ASTM E3282-22

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E3282 − 22
Standard Guide for
NAPL Mobility and Migration in Sediments – Evaluation
Metrics
This standard is issued under the fixed designation E3282; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 The goal of this guide is to provide a sound technical
basistodetermineifNAPLatthesiteismobileorimmobileat
1.1 This guide discusses methodologies that can be applied
the pore scale, and if mobile, whether it is stable or migrating
to evaluate the potential for the movement (that is, pore-scale
at the NAPLbody scale.The potential for NAPLmovement in
mobilityorNAPLbody-scalemigration)ofnon-aqueousphase
the sediment is a key component in the development of the
liquid (NAPL) in sediments. NAPL movement assessment in
conceptual site model (CSM) and in deciding what remedial
sediments is significantly different than in upland soils. As
options should potentially be chosen for the site to reduce
such, the frameworks for evaluating NAPL movement in
potential risks to human health and ecological receptors.
upland soils have limited applicability for sediments. In
particular, because upland NAPL conceptual site models may
1.7 Thisguidecanbeusedtohelpdevelop,orrefine,aCSM
not be applicable to many sediment sites, this guide provides a
for the sediment site. A robust CSM is typically needed to
framework to evaluate whether NAPL is mobile (at the pore
optimize potential future work efforts at the site, which may
scale) or migrating (at the NAPL body scale) in sediments.
include various risk management and remedial strategies for
the site, as well as subsequent monitoring after any remedy
1.2 Assessment of the potential for NAPL to move in
implementation.
sediment is important for several reasons, including (but not
limitedto)evaluationofrisktopotentialreceptors,theneedfor
1.8 ThisguideconsidersthemobilityofNAPLinsediments
potentialremedialaction,andpotentialremedialstrategies.For
that originated from three broad categories of potential NAPL
example, if the NAPLis migrating, sensitive receptors may be
emplacement mechanisms (Guide E3248).
impacted and this will influence the choice and timing of any
1.8.1 Migration of NAPL by advection (flow through the
remedy selected for an area of the sediment site. If the NAPL
soilporenetwork)fromanuplandsiteintotheporenetworkof
is not mobile or migrating, then remedial actions may not be
sediments beneath an adjacent water body is one category of
warranted.
NAPL emplacement mechanism. This most commonly occurs
1.3 This guide is applicable at sediment sites where NAPL
within coarse-grained strata in the sediment.
has been identified in the sediment by various screening
1.8.2 Direct discharge of light NAPL (LNAPL) into a
methods and the need for a NAPL movement evaluation is
waterway, where it is broken down by mechanical energy to
warranted (Guide E3248).
form LNAPL beads, is another category of NAPL emplace-
ment mechanism. Oil-particle aggregates (OPAs) are formed
1.4 Petroleum hydrocarbon, coal tar, and other tar NAPLs
when suspended particulates in surface water adhere to
(including fuels, oils, and creosote) are the primary focus of
LNAPL beads. Once enough particulates have adhered to an
thisguide.Theseformsofcontaminationarecommonlyrelated
LNAPL bead and the OPA becomes dense enough, it settles
to historical operations at refineries, petroleum distribution
through the water column onto a competent sediment surface,
terminals, manufactured gas plants (MGPs), and various large
where it forms an in situ deposited NAPL (IDN) and may be
industrial sites.
buried by future sedimentation.
1.5 Althoughcertaintechnicalaspectsofthisguideapplyto
1.8.3 The third category of NAPLemplacement mechanism
other NAPLs (for example, dense NAPLs [DNAPLs] such as
is DNAPL flow (that is, direct discharge of DNAPL into a
chlorinated hydrocarbon solvents), this guide does not com-
waterway), followed by settling through the water column and
pletely address the additional complexities of those DNAPLs.
depositiondirectlyontoacompetentsedimentsurface,whereit
may be buried by future sedimentation.
ThisguideisunderthejurisdictionofASTMCommitteeE50onEnvironmental
Assessment, Risk Management and CorrectiveAction and is the direct responsibil-
1.9 Ebullition-facilitated transport of NAPL from the sedi-
ity of Subcommittee E50.04 on Corrective Action.
ment to the water column by gas bubbles is not within the
Current edition approved June 1, 2022. Published June 2022. Originally
scopeofthisguide.Theevaluationofebullitionandassociated
approved in 2021. Last previous edition approved in 2021 as E3282–21a. DOI:
10.1520/E3282–22. NAPL/contaminant transport is covered in Guide E3300.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3282 − 22
Transport of NAPL due to erosional forces (for example, 1.17 This standard does not purport to address all of the
propeller wash) is not within the scope of this guide. safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
1.10 This guide (see Section 5) presents an overall frame-
priate safety, health, and environmental practices and deter-
work to evaluate if NAPL at the site is mobile or immobile at
mine the applicability of regulatory limitations prior to use.
theporescale,andmigratingorstableattheNAPLbodyscale.
