Standard Guide for Non-Aqueous Phase Liquid (NAPL) Mobility and Migration in Sediment—Conceptual Models for NAPL Emplacement and Influence on NAPL Movement

Importancia y uso:

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.

4.1.1.1 This guide does not replace the need for engaging competent persons to evaluate NAPL emplacement and movement in sediment. Activities necessary to develop a CSM should be conducted by persons familiar with NAPL-impacted sediment site characterization techniques, physical and chemical properties of NAPL in sediment, fate and transport processes, remediation technologies, and sediment evaluation protocols. Users of this guide should consider assembling a team of experienced professionals 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 E3268, E3281, and E3282), as well as the material in the References section.

4.2.2 This guide is intended to supplement the CSM developed for the sediment site according to the principles outlined for the contaminated sites CSM Guide E1689, the guide for developing a CSM for LNAPL sites (Guide E2531), and the Risk-Based Corrective Action (RBCA) Guides E1739 and E2081, by considering conditions for NAPL emplacement and advective movement that are unique to a sediment environment. Guide E3240 discusses elements of the CSM and RBCA framework that are specific to contaminated sediment sites.

4.3 Flexible Site-Specific Implementation: 

4.3.1 This guide supports users in understanding the potential emplacement and transport mechanisms for NAPL in sediment. This is an important element of an overall CSM that forms a basis for (1) investigating the nature and extent of NAPL, (2) evaluating whether (and how) human and ecological receptors may be exposed to NAPL, and (3) assessing potential remedial alternatives for NAPL.

4.3.2 Demonstrating the potential for movement of NAPL 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, has led to uncertainty in corrective action decision making, which has sometimes resulted in unrealistic expectations about remedial outcomes.

4.3.3 The emplacement and transport mechanisms for NAPL in sediment are different from those in upland environments, due to a variety of physical, geochemical, and biological differences between sediment and upland environments (see Section 5), thus necessitating this guide. This guide provides conceptual models for NAPL emplacement in sediment. This guide also provides a NAPL movement evaluation framework to categorize the NAPL as being either mobile or immobile at the pore scale or migrating or stable at the NAPL body scale.

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 evaluation of NAPL mobility and migration in sediment.

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 Other Considerations: 

4.7.1 This guide summarizes the unique characteristics influencing the presence and potential movement of NAPL in aquatic sediment environments, but this guide is not intended to provide specific guidance on sediment site investigation, risk assessment, monitoring, or remedial action.

4.7.2 For the purposes of this guide, sediment is considered a saturated material that is below a surface water body (3.1.6), whereas soil is considered a saturated or unsaturated unconsolidated material below the upland ground surface (3.2.13).

4.8 Structure and Components of This Guide: 

4.8.1 Users of this guide should review the overall structure and components of this guide before proceeding with use, including:

Section

Title

Section 1

Scope

Section 2

Referenced Documents

Section 3

Terminology

Section 4

Significance and Use

Section 5

Unique Aspects of Sediment Sites

Section 6

NAPL Emplacement Mechanisms

Section 7

NAPL Movement Assessment Framework

Section 8

Keywords

Appendix X1

NAPL Emplacement Conceptual Models

Appendix X2

Sedimentary Processes and Groundwater–Surface Water Interactions

Appendix X3

NAPL Movement Terminology

Subcomité:

E50.04

Referida por:

E2020-22, E3300-21, E2081-22, E3382-24, E2205_E2205M-22, E3344-24, E3447-24, E3281-21A, E3488-25, E3282-22, E3268-21, E3163-24, E3242-25

Volúmen:

11.05

Número ICS:

13.080.01 (Soil quality and pedology in general)

Palabras clave:

advection; emplacement; immobile; in situ deposited NAPL (IDN); migration; mobility; NAPL body; NAPL movement; non-aqueous phase liquid (NAPL); oil-particle aggregate (OPA); stable;