Office of Solid Waste EPA 9902.3-1 a
and Emergency Response July 1992
Washington, DC 20460 PB92-963614
Office of Waste Programs Enforcement
&EPA Corrective Action Glossary
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EPA 9902.3-la
April 1992
CORRECTIVE ACTION GLOSSARY
Office of Solid Waste and Emergency Response
Office of Waste Programs Enforcement
U.S. Environmental Protection Agency
401 M St. S.W.
Washington, D.C. 20460
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NOTICE
This document has been reviewed in accordance with U.S. Environmental Protection
Agency policy and approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
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CORRECTIVE ACTION GLOSSARY
INTRODUCTION
This glossary of technical terms was prepared to facilitate the use of the Correc-
tive Action Plan (CAP) issued by OSWER on November 14, 1986. The CAP presents
model scopes of work for all phases of a corrective action program, including the RCRA
Facility Investigation (RFI), Corrective Measures Study (CMS), Corrective Measures
Implementation (CMI) and interim measures.
Many technical terms are used in the CAP (e.g., matrix-spike, surrogate samples,
attenuation capacity, hydraulic conductivity, etc.). The Corrective Action Glossary
includes brief definitions of the technical terms and explains how they are used (e.g.,
field blanks are used to determine whether contamination is introduced through the
sample collection activities or from the sampling environment). In addition, expected
ranges (where applicable) are provided (e.g., hydraulic conductivity for sandy soil is
expected to be 1x10"* cm/sec). Parameters or terms not discussed in the CAP, but
commonly associated with site investigations or remediations are also included.
This document is not intended as a stand-alone site investigation/remediation
guidance, but as a supplement to other guidance such as the RCRA Facility Investigation
(RFI) Guidance (OSWER Directive 9502-00-6D). RCRA guidance documents can be
ordered by contacting the RCRA Docket Information Center, U.S. EPA, Washington,
D.C., (202) 260-9327 or the Center for Environmental Research Information (CERI) in
Cincinnati, Ohio, (513) 569-7562 or (FTS) 684-7562.
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CONTENTS
Section Page
Notice ii
INTRODUCTION 3
GLOSSARY 4
APPENDICES 48
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GLOSSARY
Absorption
Description: Penetration of a substance into another. Commonly used to refer to
absorption of a gas by a liquid.
Application: Examples include: (1) infusion of oxygen into (subsurface) water for
bioremediation; (2) absorption of TCE by leachate; (3) scrubbing or removing gases (for
example, SOX, NOX, CH4) by a liquid solvent to purify a gas stream before venting the
gas stream to the atmosphere.
Adsorption
Description: A two-dimensional process in which one substance is attracted to and
adheres on the surface of a solid substance such as unsaturated soil, aquifer material, or
activated carbon. Typically, chemicals move to a solid phase from a fluid phase that may
be water, gas, or non-aqueous phase liquid (NAPL). Rate and extent of adsorption
depends upon characteristics of the adsorbing agent as well as the chemical(s) and the
phase in which the chemical occurs, and therefore generally are measured in laboratory
or field tests. In some cases adsorption may be reversed and the adsorbed material may
move into a fluid phase from a solid phase, referred to as desorption or stripping.
Application: Adsorption of a chemical from a water phase by an adsorbing agent such
as subsurface aquifer material is commonly used to evaluate efficacy of pump and treat
remediation. The following quantitative relationship is used: Kd = CJC^ where Kd is
the partition coefficient that expresses relative concentration of a chemical in soil, Cs is
defined as concentration of chemical in the soil phase (mg/gm), and Cw is defined as
concentration of chemical in the water phase (mg/ml). Thus, units of Kd are ml/gm.
The value of Kd is often used to evaluate the effect of adsorption on retardation of rate
of movement of a chemical compared with rate of movement of water in the subsurface.
The relevant expression is: R = 1 + r Kd/n, where R is a retardation factor which
quantitatively expresses the ratio of velocity of water to velocity of the chemical, r is the
bulk density, Kd is the partition coefficient, and n is the porosity of aquifer material. As
an example, for a specific chemical/aquifer system with values for r of 1.4 gm/ml, Kd of
10 ml/gm, and n of 0.30, the value of R is 47.7, indicating that water will move by
advection through the subsurface at a rate that is 47.7 times faster than the rate of
movement of the chemical. Therefore, the volume of water required to remove the
chemical during pump and treat would be 47.7 more than one pore volume of aquifer
material to remove the chemical. Concerning metals, adsorption generally increases with
increasing pH; however, adsorption of arsenate and arsenite forms will generally increase
with decreasing pH.
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Adsorbing agent [adsorbent]
Description: A substance that has the ability to condense or hold molecules of other
substances on its surface.
Application: Examples include: (1) soil materials acting as adsorbing agents for
chemicals present in water (leachate) and gas phases in unsaturated and saturated
subsurface environments; (2) activated carbon used as an adsorbing agent to "scrub"
volatile organic chemicals present in off-gas emissions as a result of air stripping of
contaminated ground water.
Adsorbing reagent
Description: An adsorbing agent used to detect or measure molecules that sorb on its
surface.
Application: For example, Draeger tubes, used in field sampling and analysis, contain an
adsorbing agent that colorimetrically indicates concentrations of volatile organic
compounds.
Alkalinity [of water]
Description: Acid-neutralizing capacity of a water. Alkalinity is a measure of capacity of
water to neutralize acids. It is primarily a function of bicarbonate, carbonate, and
hydroxide content. Alkalinity, usually expressed as milligrams/liter (mg/L) of calcium
carbonate (CaCO3), is a measure of buffering capacity (resistance to alteration in pH) of
water. Most natural waters have substantial buffering capacity through dissolution of
carbonate-bearing minerals creating a carbonate/bicarbonate buffer system. Some
components of alkalinity will combine with toxic heavy metals and greatly reduce their
toxicity.
Application: Alkalinity is a widely used indicator to characterize water; it may also help
define an appropriate treatment for wastes. The pH of waters with low alkalinity are
more easily modified. This is useful when lowering pH is desirable (i.e., in order to
leach many metals in the process of soil washing or flushing), or conversely, increasing
pH in order to precipitate metals in the process of immobilization or attenuation.
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Appendix VIII constituents
Description: Appendix VIII in 40 CFR Part 261 is EPA's list of RCRA hazardous
constituents. It is comprised of chemicals which have toxic, carcinogenic, mutagenic or
teratogenic effects on humans or other life forms. It includes chemicals from the priority
pollutants list under the Clean Water Act, chemicals considered hazardous to transport
under Department of Transportation, chemicals identified as carcinogens by EPA's
Carcinogen Assessment Group, and chemicals which have a high acute toxicity as
identified by NIOSH's Registry of Toxic Effects of Chemical Substances list. There are
currently 418 chemicals or classes of chemicals on Appendix VIII.
Application: The main purpose of Part 261, Appendix VIII is to identify the universe of
chemicals of concern under RCRA. EPA uses Appendix VIII to determine if a waste
contains hazardous constituents and therefore should be considered for listing under 40
CFR Section 261.11 (Appendix VIII, however, should not be used by a generator
identifying hazardous waste under Part 261, Subparts C & D. Appendix VIII is much
broader than the actual hazardous waste lists in 40 CFR Sections 261.31-261.33.).
Owners/operators of RCRA facilities use Appendix VIII for hazardous waste analysis
before incineration and when demonstrating clean-closure.
Appendix IX constituents
Description: Appendix IX in Part 264 is comprised of those constituents on the Part 261
Appendix VIII list, for which it is feasible to analyze in ground-water samples, plus 17
chemicals routinely monitored in the Superfund program.
Application: Pursuant to 40 CFR Part 264, Subpart F Ground-Water Monitoring
requirements, owner/operators of land-based hazardous waste disposal facilities that
have shown statistically significant increases over background concentrations for indicator
parameters, waste constituents, or reaction products, must analyze samples from all
monitoring wells at the compliance point to determine where Appendix IX constituents
are present and at what concentrations. This analysis must be conducted at least
annually.
ASTM classification [of soil]
Description: Definitions of soil types developed by the American Society for Testing and
Materials (ASTM). These definitions are primarily based on soil grain size, plasticity,
and strength.
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Application: This information aids in estimating effects of a soil on infiltration and
retardation of chemicals and leachates and can give an indication of hydraulic
conductivity. For example, retardation of a chemical generally increases as clay content
increases. Greater hydraulic conductivity makes it more feasible to introduce materials
such as water, air, oxygen, etc., to accomplish remediation using pump and treat, soil
washing and flushing, bioremediation, soil vacuum extraction, etc.
Atmospheric pressure
Description: Pressure exerted by air, also known as barometric pressure. This pressure is
14.696 pounds per square inch (psi) at sea level, where it will support a column of
mercury 760 mm high (approximately 30 inches). Atmospheric pressure decreases with
altitude.
Application: Atmospheric pressure affects water levels in piezometers under confined
conditions, and should be considered when measuring water levels in a confined system.
Changes in atmospheric pressure can also affect soil gas migration, and may result in
"barometric pumping" of volatile chemicals out of surface soils into the atmosphere.
Attenuation capacity
Description: Ability or tendency of a hydrogeologic unit to retard the transport rate, or
reduce concentrations of hazardous constituents migrating through the unit.
Contaminants present in soil or geologic materials with a low attenuation capacity are
transported greater distances over a given time than in materials with a high attenuation
capacity. While slow-moving contaminants may take longer to reach a receptor, high
attenuation capacity may also increase time and cost required to achieve cleanup criteria.
Application: Attenuation capacity often refers to ability of subsurface systems to
immobilize metals. Attenuation capacities are indicated by high cation exchange
capacity (CEC), high clay content, and high organic matter (OM) or organic carbon
(OC).
Bacteria
Description: Microscopic, usually single-celled, prokaryotic organisms which reproduce
by binary fission. Bacteria play an important role in ecological processes, and are
characterized by very diverse metabolic capabilities. The vast majority of bacteria are
harmless or beneficial to man; many are essential.
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Application: Bacteria play a vital role in environmental processes. Their primary
function is to decompose or biodegrade complex organic molecules in nature. Therefore,
they are vital in carbon and nutrient cycling in natural systems. Bacteria are utilized in
treatment of both domestic and industrial wastes. Biodegradation of toxic or hazardous
wastes requires healthy populations of bacteria capable of metabolizing specific
molecules, (see Bioremediation)
Bench scale - see Treatability Studies
Bioaccumulation
Description: The processes whereby organisms remove contaminants present at non-
toxic levels from the surrounding environment, and accumulate or store these
contaminants in their tissues. Bioaccumulation often results in contaminant
concentrations within specific tissues or organs of exposed organisms which are much
higher than concentrations in the organism's surrounding environment (see
Bioconcentration). The concentration of contaminants often increases with each higher
step in the food chain as a result of bioaccumulation (see Biomagnification).
Application: Bioaccumulation should be considered when evaluating the impact of
releases on receptors and in migration pathways during risk assessments. Many organic
contaminants such as PCBs and pesticides tend to accumulate in fatty tissues. The
octanol:water partition coefficient (Kow) of an organic contaminant may indicate
tendency of a chemical to partition between fat tissue (assumed to be similar to octanol)
and water, and therefore indicate tendency to concentrate in body fat tissue after intake
from water or food. Metals such as mercury and lead also tend to accumulate in target
organs, and are often concentrated in bacterial or plant biomass.
Bioassay
Description: A test used to evaluate the biological effects of a chemical or a mixture of
chemicals by measuring its (their) effect on a living indicator organism.
Application: Bioassays are commonly used to evaluate the effect of chemical addition on
soil microbial activity, and therefore indicate potential adverse effect on bioremediation
processes. Commonly used bioassays include soil respiration measured as CO2 evolution,
dehydrogenase activity, and nitrification potential. A decrease in activity indicates
potential adverse effects on bioremediation rate and extent. Other tests that measure
toxic effects on non-soil organisms to assess the rate and extent of detoxification of a
waste/soil mixture include the Ames Salmonella typhimurium/mammalian microsome
mutagenicity test to measure aqueous and solid phase changes in mutagenicity, and the
Microtox assay to measure changes in the toxicity of leachate.
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Bioconcentration
Description: The result of bioaccumulation. Long-term exposure to contaminants which
bioaccumulate can lead to gradual increases in contaminants within individual organisms.
Concentration of contaminants in specific tissues or target organs can therefore increase
to toxic levels even though exposures are below acute toxicity thresholds. Common
locations where contaminants bioconcentrate include bacterial cell walls and inclusion
bodies, plant roots and leaves, and fatty tissues of animals (fat, liver, reproductive
organs)
Application: Extent of bioconcentration is useful in evaluating exposure scenarios in risk
assessment. This is usually done through quantitative calculation of bioconcentration
factors (BCF).
Bioconcentration Factor (BCF)
Description: Ratio of the concentration of the constituent in the whole body of an
organism (e.g., a fish) or specific tissue (e.g., fat, liver) to the concentration in water.
Application: Bioconcentration factors are often estimated to be proportional to the
octanol/water partition coefficient (kow). Constituents exhibiting a BCF greater that 1.0
indicate bioaccumulation, and thus potential magnification of risk. Generally,
constituents exhibiting a BCF greater than 100 cause the greatest concern.
Biochemical oxygen demand (BOD)
Description: BOD is the amount of dissolved oxygen required to meet the metabolic
needs of aerobic microorganisms in water high in organic matter, such as sewage. While
BOD measures only biodegradable organics, non-biodegradable materials can exert a
demand on the available oxygen in an aquatic environment. BOD may be a useful
indicator parameter if a release is due primarily to degradable organic wastes. National
Pollution Discharge Elimination System (NPDES) effluent discharge limits for BOD are
industry specific.
Application: BOD is measured quantitatively as mg/L of oxygen required to satisfy the
oxygen demand of chemicals present in a liter of water, and is usually reported as oxygen
requirement over a 5-day period (i.e., BOD5). A major assumption is often made that
the consumption of oxygen by microorganisms in the presence of a chemical is an
indication of the biodegradation of the chemical. The relative aerobic biodegradability
of chemicals may be ranked using BOD5 to indicate the relative oxygen demand.
Chemicals that may be biodegradable at a low concentration may be toxic to
microorganisms at the concentration used in the BOD5 test and, therefore, may not
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biodegrade under test conditions. Industrial and other hazardous chemicals may be
biodegradable, but require bacterial seeds adapted to the compounds before yielding an
accurate BOD test.