1.18 This international standard was developed in accor-
It provides guidance on approaches and methodologies that
dance with internationally recognized principles on standard-
address questions regarding NAPL movement evaluation.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.11 This guide (see Section 6) discusses the use of data
mendations issued by the World Trade Organization Technical
from various laboratory tests (Appendix X1), calculation
Barriers to Trade (TBT) Committee.
methodologies, and other methodologies to technically evalu-
ate if NAPL in sediment at various locations in the site is
2. Referenced Documents
mobile or immobile at the pore scale, and stable or migrating
2.1 ASTM Standards:
at the NAPL body scale. This evaluation can be performed
D425Test Method for Centrifuge Moisture Equivalent of
using tiered and weight of evidence (WOE) frameworks. For
Soils
example, it may be possible that NAPLis mobile or migrating
D445Test Method for Kinematic Viscosity of Transparent
inonepartofthesite,butisimmobileinotherpartsofthesite.
and Opaque Liquids (and Calculation of DynamicViscos-
There are currently no industry standard tiered and WOE
ity)
frameworks to evaluate if NAPL in sediment is mobile or
D854Test Methods for Specific Gravity of Soil Solids by
migrating, but illustrative examples of such frameworks are
Water Pycnometer
presented in Appendix X2. Case studies demonstrating the
D971Test Method for Interfacial Tension of Insulating
application of the example tiered and WOE frameworks
Liquids Against Water by the Ring Method
exhibited in Appendix X2 are presented in Appendix X3.
D1481Test Method for Density and Relative Density (Spe-
1.12 This guide (see Section 7) discusses applicable labo-
cific Gravity) of Viscous Materials by Lipkin Bicapillary
ratory centrifuge testing methodologies that are used to evalu-
Pycnometer
ate NAPL mobility or immobility at the pore scale under the
D2216Test Methods for Laboratory Determination ofWater
applicable test conditions (also see Appendix X4). Appendix
(Moisture) Content of Soil and Rock by Mass
X5 discusses the laboratory preparation of sediment samples
D5084Test Methods for Measurement of Hydraulic Con-
used in centrifuge testing.
ductivity of Saturated Porous Materials Using a Flexible
Wall Permeameter
1.13 This guide (see Section 8) discusses applicable labo-
D5856Test Method for Measurement of Hydraulic Conduc-
ratory water drive testing methodologies that are used to
tivity of Porous Material Using a Rigid-Wall,
evaluate NAPLmobility or immobility at the pore scale under
Compaction-Mold Permeameter
the applicable test conditions.This section discusses both rigid
D6836Test Methods for Determination of the Soil Water
wall and flexible wall permeameter testing (also see Appendix
Characteristic Curve for Desorption Using Hanging
X6). Appendix X5 discusses the laboratory preparation of
Column, Pressure Extractor, Chilled Mirror Hygrometer,
sediment samples used in water drive testing.
or Centrifuge
1.14 This guide (see Section 9) discusses calculation meth-
D6913Test Methods for Particle-Size Distribution (Grada-
odologies that provide insight into pore-scale NAPL mobility
tion) of Soils Using Sieve Analysis
and NAPL body-scale migration at the site. To perform some
D7263Test Methods for Laboratory Determination of Den-
of these calculations, NAPL property data such as density,
sity and Unit Weight of Soil Specimens
viscosity, and NAPL–water interfacial tension are needed (see
D7928Test Method for Particle-Size Distribution (Grada-
Appendix X1). The calculation methodologies include NAPL
tion) of Fine-Grained Soils Using the Sedimentation
density versus hydraulic gradient calculations; pore entry
(Hydrometer) Analysis
pressure calculations; critical NAPL layer thickness calcula-
E2531Guide for Development of Conceptual Site Models
tions;andNAPLporevelocitycalculations(alsoseeAppendix
and Remediation Strategies for Light Nonaqueous-Phase
X7 and Appendix X8).
Liquids Released to the Subsurface
E2856Guide for Estimation of LNAPL Transmissivity
1.15 This guide (see Section 10) presents other field obser-
E3164Guide for Sediment Corrective Action – Monitoring
vation approaches that are useful in evaluating pore-scale
E3248GuideforNAPLMobilityandMigrationinSediment
NAPLmobility and NAPLbody-scale migration. These meth-
–Conceptual Models for Emplacement and Advection
odologies include vertical profiles of NAPLsaturation (includ-
E3281Guide for NAPL Mobility and Migration in Sedi-
ing isopach mapping of the thickness of unimpacted sediment
ments – Screening Process to Categorize Samples for
above the NAPLzone); and installation of monitoring wells in
sediment.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
1.16 Units—The values stated in SI or CGS units are to be
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
regarded as the standard. No other units of measurement are
Standards volume information, refer to the standard’s Document Summary page on
included in this standard. the ASTM website.
E3282 − 22
Laboratory NAPL Mobility Testing tively expand in any direction under observed or reasonably
E3300Guide for NAPL Mobility and Migration in Sedi- anticipated field conditions E3248
ment – Evaluating Ebullition and Associated NAPL/
3.2 Definitions of Terms Specific to This Standard:
Contaminant Transport
3.2.1 conceptual site model (CSM), n—a professional inter-
pretation of site data that serves as a systematic planning
3. Terminology
instrument, a communication device, and an optimization and
decision tool.
