United States R.S. Kerr Office of Solid Waste Publication: 9355.4-07FS
Environmental Environmental and Emergency January 1992
Protection Agency Research Laboratory Response
SEP A Estimating Potential for Occurrence
of DNAPL at Superfund Sites
Office of Emergency and Remedial Response
Hazardous Site Control Division (OS-220W) Quick Reference Fact Sheet
GOALS
The presence of Dense Nonaqueous Phase Liquids (DNAPL) in soils and aquifers can control the ultimate success or failure
of remediation at a hazardous waste site. Because of the complex nature of DNAPL transport and fate, however, DNAPL
may often be undetected by direct methods, leading to incomplete site assessments and Inadequate remedial designs. Sites
affected by DNAPL may require a different "paradigm," or conceptual framework, to develop effective characterization and
remedial actions (2).
To help site personnel determine if DNAPL-based characterization strategies should be employed at a particular site, a
guide for estimating the potential for DNAPL occurrence was developed. The approach, described in this fact sheet,
requires application of two types of existing site information:
Historical Site Use Information Site Characterization Data
By using available data, site decision makers can enter a system of two flowcharts and a classification matrix for estimating
the potential for DNAPL occurrence at a site. If the potential for DNAPL occurrence is low, then conventional site
assessment and remedial actions may be sufficient. If the potential for DNAPL is moderate or high, however, a different
conceptual approach may be required to account for problems associated with DNAPL in the subsurface.
BACKGROUND
DNAPLs are separate-phase hydrocarbon liquids that are denser than water, such as chlorinated solvents (either as a single
component or as mixtures of solvents), wood preservative wastes, coal tar wastes, and pesticides. Until recently, standard
operating practice in a variety of industries resulted in the release of large quantities of DNAPL to the subsurface. Most
DNAPLs undergo only limited degradation in the subsurface, and persist for long periods while slowly releasing soluble
organic constituents to ground water through dissolution. Even with a moderate DNAPL release, dissolution may continue
for hundreds of years or longer under natural conditions before all the DNAPL is dissipated and concentrations of soluble
organics in ground water return to background levels.
DNAPL exists in the soil/aquifer matrix as free-phase DNAPL and residual DNAPL. When released at the surface, free-
phase DNAPL moves downward through the soil matrix under the force of gravity or laterally along the surface of sloping
fine-grained stratigraphic units. As the free-phase DNAPL moves, blobs or ganglia are trapped in pores and/or fractures by
capillary forces (7). The amount of the trapped DNAPL, known as residual saturation, is a function of the physical
properties of the DNAPL and the hydrogeologic characteristics of the soil/aquifer medium and typically ranges from 5% to
50% of total pore volume. At many sites, however, DNAPL migrates preferentially through small-scale fractures and
heterogeneities in the soil, permitting the DNAPL to penetrate much deeper than would be predicted from application of
typical residual saturation values (16).
Once in the subsurface, it is difficult or impossible to recover all of the trapped residual DNAPL. The conventional aquifer
remediation approach, ground water pump-and-treat, usually removes only a small fraction of trapped residual DNAPL
(11, 21, 26). Although many DNAPL removal technologies are currently being tested, to date there have been no field
demonstrations where sufficient DNAPL has been successfully recovered from the subsurface to return the aquifer to
drinking water quality. The DNAPL that remains trapped in the soil/aquifer matrix acts as a continuing source of dissolved
contaminants to ground water, preventing the restoration of DNAPL-affected aquifers for many years.
-------
DNAPL TRANSPORT AND FATE - CONCEPTUAL APPROACHES
The major factors controlling DNAPL migration in the subsurface include the following (5):
the volume of DNAPL released;
the area of infiltration at the DNAPL entry point to the subsurface;
the duration of release;
properties of the DNAPL, such as density, viscosity, and interfacial tension;
properties of the soil/aquifer media, such as pore size and permeability;
general stratigraphy, such as the location and topography of low-permeability units;
micro-stratigrapnic features, such as root holes, small fractures, and slickensides found in silt/clay layers.
To describe the general transport and fate properties of DNAPL in the subsurface, a series of conceptual
models (24) are presented in the following figures:
Case 1: DNAPL Release to Vadose Zone Only
After release on the surface, DNAPL moves
vertically downward under the force of gravity
and soil capillarity. Because only a small amount
of DNAPL was released, all of the mobile DNAPL
is eventually trapped in pores and fractures in the
unsaturated zone. Infiltration through the
DNAPL zone dissolves some of the soluble
organic constituents in the DNAPL, carrying
organics to the water table and forming a
dissolved organic plume in the aquifer. Migration
of gaseous vapors can also act as a source of
dissolved organics to ground water (13).