Biodegradability
Description: Tendency of a substance to break down or decompose as a result of the
metabolic activities of microorganisms. Factors that affect biodegradability of
contaminants include chemical characteristics (concentration, molecular structure, and
toxicity of the contaminants), and environmental characteristics (moisture content,
presence or absence of oxygen or other electron acceptors in the soil, availability of
contaminants to micro-organisms, availability of other organic and inorganic nutrients for
metabolism, and other factors such as pH and temperature), and microbial
characteristics (microbial populations and microbial adaptation or acclimation).
Transformation products often have different physical, chemical and/or toxicological
characteristics than the original contaminants. These products also may be hazardous
constituents and should be considered in developing monitoring programs.
Application: Biodegradability potential of a compound is important in determining
feasibility of using bioremediation as a treatment technology. The greater the
biodegradation potential of a compound, the greater is the susceptibility of the
compound to a bioremediation process. Biodegradability is often expressed
quantitatively as "half-life", or time required to decrease chemical concentration by 50%.
Most commonly, half-life is calculated based on a first-order kinetic model as follows: t^2
= -0.693/k, where t^2 is the half-life value, -0.693 is the natural logarithm of 0.5, and k is
the slope of the line describing decrease in concentration of a chemical with increase in
time of reaction. Half-life values are calculated for specific chemical/environmental
conditions as described above. Shorter half-lives indicate higher biodegradation
potential. Estimates of aerobic biodegradability for several compounds are provided in
Table 3 of Appendix 1.
Biomagnification
Description: Increasing concentration of contaminants with each higher step in
ecosystem food chains as a result of bioaccumulation. Critical levels of contaminants
may occur within specific populations high in ecological food chains. Predators such as
raptors and fish therefore can receive much higher doses of contaminants than indicated
by ambient environmental concentrations.
Application: The classic example of biomagnification is the impact of the pesticide DDT
on bird-of-prey (raptor) populations. Reproductive failures in many raptor populations
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in the early 1960s were shown to be caused by high concentrations of DDT in
reproductive tissues. The source of DDT was traced to prey populations.
Bioremediation
Description: Includes any of a variety of engineered treatment alternatives which utilize
biological degradation or transformation of waste components to achieve remediation
goals. Bioremediation systems can be grouped into ex-situ and in-situ approaches.
Types of systems include solid (soil), aqueous (ground water, leachate), or mixed phase
(slurry, subsurface aquifer).
Application: Many contaminants are biodegradable under appropriate conditions.
Biodegradation represents a solution rather than a disposal technology; however, various
types of bioremediation systems are being evaluated as cost-effective alternative
technologies. Ex-situ treatment systems include prepared bed soil reactors, composting,
soil slurry bioreactors, bioreactors for extracted ground water, forced-air soil pile
approaches, etc. In-situ systems include surface soil systems, recirculating ground water
(saturated zone), bioventing (unsaturated zone), and combination approaches.
Performance evaluations for this area of developing technology are beginning to be
performed in full scale demonstrations.
Biotransformation [of the waste]
Description: Refers to partial alteration of a parent compound into intermediate
products by microorganisms. Intermediate products may be less or more toxic than the
parent compound. This is an important process to consider when selecting constituents
to monitor, as both parent and intermediate constituents may be transformed over time.
Samples generated from different phases of the subsurface in microcosm studies can be
analyzed for intermediate product generation and degradation in order to evaluate the
rate and extent of treatment of a parent compound.
Application: An example of a biotransformation reaction that results in formation of a
more toxic intermediate compound is the conversion, under anaerobic conditions, of
trichloroethylene (TCE) to vinyl chloride (VC). VC is a known human carcinogen and is
more persistent under anaerobic conditions than TCE. Under aerobic conditions, TCE
may be biotransformed to TCE-epoxide, an intermediate that is toxic to microorganisms
transforming TCE. Another example is biotransformation of polycyclic aromatic
hydrocarbons (PAHs) in the human liver and by some soil fungi to chemical epoxide
intermediates, which are mutagenic, but can be easily degraded biologically and
chemically through hydrolytic mechanisms.
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Blanks [analytical, quality assurance]
Description:
Equipment blanks (or rinsate blanks) - Laboratory-distilled, deionized water that
is poured through decontaminated field equipment and then collected in sample
bottles for analysis. Equipment blanks are used to determine whether
contamination was introduced from sample collection equipment.
Field blanks A water sample collected for analysis by placing laboratory
distilled, deionized water directly into a sample container in the field during and
at the location of field samples. Field blanks are used to determine whether
contamination is introduced from sample containers or sampling methodology,
such as contact with air.
Method blanks - Laboratory-distilled, deionized water that is subjected to the
same laboratory procedures as samples. Method blanks are prepared and
analyzed in the laboratory to determine whether contamination is introduced from
the analytical process.
Trip blanks Laboratory-distilled, deionized water in a sample container that
accompanies empty sample bottles to the field as well as samples returning to the
laboratory for analysis. Trip blanks are used to determine whether contamination
was introduced to the sample from air on the site or during shipping or storage.
Bulk density
Description: Mass of dry soil per unit volume, including air space. Bulk density values
are affected by soil structure (for example, degree of compaction) and texture (for
example, clay content and type). Dry bulk density values are typically 1.6 - 1.8 g/cm3for
sandy soils, 1.3 - 1.6 g/cm3 for loamy soils, and 1.0-1.3 g/cm3 for clayey soils and soils
high in organic content.
Application: Bulk density values can give an indication of porosity of a soil, which is
important in evaluation of permeability and in selection of remedial technologies.
Porosity is calculated by: % Porosity = (1 - Bulk Density/Particle Density) x 100, where
particle density is defined as dry mass of soil particles divided by solid (not bulk) volume
of the particles. Bulk density values are also used in calculation/characterization of
retardation of contaminants (See Adsorption).
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Calibration gases [zero and span]
Description: Gases used to calibrate sampling or analytical equipment.
Application: A zero gas is a gas that has been certified as being free from contaminants
being measured; this gas is used to ensure that the scale on the instrument being
calibrated reads zero when no contaminants are present. A span gas is a standard gas
whose properties are well-known, and which is present at a known concentration; this gas
is used to ensure that the analyzer instrument is set for the concentration range of
contaminants to be measured.
Cation
Description: An ion having a positive charge (such as an oxidized metal) with a
tendency to attract anions and/or negative ends of molecules.
Application: Many metals are cations (for example, lead, zinc, trivalent mercury, and
cadmium). Quantitative application with regard to attenuation and treatment is in the
measurement of cation exchange capacity (CEC).
Cation exchange capacity (CEC)
Description: Ability of a formation or material to adsorb positively charged atoms or
molecules such as metal ions. For example, CEC typically ranges from 5 to more than
200 milliequivalents per 100 grams of subsurface material (meq/100 grams).
Application: CEC aids in predicting contaminant movement through soils and
availability of contaminants to geological systems. CEC is an important factor in
evaluating transport of lead, cadmium, and other toxic metals. Soils with a high CEC
will generally retain correspondingly high levels of these inorganics.
Chemical oxygen demand (COD)
Description: A measure of chemically oxidizable material in water or wastewater,
including organic as well as some inorganic chemicals such as sulfides. COD, generally
expressed as mg/L, may be a useful indicator parameter if a release is due primarily to
degradable organic wastes. NPDES effluent discharge limits for COD are industry
specific.
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Application: COD is generally used in combination with BOD5 values. COD may be
used to indicate presence of organic chemicals that are more recalcitrant or refractory to
microorganisms, and therefore are not reflected in the BOD5 test. When COD values
are high and BOD values are low for a sample, the waste may contain complex organic
chemicals that require treatment through physical or chemical processes rather than
through biological treatment.
Chemical transformation
Description: Chemical degradation processes, including chemical oxidation, reduction,
hydrolysis and photolysis, that change a chemical into one or more new chemical species.
This factor is important in evaluating fate of chemicals in the environment and should be
considered in designing sampling and analysis programs (see photolysis and hydrolysis).
Application: Chemical transformation may represent the major initial or subsequent
degradation pathways for many chemicals, and should be measured in treatability studies
in order to assess efficacy of utilizing chemical treatment methods. Chemical
transformations through hydrolysis are important for many pesticides as well as epoxides
or chlorinated aliphatic compounds. For example, TCE-epoxide can be easily hydrolyzed
in ground water and soil environments. Photolysis reactions are important for many
chemicals volatilizing into the atmosphere or present at the surface of soil.
Concentration profiles
Description: Graphical representations of the horizontal and vertical locations
(distribution) of contaminant concentration levels on maps and cross sections.
Application: Concentration profiles are prepared as part of site characterization
activities, and indicate the relative homogeneity or heterogeneity of contamination at a
site. These profiles help illustrate the nature^ degree, and extent of contamination.
Based on this information, strategies are developed for placement of injection and
extraction wells for treatment as well as for monitoring well locations in order to match
treatment location with contamination location.
Conductivity [electrical, of water]
Description: A measure of the capacity of a water to conduct electric current (Also
known as specific conductance). Conductivity generally rises with increased concentration
of dissolved (ionic) species. The nature of dissolved substances, their actual and relative
concentrations, temperature, and ionic strength of the water sample affect specific
conductance. Conductivity is expressed as micromhos/cm.
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Application: Variations in specific conductance may indicate presence of contamination
release points. Waters with high salinities or high total dissolved solids can be expected
to exhibit high conductivity. The RCRA Ground-Water Monitoring Technical
Enforcement Guidance Document (September 1986, OSWER 9950.1) recommends using
conductivity as a real-time indicator of the representativeness of monitoring well water to
formation ground water. This application may be used when purging monitoring wells to
ensure collection of a representative sample.
Range of Values of Conductivity
Water Type
Freshly distilled water
Raw and finished waters
Highly mineralized water
Value (micromhos/cm)
0.5-2.0
50 - 500
500 - 1,000
Control charts [laboratory, process]
Description: A graphical plot of test results to allow analysis and interpretation of
fluctuations of measurements on successive random samples. Control charts are based
on means and standard deviations derived from repetitious analysis of known quality
control standards. Control charts indicate whether the process or analytical method is in
control with respect to defined parameters.
Application: Control charts are used typically in chemical laboratories for verification of
quality of results. Quality assurance samples are analyzed on a regular frequency to test
validity of the method. Control charts are used in process monitoring over time, and are
important in ensuring internal quality control.
Demographics
Description: Vital statistics of human populations, including size, growth, density, and
distribution.
Application: This information aids in estimating human exposure to potential or actual
releases of contaminants, and therefore is used in risk assessment and risk management
models.
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Dense non-aqueous phase liquid (DNAPL)
Description: A liquid that is not miscible with water and has a density greater than
water (> 1.0 gm/ml). Examples include chlorinated solvents such as trichloroethylene
(TCE), tetrachloroethylene (PCE), 1,1,1-trichloroethane (TCA), carbon tetrachloride,
pentachlorophenols, dichlorobenzene, and creosote wood treating oils. (See LNAPL and
Density). DNAPLs may be present in the unsaturated as well as saturated zone. The
presence of DNAPLs complicates site characterization and generally decreases efficiency
of pump and treat systems in recovering subsurface contamination. The high density of
DNAPLs provides a driving force that can carry product deep into aquifers.
Application: With regard to site characterization, DNAPLs may be present in the
unsaturated zone in four phases: gaseous, solid, aqueous, and immiscible hydrocarbon
(DNAPL). For example, TCE introduced into the subsurface as a DNAPL may partition
onto soil, volatilize into soil gas, and solubilize into the water phase, resulting in
contamination of all four phases. In the saturated zone, TCE may also be present in the
solid, aqueous, and immiscible phases, but would not be present in a gas phase.
Information concerning chemical properties, therefore, is important for designing site
characterization plans and for taking site samples. The combination of high density and
low viscosity is important with regard to transport of DNAPLs in the subsurface.
Subsurface drains have been used for recovery of DNAPLs from relatively shallow
aquifers (approximately 20 feet below ground surface). A DNAPL recovery drainline is
placed below a water table depression drainline, and both lines are pumped to
accomplish in situ subsurface separation of oil and water.
Care must be taken when monitoring DNAPL in pools. For example, if the well
screen is located entirely in the DNAPL layer, the DNAPL will rise in the well if the
hydrostatic head of water is reduced by pumping or bailing. If the well screen extends
into the barrier layer, the DNAPL measured thickness will exceed that in the formation
by the length of the well below the barrier surface. Both of these scenarios will result in
a greater DNAPL thickness in the well and thus a false indication (overestimation) of
the actual DNAPL thickness will result (EPA 540/4-91/002).
Density
Description: Mass of a material contained in a specific volume. Generally expressed in
units of grams/cubic centimeter (g/cc). Density of a compound indicates whether the
compound is heavier or lighter than water. (Density of water is approximately 1.0 g/cc -
see Specific gravity). Liquid compounds with densities greater than 1.0 g/cc and of only
limited water solubility are referred to as dense non-aqueous phase liquids (see
DNAPLs) and may migrate vertically under influence of gravity. Liquid compounds with
densities less than water and of only limited water solubility are referred to as light non-
aqueous phase liquids (see LNAPLs).
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Application: Density information may be used to determine where a chemical spill or
release is likely to be found in the subsurface. DNAPLs may migrate downward under
influence of gravity until an impermeable layer is encountered. LNAPLs tend to remain
associated with the top of a water table and become smeared throughout a zone as a
result of water table fluctuation. Therefore, density information may be used to identify
where a waste is likely to migrate or be located in the subsurface. Values for this
parameter for selected contaminants are provided in Table 3 of Appendix 1.
Deposition area
Description: Physical location(s) where particles of contaminants, sediment, etc.
suspended in water (or air) fall out of suspension.
Application: Knowledge of past depositional environments helps identify stratigraphic
features that may influence contaminant migration. This information aids in identifying
and evaluating past and current releases to ground water, surface-water, or air migration
pathways.
Discharge [of ground water]
Description: Removal of water from the saturated zone to areas of discharge.
Generally, discharge areas are topographical lows at or near the surface of the land (i.e.,
streams, springs, wetlands, etc.). Discharge occurs in response to differences in hydraulic
head.
Application: This information helps determine ground-water flow direction and define
potential contaminant migration pathways. Ground water flows from areas of high
hydraulic pressure (head) toward areas of lower hydraulic pressure.
Dissolved oxygen (DO) profiles
Description: Graphical representation of dissolved oxygen as a function of depth or area
in lakes, rivers, ground water, unsaturated soil systems, etc., to obtain representative in
situ conditions which characterize redox status of the system. Dissolved oxygen is
generally expressed as mg/L or as percent of saturation. Profiles can be used to monitor
conditions at a specific point in time, or to monitor changes over time. Generally for
surface water, dissolved oxygen concentrations of less than 4 mg/L are not adequate to
support most aquatic life. In unpolluted surface water, oxygen is usuall}' present in
concentrations of 8 mg/L or more. In unsaturated soils, a minimum air-filled pore space
of 10 percent is usually required for aerobic metabolism. Polluted ground-water systems
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are often depleted of oxygen as a result of bacterial degradation of the contaminants and
minimal re-aeration potential.