3.1 Definitions:
3.1.1 immobile NAPL, n—NAPL that does not move by
3.2.2 density-driven gradient, n—hydraulic gradient due to
advection within the connected void spaces within sediment
thedensityorbuoyancyofNAPLcomparedtothesurrounding
under specified physical and chemical conditions, as may be
water.
demonstrated by laboratory testing, or may be interpreted
3.2.2.1 Discussion—Density-driven gradient is given by the
based on mathematical calculations or modeling. E3248
density difference between the NAPL density (ρ ) and water
n
3.1.2 in situ deposited NAPL (IDN) sediment, n—NAPL-
density (ρ ) divided by the water density; ρ may differ
w n
containing sediment resulting from the deposition of OPAs.
significantly from that of the original NAPL when it was
E3248
released to the environment, due to NAPL weathering. Site-
3.1.3 migrating NAPL, n—NAPL that can move at the
specific influences on water density (for example, due to
NAPL body scale, such that the NAPL body may advectively
salinity) should also be considered.
expand in at least one direction under observed or reasonably
3.2.3 dynamic and kinematic viscosities of NAPL (µ and
n
anticipated field conditions. E3248
ν ), n—measurementsoftheinternalfrictionthatoccurswithin
n
NAPL during movement, or of the resistance of the NAPL to
3.1.4 mobile NAPL, n—NAPLthat may move by advection
flow.
withintheconnectedvoidspacesofthesedimentunderspecific
physical and chemical conditions, as may be demonstrated by
3.2.3.1 Discussion—For advectively emplaced NAPLs, vis-
laboratory testing, or as may be interpreted based on math-
cosities are inversely proportional to the NAPL flow velocity
ematical calculations or modeling. E3248
(if migrating); these parameters also may differ significantly
3.1.5 non-aqueous phase liquid, NAPL, n—chemicals that from those of the original NAPL due to weathering.
3.2.4 hydraulic gradient, n—hydraulic head difference be-
are insoluble or only slightly soluble in water that exist as a
separate liquid phase in environmental media. E3248 tween two points, divided by distance between the points; it is
the driving force for water flow and can be a significant factor
3.1.5.1 Discussion—NAPL may be less dense than water
in NAPL flow.
(light non-aqueous phase liquid [LNAPL]) or more dense than
3.2.5 immobile saturation, n—the maximum NAPL satura-
water (dense non-aqueous phase liquid [DNAPL]).
tion where NAPL is still immobile.
3.1.6 NAPL advection, n—the process of NAPL movement
in the subsurface due to pressure and gravitational forces.
3.2.5.1 Discussion—In practice, the immobile saturation is
E3248
the greatest NAPL saturation that does not exhibit pore-scale
mobility for a set of specific site conditions (for example,
3.1.7 NAPL body, n—sediment where the NAPL present
NAPL viscosity, NAPL composition, sediment composition,
exhibits movement. E3248
sediment pore size distribution, NAPL pressure gradient). The
3.1.7.1 Discussion—NAPL is mobile at the pore scale and
immobile saturation can vary, depending on the variability of
either stable or migrating at the NAPLbody scale. The NAPL
the site conditions.
bodyexcludesanyportionoftheNAPLzonewheretheNAPL
3.2.6 interfacial tension, n—interfacialtensiondescribesthe
is immobile at the pore scale.
amount of work that would be required to increase the surface
3.1.8 NAPL movement, n—any process where NAPLexhib-
area of an interface between two fluid phases.
its advective flow at any scale within the sediment; NAPL
3.2.6.1 Discussion—Interfacial tension reflects the concept
movement includes NAPL mobility at the pore scale and
that the interface between two fluids will tend toward a
NAPL migration at the NAPL body scale. E3248
minimum possible surface area (as a drop of oil submerged in
3.1.9 NAPL zone, n—sediment where NAPL is present in
water would, in the absence of other forces, take a spherical
any state; the NAPL can be mobile or immobile at the pore
form). Interfacial tension pairs (generally symbolized as σ,
scale, and if mobile at the pore scale, stable or migrating at the
accompanied by a two-letter description of a fluid pair—such
NAPL body scale. E3248
as σ for NAPL–water interfacial tension) are used in pore
nw
3.1.10 pore scale, n—thescaleoftheconnectedvoidspaces
entry pressure calculations.
within the sediment. E3248
3.2.7 NAPL footprint, n—a two-dimensional projection of
the NAPL zone in the horizontal plane.
3.1.11 sediment, n—a matrix of pore water and particles
including gravel, sand, silt, clay, and other natural and anthro-
3.2.8 NAPL saturation (S ), n—percentageoftheporespace
n
pogenic substances that have settled at the bottom of a tidal or that is occupied by NAPL.
non-tidal body of water. E3164
3.2.9 oil-particle aggregate (OPA), n—aparticleformedina
3.1.12 stable NAPL, n—NAPL that does not move at the surface water body resulting from the adherence to (or pen-
NAPL body scale, such that the NAPL body will not advec- etration into) an oil droplet by minerals or organic material.
