Tom Daigle is a geologist and project manager leading GEI’s LNAPL transmissivity testing practice. Mr. Daigle specializes in both the field testing procedures and analysis methods for LNAPL site characterization, transmissivity metrics, and remediation. He has been with GEI over 10 years working on a wide range of environmental projects and supporting GEI’s civil and geotechnical engineering services.
LNAPL Transmissivity at Complex Sites: Innovative Field Testing and Analysis Methods
Sites impacted by light non-aqueous phase liquid (LNAPL) present unique challenges for site management and remediation. LNAPL transmissivity is the preferred metric used by industry professionals to assess the feasibility of LNAPL hydraulic recovery rather than relying on measured apparent LNAPL thickness in wells. Techniques will be presented to overcome challenges in transmissivity testing such as: small apparent NAPL thickness, fluctuating water tables, long test durations, confined or perched hydrogeologic conditions, etc. GEI will discuss pre-test data needs, optimal test method selection, and multiple analysis tools available to accurately measure and report transmissivity under a variety of complex site conditions. GEI will also discuss innovative technology developed in recent years to support transmissivity field testing and analysis. The importance of collecting accurate and reliable transmissivity data is more apparent as the metric gains nationwide regulatory acceptance and may be used to advance sites toward remediation and regulatory end points.
NAPL Mobility in Sediments: Categorizing NAPL Migration Potential Using a Multiple Lines of Evidence Approach
Quantifying NAPL mobility in sediments is critical when evaluating remedial alternatives and remediation engineering design. NAPL mobility in sediments cannot readily be evaluated using methods that are typically effective at upland sites. This case study presents a regulatory-approved risk-based approach to categorize NAPL in sediment as residual (immobile), mobile, or potentially migrating. The approach is designed in a logical and progressive step-wise fashion with “off ramps” after each step if the NAPL mobility is defined at that point. Thus, it is not necessary to complete the entire process, but only to conduct sufficient analysis to define the NAPL mobility potential. If NAPL in sediment is determined to be residual (immobile), then isolation and containment may be appropriate remedial actions. If NAPL is determined to be mobile or migrating, then additional remedial actions may be necessary to eliminate the potential for NAPL to migrate beyond its existing extent.