Application: Dissolved oxygen profiles may indicate presence of anaerobic or anoxic
zones where aerobic degradation may be inhibited. DO profiles may be used for
monitoring and sampling purposes. For example, when DO values at a contaminated
aquifer site increase from near zero to near saturation levels (about 10 mg/L),
bioremediation may be near completion. Core sampling and analysis may then be used
to confirm that no contamination remains in aquifer materials. This approach also may
be useful at a site where bioremediation is used for unsaturated soils, i.e., when surface
soil bioremediation or bioventing is being applied to the site. DO profiles may also be
useful in delineating areas of contamination. Areas of low DO in either soil gas or
ground water may indicate high metabolic activity resulting from presence of
biodegrading contaminants.
Dynamic viscosity
Description: Dynamic viscosity provides an indication of the ease with which a
compound (in its pure form) will flow. Dynamic viscosity has dimensions of mass per unit
length per unit time. The dynamic viscosity of water is approximately 1.0 centipoise (cp).
Application: Mobility of a compound in its pure form is inversely proportional to its
dynamic viscosity. Mobility can be rated as high for compounds with values less than 0.6
cp, moderate for compounds with values between 0.6 and 1.0 cp, and low for compounds
with values greater than 1.0 cp. Dynamic viscosity values for selected contaminants are
provided in Table 3 of Appendix 1.
Evapotranspiration
Description: Combined water loss due to free-water and soil- moisture evaporation, and
plant transpiration. Along with surface runoff, evaporation must be subtracted from total
precipitation to determine infiltration rates.
Application: Evapotranspiration rates are used to calculate infiltration rates, which are
required for the assessment of contaminant transport processes (e.g., leaching) in the
vadose (unsaturated) zone and recharge potential to the ground water. Also,
augmentation of evapotranspiration through use of vegetation may represent an
approach for decreasing downward migration of chemicals toward ground water and
allow destruction of contaminants within the vadose zone by chemical and/or biological
processes.
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Exchange capacity See Cation exchange capacity (CEC).
Flash point
Description: Lowest temperature at which a liquid or volatile solid gives off sufficient
vapor to form an ignitable mixture with air.
Application: RCRA regulations in 40 CFR Part 261.21 use the flash point to determine
whether certain wastes exhibit the hazardous waste characteristic of ignitability. A liquid,
other than certain aqueous wastes, having a flash point less than 60° C (140° F) is a
RCRA hazardous waste.
Floodplain
Description: Area bordering a stream or river that becomes flooded when the stream or
river overflows its channel. These areas are typically defined as 10-, 50- and 100-year
floodplains.
Application: Delineation of a floodplain aids in evaluating potential for washout,
potential release to the surface-water migration pathway, design of remedial actions, and
assessment of siting of treatment, storage, or disposal facilities.
Freeboard
Description: Vertical distance between the brim of an open-topped tank or surface-
impoundment and surface of the waste contained in the tank or surface impoundment.
Application: RCRA regulations for hazardous waste tank systems and surface
impoundments (40 CFR Parts 264 and 265, Subparts J and K, respectively) require
owners or operators to maintain sufficient freeboard in uncovered tanks and surface
impoundments to prevent overtopping by wave or wind action or by precipitation.
Henry's Law
Description: Describes solubility of a gas in equilibrium with a liquid quantitatively as
Henry's law constant. Equilibrium partial pressure of a contaminant in air is
proportional to the solution concentration of contaminant.
Application: Henry's Law is applied in evaluating the tendency of contaminants to
volatilize out of water into surrounding air.
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Henry's Law Constant
Description: Indication of the partitioning ratio of a chemical between air and water
phases at equilibrium. Henry's law constant is directly proportional to vapor pressure of
a compound and inversely proportional to water solubility of a compound. The larger the
value of Henry's law constant for a chemical, the greater is the tendency of the
constituent to volatilize from water surrounding soil particles into soil pore spaces or into
air above the ground surface. Henry's law constant is strongly influenced by
temperature; for example, for many volatile hydrocarbons, Henry's law constant increases
about threefold for every 10° C temperature rise.
Application: Compounds with higher Henry's law constants (greater than 10"3 atm-
m /mole) are amenable to treatment with vacuum extraction technologies. The Henry's
law constant should also be considered in assessing potential for natural inter-media
transport of constituents from soil gas to the air. Henry's Law constant values for
selected contaminants are provided in Table 3 of Appendix 1.
Hydraulic Conductivity
Description: A measure of soil or aquifer permeability (i.e., the ease with which water
at the prevailing viscosity will flow through soil or aquifer materials.) Hydraulic
conductivity is dependent on porosity, grain size, sorting, consolidation, cementation,
fracturing, and other soil and rock factors. Units are commonly given as
centimeters/second, gallons per day/square foot, feet/day, or meters/day. Saturated
hydraulic conductivity occurs when all of the pore space (porosity) is filled with fluid,
generally water, and is a constant for a given system. Unsaturated hydraulic conductivity
occurs when part of the pore space is filled with air and therefore the available cross-
sectional area available for water flow is reduced. Consequently unsaturated hydraulic
conductivity is a function of water content and is always less than saturated hydraulic
conductivity for the same subsurface material. Appendix 2 provides hydraulic conductivity
unit conversions.
Application: Hydraulic conductivity is used to evaluate flow through porous media using
Darcy's Law, Q = -KA (dh/dl), where Q is in units of volume/time, K is the hydraulic
conductivity (length/time), A is the cross-sectional area for flow (distance2), and (dh/dl)
is the hydraulic gradient. The negative sign indicates that flow is in the direction of
decreasing gradient (decreasing hydraulic head). An aquifer or unsaturated soil of high
conductivity will allow greater fluid flow (water or air ) and also greater free product
recovery than a subsurface characterized by low hydraulic conductivity for a given
hydraulic gradient. However, contaminant transport and spreading will also be
correspondingly greater with greater hydraulic conductivity unless the hydraulic gradient
is zero. A value for hydraulic conductivity lower than 10"6 cm/sec will limit the efficacy
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of pump and treat for remediation; a value lower than 10"5 cm/sec will limit the efficacy
of soil flushing and in situ bioremediation.
jjangg of Typical Values of Hydraulic Conductivity
Geologic Formation cm/s
Unconsolidated Deposits:
Gravel 10'1 - 102
Sand lO'5 - 1
Silt 10"7 - ID'3
Clay 10"10 - lO'7
Rocks:
Permeable basalt 10" - 1
Karst limestone 10"4 - 1
Sandstone 10"8 - W4
Limestone, dolomite 10" - 10
Shale 10"11 10"7
Fractured igneous and
metamorphic rocks 10"6 - 10"2
Unfractured igneous and
metamorphic rocks 10"12 10"8
Hydraulic Gradient
Description: Change in static head per unit distance in a given direction. The hydraulic
gradient defines direction of flow and may be expressed on maps of water level
measurements taken at a facility. Ground water flow velocity is directly related to
hydraulic gradient. Both vertical and horizontal gradients should be characterized.
Application: Hydraulic gradient information is used in conjunction with hydraulic
conductivity to determine the rate at which water will flow through an aquifer. Flow rate
may be increased by increasing the hydraulic gradient to move more water through the
subsurface for pump and treat or soil washing remediations, or for application of
nutrients for bioremediation. Conversely, flow may be decreased by decreasing the
hydraulic gradient to move water more slowly for containment or to reduce the further
spread of contamination on-site and off-site.
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Hydrolysis
Description: The chemical reaction of a compound with water or an aqueous solution to
form a new compound containing a carbon-oxygen bond.
Application: Hydrolysis is a significant environmental degradation process for many
organic chemicals and is dependent upon acidity and hydroxyl ion concentrations. For
example, hydrolysis of TCE-epoxide is an important environmental reaction in the
chemical degradation of TCE. This process should be considered in designing
remediation as well as sampling and analysis programs. The following table provides
examples of hydrolysis rates for specific compound types:
Range of Hydrolysis Values for Selected Compounds
Organic Compound Type Half-Life(average)
Alkyl and benzyl halides 2 hours
Epoxides 1 day
Aliphatic acid esters 6 days
Alkyl halides 9 days
Phosphoric acid/thiophosphoric acid esters 100 days
Carbamates 4 years
Aromatic acid esters 15 years
Polyhalomethanes 100 years
Phosphoric acid esters/Dialkylphosphonates 220 years
Amides 500 years
In situ methods
Description: Methods or technologies that can be used to remediate or analyze
contamination directly in the environmental media where the contamination is located.
Contaminated material is not removed but is treated or analyzed in-place.
Application: Chemical, physical, and biological processes applied for in situ treatment
have been described and documented, including applications and limitations, in the
following U.S. EPA publications: (1) Review of In-Place Treatment Technologies for
Contaminated Surface Soils, Volumes 1 and 2, EPA-540/2-84-003a,b; (2) Handbook on
In Situ Treatment of Hazardous Waste Contaminated Soils, EPA/540/2-90-002; and (3)
Bioremediation of Contaminated Surface Soils, EPA/600/9-89/073.
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Infiltration
Description: The first of three stages of liquid transmission in the vadose zone; the
second is identified as percolation; the third is recharge. Infiltration is the flow of a fluid
(usually water, which possibly may contain contaminants) across the land surface into a
subsurface area. Infiltration usually is the downward flow of fluids through soil layers or
movement of ground water into another subsurface area. Infiltration losses in canals and
impoundments are generally described as "seepage" losses. Infiltration rates decrease
with time after the onset of rainfall and ultimately reaches an approximately constant
rate. Factors affecting infiltration of water and contaminants include soil texture, soil
structure, initial water content, presence of shallow impeding layers or water tables,
water temperature, entrapped and confined air, and biological activity. Typical values
are, for clay, less than 0.1 inch/hour, and for sand, more than 2.0 inches/hour.
Application: Infiltration values are used to estimate recharge and contaminant loading
to aquifers, and therefore are used in fate and transport analyses, assessment of spread
of contamination, assessment of remediation alternatives, and exposure assessments.
One form of quantitation of infiltration is given by the Green and Ampt equation:
Vi=
where V; is the infiltration rate, K is the hydraulic conductivity of the wetted zone, t^ is the
depth of water above the soil, hcr is the critical pressure head for soil wetting, and Lf is the
depth of the wetting front. A simpler relationship using infiltration is the calculation of pore
velocity through the vadose zone, assuming long-term (greater than one month) infiltration
data: v = I/O, where v is the pore velocity, I is the infiltration rate, and O is the average
long-term steady state soil moisture content. As an example, if the long-term intake rate
of a pond is two feet per day, and the water content of the vadose zone is 25 percent, the
average velocity would be 2/0.25 = 8 feet per day. If the water table is 100 feet below
ground surface, the travel time of fluids to the water table would be 100/8 = 12.5 days.
Interferences
Description: Undesired responses of analytical equipment caused by a substance in the
sample matrix other than the one being measured.
Application: Interferences may result in analytical results that are either too high or too
low. Interferences may be evaluated by spiking the sample matrix with known chemicals
and measuring the efficiency of recovery from the matrix. Trapping of the compound in the
matrix results in low percent recovery, and are referred to as negative interference.
Recovery of more than 100% of the spike implies that the matrix contains some compound
which is "perceived" incorrectly as the analyte. These interferences are known as positive.
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Inversions [temperature, air]
Description: Usually refers to temperature inversions, an atmospheric condition caused
when a layer of warm air prevents mixing or escape of cooler air trapped beneath it.
Application: Inversions trap contaminants that might otherwise be dispersed, resulting in
higher environmental concentrations and exposures to receptors. Thermal inversions often
occur in situations where cities are located in geographic settings such as valleys or bowls
where air masses can be trapped. Air quality at sites located in such areas may be adversely
impacted by inversions, and Corrective Action Plans should take this into consideration.
Ion exchange capacity - See Cation exchange capacity (CEC).
Isopleth plots
Description: Maps consisting of lines depicting points of equal value (for example,
elevation, contaminant concentrations or any quantity that can be numerically measured and
geographically plotted). Isopleths often represent an approximation of contamination, not
the actual distribution of a substance. Isopleths may overlook major heterogeneities in
contaminant distribution, e.g., if a sample is from a clay lens in a sandy aquifer, the resulting
isopleth may be inaccurate. The method used to create isopleth plots (Kriging, triangulation,
"professional judgement", variogram analysis, etc.) should be documented.
Application: Isopleth plots can be used to assist in site characterization as well as to assess
rate and extent of remediation in a 3-dimensional framework. Plots can be used to show
3-dimensional patterns of decrease in contamination concentration in a soil profile as a
result of treatment.
Kinematic viscosity
Description: Ratio of dynamic viscosity to density. Kinematic viscosity of a compound
provides an indication of the ease with which the compound (in its pure form) will percolate
through the subsurface. The lower the kinematic viscosity of a compound, the greater will
be its tendency to migrate in a downward direction.
Application: Kinematic viscosity is of particular importance with regard to the movement
of DNAPLs in aquifers. The lower the kinematic viscosity of a DNAPL, the greater will be
the ease with which the DNAPL will move downward and penetrate the finer grained layers
in the subsurface. The kinematic viscosity of water is approximately 1.0 centistokes (cs).
Mobility can be rated as high for compounds with values less than 0.4 cs, moderate for
compounds with values between 0.4 and 0.8 cs, and low for compounds with values greater
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than 0.8 cs. Values for this parameter for selected contaminants are provided in Table 3
of Appendix 1.
Laboratory scale - see Treatability Studies
Leachability
Description: Dissolution of soluble constituents from waste, soil, rocks, or other media by
the action of aqueous solutions. This factor aids in evaluating potential for migration of
contaminants from a contaminated media, such as a landfill.
Application: Leachability of a compound is directly related to water solubility which governs
extent to which a compound will partition in the aqueous phase. Water solubility has been
ranked high for chemicals present at concentrations greater than 1,000 mg/L, moderate for
chemicals present at concentrations between 1 and 1,000 mg/1, and low for chemicals
present at concentration less than 1 mg/L. Leachability can also be evaluated using the
relationship between concentration of a chemical in soil and in water when the system is at
equilibrium: Kd = CS/CW (See Adsorption).