E3282 − 22
3.2.10 relative permeability, n—for advectively emplaced in the surface sediment to maintain access to oxygenated
NAPL, the ratio of the permeability of a fluid at partial overlyingwater.Thesebenthicorganismsareatthebaseofthe
saturation to the permeability of the same fluid at 100 % food chain. If NAPL in subsurface sediment is not migrating,
saturation. theNAPLwillnotmoveintothesurfacesedimentandresultin
exposure to benthic organisms. NAPL that is stable and only
3.2.10.1 Discussion—In a system containing advectively
present in subsurface sediment likely does not pose a risk to
emplaced NAPLand water, only a fraction of the pore space is
human or ecological receptors, because there is no completed
occupied by each fluid, so this diminishes the permeability of
pathwaytoexposureiftheoverlyingsedimentremainsinplace
eachfluid.Thepermeabilityofafluidincreaseswithincreasing
(that is, it is not dredged or eroded). With no completed
saturation (that is, by increasing the fraction of large pores
exposure pathway, removal of the NAPL in the subsurface
occupied). At (or below) a threshold NAPL saturation, the
sediment may not be needed during any remedy. Therefore,
relative permeability is zero and the NAPL is immobile (1).
understanding the potential for movement of NAPL in sedi-
Relative permeability is not a relevant concept for IDN
ments is a key factor in the management of contaminated
sediments.
sediment sites. Knowledge of NAPLmovement is required for
3.2.11 undisturbed sample, n—sediment particles that have
developing effective remedial options for NAPL impacted
not been rearranged relative to one another by anthropogenic
sediments and for long-term management of sediment sites.
activity including the collection, transport, and analysis of the
4.5 The user of this guide should review the overall struc-
sample.
ture and components of this guide before proceeding with use,
3.2.11.1 Discussion—In common usage, the term “undis-
including:
turbed sample” describes particles that have been rearranged,
Section 1 Scope
but only to a slight degree.
Section 2 Referenced Documents
3.2.12 water saturation (S ), n—percentage of the pore Section 3 Terminology
w
Section 4 Significance and Use
space of a sediment that is occupied by water.
Section 5 NAPL Mobility and Migration Evaluation Framework
Section 6 Tiered and Weight of Evidence NAPL Movement Evaluation
4. Significance and Use
Approaches
Section 7 Centrifuge Test Methods
4.1 Hydrophobic organic liquids (for example, petroleum
Section 8 Water Drive Test Methods
hydrocarbons, coal tars) may exist in the environment for long
Section 9 Calculation Methods for Potential Vertical Movement of NAPL
Section 10 Field Observation Methodologies
periods of time as NAPLs. Standardized guidance and test
Section 11 Keywords
methods do not exist to assess NAPL movement (both pore-
Appendix X1 Laboratory Analysis Methods Commonly Used in NAPL
scale mobility and NAPL body-scale migration) in sediment. Movement Evaluations (non-mandatory)
Appendix X2 Illustrative Examples of Tiered and WOE Approaches to Evaluate
Literaturesearcheshaveresultedinalimitedbodyofavailable
NAPL Movement (non-mandatory)
and applicable research. Current research has focused on
Appendix X3 Case Studies (non-mandatory)
site-specificsedimentNAPLmovementevaluationapproaches. Appendix X4 Additional Information on Centrifuge Testing Technology in NAPL
Mobility Testing (non-mandatory)
4.2 Standardized guidance and test methods currently exist
Appendix X5 Laboratory Handling and Preparation of Sediment Cores (non-
mandatory)
for assessing NAPL mobility and migration at upland sites,
Appendix X6 Additional Information on Water Drive Test Methods in NAPL
fromorganizationssuchasASTMInternational(GuidesE2531
Mobility Testing (non-mandatory)
andE2856),InterstateTechnologyandRegulatoryCouncil (2),
Appendix X7 NAPL Net Vertical Gradient Calculation Method (non-mandatory)
Appendix X8 NAPL Effective Hydraulic Conductivity Estimation Methods (non-
and the American Petroleum Institute (3, 4). Approaches
mandatory)
commonly used in upland sites may or may not be applicable
References
for any given sediment site. This guide provides perspectives
4.6 Activities described in this guide should be conducted
on the applicability of various methodologies for specific
by persons familiar with NAPL-impacted sediment site char-
sediment conditions.
acterization techniques and sediment remediation science and
4.3 This guide describes various methodologies that are
technology, as well as sediment NAPLmobility and migration
useful in sediment NAPL movement evaluation, such as
assessment protocols and methodologies.
laboratory test methods, calculation approaches, and field
4.7 This guide may be used by various parties involved in
observation interpretation. The guide then provides frame-
sediment programs, including regulatory agencies, project
workstoevaluatethedatageneratedfromthesemethodologies
sponsors, environmental consultants, toxicologists, risk
to determine if the NAPL observed in the sediments under in
assessors, site remediation professionals, environmental
situ conditions exhibits movement of any kind.
contractors,analyticaltestinglaboratories,datavalidators,data
4.4 Importantexposurepathwaysinuplandsitesareusually
reviewers and users, and other stakeholders, which may
not applicable to sediment sites. The U.S. Environmental
include, but are not limited to, owners, buyers, developers,
Protection Agency notes, “Contaminants in the biologically
lenders, insurers, government agencies, and community mem-
active layer of the surface sediment at a site often drive
bers and groups.
exposure” (5).Inaquaticenvironments,benthicorganismslive
4.8 This guide is not intended to replace or supersede
federal, state, local, or international regulatory requirements.
