Designation: E3248 − 26Standard Guide forNon-Aqueous Phase Liquid (NAPL) Mobility and Migrationin Sediment—Conceptual Models for NAPL Emplacementand Inf l uence on NAPL Movement 1This standard is issued under the f i xed designation E3248; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide is designed for application at a wide range ofsediment sites where non-aqueous phase liquid (NAPL) ispresent or suspected to be present. This guide describesemplacement mechanisms that can result in NAPL presencewithin sediment and how the characteristics of the sediment,aquatic environment, and NAPL will inf l uence NAPL move-ment (that is, NAPL mobility at the pore scale, NAPLmigration at the NAPL body scale, or both) within sediment.This guide provides example conceptual models for NAPLemplacement in sediment to establish a common evaluationframework that can be used to assess conditions inf l uencingNAPL movement by advection in sediment. This evaluationframework for advective NAPL movement categorizes theNAPL as being either mobile or immobile at the pore scale, ormigrating or stable at the NAPL body scale (or both).1.1.1 Evaluation of the potential for NAPL to move insediment is important for several reasons, including (but notlimited to) the evaluation of risk to potential receptors, deter-mining the need for potential remedial action, and developingpotential remedial strategies. For example, if the NAPL ismigrating, sensitive receptors could be impacted and this willinf l uence the choice and timing of any remedy selected for anarea of the sediment site. If the NAPL is immobile at the porescale or is stable at the NAPLbody scale, then remedial actions(other than to address dissolved-phase contaminants solubi-lized from the NAPL) may not be warranted to address thisimmobile or stable NAPL.1.2 The conceptual models for NAPL emplacement insediment presented in this guide are a component of the overallConceptual Site Model (CSM) of the sediment site. A robustCSM is typically needed to optimize potential future workefforts at a sediment site, which may include various riskmanagement and remedial strategies for the site, as well assubsequent monitoring after remedy implementation.1.3 This guide discusses three broad categories of NAPLemplacement mechanisms.1.3.1 The f i rst category is the migration of NAPL byadvection (f l ow through the soil pore network) from an uplandsite into the pore network of sediment beneath an adjacentwater body. This NAPL emplacement most commonly occurswithin coarser-grained strata within the sediment column.1.3.2 The second category is the direct discharge of lightnon-aqueous phase liquid (LNAPL) into a surface water body,where it is broken down by mechanical energy to form LNAPLdroplets. Oil-particle aggregates (OPAs) are formed in thewater column when suspended particulates in the surface wateradhere to (or penetrate into) the LNAPL droplets originatingfrom direct discharge to the surface water body. Once enoughparticulates have adhered to (or penetrated into) an LNAPLdroplet and the OPA becomes denser than the surroundingsurface water, it settles through the water column onto acompetent sediment surface; here, it forms an in situ depositedNAPL (IDN) and it may be buried by future sedimentation.Because the LNAPLis emplaced by the deposition of the OPAsand LNAPL releases can occur at any time, the LNAPL can beemplaced throughout the sediment column, within both f i ner-and coarser-grained strata.1.3.3 The third category is dense non-aqueous phase liquid(DNAPL) f l ow. This is direct discharge of DNAPL into asurface water body, followed by the NAPL settling through thewater column and deposition directly onto a relatively compe-tent sediment surface, where it may be buried by futuresedimentation. The DNAPL typically experiences gravity f l owatop the sediment surface, until it collects in a local sedimen-tary depression. Unlike the other two emplacement categories,it is the DNAPL that is the matrix and it contains entrainedsediment particulates. As DNAPL releases can occur at anytime, the DNAPL can be emplaced throughout the sedimentcolumn, within both f i ner- and coarser-grained strata.1.4 This guide concerns the advective movement of NAPLin sediment. Ebullition-facilitated transport (EFT) of NAPLand associated contaminants (NAPL/contaminants) from thesediment into the water column by gas bubbles is not within thescope of this guide. The measurement and evaluation ofebullition and associated NAPL/contaminant transport are1 This guide is under the jurisdiction ofASTM Committee E50 on EnvironmentalAssessment, Risk Management and Corrective Action and is the direct responsibil-ity of Subcommittee E50.04 on Corrective Action.Current edition approved May 15, 2026. Published July 2026. Originallypublished in 2020. Last previous edition approved in 2025 as E3248-25. DOI:10.1520/E3248–26.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1