ONAPL
Residual
Saturation of
DNAPL in
Vadose Zone
Infiltration, Leaching
and Mobile ONAPL
Vapors
Dissolved Contaminant Plume
From DNAPL Soil Vapor
Ground Water
* Flow
Dissolved Contaminant
Plume From DNAPL
Residual Saturation
Afw. WiwIooCwiWtorOfOundwMr RtMVCh. 1969.
Case 2: DNAPL Release to Unsaturated and
Saturated Zones
If enough DNAPL is released at the surface, it can
migrate all the way through the unsaturated zone
and reach a water-bearing unit. Because the
specific gravity of DNAPL is greater than water, it
continues downward until the mobile DNAPL is
exhausted and is trapped as a residual
hydrocarbon in the porous media. Ground water
flowing past the trapped residual DNAPL
dissolves soluble components of the DNAPL,
forming a dissolved plume downgradient of the
DNAPL zone. As with Case 1, water infiltrating
down from the source zone also carries dissolved
constituents to the aquifer and contributes further
to the dissolved plume.
Residual
Saturation of
DNAPL in Soil
From Spill
Dissolved
Contaminant Plume
Residua)
Saturation In Saturated Zone
Ground Water
Row
Mm. Watrtoo Cwn tor Qragndmw RMMR*I. 1989
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CONCEPTUAL APPROACHES - Continued
Case 3: DNAPL Pools and Effect of Low-
Permeability Units
Mobile DNAPL will continue vertical migration
until it is trapped as a residual hydrocarbon (Case
1 and Case 2) or until low-permeability
stratigraphic units are encountered which create
DNAPL "pools" in the soil/aquifer matrix. In this
figure, a perched DNAPL pool fills up and then
spills over the lip of the low-permeability
stratigraphic unit. The spill-over point (or points)
can be some distance away from the original
source, greatly complicating the process of
tracking the DNAPL migration.
Dissolved
Contaminant
PUme
Residu
DNAPL
Low Permeable
^Stratigraphic Unit
Sand
Ground Water
Flow
Case 4: Composite Site
In this case, mobile DNAPL migrates vertically
downward through the unsarurated zone and the
first saturated zone, producing a dissolved
constituent plume in the upper aquifer. Although
a DNAPL pool is formed on the fractured clay
unit, the fractures are large enough to permit
vertical migration downward to the deeper
aquifer (see Case 5, below). DNAPL pools in a
topographic low in the underlying impermeable
unit and a second dissolved constituent plume is
formed.
Dissolved
Contaminant
Plumes
Residual DNAPL
*
DNAPL Pool
Sand
Aim. Witwtto Cftrn tor Ground Wanr Rnrnich. 19M.
Clay
Case 5: Fractured Rock or Fractured Clay System
DNAPL introduced into a fractured rock or
fractured day system follows a complex pathway
based on the distribution of fractures in the
original matrix. The number, density, size, and
direction of the fractures usually cannot be
determined due to the extreme heterogeneity of a
fractured system and the lack of economical
aquifer characterization technologies. Relatively
small volumes of DNAPL can penetrate deeply
into fractured systems due to the low retention
capacity of the fractures and the ability of some
DNAPLs to migrate through very small (<20
microns) fractures. Many day units, once
considered to be relatively impermeable to
DNAPL migration, often act as fractured media
with preferential pathways for vertical and
horizontal DNAPL migration.
Fractured
Rock or
Fractured
Clay .
Ater. VMMloo C«nn tor Oreund WMr RnMitfi. 1
-------
DoesHistorical Site Use Information Indicate Presence of PNAFL?
YES
u
c
o
-i
i
I
8
c
g
Does the
industry type suggest a high
probability of historical
DNAPL release?
(see Table!)
Does a
process or waste
practice employed at the site
suggest a high probability of
historical DNAPL release?
(see Table 2)
Were any
DNAPL-related chemicals
used in appreciable quantities at the site?
(> 10-50 drums/year)
(see Table 3)
Co To Next Page
INSTRUCTIONS
I. Answer questions in Flowchart 1
(historical site use info. page 4).
