ASTM E2856-13(2021)

Standard Guide for Estimation of LNAPL Transmissivity

SIGNIFICANCE AND USE
4.1 Application:  
4.1.1 LNAPL transmissivity is an accurate metric for understanding LNAPL recovery, is directly proportional to LNAPL recoverability and tracking remediation progress towards residual LNAPL saturation.  
4.1.2 LNAPL transmissivity can be used to estimate the rate of recovery for a given drawdown from various technologies.  
4.1.3 LNAPL transmissivity is not an intrinsic aquifer property but rather a summary metric based on the aquifer properties, LNAPL physical properties, and the magnitude of LNAPL saturation over a given interval of aquifer.  
4.1.4 LNAPL transmissivity will vary over time with changing conditions such as, seasonal fluctuations in water table, changing hydrogeologic conditions and with variability in LNAPL impacts (that is, interval that LNAPL flows over in the formation and LNAPL pore space saturation) within the formation.  
4.1.5 Any observed temporal or spatial variability in values derived from consistent data collection and analysis methods of LNAPL transmissivity is not erroneous, rather is indicative of the actual variability in subsurface conditions related to the parameters encompassed by LNAPL transmissivity (that is, fluid pore space saturation, soil permeability, fluid density, fluid viscosity, and the interval that LNAPL flows over in the formation).  
4.1.6 LNAPL transmissivity is a more accurate metric for evaluating recoverability and mobile LNAPL than gauged LNAPL thickness. Gauged LNAPL thickness does not account for soil permeability, magnitude of LNAPL saturation above residual saturation, or physical fluid properties of LNAPL (that is, density, interfacial tension, and viscosity).  
4.1.7 The accurate calculation of LNAPL transmissivity requires certain aspects of the LNAPL Conceptual Site Model (LCSM) to be completely understood and defined in order to calculate LNAPL drawdown correctly. The methodologies for development of the LCSM are provided in Guide E2531. The general conceptual site model aspe...
SCOPE
1.1 This guide provides field data collection and calculation methodologies for the estimation of light non-aqueous phase liquid (LNAPL) transmissivity in unconsolidated porous sediments. The methodologies presented herein may, or may not be, applicable to other hydrogeologic regimes (for example, karst, fracture flow). LNAPL transmissivity represents the volume of LNAPL (L3) through a unit width (L) of aquifer per unit time (t) per unit drawdown (L) with units of (L2/T). LNAPL transmissivity is a directly proportional metric for LNAPL recoverability whereas other metrics such as apparent LNAPL thickness gauged in wells do not exhibit a consistent relationship to recoverability. The recoverability for a given gauged LNAPL thickness in a well will vary between different soil types, LNAPL types or hydrogeologic conditions. LNAPL transmissivity accounts for those parameters and conditions. LNAPL transmissivity values can be used in the following five ways: (1) Estimate LNAPL recovery rate for multiple technologies; (2) Identify trends in recoverability via mapping; (3) Applied as a leading (startup) indicator for recovery; (4) Applied as a lagging (shutdown) indicator for LNAPL recovery; and (5) Applied as a robust calibration metric for multi-phase models (Hawthorne and Kirkman, 2011 (1)2 and ITRC ((2)). The methodologies for LNAPL transmissivity estimation provided in this document include short-term aquifer testing methods (LNAPL baildown/slug testing and manual LNAPL skimming testing), and long-term methods (that is, LNAPL recovery system performance analysis, and LNAPL tracer testing). The magnitude of transmissivity of any fluid in the subsurface is controlled by the same variables (that is, fluid pore space saturation, soil permeability, fluid density, fluid viscosity, the interval that LNAPL flows over in the formation and the gravitational acceleration constant). A direct mathematical relationship exists between th...

General Information

• Status: Published
• Publication Date: 31-Mar-2021
• ICS: 13.080.05 - Examination of soils in general
• Technical Committee: E50 - Environmental Assessment, Risk Management and Corrective Action
• Drafting Committee: E50.04 - Corrective Action

Relations

• Refers: ASTM D5088-20 - Standard Practice for Decontamination of Field Equipment Used at Waste Sites
• Effective Date: 01-May-2020
• Refers: ASTM D5088-15a - Standard Practice for Decontamination of Field Equipment Used at Waste Sites
• Effective Date: 01-Aug-2015
• Refers: ASTM D5088-15 - Standard Practice for Decontamination of Field Equipment Used at Waste Sites
• Effective Date: 15-Jan-2015
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM D653-09 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Jan-2009
• Refers: ASTM D653-08a - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Dec-2008
• Refers: ASTM D653-08 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Nov-2008
• Refers: ASTM D5088-02(2008) - Standard Practice for Decontamination of Field Equipment Used at Waste Sites
• Effective Date: 15-Sep-2008
• Refers: ASTM D653-07f - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 15-Dec-2007
• Refers: ASTM D653-07e - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Nov-2007
• Refers: ASTM D653-07d - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2007
• Refers: ASTM D653-07c - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Jul-2007
• Refers: ASTM D653-07b - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-May-2007
• Refers: ASTM D653-06 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Nov-2006

Overview

ASTM E2856-13(2021), Standard Guide for Estimation of LNAPL Transmissivity, provides established methodologies for the field estimation and calculation of light non-aqueous phase liquid (LNAPL) transmissivity in unconsolidated porous sediments. Developed by ASTM International, this guide is key for environmental professionals involved in the characterization, recovery, and remediation of sites impacted by LNAPL contamination, such as petroleum hydrocarbons.

LNAPL transmissivity quantifies the capacity of an aquifer to transmit mobile LNAPL over a given interval. Unlike simple gauged thickness measurements, this metric reflects the combined influence of soil and fluid properties, as well as LNAPL saturation levels. This standard presents various field methods, data evaluation techniques, and guidance for selecting approaches best aligned with site-specific hydrogeology.

