ASTM E3282-22

1.1''This guide discusses methodologies that can be applied to evaluate the potential for the movement (that is, pore-scale mobility or NAPL body-scale migration) of non-aqueous phase liquid (NAPL) in sediments. NAPL movement assessment in sediments is significantly different than in upland soils. As such, the frameworks for evaluating NAPL movement in upland soils have limited applicability for sediments. In particular, because upland NAPL conceptual site models may not be applicable to many sediment sites, this guide provides a framework to evaluate whether NAPL is mobile (at the pore scale) or migrating (at the NAPL body scale) in sediments.

1.2''Assessment of the potential for NAPL to move in sediment is important for several reasons, including (but not limited to) evaluation of risk to potential receptors, the need for potential remedial action, and potential remedial strategies. For example, if the NAPL is migrating, sensitive receptors may be impacted and this will influence the choice and timing of any remedy selected for an area of the sediment site. If the NAPL is not mobile or migrating, then remedial actions may not be warranted.

1.3''This guide is applicable at sediment sites where NAPL has been identified in the sediment by various screening methods and the need for a NAPL movement evaluation is warranted (Guide E3248).

1.4''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 refineries, petroleum distribution terminals, manufactured gas plants (MGPs), and various large industrial sites.

1.5''Although certain technical aspects of this guide apply to other NAPLs (for example, dense NAPLs [DNAPLs] such as chlorinated hydrocarbon solvents), this guide does not completely address the additional complexities of those DNAPLs.

1.6''The goal of this guide is to provide a sound technical basis to determine if NAPL at the site is mobile or immobile at the pore scale, and if mobile, whether it is stable or migrating at the NAPL body scale. The potential for NAPL movement in the sediment is a key component in the development of the conceptual site model (CSM) and in deciding what remedial options should potentially be chosen for the site to reduce potential risks to human health and ecological receptors.

1.7''This guide can be used to help develop, or refine, a CSM for the sediment site. A robust CSM is typically needed to optimize potential future work efforts at the site, which may include various risk management and remedial strategies for the site, as well as subsequent monitoring after any remedy implementation.

1.8''This guide considers the mobility of NAPL in sediments that originated from three broad categories of potential NAPL emplacement mechanisms (Guide E3248).

1.9''Ebullition-facilitated transport of NAPL from the sediment to the water column by gas bubbles is not within the scope of this guide. The evaluation of ebullition and associated NAPL/contaminant transport is covered in Guide E3300. Transport of NAPL due to erosional forces (for example, propeller wash) is not within the scope of this guide.

1.10''This guide (see Section 5) presents an overall framework to evaluate if NAPL at the site is mobile or immobile at the pore scale, and migrating or stable at the NAPL body scale. It provides guidance on approaches and methodologies that address questions regarding NAPL movement evaluation.

1.11''This guide (see Section 6) discusses the use of data from various laboratory tests (Appendix X1), calculation methodologies, and other methodologies to technically evaluate if NAPL in sediment at various locations in the site is mobile or immobile at the pore scale, and stable or migrating at the NAPL body scale. This evaluation can be performed using tiered and weight of evidence (WOE) frameworks. For example, it may be possible that NAPL is mobile or migrating in one part of the site, but is immobile in other parts of the site. There are currently no industry standard tiered and WOE frameworks to evaluate if NAPL in sediment is mobile or migrating, but illustrative examples of such frameworks are presented in Appendix X2. Case studies demonstrating the application of the example tiered and WOE frameworks exhibited in Appendix X2 are presented in Appendix X3.

1.12''This guide (see Section 7) discusses applicable laboratory centrifuge testing methodologies that are used to evaluate NAPL mobility or immobility at the pore scale under the applicable test conditions (also see Appendix X4). Appendix X5 discusses the laboratory preparation of sediment samples used in centrifuge testing.

1.13''This guide (see Section 8) discusses applicable laboratory water drive testing methodologies that are used to evaluate NAPL mobility or immobility at the pore scale under the applicable test conditions. This section discusses both rigid wall and