Soil Vapor Survey at the LLNL (Lawrence Livermore National Laboratory) Site 300 General Services Area, Adjacent Portions of the Connolly and Gallo Ranches and the Site 300 Landfill Pit 6 Area.

摘要

During October through December 1988, a soil vapor survey was conducted by Weiss Associates at the Lawrence Livermore National Laboratory Site 300 General Services Area (GSA), adjacent portions of the Connolly and Gallo Ranches, and at the Site 300 Landfill Pit 6 area. The purpose of the investigation was to aid in identifying the sources and the extent of trichloroethylene (TCE) previously found in ground water and soil at, or near, these sites. Using a soil vapor probe, samples were collected at 133 locations from depths of 2 to 15 ft below the surface. Analyses were initially done in the field using a Photovac portable gas chromatograph with a photoionization detector calibrated to detect TCE. During the later portion of the study a mobile laboratory was used that had a gas chromatograph equipped with both Hall electroconductivity and photoionization detectors. This permitted identification of the spectrum of EPA Method 601 volatile organic compounds (VOCs) by a modified EPA Method 8010. Extensive quality assurance/quality control (QA/QC) procedures were followed to ensure consistent system performance and no cross-contamination between samples or sites. Soil vapor concentrations were measured in parts per million on a volume to volume basis (ppM/sub v/v/). TCE concentrations detected in the soil vapor ranged from a high of 628 ppM/sub v/v/ to a low of not detected (ND) at less than 0.001--0.005 ppM/sub v/v/. The highest concentration was found next to monitor well W-7F, near a decommissioned drywell (sump) at the southern boundary of the GSA. Several locations exhibited ND concentrations. Fourteen locations analyzed by a mobile laboratory had tetrachloroethylene (PCE), 1,1-dichloroethylene (1,1-DCE) and/or 1,1,1-trichloroethane (1,1,1-TCA) at concentrations considerably lower than the TCE in the same sample. 17 refs., 15 figs., 2 tabs. (ERA citation 14:029392)