ASTM E3281-26

1.1 Many contaminants (such as petroleum products and coal tar) are emplaced in sediment in the form of an immiscible liquid known as a non-aqueous phase liquid (NAPL). NAPL can either be a light non-aqueous phase liquid (LNAPL) that is less dense than water or a dense non-aqueous phase liquid (DNAPL) that is denser than water.

1.2 This guide is designed for general application at a wide range of sediment sites where NAPL is present or suspected to be present in the sediment. This guide describes a framework to use field screening methods, specifically visual observations and the results of sediment-water shake tests, to categorize the relative amount of NAPL contained in a sediment sample. This categorization can then be utilized to select collocated sediment samples for laboratory testing to determine if the NAPL in the selected sample interval is mobile or immobile at the pore scale, or for any other chemical or physical testing.

1.2.1 Standardized guidance and test methods currently exist for assessing NAPL mobility at upland sites, from organizations such as ASTM (Guides E2531 and E2856), Interstate Technology & Regulatory Council (1) and the American Petroleum Institute (2, 3).

1.2.2 There is no current industry standard methodology to select sediment samples for laboratory NAPL mobility testing, so the use of different methodologies is possible. This guide focuses on a sample selection framework that uses visual observations and sediment-water shake test results. This framework has the advantage of being simple to use and, if applied in a disciplined manner, has been demonstrated to provide good results in the field.

1.3 This guide does not address methods and means of sample collection (see Guide E3268) or various sediment sample physical testing and chemical analytical methods (see Guide E3163).

1.4 This guide concerns the identification of sediment samples to submit for laboratory NAPL mobility testing, the results of which are used in evaluating the advective movement of NAPL in sediment. Ebullition-facilitated transport (EFT) of NAPL and associated contaminants (NAPL/contaminants) from the sediment into the surface water column by biogenic gas bubbles generated within the sediment is not within the scope of this guide. The measurement and evaluation of ebullition gas and NAPL/contaminant fluxes are discussed in Guides E3300 and E3447. Processes associated with NAPL movement due to erosion (for example, caused by propeller wash) are also not within the scope of this guide.

1.5 Petroleum hydrocarbon, coal tar, and other tar NAPLs (including fuels, oils, and creosote) are the primary focus of this guide. These forms of contamination are commonly related to historical operations at petroleum refineries, petroleum distribution terminals, manufactured gas plants, and various large industrial sites.

1.5.1 Although certain technical aspects of this guide apply to other NAPLs (for example, DNAPLs such as chlorinated hydrocarbon solvents), this guide may not completely address the additional complexities of those other NAPLs.

1.6 Related ASTM Standards— This guide is related to several other guides that cover various aspects of NAPL mobility and migration in sediment. Guide E3248 provides guidance on NAPL emplacement mechanisms in sediment and the differences between NAPL in sediment and upland soil; this guide also outlines a framework to be used to determine whether a NAPL movement assessment should be performed at a sediment site.

• Guide E3268 provides guidance on the collection, field screening, and handling of sediment samples that are representative of in situ conditions for laboratory geotechnical and NAPL mobility testing.
• Guide E3282 discusses metrics (for various lines of evidence (LOEs)) used to evaluate whether NAPL is mobile or immobile at the pore scale; and if the NAPL is mobile, this guide describes other metrics (using additional LOEs) to evaluate whether NAPL is migrating or stable at the NAPL body scale. Guide E3282 also presents example decision analysis frameworks for evaluating whether NAPL is immobile or mobile at the pore scale, and if mobile, stable or migrating at the NAPL body scale.
• Guide E3300 discusses ebullition fundamentals and how to obtain ebullition gas and NAPL/contaminant EFT fluxes (which can be used to estimate NAPL/contaminant loading to the surface water body).
• Guide E3447 discusses the use of flux chambers to measure EFT fluxes, which can be used to estimate NAPL/contaminant loading to the surface water body.

1.7 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.7.1 Exception— In some cases, U.S. customary units are used.

1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.9 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.

4.1 Intended Users:

4.1.1 This guide may be used by various parties involved in programs evaluating the movement of NAPL in sediment, including regulatory agencies, project sponsors, environmental consultants, risk assessors, site remediation professionals, environmental contractors, analytical testing laboratories, data reviewers and users, and other stakeholders, which may include (but are not limited to) owners, buyers, developers, lenders, insurers, government agencies, and community members and groups.

4.1.2 This guide does not replace the need for engaging competent persons to evaluate NAPL movement in sediment. Activities necessary to determine NAPL mobility at the pore scale should be conducted by persons familiar with NAPL-impacted sediment site characterization techniques, physical and chemical properties of NAPL in sediment, and protocols to assess NAPL movement in sediment. Users of this guide should consider assembling a team of experienced professionals (4.1.1) with appropriate expertise to scope, plan, and execute sediment NAPL data acquisition activities.

4.2 Reference Materials:

4.2.1 This guide should be used in conjunction with other ASTM guides listed in 2.1 (especially Guides E3248, E3268, and E3282), as well as the material in the References section.