Key Topics

• Field Data Collection: The guide covers multiple short-term and long-term field testing methods including baildown/slug tests, manual LNAPL skimming, recovery system performance analysis, and LNAPL tracer testing.
• Calculation Methodologies: It presents procedures for calculating LNAPL transmissivity using data from the above tests, emphasizing the accuracy and reproducibility of results.
• Practical Considerations:
  • LNAPL transmissivity is dependent not only on aquifer characteristics but also on LNAPL physical properties (density, viscosity) and saturation.
  • Results may vary over time due to seasonal groundwater fluctuations, site remediation activities, or changes in LNAPL distribution.
• Metric Significance:
  • Provides a more reliable measure of LNAPL recoverability than gauged thickness.
  • Used for tracking remediation progress and understanding LNAPL behavior in the subsurface.

Applications

ASTM E2856-13(2021) is widely applicable in the following scenarios:

• Estimating Recovery Rates: Supports the assessment of potential LNAPL recovery rates for various remediation technologies and helps in selecting effective strategies for site cleanup.
• Remediation Monitoring: LNAPL transmissivity serves as both a leading (startup) and lagging (shutdown) indicator during active recovery operations, allowing practitioners to track progress toward residual saturation and determine shutdown thresholds.
• Mapping and Trend Analysis: Enables the mapping of recoverability trends at impacted sites, aiding in the delineation of mobile LNAPL zones and prioritization of remediation efforts.
• Model Calibration: Used as a robust parameter for multi-phase flow modeling, enhancing predictive accuracy in site-specific conceptual models (LCSMs).
• Comparative Evaluation: Offers a standardized way to compare site conditions across different locations or times, supporting regulatory reporting and closure justification.

Related Standards

Several ASTM standards and guidance documents are referenced within ASTM E2856-13(2021), providing complementary methods and definitions:

• ASTM D653: Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D5088: Practice for Decontamination of Field Equipment Used at Waste Sites
• ASTM D5521: Guide for Development of Groundwater Monitoring Wells in Granular Aquifers
• ASTM E2531: Guide for Development of Conceptual Site Models and Remediation Strategies for LNAPLs
• ITRC Guidance: State-of-practice for LNAPL management and conceptual modeling

By referencing ASTM E2856-13(2021) and its related standards, environmental professionals and remediation specialists can ensure scientifically robust, defensible, and effective LNAPL transmissivity estimates-critical for regulatory compliance, site management, and protection of groundwater resources.

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Keywords: ASTM E2856-13, LNAPL transmissivity, field methods, LNAPL recovery, petroleum hydrocarbons, aquifer remediation, ASTM standard, environmental site assessment

Standards Content (Sample)