Light non-aqueous phase liquids (LNAPL)
Description: A liquid that has a density less than water and therefore floats above the water
table. Examples include automotive and aviation gasolines, jet fuels, most oils, kerosene,
and working solutions such as carrier oils used in wood preservation (See Density). Presence
of an LNAPL complicates site characterization and generally decreases efficiency of pump
and treat systems in recovering subsurface contamination. An LNAPL moves in response
to pressure gradients and gravity. LNAPLs generally flow in the direction of decreasing
hydraulic gradient of the water table. LNAPLs can become trapped in pore spaces by
capillary forces and become difficult to remove through free product recovery pumping. The
residual saturation in pore spaces can be a significant source of contamination to air, water,
and contiguous soil in the subsurface. Residual saturation may be created with fluctuations
in ground water depth as well as with drawdown cones created in the process of free product
removal using pumping systems. Pump and treat applications may be severely limited by
the amount and type of residual saturation.
Application: Data requirements for site characterization of LNAPLs in the subsurface
include: (1) specific gravity (density), (2) viscosity, (3) residual saturation, (4) relative
permeability/saturation/capillary pressure relationships, and (5) LNAPL thickness and
distribution. LNAPLs that comprise a free phase that floats on the surface of the water
table may be stabilized through product recovery using a pumping system, if the site is
sufficiently permeable to allow flow and extraction of LNAPLs. Physical recovery
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techniques for removing LNAPLs include: (1) single pump systems producing a mixture of
hydrocarbon and water that must be separated, (2) two-pump, two-well systems utilizing one
pump to produce a water table gradient and a second well to recover floating product; or
(3) single wells with two pumps in which a lower pump produces a gradient and an upper
pump collects free product. All pumping systems create a cone of depression, or drawdown
cone, which may introduce LNAPL into subsurface material previously uncontaminated and
create residual saturation. Stabilization methods for LNAPLs in the subsurface should
account for potential smearing and avoid or minimize moving the product into
uncontaminated areas where more product can be held at residual saturation.
Lithology
Description: Description of the composition of unconsolidated deposits or rocks including
physical and chemical characteristics such as color, mineralogic composition, hardness,
packing, and grain size.
Application: Lithology should be considered in the evaluation of potential contaminant
migration pathways. Mineralogy and grain size may qualitatively indicate chemical reaction
potential; for example, clays have high reaction potential while sands have little chemical
reaction potential.
Mass balance
Description: An approach to evaluation of fate and transport of contaminants in an
environmental system that involves accounting for distribution, transport, and biotic and
abiotic reactions of a chemical in subsurface fluid and solid phases. The tendency of a
chemical to be distributed among different compartments in the subsurface can be
quantified through determination of partition coefficients between soil and water (K
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Application: A mass balance approach may be utilized for integrating data collection
activities in order to simultaneously address site characterization and remediation technology
selection. The information obtained in a mass balance approach is used specifically to
address the following issues: (1) characterization, (2) assessment of the problem, (3)
treatment train selection, and (4) monitoring. Characterization of the waste/soil/site
addresses the question "Where is the contamination and in what form(s) does it exist?" The
second step, assessment of the problem, utilizes chemical mass balance information to
address the question "Where is the contamination going under the influence of natural
processes?" The problem can be defined in the context of mobility versus degradation for
chemicals. Using mathematical models that incorporate mass balance information,
chemicals can be ranked in order of their relative tendencies to leach, volatilize, degrade,
and to remain in-place under site-specific conditions. Containment and/or treatment options
can then be selected that are chemical-specific and that address specific escape and
attenuation pathways (third step). Treatment trains can be selected to address specific waste
phases at specific times during remediation (volatile, leachate, solid phase, pure product),
with the selection dependent upon results of a mass balance evaluation through time to
identify the fate of each waste phase. Finally monitoring programs can be designed for
specific chemicals in specific phases in the subsurface at specific times (fourth step). Thus
the chemical mass balance approach assists in collecting specific information that is
transferrable among all four issues and also addresses the technical issues of subsurface
remediation within the context of regulatory goals.
Material and energy balance
Description: An accounting of all the mass and energy entering a reaction or system and
all those that leave it in a given time period. This description is appropriate for one
treatment process or one technology.
Application: For example, a material balance for a hazardous waste incinerator would
involve the input of fuel, waste, and air; the output of combustion products and any
unconsumed compounds, plus the accumulation and removal of deposits (ash) in the
incinerator. The evaluation of a material and energy balance are essential in assessing
treatment processes and in residuals management.
Maximum Contaminant Level (MCL)
Description: Under Section 141 of the Safe Drinking Water Act, as amended, the maximum
permissible level of a contaminant in water delivered to any user of a public water system.
MCLs reflect health factors and the technical and economic feasibility of recovering
contaminants from the water supply.
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Application: For RCRA corrective action, MCLs are often used as cleanup standards.
Values for this parameter for selected contaminants are provided in Table 3 of Appendix
1.
Melting point
Description: The temperature at which a solid begins to melt and change state to liquid.
An indication of the physical state of a pure compound at field temperatures.
Application: Compounds with melting points above 30° C, for example, would be expected
to be relatively immobile in pure form. Such compounds would be of primary concern when
in the dissolved phase, either in water or another solvent. Compounds with melting points
lower than 30° C may be present as mobile non-aqueous phase liquids (NAPLs) in
subsurface environments. Values for this parameter for selected contaminants are provided
in Table 3 of Appendix 1.
Method detection limit
Description: Minimum concentration of an analyte that can be measured by a particular
analytical method and reported with 99 percent statistical confidence. This is determined
from analysis of a sample in a given matrix. Detection limits should be specified at or below
levels of concern.
Application: Method detection limits provide a lower boundary for measurement of the
clean-up level for a particular process or technology.
Mineral content
Description: The level of naturally occurring inorganic materials in soils, rocks, aquifer
sediments, ground water, or wastes.
Application: Information concerning mineral content is important in assessing the reactivity
of soil or geologic materials with contaminants and the migration of contaminants through
the materials. For example, high levels of naturally occurring dissolved iron may be oxidized
to insoluble iron near recovery or injection wells, and thus be responsible for reducing water
transmitting properties of an aquifer. Also, high concentrations of soluble iron in water
pumped to the surface for further treatment (pump and treat) may clog above ground
treatment systems that use air stripping or carbon adsorption. Mineral content of the
subsurface also indicates relative chemical reaction (including adsorption and chemical
degradation) potential; for example, clay minerals are more chemically reactive than silt and
sandy minerals.
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Moisture content [of soil]
Description: Water lost from a soil upon drying to a constant mass at 105- C, expressed
either as mass of water per unit mass of dry soil or as the volume of water per unit bulk
volume of soil.
Application: Knowledge of the moisture content of a soil provides information concerning
the amount of water present for biological activity, amount of pore space occupied by soil
air, and amount of water available to act as a solvent for contaminants and nutrients. The
amount of soil water influences soil temperature, and is critical for biodegradation of
contaminants.
Octanol/water partition coefficient
Description: Measure of the extent to which a chemical partitions between an aqueous
phase and an organic phase (octanol). Kow is the ratio of concentration of a chemical in
octanol to concentration of the chemical in water.
Application: This parameter can be used to predict extent of sorption of organic chemicals
onto soils. Kow can also be used as a basis for estimating relative bioconcentration factors
(see Bioconcentration factor). In transport models, Kow is frequently converted to K^ (see
Organic carbon adsorption coefficient), a parameter that takes into account the organic
content of the soil. The higher the value of Kow (or K^), the greater the tendency of a
constituent to adsorb to soils containing appreciable organic carbon. Kow values can also
be used to evaluate efficacy of remediation technologies. For example, pump and treat
technology is best suited for managing chemicals with log Kow values less than 3.5; pulsed
pumping is appropriate for chemicals with log Kow values between 2.5 and 4.5; in situ
vitrification is appropriate for chemicals with log Kow values greater than 4.5. Values for
this parameter for selected contaminants are provided in Table 3 of Appendix 1.
Organic carbon adsorption coefficient (K^)
Description: Ratio of the amount of constituent adsorbed per unit weight of organic carbon
in the soil or sediment to the concentration of the constituent in aqueous solution at
equilibrium. The tendency of a constituent to be adsorbed to soil is dependent on its
properties and on the organic carbon content of soil or sediment. Koc can be used to
determine the partitioning of a constituent between the water column and sediment. When
constituents have a high k^, they have a tendency to partition to the soil or sediment. K^
is similar to Kn
vow
Application: Because K^ is similar to Kow, refer to the discussion under Octanol/water
partition coefficient. In addition, some specific guidance for K^ values can be given for
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specific remediation technologies. For example, pump and treat technology is best suited
for managing chemicals with log K^ values less than 3.0; pulsed pumping is appropriate for
chemicals with log K^ values between 2.0 and 4.0; in situ vitrification is appropriate for
chemicals with log K^ values greater than 4.0. Values for this parameter for selected
contaminants are provided in Table 3 of Appendix 1.
Organic carbon content
Description: Percentage, on a dry weight basis, of a soil or sediment that is composed of
organic carbon. Organic carbon, such as humic acids, is usually the result of decomposition
of plant and animal matter that occurs predominantly in the top layer of soil.
Application: Information concerning organic carbon content is important in determining
partitioning of contaminants between the soil and leachate, or into runoff phases of soil or
sediments. The organic content of upper soil layers typically ranges from 0.1 to 5 percent,
with most top soils in the range of 1 to 5 percent. Natural soil organic content may be
difficult to measure in areas of gross organic contamination, such as oily sediment. (See
Octanol/water partition coefficient, and Organic carbon adsorption coefficient.)
Organic carbon, total (TOC)
Description: Total amount of organic carbon present, expressed on a dry weight basis, in
a solid or liquid. This carbon is derived from decomposition of biotic material or the
introduction of man-made chemicals. TOC is generally expressed as mg/L when measured
in water and mg/kg in soil. Natural waters usually contain TOC less than 5 mg/L; greater
values indicate organic contamination.
Application: TOC is used as a rapid estimate of organic contamination. TOC is not specific
to a given contaminant or even to specific classes or organics. TOC measurements have
little use if a release is primarily due to inorganic wastes. TOC is a ground-water indicator
parameter in 40 CFR 264 and 265 ground-water monitoring.
Particle size distribution
Description: The various size fractions into which a soil sample separates, often expressed
as mass percentages. Soil separates, as defined by the Soil Conservation Survey of the U.S.
Department of Agriculture, include mineral particles less than 2 mm in diameter, and are
divided into the following size categories: sand, 2.0 to 0.05 mm; silt 0.05 to 0.002 mm; and
clay, less than 0.002 mm.
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Application: Particle size distributions are used to describe soil texture (See Soil texture).
The texture of a soil affects its porosity, air and water permeability, infiltration rate, and
sorptive capacity.
Pedology
Description: The study of soil; including origin, description, and classification.
Application: Pedology provides a general understanding of soils as they occur in nature.
Perched zone of saturation
Description: A discrete pocket or lens of unconfined ground water separated from an
underlying aquifer by an unsaturated zone; also known as a perched aquifer. Perched ground
water may be either permanent or temporary. Permanent perched ground water occurs
where recharge is frequent enough to maintain a saturated zone above the perching bed.
Temporary perched ground water occurs where intermittent recharge is not frequent enough
to prevent the perched water from disappearing from time to time as a result of drainage
over the edge of or through the perching bed.
Application: Identification of perched zones of saturation is essential for defining
contaminant migration pathways and monitoring for pockets of contamination. Perched
zones of saturation may be the source of contamination of deeper ground water. Perched
zones of saturation may be located using a neutron moisture logger.
Permeability
Description: Capacity of porous rock, sediment, or soil to transmit a fluid, usually water or
air. (See Hydraulic conductivity).
Application: Permeability is often used interchangeably with hydraulic conductivity.
Permeability rates as given below are often used to determine infiltration and long-term
intake rates as described under the topic of Infiltration. Units for permeability are identical
to those used for hydraulic conductivity (See Hydraulic conductivity). The following table
gives some examples:
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Soil Conservation Service Soil Permeability Rates
Descriptor Rate (inches/hour)
very slow less than 0.06
slow 0.06 to 0.2
moderately slow 0.2 to 0.63
moderate 0.63 to 2.0
moderately rapid 2.0 to 6.3
rapid 6.3 to 20.0
very rapid greater than 20
pH
Description: An expression of concentration of hydrogen ions (H+) in an aqueous
solution. The pH scale is based on disassociation of water into hydrogen and hydroxyl ions.
The term "pH" is derived from the phrase "power of hydrogen ion concentration", which
represents the value of the exponent of H+ concentration. The scale is logarithmic and has
a range from 0 to 14 units. A pH value of 7 is considered neutral and represents equal
concentrations of H+ and OH" ions at 1 x 10"7 mole/liter. Values below 7 indicate higher
concentrations of H+ and are considered to be acid. Values above 7 indicate lower
concentrations, and are considered to be basic.
Application: pH plays a vital role in chemical and biological reactions; and can be a major
factor in determining such things as reaction rate, solubility of contaminants in water,
species of metal, ionization potential, precipitation/dissolution of minerals, composition and
activity of microbial communities, metal corrosion, and toxicity of contaminants, see
Alkalinity, Redox Potential, Speciation, etc.
Photolysis
Description: Degradation of a chemical caused by direct absorption of solar energy (direct
photolysis) or by transfer of energy from other substances that absorb solar energy (indirect
photolysis). Photolysis also includes artificially induced processes such as ultraviolet
oxidation in the treatment of ground water. Photolysis potential should be considered in
designing sampling and analysis programs.
Application: Photolysis is an important degradation mechanism for photoreactive
compounds in the air, shallow surface water, and on soil surfaces; it is not an attenuation
mechanism below the soil surface or at depth in surface water. The rate and extent of
photolysis may be measured in order to assess whether photolysis is an important fate
mechanism and whether the reaction may be utilized in a remediation treatment train.
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Photolysis rate (expressed in terms of half-life values) are given for several chemicals in the
table below.
Photolysis rate
Substance Half-Life
Fluoranthene 21 hours
Sevin H days
p Cresol 35 days
Physiography
Description: Physical geography; surface features and landforms of the earth (or the area
of interest), see Topographic map.
Application: The physiography of a site affects such processes as surface runoff, erosion,
infiltration, soil slippage, and susceptibility to flooding.
Piezometer
Description: 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.
Application: Data derived from piezometers can be used in determining elevation of the
potentiometric surface of an aquifer as well as determining horizontal and vertical ground-
water flow directions. Piezometric data can also be used to calculate the hydraulic gradient,
which can be used in Darcy's law to calculate the rate of transport of water through the
saturated zone at a site, as well as changes in transport rate as a result of ground water
fluctuations. For example, if the saturated hydraulic conductivity (K) is 1CT4 cm/sec, and the
hydraulic gradient (H/L) is calculated using piezometric data [elevation in one well is
measured at 100 feet above sea level and in a second well at 70 feet above sea level), and
the wells are located at a distance of 200 feet apart, then the hydraulic gradient is (100-
70)/200 = 0.15 ft/ft], and the Darcy velocity through the section is V - K (H/L) or lO^4
(0.15) = 0.15 x 10"4 cm/sec. Determination of transport rate is an important part of
generating a chemical mass balance at a site for characterization, problem definition,
treatment train selection, and monitoring, as described under Mass balance.
