DAPSS— Document and Personnel
Security System (IMD)
DBP— Disinfection By-Product
DCI— Data Call-In
DCO— Delayed Compliance Order
DCO— Document Control Officer
DERs— Data Evaluation Records
DfE— Design for the Environment
DI— Diagnostic Inspection
DMR— Discharge Monitoring Report
DNA— Deoxyribonucleic acid
DNAPL— Dense Non-Aqueous Phase Liquid
DO— Dissolved Oxygen
DOW— Defenders Of Wildlife
DPA— Deepwater Ports Act
DPD— Method of Measuring Chlorine Residual
DQO— Data Quality Objective
DRE— Destruction and Removal Efficiency
DRES— Dietary Risk Evaluation System
DRMS— Defense Reutilization and Marketing
DRR— Data Review Record
DS— Dichotomous Sampler
DSAP— Data Self Auditing Program
DSCF— Dry Standard Cubic Feet
DSCM— Dry Standard Cubic Meter
DSS— Decision Support System; Domestic
DT— Detectors (radon) damaged or lost;
DU— Decision Unit. Ducks Unlimited;
DUC— Decision Unit Coordinator
DWEL— Drinking Water Equivalent Level
DWS— Drinking Water Standard
DWSRF— Drinking Water State Revolving
DDT— The first chlorinated
hydrocarbon insecticide chemical name—
Dichloro-Diphenyl-Trichloroethane. It has
a half-life of 15 years and can collect in
fatty tissues of certain animals. EPA banned
registration and interstate sale of DDT for
virtually all but emergency uses in the United
States in 1972 because of its persistence
in the environment and accumulation in the
Dead End— The end of a
water main which is not connected to other
parts of the distribution system.
Deadmen— Anchors drilled
or cemented into the ground to provide additional
Decant— To draw off the
upper layer of liquid after the heaviest material
(a solid or another liquid) has settled.
Decay Products— Degraded
radioactive materials, often referred to as
“daughters” or “progeny”;
radon decay products of most concern from
a public health standpoint are polonium-214
of chlorine from a substance.
Decomposition— The breakdown
of matter by bacteria and fungi, changing
the chemical makeup and physical appearance
of harmful substances such as noxious chemicals,
harmful bacteria or other organisms, or radioactive
material from exposed individuals, rooms and
furnishings in buildings, or the exterior
Deep-Well Injection— Deposition
of raw or treated, filtered hazardous waste
by pumping it into deep wells, where it is
contained in the pores of permeable subsurface
A material added to a suspension to prevent
Defluoridation— The removal
of excess flouride in drinking water to prevent
the staining of teeth.
Defoliant— An herbicide
that removes leaves from trees and growing
Degasification— A water
treatment that removes dissolved gases from
Degree-Day— A rough measure
used to estimate the amount of heating required
in a given area; is defined as the difference
between the mean daily temperature and 65
degrees Fahrenheit. Degree-days are also calculated
to estimate cooling requirements.
Delegated State— A state
(or other governmental entity such as a tribal
government) that has received authority to
administer an environmental regulatory program
in lieu of a federal counterpart. As used
in connection with NPDES, UIC, and PWS programs,
the term does not connote any transfer of
federal authority to a state.
Delist— Use of the petition
process to have a facility’s toxic designation
Demand-side Waste Management—
Prices whereby consumers use purchasing decisions
to communicate to product manufacturers that
they prefer environmentally sound products
packaged with the least amount of waste, made
from recycled or recyclable materials, and
containing no hazardous substances.
Demineralization— A treatment
process that removes dissolved minerals from
Denitrification— The biological
reduction of nitrate to nitrogen gas by denitrifying
bacteria in soil.
Dense Non-Aqueous Phase Liquid
(DNAPL)— Non-aqueous phase liquids such
as chlorinated hydrocarbon solvents or petroleum
fractions with a specific gravity greater
than 1.0 that sink through the water column
until they reach a confining layer. Because
they are at the bottom of aquifers instead
of floating on the water table, typical monitoring
wells do not indicate their presence.
Density— A measure of
how heavy a specific volume of a solid, liquid,
or gas is in comparison to water. depending
on the chemical.
Depletion Curve— In hydraulics,
a graphical representation of water depletion
from storage-stream channels, surface soil,
and groundwater. A depletion curve can be
drawn for base flow, direct runoff, or total
Depressurization— A condition
that occurs when the air pressure inside a
structure is lower that the air pressure outdoors.
Depressurization can occur when household
appliances such as fireplaces or furnaces,
that consume or exhaust house air, are not
supplied with enough makeup air. Radon may
be drawn into a house more rapidly under depressurized
Process by which a chemical penetrates the
skin and enters the body as an internal dose.