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: E2856 − 13 (Reapproved 2021)
Standard Guide for
Estimation of LNAPL Transmissivity
This standard is issued under the fixed designation E2856; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope ing the relationship of discharge versus drawdown for the
occurrence of LNAPLin a well, which can be used to estimate
1.1 This guide provides field data collection and calculation
the transmissivity of LNAPL in the formation. The focus,
methodologies for the estimation of light non-aqueous phase
therefore,istoprovidestandardmethodologyonhowtoobtain
liquid (LNAPL) transmissivity in unconsolidated porous sedi-
accurate measurements of these two parameters (that is,
ments. The methodologies presented herein may, or may not
discharge and drawdown) for multi-phase occurrences to
be, applicable to other hydrogeologic regimes (for example,
estimate LNAPL transmissivity.
karst, fracture flow). LNAPL transmissivity represents the
volume of LNAPL(L ) through a unit width (L) of aquifer per
1.2 Organization of this Guide:
unit time (t) per unit drawdown (L) with units of (L /T).
1.2.1 Section 2 presents documents referenced.
LNAPL transmissivity is a directly proportional metric for
1.2.2 Section 3 presents terminology used.
LNAPL recoverability whereas other metrics such as apparent
1.2.3 Section 4 presents significance and use.
LNAPL thickness gauged in wells do not exhibit a consistent
1.2.4 Section 5 presents general information on four meth-
relationship to recoverability. The recoverability for a given
ods for data collection related to LNAPL transmissivity calcu-
gauged LNAPLthickness in a well will vary between different
lation. This section compares and contrasts the methods in a
soil types, LNAPLtypes or hydrogeologic conditions. LNAPL
way that will allow a user of this guide to assess which method
transmissivity accounts for those parameters and conditions.
most closely aligns with the site conditions and available data
LNAPLtransmissivity values can be used in the following five
collection opportunities.
ways: (1) Estimate LNAPL recovery rate for multiple tech-
1.2.5 Sections 6 and 7 presents the test methods for each of
nologies; (2) Identify trends in recoverability via mapping; (3)
the four data collection options.After reviewing Section 5 and
Applied as a leading (startup) indicator for recovery; (4)
selecting a test method, a user of this guide shall then proceed
Applied as a lagging (shutdown) indicator for LNAPL recov-
to the applicable portion of Sections 6 and 7 which describes
ery; and (5) Applied as a robust calibration metric for multi-
the detailed test methodology for the selected method.
phase models (Hawthorne and Kirkman, 2011 (1) and ITRC
1.2.6 Section 8 presents data evaluation methods. After
((2)). The methodologies for LNAPLtransmissivity estimation
provided in this document include short-term aquifer testing reviewing Section 5 and the pertinent test method section(s) of
Sections6and7,theuserofthisguideshallthenproceedtothe
methods (LNAPL baildown/slug testing and manual LNAPL
skimming testing), and long-term methods (that is, LNAPL applicable portion(s) of Section 8 to understand the method-
ologies for evaluation of the data which will be collected. It is
recovery system performance analysis, and LNAPL tracer
testing). The magnitude of transmissivity of any fluid in the highly recommended that the test methods and data evaluation
procedures be understood prior to initiating data collection.
subsurface is controlled by the same variables (that is, fluid
pore space saturation, soil permeability, fluid density, fluid
1.3 The values stated in inch-pound units are to be regarded
viscosity, the interval that LNAPL flows over in the formation
as standard. The values given in parentheses are mathematical
and the gravitational acceleration constant). A direct math-
conversions to SI units that are provided for information only
ematical relationship exists between the transmissivity of a
and are not considered standard.
fluid and the discharge of that fluid for a given induced
1.4 This standard does not purport to address all of the
drawdown. The methodologies are generally aimed at measur-
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
ThisguideisunderthejurisdictionofASTMCommitteeE50onEnvironmental
priate safety, health, and environmental practices and deter-
Assessment, Risk Management and CorrectiveAction and is the direct responsibil-
mine the applicability of regulatory limitations prior to use.
ity of Subcommittee E50.04 on Corrective Action.
Current edition approved April 1, 2021. Published June 2021. Originally
1.5 This document is applicable to wells exhibiting LNAPL
approved in 2011. Last previous edition approved in 2013 as E2856 –13. DOI:
consistently (that is, LNAPL transmissivity values above zero).
10.1520/E2856–13R21.
This methodology does not substantiate zero LNAPL transmis-
The boldface numbers in parentheses refer to the list of references at the end of
this standard. sivity; rather the lack of detection of LNAPL within the well
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2856 − 13 (2021)
combined with proper well development and purging proce- 3.1.8 equilibrium fluid levels—gauged fluid levels that rep-
dures are required to confirm zero LNAPL transmissivity. resent the oil head and the water head or the calculated
1.6 This document cannot replace education or experience water-table elevation of the formation. Under equilibrium fluid
and should be used in conjunction with professional compe- levels no net oil or water flow occurs between the formation
tence in the hydrogeology field and expertise in the behavior of and the well.
LNAPL in the subsurface.
3.1.9 fluid level—the level of a fluid interface (either air/oil,
1.7 This document cannot be assumed to be a substitute for
LNAPL/water, or potentiometric surface).
orreplaceanylawsorregulationswhetherfederal,state,tribal
3.1.10 formation thickness (b )—the interval that LNAPL
nf
or local.
flows over in the formation. For unconfined conditions this is
1.8 This international standard was developed in accor-
approximatelyequaltothegaugedLNAPLthickness.Confined
dance with internationally recognized principles on standard-
and perched conditions the gauged LNAPL thickness under
ization established in the Decision on Principles for the
equilibrium conditions is not equal to the formation thickness.
Development of International Standards, Guides and Recom-
(L)
mendations issued by the World Trade Organization Technical
3.1.11 gauged LNAPL thickness (b )—The difference be-
Barriers to Trade (TBT) Committee.
n
tween the gauged air/LNAPL interface and the water/LNAPL
interface in a well. (L)
2. Referenced Documents
3.1.12 hydraulic conductivity (derived via field aquifer
2.1 ASTM Standards:
tests)—the volume of water at the existing kinematic viscosity
D653 Terminology Relating to Soil, Rock, and Contained
that will move in a unit time, under a unit hydraulic gradient,
Fluids
through a unit area, measured at right angles to the direction of
D5088 Practice for Decontamination of Field Equipment
flow. (L/t)
Used at Waste Sites
D5521 Guide for Development of Groundwater Monitoring
3.1.13 LNAPL—Light Non Aqueous Phase Liquid.
Wells in Granular Aquifers