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Pilot scale - see Treatability Study
Plumes [immiscible or dissolved]
Description: An area of contaminated water (or pure contaminant) originating from a
specific source. Ground-water plumes are influenced by such factors as local ground-water
flow patterns and density of contaminant(s). Surface-water plumes are influenced by water
current and density of the contaminant. An immiscible plume occurs where the contaminant
is either more dense or lighter than water (i.e., the contaminant is a NAPL), and hence is
found below or on top of the water, but not mingled with the water layer. A dissolved
plume occurs where the contaminant is soluble in water. Dissolved plumes are often
associated with immiscible plumes.
Application: Plume delineation in three dimensions is essential as part of site
characterization activities. A chemical mass balance approach may be used (See Mass
balance).
Porosity
Description: Percentage of void or pore space within a rock or soil/sediment. Porosity may
be expressed as a decimal fraction or as a percentage. Due to processes such as
cementation, effective porosity is a more accurate measure of water available in a formation.
Porosity and soil texture are used to assist in evaluating hydraulic conductivity. With respect
to the movement of a fluid, only the system of interconnected pore space is significant. In
general, the greater the porosity, the more readily fluids may flow through the soil. An
exception is a clayey soil, which usually tightly holds fluids by capillary forces.
Application: Porosity is used in the equation that describes the relative velocities of water
and a chemical in the subsurface, i.e., the retardation of a chemical in the subsurface: R
= 1
+ r Kd/n (See Adsorption).
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Range of Values of Absolute Porosity
Geologic Material Percent
Unconsolidated deposits
Gravel 25 - 40
Sand 25 - 50
Silt 35 - 50
Clay 40 - 70
Rocks
Fractured basalt 5-50
Karst limestone 5 - 50
Sandstone 5-30
Limestone, dolomite 0-20
Shale 0 10
Fractured crystalline rock 0 - 10
Dense crystalline rock 0 5
Effective Porosity The amount of interconnected pore space available for fluid
transmission. It is expressed as a percentage of the total volume occupied by
interconnected pore space. This information aids in evaluating the rate at which
ground water and contaminants can migrate through different geologic units.
Potentiometric (surface) map
Description: A contour map of ground-water pressure head for a given water bearing zone.
It represents the levels to which water will rise in wells cased to and screened in that water
bearing zone.
Application: Ground-water flow directions will be perpendicular to the contours and
towards areas of lower potential. Contours that are closer together indicate a greater
hydraulic gradient, which influences ground-water flow velocity.
Qualitative and quantitative flow sheets [for corrective measures design]
Description: Charts or line drawings used to indicate successive steps in a process design.
A flow sheet carries information such as temperatures, pressures, flow rates, and process
equipment at varying points in the process.
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Application: Flow sheets provide sufficient detail for process design and cost prediction.
Evaluation of the flow sheets for corrective measures design is conducted to determine
whether the design will achieve the stated objective.
Reagent
Description: A substance used in a chemical reaction to detect, measure, examine, or
produce other substances.
Application: These substances may be used to support laboratory analysis or treatment
processes.
Reagent quality control checks
Description: Methods established to ensure that reagents used for analytical procedures are
of the quality required for accurate laboratory analysis.
Recharge
Description: Addition of water into the zone of saturation; for example, a recharge area
occurs where rainwater soaks through the earth to reach an aquifer. In designing a ground-
water corrective action program, accurate estimates of recharge amounts are essential to
ensure that appropriate ground-water pumping rates achieve the desired zone of capture.
Recharge rates are equal to deep percolation rates in the area of the ground water.
Application: Percolation rates, and therefore recharge rates in the vicinity of the ground
water, are described by modifications of Darcy's law for saturated systems. An approach
for estimating recharge from large spreading areas and extensive impoundments is to apply
Darcy's law (See Hydraulic conductivity).
Redox potential (Eh)
Description: Expression of the electron density of a system. This is a numerical
measurement, referred to as Eh and measured in volts, of the oxidation/reduction properties
of an environment. As a system becomes more reduced, there is an increased electron
density and decreased potential. Redox potential is directly correlated with dissolved oxygen
(DO) concentrations. High DO in aqueous systems (>4 mg/L) results in high Eh and
oxidizing conditions. Low DO (< 1 mg/L) results in low Eh and reducing conditions.
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Application: Eh also has a direct effect on metal speciation. Equilibrium speciation of
some metals is dependent on the Eh and pH of a system. Eh-pH diagrams are often used
to illustrate predominant dissolved and mineral species at equilibrium. For example, with
iron, in well-aerated soils with pH above 4, hydrous ferric oxide minerals and coatings are
considered to be the soil minerals controlling equilibrium aqueous Fe+3 concentrations. As
the system becomes more reduced (lower Eh values), Fe+2 may be expected to predominate
up to pH 8. As oxygen becomes limited in the subsurface, a variety of anoxic oxidation
processes will follow and will be influenced by the redox potential. Microbial metabolism
in a soil system is accomplished by aerobic and facultative microorganisms at redox
potentials ranging from about 600 to 0 millivolts, while at potentials from 0 to about -200
millivolts, obligate anaerobes are predominant. Where sulfates, nitrates, iron, manganese,
and carbonates are available, as affected by redox conditions, these electron acceptors may
influence degradation of organic chemical contaminants. As redox potential decreases,
electron acceptors will be used in the order: nitrate, ferric iron, manganese dioxide, ferric-
oxy hydroxides, sulfate, and carbonate for the degradation of organic contaminants.
Residual saturation
Description: Saturation below which fluid drainage will not occur (Also referred to as
irreducible saturation). Residual saturation depends mainly on two factors: (1) distribution
of soil pore sizes, and (2) type of immiscible fluid involved. Residual saturation is difficult
to estimate accurately and is subject to considerable error. The amount of oil normally
retained in soil is between 15 and 40 liters per cubic meter.
Application: See LNAPLs, DNAPLs, and Density.
Samples
Description:
"Blind" quality control samples Samples submitted by an outside source to
determine the quality of analyses performed by a particular laboratory. These
samples may be prepared with an exact concentration of a constituent that is
unknown to the laboratory. Alternatively, these samples may be blanks or duplicates
that are not labeled as such (the latter are also known as "blind duplicates"). These
samples are used to determine the internal quality control of analytical work.
Calibration check samples - Samples of known concentrations of a substance that are
analyzed to verify the accuracy of an instrument's readings. The readings can then
be used to prepare calibration curves for further analysis of actual samples.
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Composite samples - Samples prepared by mixing two or more grab samples that
typically represent an average value over a period of time or within a given area.
Composite samples reduce costs of sampling and analyses, but do not allow
determinations of the highest and lowest contaminant concentrations within the
sampling area.
Grab samples Discrete samples taken from one specific sampling point at a specific
time.
Laboratory control samples - Samples of known chemical concentration or physical
characteristics that are used in the laboratory to assess analytical precision and
accuracy.
Matrix-spiked samples - Samples to which known amounts of certain chemicals are
added before extraction or digestion and analysis. The percent recovery of each
chemical is calculated to assess potential effects of the sample matrix on analyte
recovery.
Replicate samples - Samples that have been divided into two or more portions at
some step in the measurement process. A sample may be replicated in the field or
at different points in the analytical process. Information derived from replicate
samples is necessary to analyze quality of data.
Sample matrix- Physical and chemical properties that describe a sample, for
example, soil, sludge, water. Knowledge of the sample matrix is necessary to devise
proper handling and analytical procedures. Interferences inherent in the sample
matrix can affect detection limits. For example, normal detection limits may be
impossible to achieve in some soils contaminated with oils.
Surrogate samples - Samples that are spiked prior to analysis with organic
compounds that are not normally found in environmental samples but are similar to
analytes of interest. Percent recoveries are calculated for each surrogate. Surrogate
samples are used to determine possible interferences.
SCS soil classification
Description: Soil classification system developed by the U.S. Department of Agriculture's
(USDA) Soil Conservation Service (SCS). The system was primarily developed for
agricultural purposes. The system provides information on typical soil profiles (e.g., 1-foot
fine sandy loam over gravelly sand, depth to bedrock 12 feet), chemical characteristics and
ranges of permeabilities for each layer, and approximate particle size ranges. These values
are not generally accurate enough for predictive purposes, and should not be used to replace
field data. (See ASTM classification [of soil])
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Application: Knowledge of the classification of a soil provides information on potential
water and air permeability of soil and potential for assimilation of waste constituents in soil.
Sensitive subgroups
Description: Environmentally sensitive groups (e.g., wetlands) or human population groups
with high sensitivity to chemical exposure (e.g., infants, children, elderly people, pregnant
women, and people with chronic illnesses). Associated land uses include schools, day care
centers, hospitals, nursing homes, and retirement communities.
Application: Information on sensitive subgroups should be collected during risk assessments.
Soil texture
Description: Relative proportions of the various soil separates (See Particle size
distribution) as described by classes of soil texture shown in the soil textural triangle. The
soil textural triangle for the U.S. Department of Agriculture system of soil classification is
presented in Appendix 3.
Application: Texture of a soil affects its porosity, air and water permeability, infiltration
rate, and sorptive capacity.
Soil-water partition coefficient (kd)
Description: The ratio of adsorbed contaminant concentration to the dissolved
concentration at equilibrium. The soil-water partition coefficient is generally used to
quantify soil sorption. The extent to which a constituent is absorbed depends on chemical
properties of the constituent and of the soil (See Adsorption).
Application: This parameter will aid in predicting contaminant migration through the soil
matrix (See Adsorption).
Solubility [of waste]
Description: Maximum concentration at which a constituent can dissolve in water at a given
temperature. Solubility in water governs the extent to which a contaminant will partition into
the aqueous phase. The greater the water solubility of a compound, the greater will be the
tendency for that compound to migrate with the aqueous advective flow component. Water
solubility values, in conjunction with vapor pressure can provide an assessment of the
potential for volatilization (See Henry's law constant).
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Application: Solubility is an important function affecting the release and subsequent
migration or fate of a constituent in the ground-water or surface-water environment.
Chemicals with higher water solubilities are more amenable to removal from the subsurface
by pump and treat technology. These same compounds, however, are more likely to migrate
through the vadose zone to ground water (See Leachability). Values for this parameter for
selected contaminants are provided in Appendix 1.
Sorption
Description: A general term that encompasses the processes of absorption, adsorption,
desorption, and ion exchange. Sorption is a major subsurface chemical process that affects
fate and transport of contaminants (See Absorption, Adsorption, and Cation Exchange
Capacity).
Sorptive capacity
Description: Potential for materials to chemically sorb contaminants and thereby retard
contaminant migration. Major soil parameters that influence sorption include total organic
carbon content and particle size distribution. This information aids in predicting
contaminant movement through soils (See Absorption, Adsorption, and Cation Exchange
Capacity). The following table gives examples of the sorptive capacity of some geologic
materials:
Sorptive Capacity
Values
High
Medium
Low
Geologic Materials
Clays, organic rich sediments, silts
Sands
Limestones, dolomites, gravels, clean sands
Metamorphic and igneous rocks
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Speciation [metals]
Description: The wide range of transformation processes by which metallic chemical
compounds form and are transformed. Speciation can occur in all environmental media.
The final form or speciation of a metal in a given environment affects its solubility, sorption
properties, and toxicological properties. Speciation may change as a result of sampling
effects. For example, collection of a ground-water sample may result in oxidation of the
sample, which changes speciation.
Application: Change in chemical species may affect inter-phase transfer. For example,
mercury in the + 2 form (Hg+2) is soluble but may be reduced by microorganisms to the
elemental form (Hg°), which is volatile. Volatile forms of selenium and arsenic (AsH3) may
also be formed under reducing conditions through changes in chemical species. The selenate
form (SeO42~) will dominate under oxidizing conditions, while the selenite form (SeO32~) will
dominate under increasingly reducing conditions. The arsenate form (AsO43~) will dominate
under oxidizing conditions while the arsenite form, which is more toxic and mobile, will form
under reducing and acidic conditions. Property change associated with a change in species
may be utilized in remediation strategies to remove and recover soluble and non-volatile
metals as volatile species. Another application of speciation is reduction of hexavalent
chromium (Cr+6), which exists as a highly toxic and highly mobile hydrated anion in the
subsurface, to trivalent chromium (Cr+3), which is less toxic and exists in the form of a
cation. The change in speciation from hexavalent to trivalent results in reduced mobility in
a subsurface environment because the soil is generally negatively charged and has a finite
cation exchange capacity. Cyanide ion (CN~) predominates in aqueous solution only at pH
values greater than 9. Hydrogen cyanide (HCN) predominates at pH values less than 9.
HCN is volatile (vapor pressure of 741 mm Hg at 25° C) and toxic, while CN" tends to
complex with iron. Iron may occur as the mobile ferrous form (Fe+2) in reducing
conditions, and as the less mobile ferric form (Fe+3) under oxidizing conditions.
Compounds and metals complexed to iron may be removed from the subsurface under
oxidized conditions. Conversely, compounds and metals adsorbed to iron my be increasingly
mobilized under reduced conditions. Precipitated iron may hinder treatment processes such
as in situ bioremediation and air stripping.
Specific Conductance See Conductivity
Specific yield
Description: Ratio of the volume of water that will drain under gravity to the total volume
of saturated material. In an unconfined aquifer, the specific yield is the ratio of the
drainable volume of water due to gravity to the bulk volume of the aquifer medium (some
liquid will be retained in the pore spaces). Specific yield is used only for unconfined
aquifers, as confined aquifer materials generally are not dewatered during pumping. Specific
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yields of unconfined aquifers are much higher than storativities of confined aquifers. The
usual range of specific yield is 0.01-0.30. Specific yield is also known as effective porosity
for unconfined systems. Specific yield values may be necessary to perform complex ground-
water modeling.
Application: Because specific yield is also known as effective porosity, see Porosity and
Effective Porosity.
