Source Zone Delineation Demonstration Report - Triad Resource ...

1.0 INTRODUCTIONThis report documents the results of the Source Zone Delineation Demonstration at Operable Unit 12 (OU12), Hill Air Force Base (AFB) in Utah (see Figure 1-1). The demonstration was conducted to investigatevolatile organic compound (VOC) contamination in the vadose zone of the suspected OU 12 source areausing rapid decision-making based on real-time data collected in the field via a dynamic work planapproach. The investigation consisted of two technology demonstrations – (1) wireline cone penetrometersystem for multiple tool usage and (2) soil vapor extraction (SVE) for vadose zone characterization.Sampling and analysis was conducted in the field via direct sampling ion trap mass spectrometry(DSITMS) for rapid identification of contaminant concentrations. Real-time data was required due to therapid soil sampling capability of the wireline tool and to obtain adequate characterization of vapor-phasecontaminant concentration profiles as a function of time across a varied flow regime. Additionally,optimization of vapor extraction rates and location of investigation was optimized as a result ofimmediate concentration profiles. This investigation represents the next progression in thecharacterization of OU 12 and builds upon the active soil-gas survey completed in the suspected sourcezone at OU 12 in October 2001 and March 2002 [MWH, 2002a].1.1 Project ObjectivesThe objectives for the Source Zone Delineation Demonstration at OU 12 included:Locating and spatially-defining any existing source of trichloroethene (TCE) in the vadose zone andcapillary fringe of the suspected OU 12 source zone;Demonstrating the ability of ARA’s Wireline CPT system and Tri-Corders Environmental, Inc.DSIMTS to rapidly characterize contaminant distribution within the vadose zone; andDemonstrating the ability of SVE to characterize the spatial and phase distribution of VOC masswithin the vadose zone.1.2 Dynamic Work Plan ApproachA dynamic work plan approach was utilized during the OU 12 Source Zone Delineation Demonstration.The dynamic work plan approach focuses on the decision-making process that integrates the datagenerated in the field to facilitate a rapid, cost effective characterization of the site. Formulated as adecision tree during the planning process, the dynamic work plan adapts site investigative activities inrelation to the evolving, usually on a daily basis, conceptual site model (CSM). Dynamic work planshave been successfully demonstrated for over ten years by various parties [Burton, 1993 and Robbat,1997]. Implementation of a dynamic work plan requires on-site generation and interpretation of data sothat results are available fast enough to support the rapidly evolving on-site decision-making. Althoughnot a new concept, recent advances in field analytical instrumentation and computerization have enableddynamic work plans to be utilized in the characterization of complex sites.March 2003 1-1 OU 12 Demonstration ReportFinal