields.
Any discernible, confined, or discrete conveyance from which pollutants are or may be
discharged, including (but not limited to) pipes, ditches, channels, tunnels,
conduits,,wells,containers, rolling stock, concentrated animal feeding operations, or
Any solute or cause of change in physical properties that renders water unfit for a
When the contaminant concentration levels restrict the potential use of groundwater.
Any of numerous natural and synthetic compounds of usually high molecular weight
consisting of up to millions of repeated linked units, each a relatively light and simple
molecule. Polymer, when used in conjunction with bentonite in the drilling fluid, enhances
viscosity and gel strength, lowers filtration rate, and increases lubricity. The use of a
polymer is recommended when boring in clay or shale.
Total space in an aquifer medium not occupied by solid soil or rock particles.
Ratio of the total volume of voids to the total volume of a porous medium. The percentage
of the bulk volume of a rock or soil that is occupied by interstices, whether isolated or
connected. Porosity may be primary, formed during deposition or cementation of the
material, or secondary formed after deposition or cementation, such as fractures.
When locating with a Digitrak&, this is the point directly above the drill head where
the locator readout changes from + to -.
Suitable for human consumption as drinking water.
A surface that represents the level to which water will rise in wells penetrating a
confined aquifer. If the head varies significantly with depth in the aquifer, then there
may be more than one potentiometric surface. The water table is a particular
potentiometric surface for an unconfined aquifer.
A hole dug to expose underground utilities crossing the proposed bore path.
Also known as confined aquifer. (See confined aquifer.)
Hydrostatic pressure expressed as the height (above a measurement point) of a column of
water that the pressure can support.
Pressure exerted by a fluid at rest.
An electronic device that fits inside the drill head and sends out a signal used to locate
the head, read pitch and roll, and determine depth.
Potential responsible parties. Waste generators who are responsible for the ultimate fate
of toxic wastes. Includes property owners, industries, government agencies, etc. The
current federal laws make the PRPs liable in perpetuity for these wastes.
The specific gravity of water.
public water supply system
System for provision to the public of piped water for human consumption. Such a system has
at least 15 service connections or regularly serves at least 25 individuals daily or at
least60 days out of the year. The ten-n includes any collection, treatment, storage, and
distribution facilities under control of the operator of such system and used primarily in
connection with the system, and any collection or pretreatment storage facilities not
under such control that are used primarily in connection with the system.
A test that is conducted to determine aquifer or well characteristics. A test
made by pumping a well for a period of time and observing the change in hydraulic head in
the aquifer. A pumping test may be used to determine the capacity of the well and the
hydraulic characteristics of the aquifer. Also called aquifer test.
Plastic pipe that can be used as well casing material.
A step in the heat treating process to cool hot metal which causes it to harden. The most
common quench mediums are brine, water, oil, and air. The greatest hardness and strength
for most materials are obtained by brine or water quenching. However, this also produces
the most distortion and cracking. Oil or air quenching will produce less distortion and
cracking but also less strength and hardness.
Highest-grade sodium bentonite manufactured by Baroid Drilling Fluids, Inc. This drilling
fluid mix develops a cost-effective low solids slurry with high viscosity, high gel
strength,and controlled filtration rate to provide formation and hole stabilization.
A white granular pure grade polymer manufactured by Baroid Drilling Fluids, Inc. When
added to a premixed bentonite slurry, it improves clay/shale stabilization and enhances
all properties of a bentonite slurry used in boring.
The actual boring machine which includes drive head, controls, vise, etc.
The flow of water in an aquifer toward a vertical well.
radius of influence
The radial distance from the center of a wellbore to the point where there is no lowering
of the water table or potentiometric surface (the edge of its cone of depression). The
radial distance from an extraction well that has adequate air flow for effective removal
of contaminants when a vacuum is applied to the extraction well.
range of influence
The area that can be remediated by an extraction well in an SVE system.
A physical law which describes the relationship between the vapor pressure of a component
over a solution, the vapor pressure of the same component over pure liquid,and the mole
fraction of the component in the solution.