Volume of Water Yielded/Volume of Rock
Material Ratio Range
Sedimentary
Sandstone(fine) 0.02 - 0.40
Sandstone (medium) 0.12 - 0.41
Siltstone 0.01 0.33
Sand (fine) 0.01 - 0.46
Sand (medium) 0.16 - 0.46
Sand (coarse) 0.18 - 0.43
Gravel (fine) 0.13 - 0.40
Gravel (medium) 0.17 - 0.44
Gravel (coarse) 0.13 - 0.25
Silt 0.18 - 0.39
Clay 0.01 - 0.18
Limestone 0.00 - 0.36
Wind-Laid
Loess 0.14 - 0.22
Eolian Sand 0.32 - 0.47
Tuff 0.02 - 0.47
Metamorphic Rock
Schist 0.22 - 0.33
Stereographic analysis
Description: Three-dimensional visualization of surface features created by viewing an
overlapping pair of photographs taken at different angles through a binocular optical
instrument (i.e., a stereoscope)
Application: This analysis may be used to identify potential contaminant pathways,
potential sites for treatment, storage, or disposal facilities, or topographic factors that
influence ground-water systems,
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Storativity
Description: The volume of water that an aquifer releases from or takes into storage per
unit surface area of aquifer per unit change in the component of pressure head normal to
that surface (Also referred to as storage coefficient). The storage coefficient for an
unconfined aquifer corresponds to its specific yield. In confined aquifers, if the aquifer
remains saturated, changes in pressure produce only small changes in storage volume.
Application: Storativity values may be used to determine how rapidly the flow system will
respond to pumping. This factor is important for pump and treat systems where pulsed
pumping is used. Storativity can be used to help determine the cycle duration of pumping.
Stratigraphy
Description: Description of original rock succession and age of rock layers ("strata"), as well
as their formation, distribution, composition, fossil content, and geophysical and geochemical
properties. Descriptors include strike (the direction taken by a structural surface) and dip
(measured perpendicular to the strike; the angle that a geological feature makes with the
horizontal). Stratigraphy also encompasses unconsolidated materials, such as soils.
Application: Knowledge of stratigraphic features is critical to the design, monitoring, and
corrective action programs, as these features will largely influence contaminant migration
pathways. For example, stratigraphic information will aid in determining potential fracture
flow pathways, estimating extent of flow, and defining the hydrogeologic framework.
Temporal changes
Description: Changes in the value of measured parameters over time. In hydraulic
gradients, those variations due to seasonal or daily influences, river, estuarine, or marine
tidal movement, and human activity (for example, ground-water pumping, changes in land
use, and waste disposal practices).
Application: This factor is critical for evaluating surface-water and ground-water pathways
and receptors. For example, temporal changes in ground water levels may cause smearing
of LNAPLs as the level of ground water decreases and increases, resulting in the change of
free product to residual saturation in the subsurface. Remediation using LNAPL free
product recovery pumps will be based upon location and depth of the LNAPL with respect
to the water table. Therefore changes in water table elevation must be monitored through
time to accurately locate and remove free product occurring on top of the water table. For
treatment of the residual saturation of LNAPLs, see LNAPLs and Residual saturation.
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Total Dissolved Solids (TDS)
Description: The total amount of solids that remain when a water sample is evaporated to
dryness. TDS includes carbonates, sulfates, chlorides, nitrates, phosphates, metallic ions,
iron, calcium, potassium, and others that pass through a fine, glass-fiber filter (usually 0.45
micron). TDS is a basic measure of water quality.
Application: As TDS increases, conductivity of the water also generally increases. See
Conductivity [of water].
Total Dissolved Solids
Class Values (mg/L)
Drinking water < 500
Fresh water 0 1,000
Brackish 1,000 - 10,000
Saline 10,000 - 100,000
Total Suspended Solids (TSS)
Description: Undissolved organic and inorganic particulate matter in water that contributes
to turbidity. TSS is measured as the dehydrated weight of organic and inorganic solids
retained on a fine, glass-fiber filter (usually 0.45 micron).
Application: TSS is an important parameter for above ground treatment units utilized as
part of pump and treat remediation, including activated carbon, air stripping, ion exchange,
and reverse osmosis treatment units. TSS will physically clog these units and decrease
efficiency and performance time. TSS should be evaluated for potential impacts on above-
ground treatment processes.
Transects
Description: A type of vertical profile that represents data along a plane.
Application: For soil and ground-water data, several cores or monitoring wells are selected
that are in approximately a straight line through the areas of interest. The information is
then graphically displayed as a cross section.
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Transmissivity
Description: Transmissivity is defined as the hydraulic conductivity multiplied by the
thickness of a confined aquifer. In an unconfined aquifer, transmissivity is not as well
defined as in a confined aquifer. Transmissivity in an unconfined aquifer is defined as the
hydraulic conductivity multiplied by saturated thickness of the aquifer. Transmissivities
greater than 0.015 meter2/second represent aquifers suitable for use as water wells.
Application: Subsurface environments with high transmissivities are appropriate for pump
and treat technology, vacuum extraction, soil flushing, and bioremediation, which rely on
delivery and recovery of fluids or air for accomplishing subsurface remediation.
Treatability studies [laboratory, bench, pilot, field]
Description: An organized series of experiments designed to determine the best approach
for treating wastes. Extent and scope of treatability studies range from laboratory-scale
"proof-of-concept" efforts to field-scale demonstrations. In general, treatability studies start
at the laboratory scale and proceed through intermediate steps to pilot-scale or field-scale
studies. As this process continues, information that is generated answers increasingly
specific questions concerning feasibility, design, cost, and performance. The cost and
complexity of treatability studies therefore increases with scale.
Laboratory-scale
Small-scale (jar, beaker, column) screening studies performed to determine
if specific wastes can be treated by specific processes or approaches. Often
"proof-of-concept", these studies are used for preliminary screening of
treatment alternatives. Laboratory studies usually generate qualitative
information concerning general validity of a treatment approach. They do not
provide quantitative information concerning cost, design, or performance.
Laboratory-scale studies involve small volumes or masses of test material,
utilize primarily batch tests, and can screen a large number of parameters to
identify those critical for further testing.
Bench-scale
Intermediate scale studies (often performed in a laboratory) which are
designed to provide quantitative information to evaluate performance of a of
remediation technology. Bench-scale studies generally are intended to answer
specific design, operations, and cost questions, and are more detailed than
laboratory studies. They can be used to obtain a mass balance of chemicals
within a system to determine fate of the chemicals, including interphase
transfer and/or reaction (for example, volatilization, sorption, desorption,
biodegradation, chemical degradation, etc.), in order to evaluate technology
performance. The equipment and experiments are designed to simulate basic
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operation of the treatment process. The mass or volume of materials tested
is greater than laboratory-scale experiments, and tests can be either batch or
continuous.
Pilot-scale
Large-scale experiments designed to provide detailed, quantitative, cost and
design data to optimize performance of a technology under anticipated field
conditions. Pilot-scale experimental and equipment designs simulate
operational configurations as close as possible to the anticipated full-scale
systems. The mass or volume of tested waste is much larger than laboratory
or bench-scale studies. Pilot-scale study designs usually build on results from
laboratory and bench-scale studies, and are generally more complex and
costly.
Field-scale
Field demonstrations of treatment technology developed from treatability
studies. Field demonstrations are intended to monitor performance of
treatment systems under real world conditions at approximately full scale.
Field studies are designed to monitor performance and identify problems not
encountered at less than full scale operations.
Treatment train
Description: A combination of treatment technologies that are used at one time or that are
used sequentially at a site in order to match a specific technology to a specific contaminated
phase. A treatment train is selected after a site characterization is conducted to define the
problem at a site with regard to which phases are contaminated and what is the potential
or actual exposure pathway for each phase. Treatment trains are then selected to control
specific chemicals in specific phases, and therefore can be chemical-and-phase-specific.
Application: For example, a treatment train for creosote contaminated soil and aquifer
material may involve: (1) product removal using a pumping system, (2) flushing with water
and/or surfactant solution using pump and treat technology, and (3) in situ biodegradation
of trapped residual saturation. Another example may include product removal of LNAPL,
followed by vacuum extraction of volatile materials, followed by biodegradation of residual
saturation and of sorbed chemicals.
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Vapor pressure
Description: The pressure of vapor in equilibrium with a pure liquid or solid. Vapor
pressure is a function of the chemical of interest and temperature. Units of measurement
are generally expressed in millimeters of mercury (mm Hg). For comparative purposes, the
vapor pressure of water at 20° C is 17.5 mm Hg. Constituents with high vapor pressures are
more likely to be released in the gaseous form than those with low vapor pressures,
depending on other factors such as relative solubility and concentration. For example, at
high concentrations, releases can occur even though the vapor pressure of a constituents is
relatively low. This factor is important in evaluating the potential for contaminants to be
released to moist air as vapor, e.g., when excavating soils or extracting ground water for
subsequent treatment (See Henry's Law Constant). Within a mixture of chemicals in a
NAPL, chemicals will volatilize according to Raoult's law, i.e., volatilization will be a
function of the mole fraction of a chemical as well as the vapor pressure of the chemical.
Values of vapor pressure for selected contaminants are provided in Table 3 of Appendix 1.
Application: Vapor pressure values for chlorinated hydrocarbons generally increase with
decreasing chlorine content. In situ steam stripping facilitates the removal of residual
organics with vapor pressure values between 10"3 and 10° mm Hg, such as many NAPLs,
from the vadose zone.
Vertical flow rate
Description: The rate of vertical travel of water and contaminants from unsaturated soil to
the saturated zone as well as the upward or downward movement within the unsaturated or
saturated zone. The vertical flow rate is dependent on factors such as volumetric water
content, adsorption and desorption parameters, hydraulic conductivity, and pressure head.
Information concerning vertical flow rate aids in identifying and predicting the vertical
distribution of contaminants and ground-water flow patterns.
Application: For downward migration through the vadose zone, see Infiltration and
Recharge. Water, and consequently chemicals, can also be advected in the upward direction
in the unsaturated zone due to evapotranspiration and changes in hydraulic gradient when
the gradient is in the upward direction. Calculations concerning upward and downward
direction in the vadose zone are based on a modified Darcy's law:
J = K(q)(dH/dz),
where J is the Darcy flux or velocity, K(q) is the hydraulic conductivity based on soil
moisture content, and (dH/dz) is the hydraulic gradient that is primarily a function of matric
potential, and not gravity, in the unsaturated zone. Accurate analysis of transient water
movement in the unsaturated zone, including upward and downward flow, is a complex
process, is generally not influenced by gravity, and requires a level of detail and more
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explanation than is appropriate in this document. The reader is advised to seek texts and
articles on unsaturated flow physics or consult with someone with specific expertise in this
area.
Viscosity [of waste]
Description: The property of a fluid describing its resistance to flow. Viscosity of any bulk
liquid wastes should be determined to estimate potential mobility in soils. A liquid with a
lower viscosity will generally travel faster than one with a high viscosity.
Application: See Dynamic Viscosity and Kinematic Viscosity.
Water quality criteria
Description: Under Section 303 of the Clean Water Act (40 CFR Part 131), water quality
criteria are comprised of numeric and narrative criteria. Numeric criteria are scientifically
derived ambient concentrations developed by EPA or states for various pollutants of
concern to protect human health and aquatic life. Narrative criteria are statements that
describe the desired water quality goal.
Water quality standard
Description: Under Section 304 of the Clean Water Act (40 CFR Part 131), water quality
standards are regulations which consist of the beneficial designated use or uses of a water-
body, the numeric and narrative water quality criteria that are necessary to protect the use
or uses of that particular water-body, and an antidegradation statement.
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APPENDIX 1
Tables 1, 2, and 3
Subsurface Contamination Reference Guide
EPA/540/2-90/011
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Subsurface
Remediation
Guidance
Tables 1&2
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Table 1. Contaminants Commonly Found at Superfund Sites
Halogenated Volatile Organics
Liquid Solvents
Carbon Tetrachlonde
Chlorobenzene
Chloroform
Cis-1,2-dichloroethylene (d)
1,1-Dichloroethane (a)
1,2-Dichloroethane
1,1-Dichloroethylene
1,2-Dichloropropane (a)
Ethylene Dibromide (g)
Methylene Chloride
1,1,2,2-Tetrachloroethane
Tetrachloroethylene
Trans-1,2-dichloroethylene (d)
1,1,1 -Trichloroethane
1,1,2-Trichloroethane
Trichloroethylene
Gases
Chloroethane
Vinyl Chloride
Non-Haloaenated Volatile
Qrganics
Ketones/Furans
Methyl Ethyl Ketone
4-Methyl-2-Pentanone
Tetrahydrofuran
Aromatics
Benzene(g)
Ethyl Benzene (g)
Styrene
Toluene (g)
m-Xylene (g)
o-Xylene (g)
p-Xylene (g)
Inorganics
Arsenic (As)
Cadmium (Cd)
Chromium (Cr)
Cyanide (CN)
Lead(Pb)
Mercury (Hg)
Selenium (Se)
Iron (Fe) *
Halogenated Semivolatile
Organics
PCBs (b)
Aroclor 1242
Aroclor 1254
Aroclor 1260
Pesticides
Chlordane
ODD
DDE
DDT
Dieldrin
Chlorinated Benzenes
1,2-Dichlorobenzene
1,4-Dichlorobenzene
Chlorinated Phenols
Pentachlorophenol (w)
2,3,4,6-Tetrachlorophenol
Non-Halogenated Semivolatile
Organics
PAHs (e)
Acenaphthene
Anthracene
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(ghi)perylene
Benzo(k)tluoranthene
Chrysene
Dibenz(a,h)anthracene
Fluoranthene
Fluorene
lndeno(1,2,3-cd)pyrene
2-Methyl naphthalene
Naphthalene
Phenanthrene
Pyrene
Non-Chlorinated Phenols
m-Cresol (e)
o-Cresol (e)
p-Cresol (e)
2,4-Dimethylphenol (e)
2,4-Dinitrophenol
Phenol
(a) may be component of antiknock fluids added to fuel oils
(b) constituent in some oils, greases, dielectric liquids, and thermostatic fluids
(d) may be present in dye or lacquer solutions
(e) constituent of crude oil fractions (including fuel and motor oils) and/or coal tar
fractions (including creosote); creosote may be present as DNAPL
(g) constituent in fuel oils (e.g. gasoline)
(w) combined with fuel oil #2 or kerosene when used as wood preservative
Note: Some contaminants listed may be present in subsurface as biological or chemical degradation products of others
* Although not normally classified as a contaminant, iron may strongly impact the subsurface behavior of other
contaminants and may govern which treatment processes can or cannot be used.