Instead, this guide may be used to complement and support
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
the standard. suchrequirements.Anyremedialactionstakenshouldmeetthe
E3282 − 22
regulatory standards for the regulatory entity under which the understand the NAPL emplacement mechanisms at a site
corrective action is being performed. before starting the NAPL movement evaluation. Professional
judgment will need to be applied by technical experts to
4.9 This guide provides a framework based on overarching
ascertain which evaluation methodologies will be useful at a
features and elements that should be customized by the user,
specific site.The approaches cited may not be applicable at all
based on site-specific conditions, regulatory context, and
sediment sites.Appendix X3 of Guide E3248 provides further
program objectives for a particular sediment site. This guide
description of the movement of NAPL at the pore and NAPL
should not be used alone as a prescriptive checklist.
body scales.
4.10 Assessment of NAPL movement in sediments is an
5.2 As discussed in Section 7.2 of Guide E3248, the NAPL
evolving science. This guide provides a systematic, yet
movement evaluation considers the potential for NAPLmove-
flexible, framework to accommodate variations in approaches
ment at both the pore (that is, void) and NAPL body scales
by regulatory agencies and users, based on project objectives,
(Fig. 1). If the evaluation determines that the NAPL is
site complexity, unique site features, programmatic and regu-
immobile at the pore scale, then it must also be stable at the
latory requirements, newly developed guidance, newly pub-
NAPL body scale, so no further evaluation is necessary. If the
lished scientific research, use of alternative scientifically based
evaluation determines that the NAPL is mobile at the pore
methods and procedures, changes in regulatory criteria, ad-
scale, then further evaluation is required to interpret if the
vances in scientific knowledge and technical capability, mul-
NAPL is stable or migrating at the NAPL body scale.
tiple line of evidence (LOE) approaches, and unforeseen
circumstances.
5.3 Fig. 2 presents an example investigative process to
evaluate if NAPL at a site is mobile or immobile at the pore
4.11 Use of this guide supports multiple LOE approaches,
scale, as well as if it is migrating or stable at the NAPL body
usingtieredorWOEevaluationframeworks,fortheevaluation
scale.Notethatthethresholdbetweenmobilityandimmobility
of NAPL movement in sediments.
willdependonanumberoffactors,includingsedimenttexture.
4.12 Use of this guide is consistent with the sediment
Depending on the goals of the NAPL movement evaluation,
risk-based corrective action (RBCA) process that guides the
different questions from the ones presented in Fig. 2 could be
user to obtain the appropriate data; acquire and evaluate
posed that are tailored to site-specific conditions. Fig. 2 also
additional data; and refine goals, objectives, receptors, expo-
provides guidance on the types of laboratory tests, calculation
sure pathways, and the CSM. As the sediment RBCA process
methods or field data that will be useful in this evaluation.The
proceeds, data and conclusions reached at each step of the
evaluation methodologies outlined in Fig. 2 will help answer
process help focus subsequent evaluation. This integrative
the key question of whether the NAPL in the sediment can
process results in efficient, cost-effective decision-making and
migrate upward toward sensitive receptors (for example, ben-
timely, appropriate response actions for NAPL-impacted sedi-
thicorganismsinthebiologicallyactivezoneofthesediment).
ments.
Note that Steps 1 and 2 outlined in Fig. 2 concern NAPL
mobility evaluation at the pore scale, while Steps 3 through 6
5. NAPL Mobility and Migration Evaluation Framework
concern NAPL migration evaluation at the NAPL body scale.
5.1 After NAPL has been confirmed to be present in
5.4 Typically,thefirststepinaNAPLmovementevaluation
sediment at a site, the decision should be made whether to
is to evaluate if the NAPL is mobile at the pore scale. NAPL
perform a NAPL emplacement and movement evaluation for
mobility at the pore scale requires collecting undisturbed
sediment; this can be done using the process described in Fig.
sediment samples and performing laboratory tests. This in-
2 of Guide E3248. A full discussion of various emplacement
volves identifying the sediment intervals to obtain samples
mechanisms is provided in Appendix X1 of Guide E3248.In
from cores for the NAPL movement evaluation. Examples of
particular, Fig. X1.9 of Guide E3248 provides guidance on
commonly used field screening methods for this task are
how to interpret the most likely NAPL emplacement
presented in Table 2.
mechanism, based on field data. Table 1 briefly contrasts some
key differences in characteristics between the three major 5.5 In general, sediment cores should be collected using
methodologies that minimize disturbance of the sediment. It is
categories of NAPL emplacement. It is useful (if possible) to
TABLE 1 Key Characteristics for Different NAPL Emplacement Mechanisms
Emplacement Mechanism
Emplacement Condition
Advective OPA Deposition DNAPL Surface Flow
Source Directly related to upland source Not physically connected to upland Directly related to upland discharge
discharge source source
Extent Spatially limited; typically located along Can be spatially large (many hectares) Typically located along shoreline; can
shoreline and found far from shoreline move farther from shoreline in some
circumstances
NAPL Location in Strata NAPL typically found in sand and more NAPL typically disconnected at pore DNAPL is the matrix, with solid grains
permeable strata scale; present throughout the sediment embedded within and surrounding this
matrix
E3282 − 22
NOTE 1—Each line indicates an evaluation is performed.