3.1.14 LNAPL baildown test—a procedure which includes
E2531 Guide for Development of Conceptual Site Models
the act of removing a measured LNAPL volume from a well
and Remediation Strategies for Light Nonaqueous-Phase
and filter pack to induce a head differential and the follow-up
Liquids Released to the Subsurface
gauging of fluid levels in the well.
3.1.15 LNAPL borehole volume—the volume of LNAPL
3. Terminology
existing within the casing and the drainable volume existing
3.1 Definitions:
within the filter pack of a well. Based on effective radius and
3.1.1 air/LNAPL interface (Z )—The surface shared by air
an
gauged thickness of LNAPL. (L )
and LNAPL in a control well. (L)
3.1.16 LNAPLslug test—a procedure which includes the act
3.1.2 calculated water-table elevation (Z )—thetheoreti-
CGW
of removing or displacing a known volume of LNAPL from a
cal location of the air/water surface based on a density
well to induce a head differential and the follow-up gauging of
correction if LNAPL were not present in a well. (L)
fluid levels in the well.
3.1.3 confined LNAPL—LNAPL trapped in an aquifer be-
3.1.17 LNAPL specific yield (S )—the volume of LNAPL
yn
neathalayerthatexhibitsaporeentrypressuregreaterthanthe
an aquifer releases or takes into storage per unit surface area of
capillary LNAPL head, thereby impeding the upward migra-
the aquifer per unit change in LNAPL head for gravity
tion of LNAPL limits the upward movement of the LNAPL.
drainage conditions. (unitless)
The term confined LNAPLis used because the mobile LNAPL
3.1.18 LNAPLspecific yield filter pack (S )—thevolumeof
is under pressure greater than gauge pressure against the yf
LNAPL released or takes into storage per unit surface area of
underside of the LNAPL confining layer.
the filter pack per unit change in LNAPL head for gravity
3.1.4 control well—well by which the aquifer is stressed or
drainage conditions. (unitless)
tested.
3.1.19 LNAPL storage coeffıcient (S)—the volume of
n
3.1.5 discharge—the flow of a fluid into or out of a well.
LNAPL an aquifer releases from or takes into storage per unit
(L /t)
surfaceareaoftheaquiferperunitchangeinLNAPLhead.For
3.1.6 drawdown—a pressure differential in terms of fluid
a confined aquifer, it is based on the volume of fluid released
head. (L)
due to decompression. For an unconfined aquifer, the storage
3.1.7 effective well radius—the radius that represents the coefficient is approximately equal to the LNAPLspecific yield.
area of the well casing and the interconnected porosity of the (unitless)
filter pack. (L)
3.1.20 LNAPL transmissivity (T )—the volume of LNAPL
n
at the existing kinematic viscosity that will move in a unit time
under a unit hydraulic gradient through a unit width of the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
aquifer. (L /t)
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3.1.21 observation well—a well screened across all or part
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. of an aquifer.
E2856 − 13 (2021)
3.1.22 oil/water interface (Z )—The surface shared by development of the LCSM are provided in Guide E2531. The
nw
LNAPL and water in a control well. (L) general conceptual site model aspects applicable to this guide
include:
3.1.23 perched LNAPL—mobile LNAPL that accumulates
4.1.7.1 Equilibrium fluid levels (for example, air/LNAPL
in the vadose zone of a site for some time period above a layer
and LNAPL/water).
that exhibits a pore entry pressure greater than the capillary
4.1.7.2 Soil profile over which LNAPL is mobile.
LNAPL head, thereby impeding the downward migration of
LNAPL. 4.1.7.3 LNAPL hydrogeologic scenario (for example,
unconfined, confined, perched, macro pores, and so forth).
3.1.24 potentiometric surface—see calculated water-table
4.1.7.4 LNAPL density.
elevation.
4.1.7.5 Hydraulic conductivity for each soil type within the
3.1.25 radius of influence—the distance from a well that the
well screen interval.
pumping induced head differential from non-pumping condi-
4.1.7.6 Well screen interval in the vadose and saturated
tions is zero, head differentials due to background gradients
zones.
may still exist at this radius. (L)
4.1.8 Incorporation of LNAPL transmissivity can further
3.1.26 slug—a volume of water or solid object used to
LCSMsbyprovidingasinglecomparablemetricthatquantifies
induce a sudden change of head in a well.
LNAPL recoverability at individual locations across a site.
3.1.27 test well—a well by which the aquifer is stressed, for
4.1.9 Each of the methods provided in this document is
example, by pumping, injection, or change of head.
applicable to LNAPL in confined, unconfined, and perched
3.2 For definitions of other terms used in this test method conditions. Any differences in evaluation are discussed in
refer to Terminology, Guide D653. Section 5.
4.2 Purpose—The methods used to calculate LNAPL trans-
4. Significance and Use
missivity have been published over the past 20 years; however
4.1 Application: littleefforthasbeenfocusedonprovidingqualityassurancefor
4.1.1 LNAPL transmissivity is an accurate metric for un- individualtestsorrefinementoffieldprocedures.Inadditionto
summarizing the existing methods to calculate LNAPL
derstanding LNAPL recovery, is directly proportional to
LNAPL recoverability and tracking remediation progress to- transmissivity, this document will provide guidance on refined
field procedures for data collection and minimum requirements
wards residual LNAPL saturation.
for data sets before they are used to calculate LNAPL
4.1.2 LNAPLtransmissivity can be used to estimate the rate
transmissivity.
of recovery for a given drawdown from various technologies.
4.2.1 Considerations—The following section provides a
4.1.3 LNAPL transmissivity is not an intrinsic aquifer
property but rather a summary metric based on the aquifer brief review of considerations associated with LNAPL trans-
properties, LNAPL physical properties, and the magnitude of missivity testing.
LNAPL saturation over a given interval of aquifer.
4.2.1.1 Aquifer Conditions (confined, unconfined,
4.1.4 LNAPLtransmissivitywillvaryovertimewithchang-
perched)—In general, each testing type is applicable to
ing conditions such as, seasonal fluctuations in water table, confined, unconfined, and perched conditions; however, con-
changing hydrogeologic conditions and with variability in
sideration should be given to how LNAPL drawdown is
LNAPLimpacts (that is, interval that LNAPLflows over in the calculated from well gauging data relative to formation condi-
formation and LNAPL pore space saturation) within the
tions. Calculation of LNAPL transmissivity for confined and
formation.
perched conditions is possible; however, the soil profile needs
4.1.5 Any observed temporal or spatial variability in values to be considered in combination with the fluid levels to
derivedfromconsistentdatacollectionandanalysismethodsof accurately calculate drawdown. Drawdown values for perched
and confined conditions can easily be overestimated without
LNAPL transmissivity is not erroneous, rather is indicative of
the actual variability in subsurface conditions related to the proper consideration. This results in LNAPL transmissivity
being underestimated. The calculations of drawdown under
parameters encompassed by LNAPL transmissivity (that is,