2. Answer questions in Flowcliart 2
(site characterization data page 5).
3. Use "Yes." "No." and "Maybe"
answers from both flowcharts and enter
Occurrence of DNAPL matrix
(page 6).
TABLE 1
Industries with high probability
of historical DNAPL release:
Wood preservation (creosote)
Old coal gas plants
(mid-1800s to mid-1900s)
Electronics manufacturing
Solvent production
Pesticide manufacturing
Herbicide manufacturing
Airplane maintenance
Commercial dry cleaning
Instrument manufacturing
Transformer oil production
Transformer reprocessing
Steel industry coking
operations (coal tar)
Pipeline compressor stations
TABLE 2
Industrial processes or waste
disposal practices with high
probability of historical DNAPL
release:
Metal cleaning/degreasing
Metal machining
Tool-and-die operations
Paint removing/stripping
Storage of solvents in
underground storage tanks
Storage of drummed solvents
in uncontained storage areas
Solvent loading and unloading
Disposal of mixed chemical
wastes in landfills
Treatment of mixed chemical
wastes in lagoons or ponds
TABLE 3 DNAPL-Related Chemicals (20):
Note:
The potential for DNAPL release increases with the size
and active period of operation for a facility, industrial
process, or waste disposal practice.
Halogenated Volatile*
Chlorobenzene
1,2-Dichloropropane
1,1 -Dichloroethane
1,1-Dichloroethylene
1,2-Dichloroethane
Trans-1,2-Dichloroethylene
Cis-1,2-Dichloroethylene
1,1,1-Trichloroethane
Methylene Chloride
1.1.2-Trichloroethane
Trichloroethylene
Chloroform
Carbon Tetrachloride
1,1^2-TetracWoroethane
Tetrachloroethylene
Ethylene Dibromide
Halogenated
Semi-VoUtiles
1,4-Dichlorobenzene
14-Dichlorobenzcne
Arodor 1242,1254,1260
dlordane
Dieldrin
2,3,4,6-Tetrachlorophenol
Pentachlorophenol
Non-Halogenated
Semi-Volatile*
2-Methyl Napthalene
o-Cresol
p-Cresol
2,4-Dimethylphenol
m-Cresol
Phenol
Naphthalene
6enzo(a)Anthracene
Fluorene
Acenaphthene
Anthracene
Dibenzo(a,h)Anthracene
Ruoranthene
Pyrene
Chrysene
2,4-Dinitrophenol
Miscellaneous
Coal Tar
Creosote
Note: Many of these
chemicals are found
mixed with other chemicals
or comer oils.
-------
(Do Site Characterization Data Indicate Presence of DNAPL?^
u
c
o
1-*
CO
nJ
5!
8
c
o>
fc
3
u
u
Has DNAPL
been found in monitoring wells,
observed in soil cores, or physically
observed in the aquifer?
(see Table 4)
Do chemical
analyses of ground water
or soil indicate the possible presence of
DNAPL at the site?
(see Table 5)
(Standard
Reid
Program)
Is it likely that
the existing field program could
miss DNAPL at the site?
(see Table 6)
(Extensive Field Program)
Co To Next Page
INSTRUCTIONS
I. Answer questions in Flowchart I
(historical site use info. page 4).
2. Answer questions in Flowchart 2
(site characteriiation data page 5).
3. Use 'Yes," "No."and "Maybe"
answers from both flowcharts and enter
Occurrence of DNAPL matrix
(page 6).
TABLE 4
Methods to confirm DNAPL in wells:
NAPL/water interface probes that signal a
change in conductivity of the borehole fluid
Weighted cotton string lowered down well
Pumping and inspecting recovered fluid
Transparent bottom-loading bailers
Mechanical discrete-depth samplers.
In general, the depth of DNAPL accumulation
does not provide quantitative information
regarding the amount of DNAPL present (24).
Methods to confirm DNAPL in soil samples;
Visual examination of cores or cuttings may not
ye effective for confirming the presence of
DNAPL except in cases of gross DNAPL
contamination. Methods for enhancing visual
inspection of soil samples for DNAPL include:
Shaking sofl samples in a Jar with water to
separate the DNAPL from the soil (14).
Performing a paint filter test, in which soil is
placed in a filter funnel, water is added, and the
filter is examined for separate phases (20).