FIG. 1 General NAPL Movement Evaluation Framework
FIG. 2 Example NAPL Movement Investigative Process
good practice to take multiple co-located cores from each varietyofappliedhydraulicgradientsinanattempttomobilize
sampling station for the NAPL movement evaluation. One of NAPL from the sediment. To help correlate the laboratory
these cores can be used for field screening, to determine if testing to field conditions, the hydraulic gradient applied
NAPL is present or absent at this sampling station—and to during pore-scale laboratory NAPL mobility testing should be
provide qualitative information on the degree of NAPL pres- equal to or greater than (that is, more conservative) those
enceinvariousintervalsofthiscore.Laboratorytestsandfield observed or reasonably anticipated under field conditions.
observations used to evaluate NAPLmobility at the pore scale
5.7 Unlike upland sites where numerous studies have al-
are presented in Table 3.
lowed literature values to be developed, there is currently
5.6 If NAPL is demonstrated to be immobile at the pore insufficient data to develop similar consensus literature values
scale at a particular location and depth, the evaluation is for immobile saturation in sediment. The immobile saturation
complete at that location and depth, because NAPL that is values must currently be determined on a site-specific basis,
immobile at the pore scale (particularly if demonstrated to be established by the greatest measured NAPL saturation of site
immobile under conservative testing conditions) cannot be samples exhibiting immobility at the pore scale in laboratory
migrating and must be stable at the NAPL body scale. testing. Immobile saturation values can vary with pore size
Laboratory NAPL mobility tests can be performed under a distribution, density, organic content, and NAPL properties. If
E3282 − 22
TABLE 2 Common Screening Methods for Identifying Sediment Intervals for NAPL Movement Evaluation
Evaluation Methodology Application Test Method
Visual Observations Identify presence/absence of NAPL in core intervals Appendix X1 of Guide E3281
Shake Test Identify presence/absence of NAPL in core intervals Appendix X2 of Guide E3281
UV Light (Core Photography) Confirm presence/absence of NAPL in core intervals and identify apparent maxi- Section 3.4.1 of Ref. (6)
mum NAPL saturation interval for NAPL movement evaluation
LIF Confirm presence/absence of NAPL in core intervals and identify intervals N/A
where NAPL fluorescence appears elevated; these intervals can be used in the
NAPL movement evaluation. NAPL must contain polycyclic aromatic hydrocar-
bons (PAHs) for LIF to be applicable. LIF can be performed in situ or ex situ.
A
LIF can be performed on DART rods.
Hydrophobic Dye Test (NAPL Identify presence/absence of NAPL in core intervals N/A
B
FLUTe )
A
Trademarked by Dakota Technologies. http://www.dakotatechnologies.com/products/darts
B
Trademarked by Flexible Liner Underground Technologies.
Abbreviations:
LIF = laser-induced fluorescence
N/A = not applicable
TABLE 3 Example Pore-Scale NAPL Mobility Evaluation Methodologies
Emplacement Mechanism
Evaluation Test
Application Further Details
Advective OPA DNAPL
Methodology Methods
Flow Deposition Flow
Laboratory Determines if NAPL is expressed from a core sample XXX D6836 Section 7
Centrifuge Testing under very conservative conditions, at gradients much
greater than the maximum measured or expected in
the field. If no NAPL is expressed, the NAPL is
immobile at the pore scale. If NAPL is expressed, it
may be mobile at the pore scale. This documents
potential mobility, but further assessment is needed to
evaluate mobility under field conditions.
Laboratory Water Determines if NAPL is expressed from a core at a con- XXX D5084 Section 8
Drive Testing servative vertical gradient, greater than the maximum
measured or expected in the field. If NAPL is not
expressed, the NAPL is immobile at the pore scale. If
NAPL is expressed, it may be mobile at the pore scale
under field conditions.
NAPL Saturation If the NAPL saturation in sediments is less than the X X X Section 4.3 5.7
site-specific immobile saturation, then the NAPL is im- of Ref (6)
mobile at the pore scale. If the NAPL saturation is
greater than the immobile saturation, then the NAPL
may be mobile.
NAPL Presence in If NAPL consistently accumulates in a monitoring well XXX N/A 10.3
Well or Piezometer or piezometer installed in the sediment within a water
body, the NAPL is mobile at the pore scale. If no
NAPL accumulates, the NAPL is likely immobile at the
pore scale.
Abbreviations:
N/A = not applicable
X = applicable
the NAPL saturation in sediment is greater than the site- sediment. This threshold may be a range of values, rather than
specific immobile saturation values, it is potentially mobile at a single value, due to sediment and NAPL heterogeneity. For
the pore scale. Once laboratory mobility testing has been
other samples taken at the site, this immobile NAPLsaturation
performed on selected sediment samples from the site, the
value may be useful to provide a basis of comparison to
results (mobile or immobile) can be compared to the initial
evaluatewhethertheNAPLinthesampleismobileatthepore
NAPL saturation results for the samples. There may be a
scale.
