Ground Water Plume Delineation using In-Field Direct Push Technology

摘要

On site analysis of ground water is employed by NASA for the rapid and cost effective determination of the extent of migration of dissolved Volatile Organic Compounds (VOC's). Accurate plume delineation is necessary for the design of any form of remedial activity, and preliminary sampling enables site investigators to effectively locate permanent monitoring wells for further assessment. The subject study took place at a site, located in a coastal environment, where historical releases had occurred from septic tanks receiving waste from laboratories and field cleaning operations of space flight equipment. On site ground water sampling using direct push technology and analysis was performed to determine the horizontal and vertical extent of the contaminant plume. Samples were collected at various depths using a truck mounted Geoprobe (a direct push technology). The water samples were analyzed using a field gas chromatograph and the soils were logged in the field. This sampling method allows the investigator to delineate soil stratigraphy and to conduct depth specific sampling of both soils and ground water. The data collected was used to define ground water flow, determine extent of contamination and to select the locations of subsequent sampling points. The ground water and soil investigation revealed that the plume consisting of Trichloroethylene had a significant westerly component, away from the ocean. Changes in direction and contamination level of the plume have been mapped at different depths. The investigation was performed for a 3 week period and involved sampling and analysis at 49 locations. Based on this data, a 421 acre, 30-foot deep area was found to be contaminated with VOC'S, The study provided an accurate delineation of the horizontal and vertical extent of ground water contamination at this site. This data will be used to select the location of monitoring wells, thereby providing sampling points conforming to regulatory standards for analytical and hydrogeological data collection for the formal RCRA facility investigation.