-------
Table 2. Property Ratings of Chemical Classes Commonly Found at Superfund Sites (from Table 1)
and Applicable Technologies for In-Situ Treatment
Chemical
Class
Melting
Point
Water
Solubility
Vapor
Pressure
Henry'sLaw
Constant
Density
Dynamic Kinematic Log Log Aerobic Potential
Viscosity Viscosity Kov< Koc Biodegradability Subsurface
Mobility
Haloaenated Volatile Oraanics
Liquid Solvents* low moderate/high
Gases low high
Nonhaloaenated Volatile Oraanics
Ketones/furans low high
Aromatics low moderate/high
Haloaenated Semivolatile Orqanics*
PCBs low low
Pesticides high moderate
Chlorinated Benzenes low/moderate moderate
Chlorinated Phenols moderate/high moderate
high
high
high
high
moderate/high
high
moderate
high
low moderate
low low/moderate
moderate high
tow5 low1
Non-Haloaenated Semivolatile Oraanics
PAHs moderate/high tow/moderate moderate/low f.
Non-Chlorinated Pfteno/smoderate high moderde/low low/moderate
high
low
low
low
high
low/high
high
high
high
high
t
NA
f tow/moderate low/moderate f
NA low low ND
low moderate low low ND
moderate moderate/high moderate moderate high
ND
NA
high
NA
NA
high/NA
ND
NA
high
NA
NA
high/NA
high
high
high
high
moderate moderate
high high"
high
low
high
low
low
low
high
highp
moderate
high
moderate/high
high
high
moderate
low
low
moderate
low
low
high
Inorganics
Se, As, CN Cr (VI)
For detailed information on subsurface transport and f;ilt; bvtuivior for these chemicals, see Table 3.
high*'
Hg, Pb, Cd, Cr (III)
low*
-------
Table 2. Property Ratings of Chemical Classes Commonly Found at Superfund Sites (from Table 1)
and Applicable Technologies for In-Situ Treatment (continued)
ConsolidatedDeposits
UnconsolidatedDeposits" UnconsolidatedDeposits0 (SaturatedZone)
(VadoseZone) (SaturatedZone)
Chemical Fractured Karst
Class Homogeneous1 Heterogeneous2 Homogeneous' Heterogeneous' Bedrock Bedrock
Haloqenated Volatile Orqanics
Liquid Solvents'
Gases
Nonhalogenated Volatile Orqanjcs
Ketones/furans
Aroma tics
Haloqenated Semivolallle Organics*
PCBs
Pesticides
Chlorinated Benzenes
Chlorinated Phenols
Non-Haloaenated Semivolatile Oraanics
PAHs
Non-Chlorinated Phenols
Inoraanics
Se, As, CN, Cr (VI)
Hg, Pb, Cd, Cr (III)
SVE(1)
SF(5)
SVE(1)
SVEB(5)
SF(5)
SVE(1)
SF(5)
SF3(5)
ISV(5)
SF3(5)
ISV(5)
SVEB(5)
SF(5)
SF(5)
SVEB(5)
SVEB(5)
SF3(5)
SF(5)
SVEB(5)
SF(5)
ISV(5)
ISV(5)
SF3(10)
SVE(5)
SF(5)
SVE(5)
SVEB(5)
SF(5)
SVE(5)
SF(5)
ISV(5)
SP(5)
ISV(5)
SP(5)
SVF_B(5)
SF{5)
SF(5)
SVEB(10)
SVEB(10)
SP(10)
SF(10)
SVEB(10)
ISV(5)
SF(5)
ISV(5)
SP(10)
P&T + ISB(1)
P&T(1)
P&T(1)
P&T(1)
P&T + ISB(1)
P&T(5)
P&T + CE'(5)
P&T(10)
P&T + CE'(5)
P&T(10)
P&T + ISB(1)
P&T(5)
P&T + ISB(1)
P&T(5)
P&T+CE'(5)
P&T + ISB(5)
P&T + ISB(1)
P&T(1)
P&T(1)
P&T(5)
P&T + CE<(5)
P&T + ISB(5)
P&T(5)
P&T(5)
P&T(5)
P&T + ISB(5)
P&T(5)
P&T + CE<(10)
P&T(10)
P&T+CE'(10)
P&T(10)
P&T + ISB(5)
P&T(5)
P&T + ISB(5)
P&T(10)
P&T + CE'(10)
P&T + ISB(10)
P&T + ISB(5)
P&T(5)
P&T(5)
P&T(10)
P&T+CE'(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(10)
P&T(5)
P&T(5)
P&T(5)
P&T(5)
P&T(10)
P&T(10)
P&T(5)
P&T(10)
P&T(10)
P&T(5)
P&T(5)
P&T(10)
-------
Rating
Melting
Point
fC)
Water
Solubility
(mg/l)
Vapor
Pressure
(mmHg)
Henry'sLaw
Constant
(atm-nf/mol)
Density
(g/cc)
Dynamic
Viscosity
(centipoise)
Kinematic
Viscosity
(centistokes)
Log
K
ow
Log
KOC
Aerobic
Biodegradability
Potential
Subsurface
Mobility*
Table 2. Property Ratings of Chemical Classes Commonly Found at Superfund Sites (from Table 1)
and Applicable Technologies for In-Situ Treatment (continued)
QualitativeRatingKey'
Low
Moderate
High
<13.00
>13.00
<100.00
>100.00
<1.00E+00
>1.00E+00
<1.00E+03
>1.00E+03
<1.00E-03
>1.00E-03
<1.00E+00
>1.00E+00
<1.00E-05
>1.00E-05
<1.00E-03
>1.00E-03
=1
>r
<0.6
;0.6
<0.4
>0.4
<0.8
>0.8
<2.5
<3.5
>3.5
<2.2
>2.2
<3.2
>3.2
veryslowor logKoc>3.2
negligible
moderate 2.2
-------
Table 2. Property Ratings of Chemical Classes Commonly Found at Superfund Sites (from Table 1)
and Applicable Technologies for In-Situ Treatment (continued)
Treatment Technologies
P&T - Pump & Treat
ISB - Bioremediation8
CE - Chemical Extraction
ISV - In-Situ Vitrification
SF - Soil Flushing
SVE - Soil Vacuum Extraction
Uncertainty Rating Key
(1) Low
(5) Moderate
(10) High
Refers to uncertainty in restoring soil/
ground water to health-based or MCL
levels, assuming no NAPLs are present.
Biodegradative processes occur naturally in the subsurface. In situ bioremediation involves the enhancement of these
processes through the addition of amendments such as oxygen and/or nutrients
Unconsolidated deposits refer to gravel, sand, silt or clay or any combination thereof. Deposits consisting primarily
of clay are difficult to remediate and excavation or containment may be the only applicable remedial options
Indicates that the application of soil vacuum extraction will partly or primarily be for purposes of stimulating
biodegradative processes
Refers to a subsurface regime in which the variability in hydraulic conductivity is less than one order of magnitude
Refers to a subsurface regime in which the hydraulic conductivity within the treatment zone varies by more than one
order of magnitude. A heterogeneous subsurface regime may be layered (stratified) or trending. In general, a
trending subsurface regime will be more amenable to treatment than a layered subsurface regime
Water alone will not suffice as a soil flushing extractant
Refers to the use of surfactants or other chemicals to enhance the mobility of contaminants. This technology should
be considered with caution because of its limited success to date and because of the potential environmental impact
of introduced chemicals
-------
Subsurface
Remediation
Guidance
Table 3
-------
Table 3. Properties
Chemical Melting Waterf
Point Solubility
(°C) (mg/l)
of Contaminants Commonly Found at Superfund Sites
Vaporf Henry'sLawf Density! Dynamicf Kinematic! Log Log
Pressure Constant Viscosity Viscosity «o w KOC
(mmHg) (atm-m1' mo I ) (9/cc) (CP) (cs)
Aerobic
Biodegrad-
abilily
MCL(17]
(mg/l)
Halogenated Volatile Organics
Liquid Solvents
Carbon Tetrachlonde
Chlorobenzene
Chlorolorm
Cis-1 ,2-dichloroethylene(d)
I.l-Dichloroethane(a)
1,2-Dichloroethane
1,1-Dichloroethylene
1,2-Dichloropropane(a)
EthyleneDibromide(g)
MethyleneChloride
1 .1 ,2,2-Telrachloroethane
Tetrachloroethylene
Trans-1,2-dichloroethylene(d)
1,1,1-Tnchloroethane
1,1,2-Tnchloroethane
Trichloroethylene
Gases
Chloroethane(b.p.12.5C)
VinylChloride(b.p.-13.9C)
- 23 [7]
• 45 R)
- 64 [7]
- 81 [71
- 97 4 p]
- 35.4 [7]
-122.5 [7]
- 90 [7]
997[7]
- 97 [7]
- 43 [7]
- 22.7 [7]
- 50 [7]
- 32 [7]
- 36 [7]
- 87 [7]
-138.3 [7]
-157 [7]
8 E+02 [1]
4.9 E+02 [1]
8.22 E+03 [1]
3.5 E+03 [1]
5.5 E+03 [1]
8.69 E+03 [1]
4 E+02 [1]
2.7 E+03 [1]
3.4 E+03 [1]
1.32 E+04 [1]
2.9 E+03 [1]
1.5 E+02 [1]
6.3 E+03 [1]
95 E+02 [1]
4.5 E+03 [7]
1 E+03 [1]
5.7 E+03 [1]
1.1 E+03 [1]
913 E+01 [1]
88 ErOO [1]
1.6 E+02 [1]
2 E+02'[7]
1 82 E+02 [1]
6.37 E+01 [1]
5 E+02 [1]
395 E+01 [1]
1.1 E+01 (1)
3.5 E+02 [1]
4.9 E+00 [1]
1.4 E+01 [1]
2.65 E+02 [3]
1 E+02 [1]
1 88 E+01 [3]
5.87 E+01 [1]
1 E+03 [1]
2.3 E+03 [1]
2 E-02 [ 1 ]
346 E-03 '[1]
3,75 E-03 '[1]
7,5 E-03 '[1]
57 E-03 '[1]
1 1 E-03 '(I]
1.54 E-01 '[1]
36 E-03 '[1]
3 18 E-04 [1]
257 E-03 '[1]
5 E-04 '[1]
2.27 E-02 '[1]
66 E-03 '(I]
276 E-03 '[1]
1.17 E-03 J[11]
8.92 E-03 '[1]
11 E-02 [1]
6.95 E-01 [1]
1.5947 [1]
1 106 [1]
1 485 [1]
1 284 [1]
1.175 [1]
1 253 [1]
1.214 [1]
1.158 [1]
2172 [1]
1 325 [1)
1.600 [1]
1 625 [1]
1.257 [1]
1 325 [1]
1.4436 [5]
1.462 [1]
0.9414 OC[1]
0.9121 15C[3]
0965 [1]
0.756|1]
0.563 [1]
0467 [1]
0377 [1]
084 [1]
0 33 [1[
0.84 [1]
1 67621C[1]
0.43 [1]
1.77 [1]
0.89 [1]
0.404 [1]
0.858 [1]
0.119 [3]
0.570 [1]
na
na
0.605 (c)
0683 (c)
0 379 (c)
0 364 (c)
0 321 (c)
0.67 (c)
0.27 (c)
0.72 (c)
0.79 [3]
0.324 (c)
1.10 (c)
0.54 (c)
0.321 (c)
0.647(c)
0824(c)
0.390 (c)
na
na
2.83(1]
2.84(1]
1.97(1]
1 86(1]
179[1]
1.48(1]
2.13 [1]
2.02 [1]
1.76[1]
1.25(1]
2.39(1]
3.14(1]
2.09(1]
2.49(1]
2.17(4]
2.42(1]
1.43(1]
0.60(4]
2.64(1]
22 [1]
1 64(1]
1.5 [1]
1.48(1]
1.15(1]
181(1]
1.71(1]
1.45(1]
0.94 [1]
234(1]
2.82(1]
1.77(1]
2.18(1]
1 75(13]
2.10(1]
1.17(1]
0.91 [1]
D[2]
D5.A10|2]
A [2]
B[2]
A [2]
B [2]
A [2]
A [2]
nd
D [2]
N [2]
A [2]
B [2]
C [2]
C [2]
A [2]
nd
nd
5 (1)
100 (p)
nd
70 (p)
nd
5 (1)
7 (D
5 (P)
0.05(p)
5 (1)
nd
5 (P)
70(p)
200 (1)
nd
5 (f)
nd
2 (f)
Non-Halogenated Volatile Organics
Ketones/furans
Methyl ElhylKetone
4-Melhyl-2-Pentanone
Tetrahydroluran
- 86.4 [7]
- 83 [7)
-108.5 [7]
2.68 E+05 [11]
1 9 E+04 [3]
3 E+05'[6)
7.12 E+01 [3]
1.6 E+01 [3]
4.56 E+01 t(4]
2.74 E-05 t[11]
1.55 E-04 }[13]
1.1 E-04 J(14]
0.805 (5]
0.8017 [7]
0.8892 [6]
0.40 [3]
0.5848[3]
0.55 [13]
0.497(c)
0.729(c)
0.618 (c)
0.29 [17]
1.25
046 [14]
0.65 [11]
1.38(15]
nd
nd
nd
nd
nd
nd
nd
-------
Chemical
Table 3. Properties of Contaminants Commonly Found
at Superfund Sites (continued)
Melting Water t Vapor f Henry's Law f Density t Dynamict Kinematicf Log
Point Solubility Pressure Constant Viscosity Viscosity Kow
(°C) (mg/l) (mmHg) (atm-nf/mol ) (g/cc) (cp) (cs)
Aromatics
Benzene(g) 5.5 [7]
EthylBenzene(g) -94. 97 [7]
Styrene -30.6 [7]
Toluene(g) -95.1 [7]
m-Xylene(g) -50 [7]
o-Xylene(g) -25 [7]
p-Xylene(g) 13 [7]
Halogenated Semivplatile Ornanic
PCBs (b)
Aroclor1242
Aroclor1254
Aroclor1260
Pesticides
Chlordane
ODD
DDE
DDT
Dieldrin
Chlorinated Benzenes
1 ,2-Dichlorobenzene
1 ,4-Dichlorobenzene
Chlorinated Phenols
Pentachlorophenol(w)
2,3,4,6-Tetrachlorophenol
-19 [1]
10 [1]
nd
106 [1]
112 [7]
88.4 [1]
108 [7]
176.5 [7]
-17 [7]
53 [7]
190 [7]
69.5 [7]
1.78E+03 [1]
1.52E+02 [1]
3 E+02 [7]
5.15 E+02 [1]
2 E+02 [3]
1.7 E+02 [3]
1.98 E+02'[3]
S
4.5 E-01'[1]
1.2 E-02 [1]
2.7 E-03 [1]
5.6 E-02*[1]
1.60 E-0124C[7]
4.0 E-02 [7]
3.1 E-03 [1]
1.86 E-01 J[4]
1 E+02 [1]
8 E+01 [1]
1.4 E+01 [1]
1.00 E+03t[11]
7.6 E+01 [1] 5.43 E-03 '[13] 0.8765 [1]
7 E+00 [1] 7.9 E-03 '[1] 0.867 [7]
5 E+00 [7] 2.28 E-03 [7) 0.9060 [13]