Any of various tools attached to the end of the drill string and pulled through the bore
to enlarge the hole and mix the cuttings with the drilling fluid.
rear locate point
The point behind the drill head where the readout on a Digitrak locator switches from + to
-. This is also called the rear negative locate point.
an electronic unit that receives information from the transmitter. This is also referred
to as the locator.
The addition of water to the zone of saturation; also, the amount of water added. Can be
expressed as a rate (i.e., in/yr) or a volume.
An area in which there are downward components of hydraulic head in the aquifer.
Infiltration moves downward into the deeper parts of an aquifer in a recharge area.
A basin or pit excavated to provide a means of allowing water to soak into the ground at
rates exceeding those that would occur naturally.
An aquifer system boundary that adds water to the aquifer. Streams and lakes are typical
T'he business of implementing the methods for cleanup. Includes firms that specialize in
underground storage tank removal and soil vacuum extraction.
The methods of cleanup used for contaminated soils and groundwaters.
An auxiliary electronic readout that displays information received from the receiver.
Saturation below which fluid drainage will not occur.
The movement of a solute through a geologic medium at a velocity less than that of the
flowing groundwater due to sorption or other removal of the solute.
Dimensionless number expressing the ratio of inertial to viscous forces acting on the
fluid,Re = pVd/u. The number can be used to determine whether the flow is laminar or
The most commonly used method for determining the hardness of a metal.
A section of drill stem.
A donut-shaped neoprene disk that fits around the drill stem to help clean it during the
The rotational position of the drill head as it relates to a clock face.
The speed of the drill stem turning in the ground. It also relates to how fast the reamer
That part of precipitation flowing to surface streams. The total amount of water flowing
in a stream. It includes overland flow, return flow, interflow, and baseflow.
The amount of naturally occurring groundwater that can be withdrawn from an
aquifer on a sustained basis without impairing the native groundwater quality or lowering
The ratio of the volume of a single fluid in the pores to pore volume expressed as a
percentage or a fraction.
Portion of the subsurface environment in which all voids are ideally filled with water
under pressure greater than atmospheric. The zone in which the voids in the rock or soil
are filled with water at a pressure greater than atmospheric. The water table is the top
of the saturated zone in an unconfined aquifer.
Whenever a phreatic surface approaches the downstream external boundary of a flow domain,
it always terminates on it at a point that is above the water table of the body of open
water present outside the flow domain. The segment of the boundary above the water table
and below the phreatic surface is called the seepage face.
An aquifer that has a "leaky" confining unit and displays characteristics of
both confined and unconfined aquifers. (See leaky aquifer.)
This transmitter is designed to bore sewer pipe by allowing the bore to be on grade. The
probe works on a 0. I% readout.
T'he process of determining the geology, hydrology, type of contaminants and area of
contamination. Done by engineering and consulting firms.
The damage to the permeability in the proximity of a well due to drilling fluids.
A test for estimating hydraulic conductivity of an aquifer in which a rapid water-level
change is produced in a piezometer or monitoring wen, usually by introducing or
withdrawing a "slug" of water or a weight. The rise or decline in the water
level is monitored.
A subsurface wall constructed by digging a trench and backfilling it with a slurry and
designed to prevent groundwater flow.
Sodium carbonate in powdery white form used to increase the PH level of hard water. This
makes the mixing of bentonite and polymers into the drill fluid much easier.
soil venting, soil vapor extraction, soil vacuum extraction, "SVE"
All describe the process of using extraction wells as a means to deliver a vacuum
in the subsurface, thereby pulling toxic vapors to the surface to be treated by an
incineration,catalytic or absorptive process.
Net flux of solute through a hydrogeologic unit, controlled by the flow of subsurface
-water and transport mechanisms.
solute transport model
Mathematical model used to predict the movement of solutes (generally contaminants) in an
aquifer through time.
An electronic device that fits inside the drill head and transmits a signal used for
locating purposes. Also referred to as a transmitter or probe.