Dermal Exposure— Contact
between a chemical and the skin.
Dermal Toxicity— The ability
of a pesticide or toxic chemical to poison
people or animals by contact with the skin.
DES— A synthetic estrogen,
diethylstilbestrol is used as a growth stimulant
in food animals. Residues in meat are thought
to be carcinogenic.
(1) Removing salts from ocean or brackish
water by using various technologies. (2) Removal
of salts from soil by artificial means, usually
Desiccant— A chemical
agent that absorbs moisture; some desiccants
are capable of drying out plants or insects,
Design Capacity— The average
daily flow that a treatment plant or other
facility is designed to accommodate.
Design Value— The monitored
reading used by EPA to determine an area’s
air quality status; e.g., for ozone, the fourth
highest reading measured over the most recent
three years is the design value.
An air pollutant which is neither a criteria
nor hazardous pollutant, as described in the
Clean Air Act, but for which new source performance
standards exist. The Clean Air Act does require
states to control these pollutants, which
include acid mist, total reduced sulfur (TRS),
Designated Uses— Those
water uses identified in state water quality
standards that must be achieved and maintained
as required under the Clean Water Act. Uses
can include cold water fisheries, public water
supply, and irrigation.
Designer Bugs— Popular
term for microbes developed through biotechnology
that can degrade specific toxic chemicals
at their source in toxic waste dumps or in
The facility to which regulated medical waste
is shipped for treatment and destruction,
incineration, and/or disposal.
mixing within a lake or reservoir to totally
or partially eliminate separate layers of
temperature, plant, or animal life.
Destroyed Medical Waste—
Regulated medical waste that has been ruined,
torn apart, or mutilated through thermal treatment,
melting, shredding, grinding, tearing, or
breaking, so that it is no longer generally
recognized as medical waste, but has not yet
been treated (excludes compacted regulated
Destruction and Removal Efficiency
(DRE)— A percentage that represents
the number of molecules of a compound removed
or destroyed in an incinerator relative to
the number of molecules entering the system
(e.g. a DRE of 99.99 percent means that 9,999
molecules are destroyed for every 10,000 that
enter; 99.99 percent is known as “four
nines.” For some pollutants, the RCRA
removal requirement may be as stringent as
A facility that destroys regulated medical
of sulfur from fossil fuels to reduce pollution.
Detectable Leak Rate—
The smallest leak (from a storage tank), expressed
in terms of gallons- or liters-per-hour, that
a test can reliably discern with a certain
probability of detection or false alarm.
Detection Criterion— A
predetermined rule to ascertain whether a
tank is leaking or not. Most volumetric tests
use a threshold value as the detection criterion.
Detection Limit— The lowest
concentration of a chemical that can reliably
be distinguished from a zero concentration.
Detention Time— 1. The
theoretical calculated time required for a
small amount of water to pass through a tank
at a given rate of flow. 2. The actual time
that a small amount of water is in a settling
basin, flocculating basin, or rapid-mix chamber.
3. In storage reservoirs, the length of time
water will be held before being used.
Detergent— Synthetic washing
agent that helps to remove dirt and oil. Some
contain compounds which kill useful bacteria
and encourage algae growth when they are in
wastewater that reaches receiving waters.
Development Effects— Adverse
effects such as altered growth, structural
abnormality, functional deficiency, or death
observed in a developing organism.
Dewater— 1. Remove or
separate a portion of the water in a sludge
or slurry to dry the sludge so it can be handled
and disposed of. 2. Remove or drain the water
from a tank or trench.
Diatomaceous Earth (Diatomite)—
A chalk-like material (fossilized diatoms)
used to filter out solid waste in wastewater
treatment plants; also used as an active ingredient
in some powdered pesticides.
Diazinon— An insecticide.
In 1986, EPA banned its use on open areas
such as sod farms and golf courses because
it posed a danger to migratory birds. The
ban did not apply to agricultural, home lawn
or commercial establishment uses.
Dibenzofurans— A group
of organic compounds, some of which are toxic.
Dicofol— A pesticide used
on citrus fruits.
Diffused Air— A type of
aeration that forces oxygen into sewage by
pumping air through perforated pipes inside
a holding tank.
Diffusion— The movement
of suspended or dissolved particles (or molecules)
from a more concentrated to a less concentrated
area. The process tends to distribute the
particles or molecules more uniformly.
Digester— In wastewater
treatment, a closed tank; in solid-waste conversion,
a unit in which bacterial action is induced
and accelerated in order to break down organic
matter and establish the proper carbon to
Digestion— The biochemical
decomposition of organic matter, resulting
in partial gasification, liquefaction, and
mineralization of pollutants.
