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a� 1W I. Introduction The Chevron(CVX) Soil Vapor Sampling Technical Toolkit provides technical guidance to suppliers conducting vapor intrusion pathway (VIP) investigations at petroleum hydrocarbon contaminated sites. The toolkit is a collation of identified"best practices" in planning, conducting, and interpreting soil vapor surveys. Maintaining consistency in best practices across the Chevron portfolio is a primary driver for this toolkit, as this will enhance the defensibility of the soil vapor data gathered at these sites. The toolkit is intended to remain "evergreen': that is, as new best practices are developed, the toolkit will be edited to incorporate those developments. In this manner the most up-to-date technologies and methods can be implemented in the field. The toolkit is meant to be applied at petroleum hydrocarbon contaminated sites; that is, sites where biodegradation of vapor phase contaminants can play a role in attenuation. It is not meant to be applied at sites where biodegradation of vapor phase contaminants is unlikely to occur (e.g., chlorinated solvent contaminated sites). The toolkit is organized into sections focusing on soil vapor sampling probes, soil vapor sampling, analytical techniques, and data reporting. Diagrams are included to provide further description of the processes and equipment discussed. Further technical information and advice is available by contacting the Chevron Energy Technology Co. VIP Team: Tom Peargin, Staff Hydrogeologist,trpena chevrontexaco.com 510-242-5927 II. Soil vapor sampling probes Permanent soil vapor sampling probes are required for soil vapor surveys conducted for human health risk assessment to ensure that samples from a given location can be collected over a specified time period. Temporary probes (which are sampled only once) are suitable only for non-human health risk assessment soil vapor samples, such as in support of delineation of a dissolved phase contaminant plume. A. Permanent probes using hollow-stem augers Permanent soil vapor sampling probes can be installed with a drill rig equipped with a hollow-stem auger as either single-level or multilevel probes, depending on site needs and conditions. For example, multilevel probes are required to assess biodegradation of volatile organic compounds (VOCs) as a function of depth. Conversely, a single-level probe is appropriate for a site with shallow depth to groundwater(e.g., 6 ft below grade). Permanent single-level probes can be sampled multiple times to develop time series plots of changes in soil vapor VOC concentrations over time. Permanent, multilevel probes can be used to plot time series concentrations of VOCs and fixed gases (e.g., 02, CO2) to investigate biodegradation as a function of both time and depth. Augered boring installations for multilevel probes have an advantage over direct-push multilevel probes in that a smaller footprint is required for installation. Furthermore, augered multilevel probe installations enable a robust bentonite seal to be emplaced in the intervals between ETC Soil Vapor Sampling Technical Toolkit 4 Version 1.4, September 7,2005