Processes that remove solutes from the fluid phase and concentrate them on the solid phase
of a medium; used to encompass absorption and adsorption.
A method of forcing VOCs from the saturated zone into the vadose zone by pushing air into
The rate of discharge of water from the well divided by the drawdown within the well.
The volume of water flowing through a unit cross-sectional area of an aquifer.
The drawdown within a well divided by the discharge rate of water from the well (inverse
of specific capacity).
The ratio of a substance's density to the density of some standard substance, usually
As water is being drained from the interstices of soil, after drainage has stopped, the
volume of water retained in an aquifer per unit area and unit drop of the water table.
The amount of water released from or taken into storage per unit volume of a porous medium
per unit change in head.
The amount of surface area of a dispersed system per gram or per unit volume of the
The volume of water that a saturated rock or soil win yield by gravity (often used as a
synonym for effective porosity or storage coefficient of unconfined aquifers).
A specially designed back reamer that resembles a huge wood screw. This long tapered
spiral design is well suited for pushing hard obstacles out of the way.
Discrete place where groundwater flows naturally from rock or soil onto the land surface
or into a surface water body.
A point in a groundwater flow field at which the groundwater is not moving. The magnitude
of vectors of hydraulic head at the point are equal but opposite in direction.
static water level
The level of water in a well that is not being affected by withdrawal of groundwater.
A section of drill pipe.
Describes the electrical voltage differential between two points.
A warning system on all NAVIGATORs that is set off by contact with an electrical power
The amount of water released from or taken into storage per porous medium column with a
unit surface area per unit change in head. (See also storativity.)
A dimensionless term representing the volume of water an aquifer releases from or takes
into storage per unit surface area of the aquifer per unit change in head. It is equal to
the product of specific storage and aquifer thickness. In an unconfined aquifer, the
storativity is equivalent to the specific yield.
The commonly used name for a federal law called "CERCLA." This act designated a
portion of funds to be put away by generators of certain wastes for the research and
implementation of remediation processes.
Principle used for linear problems, such as confined groundwater flow, that allows
equation solutions to be added to form new solutions. For example, if within a well
field,pumping rates of the pumped wells are known, the composite drawdown at a point can
be determined by summing the drawdown caused by each individual pumped well.
A soap based substance which acts as a wetting agent to reduce the tendency of clay
cutting to stick together. It also reduces the tendency of boring tools becoming stuck by
Attaches between the back reamer and the product being pulled back to keep the product
Metal that is reheated after quenching for the purpose of making it more stress-free,
crack-free, distortion-free and slightly softening it.
The instrument used for measuring the capillary pressure in an unsaturated zone.
Used to lubricate the thread and shoulder area of the drill joint. Suitable thread
compound should have a zinc base of 40-60% by weight to withstand the pressures and torque
that is applied to the drill stem joints. Sometimes mistakenly referred to as grease.
This occurs when you push the drill stem into the ground without rotating.
time of travel (TOT)
The time required for a contaminant to move in the saturated zone from a specific point to
The rotational force applied to the drill stem joints.
Rate at which water of the prevailing kinematic viscosity is transmitted through a unit
width of the aquifer under a unit hydraulic gradient. It is equal to an integration of the
hydraulic conductivities across the saturated part of the aquifer perpendicular to the
flow paths. The rate at which water is transmitted through a unit width of an aquifer
under a unit hydraulic gradient. Transmissivity values are given in gallons per minute
through a vertical section of an aquifer one foot wide and extending the full saturated
height of an aquifer under a hydraulic gradient of one in the English Engineering System;
in the Standard International System, transmissivity is given in cubic meters per day
through a vertical section of an aquifer one meter wide and extending the full saturated
height of an aquifer under a hydraulic gradient of one. It Is a function of properties of
the liquid, the porous media, and the thickness of the porous media.
An electronic device that fits inside the drill head and transmits a signal used for
locating purposes. Also referred to as a sonde or probe.
