Light Non-Aqueous Phase Liquid (LANPL) Site Management
Light Non-Aqueous Phase Liquid (LNAPL) Management is the process of LNAPL site assessment, monitoring, LNAPL Conceptual Site Model development, identification and validation of relevant LNAPL concerns, and the possible application of remediation technologies. The presence of LNAPL can create challenges at any site. In the subsurface, LNAPL can be difficult to assess or recover accurately and can lead to:
- human health, ecological risk, and exposure concerns (e.g., vapor, groundwater, and soil contamination)
- acute-risk concerns (e.g., explosive conditions)
- migration or occurrence concerns (e.g., regulations that require recovery of “free-product” regardless of thickness, recovery to prevent potential LNAPL migration, or recovery for aesthetic or non-technical reasons).
Light, nonaqueous-phase liquid (LNAPL) management (LNAPL assessment and remediation) presents some of the greatest corrective action and cleanup compliance challenges to petroleum manufacturing, storage, and handling facilities such as refineries, bulk product terminals, gas stations, airports, and military bases.
This section provides an overview of the basic concepts of LNAPL behavior in the subsurface. The presence of LNAPL and the characterization of LNAPL in the subsurface is often determined primarily by the measurement\observation of LNAPL in monitoring wells. It is noted, however, that the relative measure of apparent thickness of LNAPL in a well, while indicative of LNAPL presence, has been shown to be a poor indicator of the magnitude, mobility or recoverability of LNAPL in the vicinity of the well.
The LNAPL Conceptual Site Model (LCSM) is the body of information describing aspects of the LNAPL and site setting necessary to satisfy the LNAPL remedial objectives. The LCSM is similar to a conceptual site model, which includes the source, pathway, and receptors, but the emphasis in the LCSM is on the source component.
This section is to provide introduction on technical tools used for LNAPL site characterization
The selected LNAPL remedial technology should align with the particular LNAPL remedial objective and LNAPL remediation goal. As indicated by the different nature of LNAPL remediation goals and performance metrics discussed in the previous section, different LNAPL remedial technologies have different applicability and capabilities.
Once the remedial action is implemented, monitoring is required to assess the protectiveness and effectiveness of the chosen Interim Remediation Monitoring (IRM). The type and frequency of monitoring should be based on the CSM developed for the site which identifies the LNAPL type, source and distribution, site specific receptor issues, hydrogeologic influences on LNAPL behavior and other factors affecting LNAPL migration and recoverability. The operational monitoring should validate the assumptions developed for the site and document that the selected IRM is effective in preventing migration, reducing mass, when practicable, and is protective of known human and ecological receptors.
Source from:ITRC LNAPL Team