NAPL saturation value below which the samples are
5.8 If NAPL is demonstrated to be mobile at the pore scale
immobile—and above which laboratory testing indicates they
duringlaboratorytestingwithahydraulicgradientgreaterthan
are potentially mobile. This threshold could allow estimation
those observed or reasonably anticipated in the field, then the
of the maximum immobile NAPL saturation value for the
E3282 − 22
stability of the NAPL body is uncertain and the evaluation 6. Tiered and Weight of Evidence NAPL Movement
must be continued. NAPL body stability (or migration) is Evaluation Approaches
commonly evaluated using the methodologies presented in
6.1 If NAPL is present in sediment, determining whether
Table 4. NAPL body migration evaluations consider in situ
NAPL is mobile at the pore scale or migrating at the NAPL
field conditions (for example, calculation of vertical gradients,
body scale is an important component of the site characteriza-
NAPL physical properties, and sediment physical property
tion process and subsequent development of a CSM.
measurements). If mathematical analysis is conducted, then
Conceptually, understanding the movement of NAPL requires
site-specific parameter input values can be obtained from the
an evaluation of the chemical and physical characteristics of
results of the pore-scale mobility tests and from additional
the NAPL, as well as overall site conditions. A single test
laboratory analyses (for example, NAPL fluid properties such
cannot necessarily determine whether NAPL is mobile or
as density, viscosity, and interfacial tension). A summary of
migrating,sotieredorWOEassessmentapproaches,relyingon
commonly used laboratory testing methods applied in NAPL
best professional judgment, are often needed. Deterministic
movementevaluationsandabriefsynopsisofeachtestmethod
analyses lend themselves to a tiered approach, but do not
are presented in Appendix X1.
preclude a WOE evaluation. Table 3 and Table 4 summarize
5.9 Once the status of the NAPL body (that is, stable or the LOEs (that is, evaluation methodologies) detailed in
migrating)hasbeendemonstrated,theNAPLmovementevalu- Sections 7–10, as well as how each could support an
ation is complete. evaluation to determine if NAPLis mobile at the pore scale or
TABLE 4 Example NAPL Body-Scale Migration Evaluation Methodologies
Emplacement Mechanism
Test
Evaluation Methodology Application Further Details
Advective OPA DNAPL
Methods
Flow Deposition Flow
Net Vertical Gradient (where If the net vertical gradient (considering the XXX N/A 9.4,
sediment–water interface is gradient due to gravity and the hydraulic Appendix X7
the exposure route of gradient) is net downward, NAPL cannot
concern) migrate upward to the sediment–water
interface. Vertical gradients can vary
temporally and can reverse in some
instances. Hence, a number of net gradient
determinations under different conditions (for
example, different seasons, different points in
the tidal cycle) may be required to
demonstrate that the net gradient is
downward most (if not all) of the time.
NAPL Body Critical Thickness To have sufficient NAPL capillary pressure at XYX N/A 9.6
the top of the NAPL body to exceed the pore
entry pressure of the overlying sediment, the
NAPL body must be thicker than a certain
critical value (which can be calculated and
compared to field observations).
NAPL Migration Distance Migrating NAPL leaves NAPL behind at XYX N/A 9.7
Prior to Depletion to Immobile immobile saturation, so that as NAPL moves,
Saturation less NAPL mass is contained in the migrating
front. Eventually, the NAPL mass in the
migrating front decreases to the point of
immobile saturation and migration ceases. If
this occurs before the NAPL reaches a
receptor, it will not be able to migrate to that
receptor.
NAPL Velocity If the NAPL velocity to a potential receptor XYX N/A 9.8
(for example, surficial sediment), is below a
de minimis threshold (this depends on the
distance to the receptor), the NAPL body is
stable. A NAPL velocity less than the
threshold translates into a very long travel
time before the NAPL could potentially reach
any receptor.
Abbreviations:
N/A = not applicable
X = applicable
Y = applicable for partially encapsulated OPAs
E3282 − 22
migrating at the NAPL body scale. Guidelines for integrating best supported by the individual LOEs (10), with conclusions
these LOEs are described in this section, using both tiered and based (in part) on applying best professional judgment.
WOE approaches.
6.3.3 Once it has been determined that NAPL is present in
the sediment, the objectives for further investigation and
6.2 Tiered Evaluation Approaches:
potentialremediationstrategiescanbeestablished.Converging
6.2.1 The evaluation of NAPL movement may be based on
LOEscanbeusedtodeterminewhetherNAPLismobileonthe
a tiered (for example, decision{tree approach), similar to
pore scale or is migrating or stable at the NAPLbody scale. In
risk{based approaches associated with water quality assess-
thisinstance,aWOEapproachforNAPLmobilityormigration
ment guidelines. Tiered approaches to environmental evalua-
canbeusedthatisbasedontheevaluationmetricspresentedin
tions are widely accepted by industry and the professional
Table 3 and Table 4. Based on site conditions and the potential
community (7). The tiered evaluation generally involves three
for performing field investigations, a number of LOEs may be
or more tiers (that is, levels), which enables the assessment to
selected from the different field methods and desktop calcula-
matchvariationsindataavailability,sitecomplexity,andstudy
tions.The LOEs used in theWOE can be equally weighted, or
objectives. A tiered approach to NAPL movement evaluation
a decision analysis approach can be used, where different
relies on sequential evaluations in tiers of increasing complex-
LOEs are unequally weighted in the WOE.
ity.