fluid pore space saturation, soil permeability, fluid density, perched and confined conditions are discussed within this
fluid viscosity, and the interval that LNAPL flows over in the document. Tidal influences or a vertical gradient on the water
formation). table also affect measurements and could distort the transmis-
sivity results. Tidal influences are discussed in more detail in
4.1.6 LNAPL transmissivity is a more accurate metric for
Appendix X1.
evaluating recoverability and mobile LNAPL than gauged
LNAPLthickness. Gauged LNAPLthickness does not account
4.2.1.2 Well Construction—Any well being tested should be
for soil permeability, magnitude of LNAPL saturation above screened over the entire mobile interval of LNAPL. For
residual saturation, or physical fluid properties of LNAPL(that
locations where multiple discrete mobile intervals exist, it may
is, density, interfacial tension, and viscosity). be preferable to screen individual wells across each mobile
4.1.7 The accurate calculation of LNAPL transmissivity interval. This will simplify the calculation of drawdown and
requires certain aspects of the LNAPL Conceptual Site Model derivation of LNAPL transmissivity. The interval of mobile
(LCSM) to be completely understood and defined in order to LNAPL does not always correspond to the elevation of the
calculate LNAPL drawdown correctly. The methodologies for air/LNAPL interface (for example, the mobile interval can be
E2856 − 13 (2021)
beneath the base of a confining layer under confined condi- baildown/slug tests may not compare well with transmissivity
tions).Appropriatelyscreenedwellscanbesubstantiatedbased values estimated using recovery system-based data (5.3) be-
on vertical delineation of the entire LNAPL impacted interval cause of the differences in scale of evaluation between the two
(see Guide E2531). methods. However, increasing or decreasing trends in trans-
4.2.1.3 LNAPL Type—No limitations have been identified missivity will be seen in both recovery system-based data and
for LNAPL type. However, the specific gravity of the LNAPL baildown testing-based data.
must contrast with that of the water to be measurable with an
5.2.5 Capital Cost—The capital cost for this method is low
interface probe.
because it can be implemented on existing wells exhibiting
4.2.1.4 Well Development—In order to derive the most
LNAPL,doesnotrequiretheconstructionofarecoverysystem
accurate LNAPL transmissivity value, appropriate well devel-
nor does it require specialized equipment above and beyond
opment should be conducted to ensure connectivity between
other methods.
LNAPL in the formation and the well (Hampton 2003) (3).
5.2.6 Test Duration—The test length timeframe is inversely
Industry experience has observed that LNAPL can require up
related to the transmissivity of LNAPL and directly related to
to several months following well installation to saturate the
the effective well radius. LNAPL baildown/slug tests may
filter pack and establish connectivity within the well. Well
require minutes to months to completely recover as LNAPL
development can help to reduce this time frame and should be
transmissivity may vary by several orders of magnitude across
completed in accordance with Guide D5521.
sites. However, in cases of slow recovery (that is, greater than
4.2.2 Analysis Method—An understanding of the analysis
a month) and where high confidence exists that the initial fluid
method and theory is necessary prior to the field testing to
levels represent equilibrium conditions, it is not necessary to
ensure that all appropriate dimensions and measurements are
allow the well to fully recover. A data set representing partial
properly recorded.
recovery combined with substantiated equilibrium fluid levels
can be used to estimate an LNAPL transmissivity or at a
4.3 Precision and Bias—At this time this document aims to
minimum place an upper bound on recoverability.
provide methodologies for data collection and analysis to yield
an accuracy of LNAPLtransmissivity values within a factor of 5.2.7 Special Considerations:
two (compared with the unknown actual value). This modest
5.2.7.1 Existenceofaverticalgradientortidalinfluenceson
accuracyisreasonablebasedontheoverallindustryexperience
the water table may limit the accuracy of the slug and/or
in implementing these procedures and the lack of comparison
baildown test, because the initial thickness in the well may be
studies. The objectives initiated through development of this
exaggerated (downward hydraulic gradient) or thin (upward
document are to provide improved guidance for more consis-
hydraulic gradient), compared with static conditions. The
tent data collection and analysis methodology, which in turn
relationships between LNAPLthickness, vertical gradient, and
will provide a larger and more accurate data set on which to
LNAPL recovery (recharge) rate may be complex and distort
base future methodology revisions and improvements.
test data and the interpretation and are beyond the scope of this
guide.
5. Method Selection
5.2.7.2 Periodic LNAPL removal events from wells have
5.1 The following section describes each of four test meth-
historically resulted in wells in a continual state of non-
ods for the user to evaluate which methodology best fits their
equilibrium and result in inaccurate equilibrium fluid levels.
data objectives, site setting, and hydrogeologic conditions. An
Equilibrium fluid level data is required for accurate drawdown
overview of this section is provided in Table A2.1 and Table
calculations. LNAPL drawdown has historically been one of
A2.2. A review of the required parameters to be measured is
the primary variables inducing significant error to LNAPL
provided in Tables A2.3-A2.9.
baildown/slug tests.
5.2.7.3 The baildown test methodology provided minimizes
5.2 Baildown/Slug Testing:
filter pack recharge effects and is applicable where formation
5.2.1 Overview—The LNAPLbaildown/slug test consists of
storativity effects are not significant in test results. Slug tests
either removing the entire LNAPL from the well casing and
will exhibit larger borehole storage effects at a given well
filter pack or the displacement of a partial volume to induce a
because the slug represents a relatively small percentage of the
head differential, respectively. Following the induction of the
LNAPLvolume in the well and filter pack. However, slug tests
head differential, fluid levels are gauged during recovery.
are more ideal for an instantaneous removal event, which is
5.2.2 Data Analysis—The LNAPL baildown/slug test field
needed where steady state conditions are not well approxi-
procedure is used in conjunction with LNAPL slug test
mated due to formation storage effects. The advantage of
analyticalprocedurestoprovideestimatesofLNAPLtransmis-
baildown test methods with their larger removal volumes and
sivity at any well exhibiting sufficient LNAPL thickness (that
stresses is the minimization of borehole storage induced errors.
is, at least 0.5 ft/15.2 cm).
The advantage of slug test methods with their smaller, faster
5.2.3 Waste Disposal—The baildown/slug test provides an
removal is the minimization of non-instantaneous effects. The
advantage over other tests in that it does not typically require
quantified magnitude of these individual differences has not