Dike— A low wall that
can act as a barrier to prevent a spill from
Diluent— Any liquid or
solid material used to dilute or carry an
Dilution Ratio— The relationship
between the volume of water in a stream and
the volume of incoming water. It affects the
ability of the stream to assimilate waste.
Dimictic— Lakes and reservoirs
that freeze over and normally go through two
stratifications and two mixing cycles a year.
Dinocap— A fungicide used
primarily by apple growers to control summer
diseases. EPA proposed restrictions on its
use in 1986 when laboratory tests found it
caused birth defects in rabbits.
Dinoseb— A herbicide that
is also used as a fungicide and insecticide.
It was banned by EPA in 1986 because it posed
the risk of birth defects and sterility.
Dioxin— Any of a family
of compounds known chemically as dibenzo-p-dioxins.
Concern about them arises from their potential
toxicity as contaminants in commercial products.
Tests on laboratory animals indicate that
it is one of the more toxic anthropogenic
Direct Discharger— A municipal
or industrial facility which introduces pollution
through a defined conveyance or system such
as outlet pipes; a point source.
Direct Filtration— A method
of treating water which consists of the addition
of coagulent chemicals, flash mixing, coagulation,
minimal flocculation, and filtration. Sedimentation
is not uses.
Direct Push— Technology
used for performing subsurface investigations
by driving, pushing, and/or vibrating small-diameter
hollow steel rods into the ground/ Also known
as direct drive, drive point, or push technology.
Direct Runoff— Water that
flows over the ground surface or through the
ground directly into streams, rivers, and
Discharge— Flow of surface
water in a stream or canal or the outflow
of ground water from a flowing artesian well,
ditch, or spring. Can also apply tp discharge
of liquid effluent from a facility or to chemical
emissions into the air through designated
Disinfectant— A chemical
or physical process that kills pathogenic
organisms in water, air, or on surfaces. Chlorine
is often used to disinfect sewage treatment
effluent, water supplies, wells, and swimming
A compound formed by the reaction of a disinfenctant
such as chlorine with organic material in
the water supply; a chemical byproduct of
the disinfection process.
Disinfectant Time— The
time it takes water to move from the point
of disinfectant application (or the previous
point of residual disinfectant measurement)
to a point before or at the point where the
residual disinfectant is measured. In pipelines,
the time is calculated by dividing the internal
volume of the pipe by he maximum hourly flow
rate; within mixing basins and storage reservoirs
it is determined by tracer studies of an equivalent
Dispersant— A chemical
agent used to break up concentrations of organic
material such as spilled oil.
Saving realized by displacing purchases of
natural gas or electricity from a local utility
by using landfill gas for power and heat.
products, other items, and packaging used
once or a few times and discarded.
Disposal— Final placement
or destruction of toxic, radioactive, or other
wastes; surplus or banned pesticides or other
chemicals; polluted soils; and drums containing
hazardous materials from removal actions or
accidental releases. Disposal may be accomplished
through use of approved secure landfills,
surface impoundments, land farming, deep-well
injection, ocean dumping, or incineration.
Disposal Facilities— Repositories
for solid waste, including landfills and combustors
intended for permanent containment or destruction
of waste materials. Excludes transfer stations
and composting facilities.
Dissolved Oxygen (DO)—
The oxygen freely available in water, vital
to fish and other aquatic life and for the
prevention of odors. DO levels are considered
a most important indicator of a water body’s
ability to support desirable aquatic life.
Secondary and advanced waste treatment are
generally designed to ensure adequate DO in
Dissolved Solids— Disintegrated
organic and inorganic material in water. Excessive
amounts make water unfit to drink or use in
Distillation— The act
of purifying liquids through boiling, so that
the steam or gaseous vapors condense to a
pure liquid. Pollutants and contaminants may
remain in a concentrated residue.
Disturbance— Any event
or series of events that disrupt ecosystem,
community, or population structure and alters
the physical environment.
Diversion— 1. Use of part
of a stream flow as water supply. 2. A channel
with a supporting ridge on the lower side
constructed across a slope to divert water
at a non-erosive velocity to sites where it
can be used and disposed of.
Diversion Rate— The percentage
of waste materials diverted from traditional
disposal such as landfilling or incineration
to be recycled, composted, or re-used.
DNA Hybridization— Use
of a segment of DNA, called a DNA probe, to
identify its complementary DNA; used to detect
Dobson Unit (DU)— Units
of ozone level measurement. measurement of
ozone levels. If, for example, 100 DU of ozone
were brought to the earth’s surface
they would form a layer one millimeter thick.
Ozone levels vary geographically, even in
the absence of ozone depletion.
