Standard Guide for Development of Conceptual Site Models and Remediation Strategies for Light Nonaqueous-Phase Liquids Released to the Subsurface
|Publication Date:||1 November 2006|
This guide applies to sites with LNAPL present as residual, free, or mobile phases, and anywhere that LNAPL is a source for impacts in soil, ground water, and soil vapor. Use of this guide may show LNAPL to be present where it was previously unrecognized. Information about LNAPL phases and methods for evaluating its potential presence are included in 4.3, guide terminology is in Section 3, and technical glossaries are in Appendix X7 and Appendix X8. Fig. 1 is a flowchart that summarizes the procedures of this guide.
This guide is intended to supplement the conceptual site model developed in the RBCA process (Guides E 1739 and E 2081) and in the conceptual site model standard (Guide E 1689) by considering LNAPL conditions in sufficient detail to evaluate risks and remedial action options.
Federal, state, and local regulatory policies and statutes should be followed and form the basis of determining the remedial objectives, whether risk-based or otherwise. Fig. 1 illustrates the interaction between this guide and other related guidance and references.
Petroleum and other chemical LNAPLs are the primary focus of this guide. Certain technical aspects apply to dense NAPL (DNAPL), but this guide does not address the additional complexities of DNAPLs.
The composite chemical and physical properties of an LNAPL are a function of the individual chemicals that make-up an LNAPL. The properties of the LNAPL and the subsurface conditions in which it may be present vary widely from site to site. The complexity and level of detail needed in the LCSM varies depending on the exposure pathways and risks and the scope and extent of the remedial actions that are needed. The LCSM follows a tiered development of sufficient detail for risk assessment and remedial action decisions to be made. Additional data collection or technical analysis is typically needed when fundamental questions about the LNAPL cannot be answered with existing information.
This guide does not develop new risk assessment protocols. It is intended to be used in conjunction with existing risk-based corrective action guidance (for example, Guides E 1739 and E 2081) and regulatory agency requirements (for example, USEPA 1989, 1991, 1992, 1996, 1997).
This guide assists the user in developing an LCSM upon which a decision framework is applied to assist the user in selecting remedial action options.
The goal of this guide is to provide sound technical underpinning to LNAPL corrective action using appropriately scaled, site-specific knowledge of the physical and chemical processes controlling LNAPL and the associated plumes in ground water and soil vapor.
This guide provides flexibility and assists the user in developing general LNAPL site objectives based on the LCSM. This guide recognizes LNAPL site objectives are determined by regulatory, business, regional, social, and other site-specific factors. Within the context of the Guide E 2081 RBCA process, these factors are called the technical policy decisions.
Remediation metrics are defined based on the site objectives and are measurable attributes of a remedial action. Remediation metrics may include environmental benefits, such as flux control, risk reduction, or chemical longevity reduction. Remediation metrics may also include costs, such as installation costs, energy use, business impairments, waste generation, water disposal, and others. Remediation metrics are used in the decision analysis for remedial options and in tracking the performance of implemented remedial action alternatives.
This guide does not provide procedures for selecting one type of remedial technology over another. Rather, it recommends that technology selection decisions be based on the LCSM, sound professional judgment, and the LNAPL site objectives. These facets are complex and interdisciplinary. Appropriate user knowledge, skills, and judgment are required.
This guide is not a detailed procedure for engineering analysis and design of remedial action systems. It is intended to be used by qualified professionals to develop a remediation strategy that is based on the scientific and technical information contained in the LCSM. The remediation strategy should be consistent with the site objectives. Supporting engineering analysis and design should be conducted in accordance with relevant professional engineering standards, codes, and requirements.
ASTM standards are not federal or state regulations; they are voluntary consensus standards.
The following principles should be followed when using this guide:
Data and information collected should be relevant to and of sufficient quantity and quality to develop a technicallysound LCSM.
Remedial actions taken should be protective of human health and the environment now and in the future.
Remedial actions should have a reasonable probability of meeting the LNAPL site objectives.
Remedial actions implemented should not result in greater site risk than existed before taking actions.
Applicable federal, state, and local regulations should be followed (for example, waste management requirements, ground water designations, worker protection).
This guide is organized as follows:
Section 2 lists associated and pertinent ASTM documents.
Section 3 defines terminology used in this guide.
Section 4 includes a summary of this guide.
Section 5 provides the significance and use of this guide.
Section 6 presents the components of the LCSM.
Section 7 offers step-by-step procedures.
Nonmandatory appendices are supplied for the following additional information:
Appendix X1 provides additional LNAPL reading.
Appendix X2 provides an overview of multiphase modeling.
Appendix X3 provides example screening level calculations pertaining to the LCSM.
Appendix X4 provides information about data collection techniques.
Appendix X5 provides example remediation metrics.
Appendix X6 provides two simplified examples of the use of the LNAPL guide.
Appendix X7 and Appendix X8 are glossaries of technical terminology relevant for LNAPL decision-making.
A reference list is included at the end of the document.
The appendices are provided for additional information and are not included as mandatory sections of this guide.
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 and health practices and determine the applicability of regulatory limitations prior to use.
This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word "Standard" in the title of this document means only that the document has been approved through the ASTM consensus process.