the disposal of large quantities of LNAPLor water that may be
been widely studied.
produced, nor does it require specialized equipment.
5.2.4 Aquifer Extent Represented—LNAPL baildown/slug 5.2.7.4 The error associated with the recharge rate calcula-
tests reflect conditions near the well, and therefore represent a tionsisdirectlyrelatedtotheerroringaugedLNAPLthickness
limited radius of influence. LNAPLtransmissivity values from measurement. Smaller equilibrium thicknesses either result in
E2856 − 13 (2021)
fewer data points being collected or data points representing hydrograph) is required to ensure initial fluid levels represent
smaller changes in well recovery. Based on the accuracy of equilibrium conditions for accurate calculation of LNAPL
estimating the LNAPL/water and air/water interface with drawdown.
available interface probes, it is possible but generally not
5.4 Recovery Data-Based Methods:
recommended to complete baildown tests at wells with a
5.4.1 This guide provides general procedures for deriving
gauged LNAPL thickness of less than 0.5 ft (for 2-in. or 4-in.
LNAPL transmissivities using data obtained from continuous
wells). Baildown/slug testing should not be attempted at wells
operation of LNAPL skimmer pumps and/or other types of
with a measured thickness of LNAPL less than 0.2 ft.
product recovery systems where aquifer conditions approach
5.3 Manual LNAPL Skimming Tests: steady-state conditions. These recovery systems are designed
to extract LNAPL, groundwater and/or formation air/vapor
5.3.1 Overview—The manual LNAPL skimming test is
from a recovery well.
conducted by removing LNAPL at a rate that maintains
5.4.2 Because LNAPL transmissivity is being continually
drawdown in the well until a consistent LNAPL recovery rate
is achieved. reduced through product recovery, steady-state conditions can
be approached but not reached. Steady-state conditions are
5.3.2 Data Analysis—This manual LNAPL skimming test
approximated when the maximum radius of influence (ROI) is
field procedure is used in conjunction with a skimming test
reached for the current drawdown induced via the given
analytical method, to derive estimates of LNAPL transmissiv-
technology.
ity.
5.4.3 The derivation of LNAPL transmissivity using recov-
5.3.3 Waste Disposal—The manual LNAPL skimming test
ery system data is based on the theory of radial fluid flow.
typically generates more waste than baildown/slug or tracer
Subsurface barriers (for example, building foundations) or
tests and less than recovery system methods.
significant heterogeneities can result in an under-estimation of
5.3.4 Aquifer Extent Represented—The manual LNAPL
LNAPL transmissivity when calculation methods involve the
skimming test provides an advantage over other tests in that;
useoftheradiusofinfluenceparameter.Theequationforradial
the longer period of time the test is performed, the larger the
fluid flow will provide an average LNAPL transmissivity for
areaoftheformationitrepresentsandtheaccuracyofrecovery
all directions. However, it will under estimate LNAPL trans-
volume estimates increase, which are used in the calculation of
missivity in directions away from a subsurface barrier.
LNAPL transmissivity.
Changes in soil type or lithologic properties affecting the
5.3.5 Capital Cost—The capital cost of this method is
hydraulic or pneumatic permeability of the formation and
relatively low as it can be completed at existing wells with
occurring within the recovery system radius of influence can
LNAPL and typically requires similar equipment to baildown
affect the accuracy of the LNAPL transmissivity results. This
tests. If LNAPL transmissivity is sufficiently high then the use
effect is not significant when the fluid production ratio equa-
of a pump could incur additional costs. This method requires
tions are used and the changes in subsurface conditions affect
less capital cost than recovery system-based or tracer tests.
all extracted fluids and phases similarly. Accounting for such
5.3.6 Test Duration—The length of the manual skimming
variability via site characterization data and accurate site
tests is inversely related to the LNAPL transmissivity and
conceptual models is necessary to achieve the most accurate
directly related to the well diameter and LNAPL storativity in
results.
the formation.The manual skimming test duration is similar or
5.4.4 If the recovery system is operating consistently and
longer in time frame compared with baildown/slug tests and a
the LCSM is well developed and understood, this method can
shorter timeframe than tracer tests.
provide high accuracy and repeatability of transmissivity
5.3.7 LNAPLskimming tests may be completed at any well
calculations. However, use of recovery system-based data for
exhibiting a gauged LNAPL thickness. This test is especially
estimation of LNAPL transmissivity requires a well-defined
useful for wells exhibiting a gauged thickness less than 0.5 ft
LCSMandfrequentmonitoringofrecoverysystemoperational
because it allows the measurement of LNAPL volume above-
parameters. LNAPL transmissivity values estimated from re-
ground. In addition, the error associated with estimating the
covery data are representative of a region within an area of
recharged LNAPL volume at this initial gauged thickness can
mobile LNAPL that is proportional to drawdown induced,
be more accurately estimated above-ground than in-situ.
recovery well spacing, and operational time. In other words,
5.3.8 Recovery system based-data transmissivity values
the area represented by an LNAPL transmissivity value is
may not compare identically with “instantaneous” and “point”
proportional to the drawdown induced, length of time run and
transmissivity method results (for example, manual skimming
distance between recovery well locations.As a result, recovery
test results) because of the differences in scale of evaluation
data transmissivity values may differ significantly from those
between the two methods. However, increasing or decreasing
obtained using “instantaneous” and “point” transmissivity
trends in transmissivity will be seen in both recovery system-
method results (for example, baildown/slug test results) be-
based data and manual skimming testing-based data.
cause of the differences in scale of evaluation between the
5.3.9 Manual LNAPL skimming tests may be conducted in methods. However, increasing or decreasing trends in trans-
all types of aquifer materials.
missivity will be seen in both recovery system-based data and
baildown testing-based data.
5.3.10 Manual LNAPL skimming tests do not provide data
to graphically estimate equilibrium fluid levels. Therefore, a 5.4.5 LNAPLtransmissivity measurement by long-term op-
good understanding of fluid level behavior (for example, eration of a skimming device or other LNAPLrecovery system
E2856 − 13 (2021)
assumes continuous operation over the temporal interval of 5.5.5 Data Analysis—Data reduction methods assume
interest. Complete knowledge and maintenance of the system steady-state conditions, which can occur under natural or
operation representing optimal conditions (for example, pump ambient conditions, or during steady-state recovery.
depthcorrespondstotheintervalofmobileLNAPLorensuring 5.5.6 The LNAPL flux measurement is representative of a
few feet outside the borehole. The LNAPL gradient is repre-
