A light, non-aqueous phase liquid (LNAPL) is a liquid such as gasoline, diesel, or other petroleum-based fuel, waste oil, and crude oil that is immiscible with water and that has a density less than that of water (<1 g/cm3). Spills or releases of LNAPLs to the environment are common at petroleum manufacturing, storage, and handling facilities such as refineries, bulk-product terminals, gas stations, airports, and military bases. LNAPLs are of regulatory importance because, once in the subsurface, they can be difficult to adequately assess and recover and thus can be a long-term source of
- risk and exposure issues (e.g., vapor, groundwater, and soil contamination)
- acute-risk concerns (e.g., explosive conditions)
- LNAPL mass concerns (e.g., regulations that require recovery of “free-product,” “free-phase hydrocarbon,” or “liquid-phase hydrocarbon”; for aesthetics or mass reduction reasons; or for potential LNAPL migration)
Corrective action and cleanup at LNAPL sites may be achieved sooner when stakeholders have a sound understanding of basic LNAPL behavior in the subsurface; appropriate LNAPL remedial objectives; and LNAPL remedial technology applicability, performance capabilities and limits, and relative costs. Unfortunately, disparate stakeholder understanding of these factors has often been a corrective action and cleanup impediment.
The ITRC LNAPLs Team formed in 2007 to address these impediments and to promote better LNAPL understanding and remediation through development of guidance and training. The team has developed a free, downloadable three-part Internet-based training to foster better understanding of LNAPL behavior in the subsurface and factors that affect LNAPL recovery (www.itrcweb.org/Training/ListEvents?TopicID=13&SubTopicID=18) : Part 1, An Improved Understanding of LNAPL Behavior in the Subsurface—State of Science vs. State of Practice, which explains how LNAPLs behave in the subsurface and examines what controls their behavior, and Part 2, LNAPL Characterization and Recoverability—Improved Analysis: Do you know where the LNAPL is and can you recover it?, and Part 3, Evaluating LNAPL Remedial Technologies for Achieving Project Goals. The team also developed a 2-day classroom training (www.itrcweb.org/Training/ListEvents?TopicID=13&SubTopicID=18): Light Non-aqueous Phase Liquids: Science, Management, and Technology.
The LNAPLs Team issued a technical overview document: Evaluating Natural Source Zone Depletion at Sites with LNAPL (LNAPL-1) explaining how LNAPL source zones naturally deplete through volatilization and dissolution and providing tools and techniques for quantifying these depletion rates. NSZD evaluations may provide a baseline against which to compare the effectiveness of current remedial strategies or for estimating the sustainability of such rates for long-term predictions.
The LNAPLs Team has also issued the technical/regulatory guidance document Evaluating LNAPL Remedial Technologies for Achieving Project Goals (LNAPL-2). This document helps stakeholders set appropriate LNAPL remedial objectives in the context of a site-specific LNAPL conceptual site model, provides tools to screen 17 LNAPL remedial technologies to identify an optimal LNAPL remedial technology to achieve the objectives, and provides example performance metrics that would be set to gauge remedial effectiveness and demonstrate achievement of the objectives. Internet-based training for the document is also available that explains key concepts and applies the screening process to an example LNAPL site.
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