4.3 Flexible Site-Specific Implementation:

4.3.1 Demonstrating the potential for NAPL movement in sediment to regulators and other stakeholders has been historically hampered by the lack of standardized terminology and characterization protocols. The complexity of NAPL movement in sediment, and the lack of agreed upon methods for analysis and interpretation of site data, have led to uncertainty in corrective action decision-making, which has sometimes resulted in unrealistic expectations about remedial outcomes.

4.3.2 Assessment of NAPL movement in sediment (including NAPL mobility at the pore scale) is an evolving science. This guide provides a systematic, yet flexible, guidance using visual observations and sediment-water shake test results to categorize sediment samples based on the relative amount of NAPL they contain and to use that categorization to identify sample locations and depth intervals for laboratory NAPL mobility testing. This categorization framework can accommodate variations in approaches by regulatory agencies and users based on project objectives, site complexity, unique site features, programmatic and regulatory requirements, newly developed guidance, newly published scientific research, use of alternative scientifically based methods and procedures, changes in regulatory criteria, advances in scientific knowledge and technical capability, multiple LOEs approach, and unforeseen circumstances.

4.4 Regulatory Frameworks:

4.4.1 This guide is to inform, complement, and support (but not supersede) the requirements or guidelines established by local, state, tribal, federal, or international agencies. As such, this guide does not provide a detailed discussion of the requirements or guidance associated with any of these jurisdictions, nor is it intended to supersede applicable regulations and guidance. Users of this guide will need to be aware of (and comply with) the regulatory requirements and guidance in the jurisdiction where the work is being performed.

4.4.2 This guide may be used to support existing regulatory decision frameworks for the selection of sediment samples for laboratory NAPL mobility testing; results of this laboratory testing can be used to evaluate NAPL mobility at the pore scale in the sediment sample (Guide E3282).

4.5 Systematic Project Planning and Scoping Process:

4.5.1 When applying this guide, users should undertake a systematic project planning and scoping process to collect information to assist in making site-specific, user-defined decisions for a particular project, including assembling an experienced team of project professionals. These practitioners should have the appropriate expertise to scope, plan, and execute a sediment corrective action program. This team may include (but is not limited to) the personnel outlined in 4.1.1.

4.6 Stakeholder Engagement:

4.6.1 Users of this guide are encouraged to engage key stakeholders early and often in the project planning and scoping process, especially regulators, project sponsors, and service providers. A concerted, ongoing effort should be made by users to continually engage regulators and other relevant stakeholders as the project progresses to gain insight, technical support, and input for resolving technical issues and challenges that may arise during project implementation.

4.7 Importance of NAPL Movement Assessments:

4.7.1 The movement (or lack of movement) of NAPL in sediment is a key factor in developing protective remedial options for NAPL-impacted sediment and for the long-term management of sediment sites. Typical exposure pathways that are addressed through risk management decisions at upland sites are usually not applicable to sediment sites. Instead, the biologically active zone (BAZ), which is the surface sediment at a sediment site, often drives sediment corrective actions because benthic organisms live here to maintain access to oxygenated overlying surface water (4). NAPL that is present in subsurface sediment below the BAZ that is not migrating (that is, NAPL that is stable at the NAPL body scale) and has overlying sediment that is expected to remain in place (that is, the sediment will not be dredged or eroded) typically does not pose a risk to human or ecological receptors, because there is no pathway for receptor exposure other than advection of dissolved-phase contaminants from the buried NAPL source to the BAZ. Removal of stable NAPL may not be warranted during remedial actions if (1) risks from dissolved-phase contaminants originating from this stable NAPL have been evaluated and found to be acceptable or (2) unacceptable risks from the dissolved-phase contaminants can be adequately mitigated by remedial actions (such as by the placement of an amended cap). Thus, understanding NAPL presence, extent, and potential movement is a key factor in managing contaminated sediment sites.

4.7.1.1 The first step in assessing NAPL movement in sediment is NAPL mobility testing to ascertain if the NAPL is mobile or immobile at the pore scale. Immobile NAPL is stable at the NAPL body scale and cannot be migrating toward a receptor, by definition (3.1.1).

4.8 Application of this Guide:

4.8.1 The use of this guide is consistent with the sediment risk-based corrective action (RBCA) process (Guide E3240) that guides users to acquire and evaluate appropriate data and use each piece of data to refine goals, objectives, receptors, exposure pathways, and the Conceptual Site Model (CSM). As the sediment RBCA process proceeds, data collected and conclusions reached at each stage helps to focus subsequent evaluations. This integrated process results in efficient, cost-effective decision-making and timely, appropriate response actions for NAPL-impacted sediment. This guide is not intended to provide specific guidance on sediment site risk assessment, monitoring, or remedial action.

4.8.2 Guide E3248 provides guidance regarding when a NAPL movement assessment is warranted at a sediment site. After confirming that NAPL is present and evaluating the nature and extent of NAPL (as appropriate), the next step in any NAPL movement evaluation is to evaluate if NAPL is mobile or