TABLES
Conditions that indicate potential for
DNAPL at site based on laboratory data:
Condition 1:
Concentrations of DNAPL-related chemicals
(see pg. 3) in ground water are > 1% of pure
phase solubility or effective solubility,
(defined in Worksheet 1, pg. 7) (25).
Condition 2:
Concentrations of DNAPL-related chemicals
on soils are > 10,000 mg/kg (equal to 1 % of
soil mass) (6).
Condition 3:
Concentrations of DNAPL-related chemicals
in ground water calculated from water/soil
partitioning relationships and soil samples
are > pure phase solubility or effective
solubilityfeee Worksheet 2, pg. 7).
Condition 4:
Concentrations of DNAPL-related chemicals
in ground water increase with depth or
appear in anomalous upgradient/across
gradient locations (25).
Note: This procedure is designed primarily for hydrogeologic settings comprised of gravel, sand, silt, or
clay and may not be be applicable to karst or fractured rock settings.
TABLE 6
Characteristics of extensive field
programs that can help indicate the
presence or absence of DNAPL (if
several are present, select "NO"):
Numerous monitoring wells, with
wells screened in topographic lows
on the surface of fine-grained,
relatively impermeable units.
Multi-level sampling capability.
Numerous organic chemical analyses
of soil samples at different depths
using GC or GC/MS methods.
Well-defined site stratigraphy, using
numerous soil borings, a cone
penetrometer survey, or geophysics.
Data from pilot tests or "early action"
projects that indicate the site
responds as predicted by
conventional solute transport
relationships, rather than responding
as if additional sources of dissolved
contaminants are present in the
aquifer (11,25).
-------
Potential for Occurrence of DNAPL at Superfund Sites J
DNAPL Category
Do Characterization Data Indicate
Presence of DNAPL? (Chart 2)
Category
I Confirmed or
high potential
for DNAPL
at site.
Implications for Site Assessment
The risk of spreading contaminants increases with the proximity to a potential DNAPL zone. Special
precautions should be taken to ensure that drilling does not create pathways for continued vertical
migration of free-phase DNAPLs. In DNAPL zones, drilling should be suspended when a low-
permeability unit or DNAPL is first encountered. Wells should be installed with short screens (£10
*eet). If required, deeper drilling through known DNAPL zones should be conducted only by using
double or triple-cased wells to prevent downward migration of DNAPL As some DNAPLs can
penetrate fractures as narrow as 10 microns, special care must be taken during all grouting,
cementing, and well sealing activities conducted in DNAPL zones.
In some hydrogeologic settings, such as fractured crystalline rock, it is impossible to drill through
DNAPL with existing technology without causing vertical migration of the DNAPL down the
borehole, even when double or triple casing is employed (2).
The subsurface DNAPL distribution is difficult to delineate accurately at some sites. DNAPL
migrates preferentially through selected pathways (fractures, sand layers, etc.) and is affected by
small-scale changes in the stratigraphy of an aquifer. Therefore, the ultimate path taken by DNAPL
can be very difficult to characterize and predict.
In most cases, fine-grained aquitards (such as clay or silt units) should be assumed to permit
downward migration of DNAPL through fractures unless proven otherwise in the field. At some
sites it can be exceptionally difficult to prove otherwise even with intensive site investigations (2).
Drilling in areas known to be DNAPL-free should be performed before drilling in DNAPL zones in
order to form a reliable conceptual model of site hydrogeology, stratigraphy, and potential DNAPL
pathways. In areas where it is difficult to form a reliable conceptual model, an "outside-in" strategy
may be appropriate: drilling in DNAPL zones is avoided or minimized in favor of delineating the
outside dissolved-phase plume (2). Many fractured rock settings may require this approach to
avoid opening further pathways for DNAPL migration during site assessment
Moderate Due to the potential risk for exacerbating ground-water contamination problems during drilling
potential for through DNAPL zones, the precautions described for Category I should be considered during site
DNAPL at site, assessment Further work should focus on determining if the site is a "DNAPL site."
HI Low potential DNAPL is not likely to be a problem during site characterization, and special DNAPL precautions
for DNAPL are probably not needed. Floating free-phase organics (LNAPLs), sorption, and other factors can
at site. complicate site assessment and remediation activities, however.