2.2 E+01 [1] 6.61 E-03 '[13] 0.8669 [1]
9 E+00 [1] 6.91 E-03 '[1] 0.8642 '[1]
7 E+00 [1] 4.94 E-03 '[1] 0.880 *[1]
9 E+00 [1] 7.01 E-03 '[1] 0.8610 *[1]
4.06 E-04'[9] 3.4 E-04 [1] 1.385 [1]
7.71 E-05'[9] 2.8 E-04 [1] 1.538 +-[9]
4.05 E-05'[9] 3.4 E-04 [1] 1.4430C[1]
1 E-05 [1] 2.2 E-04 '[1] 1.6 *[1]
1 E-06 30C[17] 7.96 E-06 t[11] 1.385 [17]
6.40 E-06 [1] 1.9 E-04 '[1] nd
1.5 E-07 [1] 2.8 E-05 '[1] 0.985 [1]
1.78 E-07 [3] 9.7 E-06 *[8] 1.75 [3]
9.6 E-01 [1] 1.88 E-03 *[1] 1.306 [1]
6 E-01 [1] 1.58 E-03 *[1] 1.2475 [1]
1.1 E-04 [1] 2.8 E-06 [1] 1.978 [1]
nd nd 1.839 *[5]
0.6468(1] 0.7379(c) 2.13 [1]
0.678 [3] 0.782 (c) 3.15 [1]
0.75! [13] 0.829 (c) 3.16 [14]
0.58 [1] 0.669 (c) 2.73 [1]
0.608(1] 0.717(3] 3.20(1]
0.802(1] 0.932(3] 3.12(1]
0.635(1] 0.753(3] 3.15(1]
nd nd 5.58 [9]
nd nd 6.03 [9]
nd nd 7.15(9]
1.104 [3] 0.69 (c) 5.48(1]
na na 5.56(1]
na na 5.69(1]
na na 6.36(1]
na na 5.34 [4]
1.302 [1] 0.997 (c) 3.38 [1]
1.258 [1] 1.008 (c) 3.39(1]
na na 5.12(1]
na na 4.1 [11]
Log
Koc
1.81 [1]
2.83(1]
nd
2.41 [1]
2.84(1]
2.84(1]
2.84(1]
5 [1]
nd
nd
4.58(1]
5.38(1]
5.41 [1]
5.48(1]
3.23 [14]
3.06[1]
3.07(1]
4.80(1]
2.0 [11]
Aerobic MCL[17]
Biodegrad-
ability (mg/l)
D[2]
D5,A10[2]
nd
D[2]
nd
nd
nd
N [2]
N [2]
N [2]
N [2]
M[2]
M [2]
M[2]
N [2]
T [2]
T [2]
A [2]
nd
5 (f)
700 (p)
nd
2000 (p)
10000(p)
10000(p)
10000(p)
nd
nd
nd
2 (P)
nd
nd
nd
nd
600 (p)
750 (f)
nd
nd
-------
Table 3. Properties of Contaminants Commonly Found
at Superfund Sites (continued)
Chemical Melting Walerf Vaporf Henry'sLawf Densityt Dynamicf Kinematicf Log Log Aerobic MCL[17]
Point Solubility Pressure Constant Viscosity Viscosity KO w Koc Biodegrad-
(°C ) (mg/l) (mmHg) (atm-m5/ mo I ) (g/cc) (cp) (cs) ability (mg/l)
Non-Haloaenated Semivolatile Orqanics
PAHs (e)
Acenaphthene
Anthracene
Benzo(a)anlhracene
Benzo(a)pyrene
Benzo(b)tluoranlhene
Benzo(ghi)perylene
Benzo(k)lluoranlhene
Chrysene
Dibenz(a,h)anthracene
Fluoranthene
Fluorene
lndeno(1 ,2.3-cd)pyrene
2-Methylnaphlhalene
Naphthalene
Phenanlhrene
Pyrene
Non-Chlorinated Phenols
Dheio
2 4-Dimeihvlphencve
2.4-Dmrtrophenol
m-Cresol(e)
o-Cresol(e)
p-Cresol(e)
92.5 [7]
216.3 [7]
167 [4]
179 [7]
167 [4]
278 [12]
217 [12]
254 [7]
266.5 [7]
107 [7]
116.7 [12]
163 [12]
34 58 [7]
80.2 [4]
100 [7]
150 [7]
41 [7]
26 [7]
112 [7]
12 [7]
31 [7]
34.8 [7]
3.88 E+00 '[8]
7.5 E-02 '[8]
1.4 E-02 '[12]
3.8 E-03 t[12]
1.4 E-02 t[11]
2.6 E-04 '[7]
4.30 E-03 }[11]
6 E-03 '[7]
2.5 E-03 i(12]
2.65 E-01 '[7]
1.90 E+00 '[8]
5.30 E-04 i[11]
2.54 E+01 '[8]
3.1 E+01 '[12]
1.18 E+00 '[8]
1.48 E-01 '[8]
8.4 E+04 [1]
6.2 E+03 *[3]
6 E+03 '[3]
2.35 E+04 [7]
3.1 E+04 40C[7]
2.40 Ej-04 40C[7]
2.31 E-02 '(8]
1.08 E-05 '[8]
1.16 E-09 i(11]
549 E-09 §(18]
5.00 E-07 t[12]
1 E-10 [14]
9.59 E-11 [14]
6.3 E-09 '[14]
1 E-10 t(12]
E-02[10]E-06[12]
6.67 E-04 '(8)
1 E-10+-[11]
6.80 E-02 '[8]
2.336E-01 '[12]
2.01 E-04 '[8]
6.67 E-06 '[8]
5.293E-01 [1]
9.8 E-02 *[3]
1.49 E-05 flU)
1.53 E-01 '[12]
2.45 E-01 '[12]
1.08 E-01 '[12]
1.20 E-03 *[c]
3.38 E-05 'JCJ
4.5 E-06 [12]
1 8 E-05 t(12]
1.19 E-05 t[11]
5.34 E-08 i[11]
3.94 E-05 t(11]
1.05 E-06 '[14]
7.33 E-08 t(11]
6.5 E-06 '(14]
7.65 E-05 '[c]
6.95 E-08 '[14]
5.06 E-02 '[c]
1.27 E-03 '[c]
3.98 E-05 '[c]
1.20 E-05 '[c]
7.80 E-07 [c]
2.5 E-06 '[c]
6.45 E-10 [11]
3.8 E-05 +-[12]
4.7 E-05 +-[12]
3.5 E-04 +-[12]
1.225(12]
1.25 [12]
1.174(12]
nd
nd
nd
nd
1.274 (7]
1.252 [12]
1.252 [12]
1.203 [12]
nd
1.0058 [12]
1.162 [12]
0.9800 [12]
1.271 [12]
1.0576 41C[1]
1.036 [7]
1.68 [3]
1.038 [7]
1.0273 [12]
1.0347 [7]
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
3.0250C[1]
na
na
21 [12]
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
3.87 46C
na
na
20 (c)
na
na
3. 92 [12]
4.45 (12]
5.61 [12]
6.06(11)
6.57 [12]
6.51 [11]
6.06(11]
5.61 (11]
6.80 [11]
4.90(12]
4.18(12]
6.5 [11]
3.86(12]
3.30(12]
4.46 [12]
4.88 [12]
1.46 (1)
2.50 [4]
1.54 [3]
1.96 [12]
1.95 [12]
1.94 [7]
3. 7 [11]
4.1 [11]
6.14(11]
6.74(11]
5.74[11]
6.2 [11]
5.74(11]
5.3 (11)
6.52(11]
4.58(11]
3.9 [11]
6.2 [11]
3.93(14]
3.11 [14]
4.1 [11]
4.58[11]
1.15(11]
2.35(14]
1.22(11]
1.43(15]
1.23(15)
1.28(15]
D[2]
A|2]
N(2]
nd
nd
nd
nd
A5,N10[2]
nd
A5,N10[2]
A [2]
nd
nd
D [2]
D [2]
D5,N10[2)
D [2]
D [2]
D [2]
nd
nd
nd
nd
nd
nd
02 (I)
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
-------
Table 3. Properties of Contaminants Commonly Found
at Superfund Sites (continued)
CHEMICAL
MCL
Inorganics
arsenic(As)
cadmium (Cd)
chromium (Cr)
cyanide (CN)
iron(Fe)
lead(Pb)
mercury(Hg)
selenium(Se)
May occur in morethanoneoxidation state in subsurface. Arsenateform(As043~) will dominate underoxidizing
conditions. Moretoxicandmobilearseniteform(As03') maydominateunderincreasingly reducing and acidic
conditions.Volatilealkylated-Ascompoundsmayformunderredudngconditions.VolatilearsinefAsHJ may
formunder highly reducing conditions. Adsorptionofarsenateandarsenite forms will generally increase withdecreasingpH.
Occursonlyindivalentforminaqueoussolutions(e.g.Cd!*,CdCI*,CdS04°).Cd2»tendstobedominantspecies.
Adsorption behaviorcorrelates with cationexchange capacity (CEC)ofsoilandaquifermaterial. Adsorption/
precipitation increases with increasingpH with most Cdprecipitatingout at pH>6.
May occur in morethanone oxidation statein subsurface. Trivalent form (Cr III) isdominant under pH and redox
conditions generally present insubsurlace.Cr III maybeconvertedto highly mobile andtoxichexavalent form
(Cr VI) underoxidizing conditions. Cr III is readily adsorbed inthesubsurfacewhileCr VI is not.
Cyanide ion (CN~ (predominatesin aqueous solution only at pH>9. Hydrogen cyanide (HCN) predominates at pH<9. H CN i s
volatile(v.p.741mmHgat25C)andtoxic.CN'behavessimilartohalideionsandtendstocomplexwithiron.Undissolvedcyanide
salts may bepresent in vadosezone.
May occur in morethan one oxidationstateinthe subsurface. Ferrous form (Fe2*) is most soluble and mobile, and
dominates underreducingconditions. Underoxidizing conditions, ferrousform isconvertedtoferricform(Fe3*).
Ferricform is less soluble, less mobile, and willtendtoprecipitate.Compoundsandmetalscomplexedtoiron may
be removed from solution throughtheprecipitationprocess.Conversely, compoundsand metals adsorbed to iron
inthesubsurface maybe increasingly mobilized under increasinglyreduced conditions. Precipitated iron may
hindertreatment processes such asin-situbioremediation and airstripping.
DominantspeciesinaqueoussolutionarePb2* underacidicconditionsandPb2*-carbonate complexes under
alkaline conditions. Adsorptionbehaviorcorrelateswithcationexchangecapacity(CEC)of soil and aquifer
material. Adsorption/precipitation JncreaseswithincreasingpHwithmostPbprecipitatingoutatpH>6. Volatile
alkylated-Pbcompoundsmaybepresentormaylorm under reducirigconditions.
Mayoccur in morethanoneoxidation state. May occur in subsurface in mercuricform(Hg2*),mercurous form
(Hg22*), elemental form (Hg°), and in alkylated form (e.g. methyl and ethyl mercury). Hg22*andHg2-are more
stable under oxidizing conditions and arestrongly adsorbed by soils. Hg°andalkylated forms are morestable under
reducing conditions. Conversion to alkylated forms may occur underreducing conditions. Hg°and a Iky la ted-
Hgforms are volatile, toxic, and may not be as strongly adsorbedbysoils.
May occurin morethan one oxidation statein subsurface. Selenateform(Se042 ) will dominate underoxidizing
conditions. Seleniteform(Se032)willdominateunderincreasingly reducing conditions. SelenideformfSe2 •) may
dominate under highly reducing conditions. Selenate and selenite are more soluble and mobile forms. Adsorption
ofselenateandselenitewillgenerallyincrease withdecreasingpH. Volatilealkylated-Secompoundsmayform
under reducing conditions.
nd
5(P)
100(p)
200 (t)
300 (f)
5(P)
2(P)
50 (p)
-------
Table 3. Properties of Contaminants Commonly Found
at Superfund Sites (continued)
A - significant degradationwithgradualadaption
B - slowtomoderateactivity.concomilantwithsigmlicant raleotvolatilizalion
C - veryslowbiodegradativeactivity.withlongadaptionperiodneeded
D - significant degradation with rapid adaption
M - notsignificantlydegradedundertheconditionsofthe testmethod
N - not significantly degiadedunderthe conditions of test method and/or precluded by extensive rate ol voiatilization
T - significantdegradationwithgradualadaptionfollowedbydeadaptiveprocessinsubsequentsubcultures(toxicity)
(a) - maybecomponentolantiknockfluidsadded to fueloils;remedialtreatment may require consideration of
constituent in oil phase
(b) - constituentinsomeoils,greases, dielectricliquids, and thermostatic fluids; remedial treatment may require
consideration of constituent in oil phase
(c) - calculated
(d) - maybepresentindyeor lacquer solutions; remedialtreatment may requireconsideration of constituent in oil phase
(e) - constituentof crude oil fractions (including fuel oils and motor oils) and/or coal tar tract ions (including creosote);
creosote maybe present as DNAPL; remedial treatment may requireconsideration of constituent in oilphase
(f) - final MCL
(g) - constituent in fuel oils (e.g. gasoline); remedial treatment may requireconsiderationof constituent in oil phase
(p) - proposed MCL
(I) - tentativeMCL
(w) - combined with lueloil #2 orkerosenewhenusedas wood preservative; remedialtreatmentmay require
consideration of constituentinoilphase
na - not applicable
nd - nodatafound
Reference
f - Valuesaregivenat20°Cunlessotherwisespecified
Valueisat25°C
J - Valueisatunknowntemperaturebutisassumedtobeat20-30°C
-------
APPENDIX 2
Table for Hydraulic Conductivity Units Conversion
Unit
1 meter/day
1 centimeter/second
1 foot/day
1 gallon/day/ ft2
m/d
1
8.64 x 102
3.05 x 10'1
4.1 x lO'2
cm/s
1.16 x lO'3
1
3.53 x 1Q-4
4.73 x 1(T5
ft/day
3.28
2.83 x 103
1
1.34 x 10'1
gal/day/ft2
2.45 x 101
2.12 x 104
7.48
1
-------
APPENDIX 3
U.S.D.A. Soil Texture Triangle
100
% by Weight Clay
Clay loam
Y//////
% by Weight Silt
100
O
O
100 90 80 70 60 50 40 30 20 10
^
% by Weight Sand
------- |