Source Zone Delineation Demonstration Report - Triad Resource ...

7.0 CONCLUSIONS AND RECOMMENDATIONSA Source Zone Delineation Demonstration was conducted in the suspected source area at OU 12 toinvestigate VOC contamination in the vadose zone using rapid decision-making based on real-time datacollected in the field. Conclusions and recommendations presented in this section are based on the resultsof the demonstration provided in Section 5.0 of this report.7.1 Demonstration ResultsThe Source Zone Delineation Demonstration consisted of two technology demonstrations – (1) wirelinecone penetrometer system for multiple tool usage and (2) soil vapor extraction for vadose zonecharacterization. Sampling and analysis were conducted in the field using DSITMS due to the rapid soilsampling 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. The results of eachdemonstration, including the capabilities of the DSITMS field analytics are discussed below.7.1.1 Wireline CPT Soil SamplingThe Wireline CPT demonstration was conducted within the vadose zone and capillary fringe underlyingthe general area defined as the suspected source zone at OU 12. During the first four days of soilsampling using the Wireline CPT sampler, approximately 205 soil samples were collected from verticaltraces at 5 discrete locations (approximately 50 samples per day). During the last five days of fieldoperations, approximately 395 soil samples were collected from vertical traces at 11 discrete locations(approximately 80 samples per day). In total, 599 soil samples were collected from vertical traces at 16discrete locations during the nine working days of the Wireline CPT demonstration. The increase insample collection (approximately 38%) that occurred during the last five days of field operations wasassociated with several aspects of the demonstration, including the arrival of additional soil samplers forthe Wireline CPT tool and an experienced Wireline CPT operator. Additionally, the decision not tocollect samples from the upper gravelly sand zone that extended from approximately 18 to 22 feet bgsdecreased the amount of soil that was lost from the Wireline soil sampler within the CPT rod. Thisresulted in a dramatic reduction in the accumulation of soil/grit in the interior of the locking and retrievalmechanism of the Wireline tool assembly.The Wireline CPT tool was successful in collecting a large number of soil samples from the vadose zonein a short investigative timeframe. However, several aspects of the Wireline CPT tool must be carefullyconsidered prior to using this technology for future investigative activities, including:Poor sample recovery resulted in the accumulation of dirt/grit in the locking and retrieval mechanismof the Wireline tool. Subsequently, a significant amount of time was spent trying to lock and unlockthe Wireline tool, and on several occasions the Wireline CPT rod had to be retracted in order to cleanthe interior of the locking and retrieval mechanism. It is recommended that deployment of a samplecatcher on the end of the Wireline CPT soil sampler be investigated to increase sample collectionefficiency.March 2003 7-1 OU 12 Demonstration ReportFinal