sufficient storage tank capacity) is necessary to obtaining
representative LNAPL transmissivity values. sentative of the LNAPL surface within the well network
density.
5.4.6 TheLNAPLtransmissivityvaluesderivedbyrecovery
5.5.7 Although the flux measurement does not require a
systemdataarebasedonfluidflowthroughaporousmediaand
uniform flow field, it is combined with the LNAPLgradient to
notkarstenvironmentsorfracturedrock.Attemptstoapplythis
calculate an LNAPL transmissivity value. The LNAPL gradi-
document to estimate LNAPL transmissivities in fractured
ent estimates assume a uniform flow field between wells.
rock, karst environments or other non-porous media may result
Therefore,thismethodismoreapplicabletoauniformLNAPL
in inaccurate LNAPL transmissivity values.
flow field. Uniform LNAPL flow fields occur in homogenous
5.4.7 Fluctuations of water table elevation during the
conditions and can be induced by active recovery.
LNAPL recovery data collection period that significantly
5.5.8 LNAPL tracer tests may be conducted in unconfined,
change the relationship between the groundwater/LNAPL
perched and confined aquifer materials where the fluid levels
interface (or the air/LNAPL interface) relative to the location
are in equilibrium with the formation.
of the recovery pump(s) can result in inaccurate transmissivity
5.5.9 Inputs for data analysis (analytical procedure) should
determinations. In addition, both horizontal and vertical pneu-
be known prior to the field testing to ensure that all appropriate
matic formation permeability must be determined when esti-
dimensions and measurements are properly recorded.
mating the air radius of influence for determining transmissiv-
5.5.10 Specialized Equipment Needed—A hydrophobic
ity using LNAPL systems that incorporate vacuum-enhanced
fluorescenttracerandaUV/VISspectrometerwithadownhole
recovery.
fiber optic cable are needed to make measurements of tracer
5.4.8 The relative depths of the recovery well screen
concentration through time.
intervals, the groundwater/LNAPL interface, the air/LNAPL
5.5.11 Screening Factors for Test Method Selection:
interface,andthedepthofpump(s)intake(s)mustbeknown.In
5.5.11.1 Using hydrophobic tracers to determine LNAPL
addition, the configuration of the well construction, interfaces,
transmissivity is a relatively new method, and it is expected
and pump(s) intake(s) must be appropriate for the specific
that this method will become more refined in the future. The
recovery system used to derive LNAPL transmissivity.
following methods have been proven at a laboratory scale
5.4.9 This guide provides analytical equations to calculate
(Smith et al, 2011) (4) and at seven field sites (Mahler et al,
LNAPL transmissivity (T ) using recovery system-based data
2011) (5).
n
from four types of remediation technologies:
5.5.11.2 Measurement of LNAPL Gradient—The local
LNAPLgradient must be measured or estimated as an input to
5.4.9.1 LNAPL only liquid removal (skimming).
the equation for LNAPL transmissivity using tracer tests.
5.4.9.2 Vacuum-enhanced LNAPL only liquid removal
(vacuum-enhanced skimming).
TEST METHODS
5.4.9.3 Water-enhanced LNAPL removal (total fluids
pumping, single or dual pump). 6. Short-Term Aquifer Testing-Based Methods
5.4.9.4 Water and vacuum-enhanced LNAPL removal
6.1 Baildown/Slug Testing Field Methods—Thistestmethod
(multi-phase fluid extraction [MPE]).
describes the field procedures involved in conducting an
instantaneous LNAPL baildown/slug test. The LNAPL
5.5 Tracer Test-Based Methods:
baildown/slugtestmethodinvolvescausingasuddenchangein
5.5.1 Overview—This tracer test field procedure shall be
LNAPL head in a control well and measuring the fluid level
utilizedinconjunctionwithatracertestanalyticalprocedureto
response within that control well. Head change is induced by
derive LNAPL flux and estimates of LNAPL transmissivity at
removing a known and measurable LNAPL volume from the
any properly screened well exhibiting LNAPL thickness
control well.
greater than 0.2 ft.
6.1.1 Apparatus—This test method describes the types of
5.5.2 Tracer tests can be conducted under conditions of a
equipment that can be used. Since there can be an infinite
natural or imposed gradient. Imposed gradient test can be
variety of testing conditions and because similar results can be
conducted about active recovery wells. Natural gradient tests
achieved with different apparatus, engineering specifications
do not require fluid extraction.
for testing equipment are not discussed in this document. This
5.5.3 Test Duration—Natural gradient tests are conducted
test method specifies the results to be achieved by the equip-
over several weeks or months and, therefore, provide
ment to satisfy the requirements of this guide.
temporally-averaged and vertically-averaged transmissivity
6.1.1.1 LNAPL Displacement Equipment—Because a vari-
values. Imposed gradient tests can be conducted in period of
ety of equipment can be used to induce a change in LNAPL
hours to days.
head, this method will not provide engineering specifications
5.5.4 Waste Disposal—LNAPL or water disposal is not of the exact means in which head is changed, but will rather
required since the testing method does not generate water or identify how common types of equipment can affect the final
LNAPL. results. Single slug displacement or removal methods such as
E2856 − 13 (2021)
solid slugs or bailers, respectively, will provide a more water phase). Then the field staff only will be required to
instantaneous change in LNAPL head. This is useful at well measure the depth to the air/LNAPL interface following
locationsexhibitinghigherLNAPLtransmissivities.Theuseof
removal of LNAPL. By only measuring the air/LNAPL inter-
solid slugs is acceptable since their volume can easily be
face less disturbance will be introduced to the well during
measured.Howeveruseofequipmentsuchasperistalticpumps
recovery since the probe does not need to penetrate the fluid
to remove the entire volume of LNAPL in the well casing and
column to measure the LNAPL/water interface. Two pressure
borehole will result in minimizing filter pack recharge effects.
transducers can still be used, where one transducer is placed in
It is strongly recommended to use equipment that can remove
the water phase and a second within the LNAPL phase;
LNAPL from the well and allow the use of graduated contain-
however, they are not necessary.
ers to measure the total volume within 10 %. Vacuum trucks at
6.1.1.4 Time Piece—Used to record the elapsed time of the
best have a detection limit of 5 gal and an accuracy of 1 gal
test.
above 5 gal (19 L). Down-hole non-intrinsically safe electrical
6.1.1.5 Graduated Container—A container for water and
pumps need to remain submerged below the air/LNAPL
LNAPLcollection that is graduated to measure within 10 % of
interface to prevent explosions; therefore down-hole electrical
total estimated recovery volume (unit conversion: 1 gallon =
pumps used to evacuate LNAPL to zero thickness, for
3.825 litres = 3,825 millilitres (mL) = 0.134 cubic feet). For
example, are not acceptable practices.
example, a container that can measure 0.1 gal (~400 mL)
6.1.1.2 In some cases the LNAPLremoval equipment avail-
able will not be able to remove LNAPL at a high enough rate intervals for an expected 1 gal (~4000 mL) of recovered
