APPLYING NATURAL SOURCE ZONE DEPLETION (NSZD) TO SITE MANAGEMENT

This presentation provides findings from one such example. The site is a recent (approximately 2010) LNAPL release at an oil refinery where LNAPL recovery is currently the primary remedy technology. LNAPL recoverability tracking (e.g., LNAPL recovery rates, transmissivities, and LNAPL: water ratios) indicate that this active portion of the remedy will continue for several years longer.  For additional information on hydrocarbon removal at this site, an NSZD data collection effort was conducted in 2016 using dynamic closed chamber, vadose zone gas measurements, thermal monitoring, and groundwater geochemistry sampling. 

The assessment allowed for a broad estimate of both natural and engineered hydrocarbon mass removal, and comparison between various attenuation mechanisms. The assessment also identified 

“incidental bioventing” that was occurring via the LNAPL recovery system. This information has been input to an updated LNAPL conceptual site model and a feasibility study for remedy options when the system transitions from LNAPL recovery. These options include not just NSZD as a standalone remedy, but hydraulic control with “incidental bioventing” to address expected remedy drivers.

This session provides a technical overview of NSZD for LNAPL, which, when appropriately evaluated, can serve as an objective benchmark by which to compare the relative effectiveness of different remedial alternatives.

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