Pesticide application in and around houses,
office buildings, motels, and other living
or working areas.
Dosage/Dose— 1. The actual
quantity of a chemical administered to an
organism or to which it is exposed. 2. The
amount of a substance that reaches a specific
tissue (e.g. the liver). 3. The amount of
a substance available for interaction with
metabolic processes after crossing the outer
boundary of an organism.
Dose Equivalent— The product
of the absorbed dose from ionizing radiation
and such factors as account for biological
differences due to the type of radiation and
its distribution in the body in the body.
Dose Rate— In exposure
assessment, dose per time unit (e.g. mg/day),
sometimes also called dosage.
Dose Response— Shifts
in toxicological responses of an individual
(such as alterations in severity) or populations
(such as alterations in incidence) that are
related to changes in the dose of any given
Dose Response Curve— Graphical
representation of the relationship between
the dose of a stressor and the biological
1. Estimating the potency of a chemical. 2.
In exposure assessment, the process of determining
the relationship between the dose of a stressor
and a specific biological response. 3. Evaluating
the quantitative relationship between dose
and toxicological responses.
The quantitative relationship between the
amount of exposure to a substance and the
extent of toxic injury or disease produced.
Dosimeter— An instrument
to measure dosage; many so-called dosimeters
actually measure exposure rather than dosage.
Dosimetry is the process or technology of
measuring and/or estimating dosage.
DOT Reportable Quantity—
The quantity of a substance specified in a
U.S. Department of Transportation regulation
that triggers labeling, packaging and other
requirements related to shipping such substances.
Downgradient— The direction
that groundwater flows; similar to “downstream”
for surface water.
Industries dependent on crop production (e.g.
canneries and food processors).
DP Hole— Hole in the ground
made with DP equipment.
Draft— 1. The act of drawing
or removing water from a tank or reservoir.
2. The water which is drawn or removed.
Draft Permit— A preliminary
permit drafted and published by EPA; subject
to public review and comment before final
action on the application.
Drainage— Improving the
productivity of agricultural land by removing
excess water from the soil by such means as
ditches or subsurface drainage tiles.
Drainage Basin— The area
of land that drains water, sediment, and dissolved
materials to a common outlet at some point
along a stream channel.
Drainage Well— A well
drilled to carry excess water off agricultural
fields. Because they act as a funnel from
the surface to the groundwater below. Drainage
wells can contribute to groundwater pollution.
Drawdown— 1. The drop
in the water table or level of water in the
ground when water is being pumped from a well.
2. The amount of water used from a tank or
reservoir. 3. The drop in the water level
of a tank or reservoir.
Dredging— Removal of mud
from the bottom of water bodies. This can
disturb the ecosystem and causes silting that
kills aquatic life. Dredging of contaminated
muds can expose biota to heavy metals and
other toxics. Dredging activities may be subject
to regulation under Section 404 of the Clean
Drilling Fluid— Fluid
used to lubricate the bit and convey drill
cuttings to the surface with rotary drilling
equipment. Usually composed of bentonite slurry
or muddy water. Can become contaminated, leading
to cross contamination, and may require special
disposal. Not used with DP methods
Drinking Water Equivalent Level—
Protective level of exposure related to potentially
non-carcinogenic effects of chemicals that
are also known to cause cancer.
Drinking Water State Revolving
Fund— The Fund provides capitalization
grants to states to develop drinking water
revolving loan funds to help finance system
infrastructure improvements, assure source-water
protection, enhance operation and management
of drinking-water systems, and otherwise promote
local water-system compliance and protection
of public health.
Drive Casing— Heavy duty
steel casing driven along with the sampling
tool in cased DP systems. Keeps the hole open
between sampling runs and is not removed until
last sample has been collected.
Drive Point Profiler—
An exposed groundwater DP system used to collect
multiple depth-discrete groundwater samples.
Ports in the tip of the probe connect to an
internal stainless steel or teflon tube that
extends to the surface. Samples are collected
via suction or airlift methods. Deionized
water is pumped down through the ports to
prevent plugging while driving the tool to
the next sampling depth.
Drop-off— Recyclable materials
collection method in which individuals bring
them to a designated collection site.
Active withdrawal of both liquid and gas phases
from a well usually involving the use of a
Dump— A site used to dispose
of solid waste without environmental controls.
Duplicate— A second aliquot
or sample that is treated the same as the
original sample in order to determine the
precision of the analytical method.
Dustfall Jar— An open
container used to collect large particles
from the air for measurement and analysis.
Dynamometer. A device used to
place a load on an engine and measure its
Dystrophic Lakes— Acidic,
shallow bodies of water that contain much
humus and/or other organic matter; contain
many plants but few fish.