6.3.4 Any of the respective LOEs may lead to the conclu-
6.2.2 Atieredapproachallowssimplecasestobecompleted
sion that NAPL is mobile at the pore scale (a positive
relatively quickly and at lower cost, whereas more complex
determination) or immobile (a negative determination).
cases can be completed with a greater (but more efficient) use
However,iftheprimaryLOEsuggeststhatNAPLisimmobile,
of resources. Tier 1 often consists of evaluations of field
then the determination of mobility turns to a WOE approach,
observations or binary field tests. Evaluations based on labo-
where additional LOEs combine to confirm a negative deter-
ratory testing; detailed analysis of field or laboratory data; or
mination. Alternatively, a number of positive determinations
the calculation of critical values are typically associated with
mayoutweighthenegativedetermination,ifthepositiveLOEs
Tier2(orgreater).Tier1evaluationmethodsaregenerallylow
cannot be explained without the presence of mobile NAPL.A
incost,easytoperform,andprovidequalitativeorquantitative
similar rationale can be used to evaluate if NAPLis migrating
information about movement; they tend to be overly conser-
or stable at the NAPL body scale, using a WOE approach.
vative and protective of project goals. Tier 2 (or greater)
Because a WOE is typically structured to answer a single
evaluation methods provide greater specificity and more
question (for example, is the NAPL mobile at the pore scale),
quantifiable/calculable results, but they are often more expen-
it is simpler to use one WOE to determine if NAPL is mobile
sive and time consuming than Tier 1 methods. When the
at the pore scale, then a second WOE to determine if NAPLis
evaluationswithinaspecifictierarecompleteandthepotential
migratingattheNAPLbodyscale.Dependingonprojectgoals,
for NAPL movement cannot be rejected, then the next tier is
it might be decided to take a tiered approach to determine
performed (8). If NAPL movement is ruled out in a tier, then
pore-scale mobility and a WOE approach to determine NAPL
performingthefollowingtiersisnotnecessary—theevaluation
body-scale migration, or vice versa.
is complete.
6.3.5 ForNAPLmovementinsedimentevaluations,thereis
6.2.3 ForNAPLmovementinsedimentevaluations,thereis
no industry standard WOE approach. An illustrative example
no industry standard tiered approach. An illustrative example
ofaWOEapproachtodetermineifNAPLatasiteismobileat
ofatieredapproachtodetermineifNAPLismobileatthepore
the pore scale is presented in Appendix X2. An illustrative
scale at a site—and if it is, if the NAPL is migrating toward a
example of another WOE approach to determine if NAPLat a
receptor—is presented in Appendix X2. Case studies demon-
site is migrating at the NAPL body scale is also presented in
stratingtheuseofthisillustrativetieredapproacharepresented
Appendix X2. A case study demonstrating the use of both of
in X3.2 and X3.3.
these illustrative WOE approaches is presented in X3.4.
6.3 Weight of Evidence Evaluation Approaches:
7. Centrifuge Test Methods
6.3.1 WOE analysis is a data and information integration
process that can be used for NAPL movement evaluations in 7.1 General Overview of Centrifuge Test Methods:
sediment, where multiple measures (for example, analytical
7.1.1 Centrifuge test methods evaluate the potential for
data,sitehistory,visualobservations)canbeusedasindividual
NAPL movement at the pore scale under different pressure
LOEstoassesstheprobabilityofNAPLmobilityormigration.
(that is, gradient) conditions.
Adiscussion of the use of LOEs in WOE analysis is provided
7.1.2 Centrifuge technology involves spinning a sediment
elsewhere (9). Relying on multiple LOEs using commonly
core sample, such that the angular velocity induces a negative
available data provides an effective method to assess NAPL
pressure that then displaces fluids from the pore network. By
movement.
measuring the relative fluid content at various displacement
6.3.2 It is critical that stakeholders approach NAPL move- pressures (that is, matric potentials resulting from the applied
ment evaluations recognizing that there may be unique and centrifugal forces), a capillary pressure curve is produced.
challenging sediment management conditions at every site and From these measurements a number of physical properties
appropriate site-specific metrics must be evaluated to deter- related to fluid distribution, content, retention, and movement
mine if management goals are achievable. The process of can be determined.The application of centrifuge technology is
weighing the evidence amounts to determining the conclusion described in Test Methods D425 and D6836, as well as in
E3282 − 22
Section 4 of Ref. (6). Environmental applications of centrifuge water is calculated by subtracting sample native weight from
technologytoevaluateNAPLmovementinporousmediahave the post-centrifuge test sample weight and adjusting for any
been reported by Soga et al. (11), Brady and Kunkel
...