-------
Worksheet 1: Calculation Of Effective Solubility (from Shiu, 1988; Feenstra, Mackay, & Cherry, 1991)
For a single-component DNAPL, the pure-phase solubility of the organic constituent can be usec! to estimate the theoretical
upper-level concentration of organics in aquifers or for performing dissolution calculations. For DNAPLs comprised of a
mixture of chemicals, however, the effective solubility concept should be employed:
e
S i = the effective solubility (the theoretical upper-level dissolved-phase concentration
Q-_ Y c i of a constituent in ground water in equilibrium with a mixed DNAPL; in mg/1)
i i i I Where ^. = the mole fraction of component i in the DNAPL mixture (obtained from a lab
analysis of a DNAPL sample or estimated from waste characterization data)
S j = the pure-phase solubility of compound i in mg/1 (usually obtained from
literature sources)
For example, if a laboratory analysis indicates that the mole fraction of trichloroethylene (TCE) in DNAPL is 0.10, then the
effective solubility would be 110 mg/1 [pure phase solubility of TCE times mole fraction TCE: (1100 mg/1) * (0.10) = 110
mg/1]. Effective solubilities can be calculated for all components in a DNAPL mixture. Insoluble organics in the mixture
(such as long-chained alkanes) will reduce the mole fraction and effective solubility of more soluble organics but will not
contribute dissolved-phase organics to ground water. Please note that this relationship i$ approximate and does not account for
non-ideal behavior of mixtures, such as co-solvency, etc.
Worksheet 2: Method for Assessing Residual NAPL Based on Organic Chemical
Concentrations in Soil Samples (From Feenstra, Mackay, and Cherry, 1991)
To estimate if NAPLs are present, a partitioning calculation based on chemical and physical analyses of soil samples from
the saturated zone (from cores, excavations, etc.) can be applied. This method tests the assumption that all of the organics
in the subsurface are either dissolved in ground water or adsorbed to soil (assuming dissolved-phase sorption, not the
presence of NAPL). By using the concentration of organics on the soil and the partitioning calculation, a theoretical pore-
water concentration of organics in ground water is determined. If the theoretical pore-water concentration is greater than
the estimated solubility of the organic constituent of interest, then NAPL may be present at the site. A worksheet for
performing this calculation is presented below; see Feenstra, Mackay, and Cherry (1991) for the complete methodology.
Step 1: Calculate Sj , the effective solubility of organic constituent of interest. See Worksheet 1, above, fc
Step 2: Determine Koc, the organic carbon-water partition coefficient from one of the following:
A) Literature sources (such as 22) or
B) From empirical relationships based on Kow, the octanol-water partition coefficient, which is also found in the
literature (22). For example, Koc can be estimated from Kow using the following expression developed for
polyaromatic hydrocarbons (8):
I Log Koc = 1.0 * Log Kow - 0.21 I Other empirical relationships between Koc
and Kow are presented in refs. 4 and 15.
Step 3: Determine foe, the fraction of organic carbon on the soil, from a laboratory analysis of clean soils from the site.
Values for foe typically range from 0.03 to 0.00017 mg/mg (4). Convert values reported in percent to mg/mg.
Step 4: Determine or estimate pb, the dry bulk density of the soil, from a soils analysis. Typical values range from 1.8 to 2.1
g/ml (kg/1). Determine or estimate sf suggests possible presence of DNAPL
Cw< Sj suggests possible absence of DNAPL
1
-------
GLOSSARY (adapted from Cherry, 1991):
DNAPL: A Dense Nonaqueous Phase Liquid. A DNAPL can be either a single-component DNAPL (comprised of only
one chemical) or a mixed DNAPL (comprised of several chemicals). DNAPL exists in the subsurface as free-phase DNAPL
or as residual DNAPL (see following definitions). DNAPL does not refer to chemicals that are dissolved in groundwater.
DNAPL ENTRY LOCATION: The area where DNAPL has entered the subsurface, such as a spill location or waste pond.
DNAPL SITE: A site where DNAPL has been released and is now present in the subsurface as an immiscible phase.
DNAPL ZONE: The portion of a site affected by free-phase or residual DNAPL in the subsurface (either the unsaturated
zone or saturated zone). The DNAPL zone has organics in the vapor phase (unsaturated zone), dissolved phase (both
unsaturated and saturated zone), and DNAPL phase (both unsaturated and saturated zone).
DISSOLUTION: The process by which soluble organic components from DNAPL dissolve in ground water or dissolve in
infiltration water and form a ground-water contaminant plume. The duration of remediation measures (either clean-up or
long-term containment) is determined by 1) the rate of dissolution that can be achieved in the field, and 2) the mass of
soluble components in the residual DNAPL trapped in the aquifer.
