Utilization of Ultra Violet Optical Screening Tool in Development of High Resolution Conceptual Site Models for three NAPL release sites.

ABSTRACT: Successful remediation and risk management of Non-Aqueous Phase Liquid (NAPL) contaminated sites requires detailed understanding of subsurface NAPL architecture and distribution. High Resolution Site Characterization (HRSC) tools allow for the collection of scale appropriate data for the heterogeneities of subsurface systems that control NAPL distribution, transport and fate. Traditional methods of subsurface investigation at NAPL sites often miss this scale of understanding, resulting in oversights or misrepresentation of NAPL plume structures within Conceptual Site Models (CSMs). The Ultra Violet Optical Screening Tool (UVOST), utilizes Laser Induced Fluorescence (LIF), to provide a method for real-time, in situ field screening of residual and non-aqueous phase hydrocarbons in undisturbed vadose, capillary fringe and saturated subsurface soils and groundwater. When the UVOST is paired with secondary high resolution data collection such as logging of electrical conductivity, a site wide model of source pollution and unconsolidated stratigraphy, two key components to predicting mobility, can be obtained. ESG carried out source zone mapping of three NAPL release sites in Alberta, Canada using the UVOST with the goal of improving the understanding of plume architecture and distribution within each sites CSM. Analysis of UVOST data with secondary HRSC data collection (electrical conductivity) and targeted soil and groundwater sampling allowed for more detailed understanding of NAPL distribution and risk at each site. Improved NAPL CSMs for all sites will allow for more thorough and accurate evaluation of risk.