Water flow in which the flow lines are confused and heterogeneously mixed. It is typical
of flow in surface water bodies (2). That type of flow in which the fluid particles move '
along very irregular paths. Momentum can be exchanged between one portion of the fluid and
another. Compare with laminar flow.
Conditions in which the upper surface of the zone of saturation forms a water table under
See water table aquifer.
An aquifer made up of loose material, such as sand or gravel, that has not undergone
Movement of water in porous medium in which the pore spaces are not completely filled with
The zone between the land surface and the water table. It includes the root
zone,intermediate zone, and capillary fringe. The pore spaces contain water, as well as
air and other gases at less than atmospheric pressure. Saturated bodies, such as perched
groundwater, may exist in the unsaturated zone, and water pressure within these may be
greater than atmospheric. Replaces the older terms "zone of aeration" and
Underground storage tanks used for the storage of fuels and other liquids. Most have
leaked contaminants into the ground around them. A program to remove all old USTs is in
place by the EPA and is scheduled to be completed by 1998.
The area immediately beneath the surface of the earth. Usually made up of soils, small
rocks, gravels, clays, etc. Above saturated zone.
The process of determining the degree to which a model is an accurate representation of
the real world from the perspective of the intended uses of the model.
velocity, average interstitial
Average rate of groundwater flow in interstices expressed as the product of hydraulic
conductivity and hydraulic gradient (specific discharge) divided by the effective
porosity. It is synonymous with average linear groundwater velocity or effective velocity.
The examination of the numerical technique in the computer code to ascertain that it truly
represents the conceptual model and that there are no inherent problems with obtaining a
The internal friction within a fluid that causes it to resist flow.
Volatile organic compounds, typically with a high vapor pressure and a tendency to
The transfer of a chemical from liquid to the gas phase. Solubility, molecular weight, and
vapor pressure of the liquid, and the nature of the air-liquid interface, affect the rate
An evaluation of all the sources of supply and corresponding discharges with respect to an
aquifer or drainage basin.
Upper surface of a zone of saturation, where that surface is not formed by a confining
unit;water pressure in the porous medium is equal to atmospheric pressure. The surface
between the vadose zone and the groundwater; that surface of a body of unconfined
groundwater at which the pressure is equal to that of the atmosphere.
water table aquifer
An aquifer in which the water table forms the upper boundary.
An area containing two or more wells supplying a public water supply system.
well, fully penetrating
A well drilled to the bottom of an aquifer, constructed in such a way that it withdraws
water from the entire thickness of the aquifer.
The condition occurring when the area of influence of a water well (the cone of
depression)overlaps that of a neighboring well or wells, as when the wells are pumping
from the same aquifer.
A filtering device used to permit the flow of liquid or air but prevents the passage of
sediments or backfill particles.
The volume of water discharged from a well per unit time.
The physical structure, facility, or devise at the land surface from or through which
groundwater flows or is pumped from subsurface, water-bearing formations.
wellhead protection area (VHPA)
The surface and subsurface area surrounding a water well or well field, supplying a public
water system, through which contaminants are reasonably likely to move toward and reach
such water well or well field.
A substance that reduces the surface tension of a liquid, causing the liquid to spread
across or penetrate more easily the surface of a solid. A soap-based wetting agent reduces
the tendency of clay cuttings to stick together. It also reduces the tendency of boring
tools becoming stuck due to adhesion.
The soil-moisture content below which plants are unable to withdraw soil moisture.
A backreamer specially designed to cut, mix, and change the form of the material that is
being pulled through to make it into a passable or manageable form.
zone of capture
Area surrounding a pumping well that encompasses all areas of features that supply
groundwater recharge to the well.
zone of contribution (ZOC)
The area surrounding a pumping well that encompasses all areas or features that
supply groundwater recharge to the well.
zone of influence (ZOI)
The area surrounding a pumping well within which the water table or
potentiometric surfaces have been changed due to groundwater withdrawal.
zone of transport (ZOT)
The area surrounding a pumping well, bounded by an isochrone and/or isoconcentration
contour, through which a contaminant may travel and reach the well.