EFFECTIVE SOLUBILITY: The theoretical aqueous solubility of an organic constituent in ground wr'.. that is in
chemical equilibrium with a mixed DNAPL (a DNAPL containing several organic chemicals). The effective solubility of a
particular organic chemical can be estimated by multiplying its mole fraction in the DNAPL mixture by its pure phase
solubility (see Worksheet 1, page 7).
FREE-PHASE DNAPL Immiscible liquid existing in the subsurface with a positive pressure such that it can flow into a
well. If not trapped in a pool, free-phase DNAPL will flow vertically through an aquifer or laterally down sloping fine-
grained stratigraphic units. Also called mobile DNAPL or continuous-phase DNAPL.
PLUME: The zone of contamination containing organics in the dissolved phase. The plume usually will originate from
the DNAPL zone and extend downgradient for some distance depending on site hydrogeologic and chemical conditions.
To avoid confusion, the term "DNAPL plume" should not be used to describe a DNAPL pool; "plume" should be used only
to refer to dissolved-phase organics.
POOL and LENS: A pool is a zone of free-phase DNAPL at the bottom of an aquifer. A lens is a pool that rests on a fine-
grained stratigraphic unit of limited areal extent. DNAPL can be recovered from a pool or lens if a well is placed in the
right location.
RESIDUAL DNAPL: DNAPL held in soil pore spaces or fractures by capillary forces (negative pressure on DNAPL).
Residual will remain trapped within the pores of the porous media unless the viscous forces (caused by the dynamic force
of water against the DNAPL) are greater than the capillary forces holding the DNAPL in the pore. At most sites the
hydraulic gradient required to mobilize all of the residual trapped in an aquifer is usually many times greater than the
gradient that can be produced by wells or trenches (26).
RESIDUAL SATURATION: The saturation (the fraction of total pore space containing DNAPL) at which DNAPL
becomes discontinuous and is immobilized by capillary forces (14). In unsaturated soils, residual saturation typically
ranges from 5% to 20% of total pore volume, while in the saturated zone the residual saturation is higher, with typical
values ranging from 15% to 50% of total pore volume (14,17). At many sites, however, DNAPL migrates preferentially
through small-scale fractures and heterogeneities in the soil, permitting the DNAPL to penetrate much deeper than would
be predicted from application of typical residual saturation values (16).
Defined Areas at a DNAPL Site
tenses and/or residual DNAPL)
DNAPL ENTRY LOCATION
(such as a former waste pond)
Ground Water Flow Direction
-------
Water Res. Research. Vol. 24 No. 8,1991.
latural Sediments, Water Res. R.. Vol. 3,1979.
References
1. Anderson, M.R., R.L. Johnson, and J.F. Pankow, The Dissolution of Residual Dense Non-Aqueous Phase Liquid (DNAPL) from a
Saturated Porous Medium, Proc.: Petrol. Hcarb. and Org. Chemicals in Ground Water. NWWA, Houston, TX, Nov., 1987.
2. Cherry, J. A., written communication to EPA DNAPL Workshop, Dallas, TX, R. S. Kerr Environmental Research Laboratory, U.S.
EPA. Ada, OK., Apr. 1991. - . ... ..-..:
.'**'.' ' . - -.
3. Connor, J.A., C.J. Newell, and O.K. Wilson, Assessment, Reid Testing, and Conceptual Design for Managing Dense Nonaqueous
Phase Liquids (DNAPL) at a Superfund Site, Proc.: Petrol. Hcarb. Org. Chemicals in Ground Water. NWWA, Houston, TX, 1989.
4. Domenico, P.A. and F. W. Schwartz. Physical and Chemical Hydrogeology. Wiley, New York, NY, 1990.
5. Feenstra, S. and J.A. Cherry, Subsurface Contamination by Dense Non-Aqueous Phase Liquids (DNAPL) Chemicals, International
Croundwater Symposium. International Assoc. of Hydrogeologists, Halifax, N.S., May 1-4,1988.
6. Feenstra, S., D. M. MacKay, and J.A. Cherry. A Method for Assessing Residual NAPL Based on Organic Chemical Concentrations in
Soil Samples, Groundwater Monitoring Review. Vol. 11. No. 2,1991.