to completely purge the control well. If this occurs during the product, or a container that can measure 1 gal (~4000 mL)
test, a slug test or any of the other LNAPL transmissivity test
intervals for an expected 10 gal (40 000 mL) of recovered
methods discussed in this document can be applied.
LNAPL.
6.1.1.3 Fluid Level Measurement Equipment—Typically,
6.1.1.6 Decontamination Equipment—Typically, LNAPL in
the air/LNAPL and LNAPL/water interfaces will be gauged
a well can foul measuring devices and should be cleaned with
using an interface probe. Currently the most precise available
an appropriate cleaning agent. If multiple wells are tested,
interface probes utilize optical and electrical resistivity tech-
equipment should be cleaned of well fluids between testing
nologies.Additionally, current technology allows for probes to
separate wells.
be relatively small ( ⁄8-in.) in diameter. The optical and
6.1.1.7 Test Forms—Test forms should be used to record the
electricalresistivitytypeinterfaceprobesincreasetheabilityto
parameters listed in 6.1.2 and 6.1.3 (that is, Conditioning &
measure fluid interfaces to typical accuracies from 0.01 ft to
Procedure). Semi-log graph paper should be used to plot data
0.02 ft (0.3 cm to 0.6 cm). The small probe diameter causes
during the test in order to understand when equilibrium is
less displacement to fluids in the well. When the recovery of
reached and the test is completed. Fig. 1 provides an example
LNAPL occurs rapidly (that is, less than 1 h), tests can be
of LNAPL thickness reaching equilibrium during a test.
conducted with an intrinsically safe pressure transducer, where
thepressuretransducerissetnearthebottomofthewell(inthe 6.1.2 Conditioning:
Graph illustrating how the frequency of gauging data should be based on consistent changes in LNAPL thickness rather than time,
and demonstrating the attainment of recharge equilibrium conditions.
FIG. 1 Gauging Data Graph
E2856 − 13 (2021)
6.1.2.1 Pre-Test Well Information—The following well con-
r = well casing radius (L),
c
structioninformationneedstobeobtainedpriortoinitiatingthe
r = well borehole radius (L), and
b
baildown tests:
S = specific yield or storage coefficient of well filter pack.
yf
(1) Borehole diameter of well to be tested (feet).
6.1.3.7 To account for borehole porosity and LNAPL
(2) Casing and screen diameter (inches).
saturation, a storage coefficient needs to be estimated. Empiri-
(3) Top of screen relative to top of casing (feet).
cal data suggest that 0.175 to 0.190 is a good value for this
(4) Bottom of screen interval relative to top of casing
parameter at any site. If viscosity of the LNAPL is known, an
(feet).
alternate method of estimating storage coefficient that has been
(5) Total well depth (feet).
tested between viscosities of 0.7 and 2 centipoises can be
(6) Verify interval that the well is screened over the
derivedbyusingEq4(Lundy,2005) (6).UsingEq2combined
formation thickness.
with viscosities of 0.5 cp and 5 cp results in a range in
6.1.2.2 Baildown/slug tests are used to evaluate the trans-
storativity of 0.23 to 0.13 where the geometric mean is 0.175.
missivity of LNAPL in the aquifer. It is recommended that the
The empirical data and Eq 4 suggest an average value of 0.175
LNAPL existing within the well and borehole need to be
and the range should not vary by more than a factor of 50 %.
occasionally evacuated prior to the baildown test in order for
S 520.0418ln~µ !10.2007 (4)
yf n
the LNAPL to stay in communication with the formation. The
maximum lag time between removal events is two years.
where:
6.1.2.3 Priortothetest,thewellbeingtestedshouldbefully
S = filter pack LNAPL specific yield, and
yf
recharged; this will ensure the starting LNAPL thickness,
µ = dynamic viscosity of LNAPL (M/Lt).
n
LNAPL head, and potentiometric surface head are all repre-
6.1.3.8 Well construction data will need to be reviewed to
sentative of equilibrium formation conditions.
evaluate if the filter pack exists over the entire gauged interval
6.1.3 Pre-Test Procedure:
ofLNAPL.Ifthewellscreenandfilterpackdonotexistacross
6.1.3.1 Measuring Pre-Test Fluid Levels—Measure the fluid
the entire gauged thickness, then the filter pack thickness, used
levels in the well before the test for a period longer than the
in Eq 1 will have to be reduced from the gauged thickness
time it will take the well to recover in order to ensure
value.
equilibriumfluidlevelsareknownandtocalculatetheeffective
6.1.4 Test Procedure:
well volume. This should be established during the initial
6.1.4.1 WheretheLNAPLtransmissivityorrechargebehav-
evacuation of LNAPL from the well prior to the test (see
ior is not well known, plan to start the baildown portion of the
6.1.2.2).
test early in the work day and on a day when you will be able
6.1.3.2 Errors associated with erroneously assumed equilib-
to return frequently to the well. This will ensure that sufficient
rium fluid levels will reduce test accuracy and may invalidate
measurement frequency can be obtained within the first8hof
the test.
the test.
6.1.3.3 Plan on gauging the well until complete equilibra-
6.1.4.2 Remove the known LNAPL volume up to a maxi-
tion occurs (Fig. 1) for wells where recovery behavior is not
mum as calculated using Eq 3. Smaller removal volumes will
well understood or the pretest gauging data is realized not to
exhibit larger filter pack recharge effects and be more instan-
represent equilibrium conditions.
taneous. Larger removal volumes will minimize filter pack
6.1.3.4 The scope of work should plan for gauging to
recharge effects although may not be instantaneous relative to
potentially be conducted over days or even weeks.
the test duration.
6.1.3.5 For unconfined conditions, the filter pack typically
6.1.4.3 Baildown/slug test LNAPL head change rate must
holds the majority of the stored LNAPL volume within the
th
be induced in a time that is 1/100 or less of the total test
effective well radius. Partial displacement or removal of the
duration,inordertoapproximateinstantaneousheadchange.If
LNAPL will result in the test being dominated by filter pack
full removal of LNAPL from filter pack and well casing
recharge.
requires longer time and an analysis method that relies on
6.1.3.6 Filter pack effects can be reduced through larger
instantaneous withdrawal is being used (for example, Cooper-
displacementvolumesforslugtestsorthecompleteremovalof
Jacob), then a slug method or alternative method should be
LNAPLinthefilterpackandcasingduringbaildowntests.The
used.
following equations can be used to approximate the volume of
6.1.4.4 Instantaneous removal or slug introduction is rela-
LNAPL within the well casing and borehole.
tive to total length of test. For example 15 min of purging can
2 2
V 5 S b π r 2 r (1)
~ !
b yf b b c
be considered instantaneous if the length of the test is 1 day or
V 5 b πr (2)
more.Non-instantaneousremovalscanpotentiallybecorrected
c n c
in conjunction with steady state based slug test solutions (that
V 5 V 1V (3)
t c b
is, Bouwer-Rice), which is discussed in Section 8. However,
where:
efforts should be made to complete the slug/fluid removal in as
V = total effective borehole LNAPL volume (L ),
t short of a timeframe as is practical so that removal approxi-
V = volume of LNAPL in
...