Michael Gefell, P.G., C.P.G., is a Principal Geologist at Anchor QEA. He holds a BA in Geological Sciences from Cornell University andMSin Geology from the University of California – Davis. Mr. Gefell has over 27 years of experience inenvironmental site assessment and remediation. Primary areasof interest include: quantitative hydrogeology, NAPL assessment, fractured bedrock, groundwater/surface-water interaction, innovative site characterization methods, modeling and remedial design. He isan Associate Editor of Ground Water journal and received the 2013 Technology Award from the National Ground Water Association.
PLATFORM PRESENTER - NAPL Characterization and Depletion: My Old Friend
Aqueous Sampling Withough NAPL Artifacts
The presence of non-aqueous phase liquids (NAPLs) can significantly complicate water sampling and lead to extreme overestimates of inferred dissolved-phase concentrations in water samples. Devices that collect “whole-water” samples can inadvertently entrain NAPLs in water samples. Passive sampling devices that rely on sorption can become fouled with NAPLs. Calculating equilibrium water concentrations for whole sediment or soil samples based on partitioning theory is also severely complicated by the presence of NAPL. The objective of this study was to test a porous, hydrophilic capillary barrier that excludes NAPL but can collect representative water samples by diffusion and/or advection through the porous barrier. This study tested three key performance factors for the sampling method: 1) wettability of NAPL on the barrier material in the presence of water; 2) non-wetting phase entry-pressure; and 3) diffusion-based equilibration of dissolved organic compounds.
Field-Scale Measurement of DNAPL Bulk Retention Capacity Using Two Independent Methods
The field program during the Feasibility Study for the SRSNE Superfund Site in Connecticut produced continuous soil cores from ground surface to refusal at 39 locations. When NAPL was encountered, the relative degree of NAPL saturation (residual/pooled) was estimated. The extent of NAPL pools and residual were estimated, and the NAPL volume calculated using site-specific parameters. In 2014 and 2015, the overburden NAPL zone was treated using in-situ thermal remediation (ISTR), which removed 225,000 kg of VOCs. We estimate 216,000 kg was NAPL, and 9,000 kg was dissolved and sorbed VOCs. Based on NAPL observations in soil cores, we estimated NAPL bulk retention of 0.018 (1.8%) and based on the ISTR mass removal we estimated NAPL bulk retention of 0.012 (1.2%). This is the first range of bulk retention values we are aware of that was obtained using two independent approaches at a DNAPL site.