7. Hunt, J.R., N. Sitar, and K.D. Udell, Nonaqueous Phase Liquid Transport and Cleanup,
8. Karickhoff, S.W., D.S. Brown, and T.A. Scott, Sorption of Hydrophobic Pollutants on N;
9. Keller, C.K., G. van der Kamp, and J.A. Cherry, Hydrogeology of Two Saskatchewan Tills, T. of Hydrology, pp. 97-121,1988.
10. Kueper, B.H. and E. O. Frind. An Overview of Immiscible Fingering in Porous Media. 1. of Cont. Hydrology. Vol. 2,1988.
11. Mackay, D.M. and J.A. Cherry, Ground-Water Contamination: Pump and Treat Remediation, ES&T Vol. 23, No. 6,1989.
12. Mackay, D.M., P.V. Roberts, and J.A. Cherry, Transport of Organic Contaminants in Ground Water, ES&T. Vol. 19, No. 5,1985.
13. Mendoza, C. A. and T. A. McAlary, Modeling of Ground-Water Contamination Caused by Organic Solvent Vapors, Ground
VVater,Vol.28,No.2.1990.
14. Mercer, J.W. and R.M. Cohen, A Review of Immiscible Fluids in the Subsurface: Properties, Models, Characterization and
Remediation, I. of Cont. Hydrology. Vol. 6,1990.
15. Olsen, R.L. and A. Davis, Predicting the Fate and Transport of Organic Compounds in Groundwater, HMC. May/June 1990.
16. Poulson, M. and B.H. Kueper, A Field Experiment to Study the Behavior of Perchloroethylene in Unsaturated Porous Medium.
Submitted to gS&T. 1991.
17. Schwille, F., Dense Chlorinated Solvents in Porous and Fractured Media: Model Experiments (English Translation), Lewis
Publishers. Ann Arbor, MI, 1988.
18. Shiu, W.Y., A. Maijanen. A.LY. Ng, and D. Mackay, Preparation of Aqueous Solutions of Sparingly Soluble Organic Substances:
II. Multicomponent System - Hydrocarbon Mixtures and Petroleum Products, Environ. Toxicology & Chemistry. Vol. 7,1988.
19. Sitar, N., J.R. Hunt, and J.T. Geller, Practical Aspects of Multiphase Equilibria in Evaluating the Degree of Contamination, Proc. of
the Int. Asso. of Hydrog. Conf. on Subsurface Cont. by Immiscible Fluids. April 18-20, Calgary, Alb., 1990.
20. US. EPA. Dense Nonaqueous Phase Liquids. EPA Ground Water Issue Paper. EPA/540/4-91-002.1991.
21. US. EPA, Evaluation of Ground-Water Extraction Remedies. Volume 1 (Summary Report). EPA/540/2-89/054,1989.
22. Verschueren. K., Handbook of Environmental Data on Organic Chemicals. Van Nostrand Reinhold, New York, NY. 1983.
23. Villaume. J.F., Investigations at Sites Contaminated with Dense Non-Aqueous Phase Liquids (NAPLs), Ground Water Monitoring
Review. Vol. 5. No. 2,1985.
24. Waterloo Centre for Ground Water Research, University of Waterloo Short Course, Dense Immiscible Phase Liquid Contaminants
fo Porous and Fractured Media. Kitchener, Ont., Oct., 1991.
25. Waterloo Centre for Ground Water Research. University of Waterloo Short Course, Identification of DNAPL Sites: An Eleven
point Approach. Kitchener, Ont, Oct. 1991.
26. Wilson, J.L and S.H. Conrad, Is Phy»kal Displacement of Residual Hydrocarbons a Realistic Possibility in Aquifer Restoration?,
Proc.: Petrol Hcarb. and Ore. Chemicals tn Ground Water. NWWA, Houston, TX, NWWA, Nov. 5-7,1984.
NOTICE: The policies and procedures set out in this document an intended solely as guidance. They are not intended, nor can they
be relied upon, to create any rights enforceable by any party in litigation with the United States. EPA officials may decide to follow
the guidance provided in this memorandum, or to act at variance with the guidance, based on an analysis of specific site
circumstances. The Agency also reserves the right to change this guidance at any time without public notice.
For more information, contact Randall R. Ross
R. S. Kerr Environmental Research Laboratory
Office of Research and Development
US. Environmental Protection Agency
Ada, Oklahoma 74820
Authors: Charles ). Newell, Groundwater Services, Inc., Houston, Texas
Randall R. Ross, R. S. Kerr Environmental Research Laboratory
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