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ADVISORY - ACTIVE SOIL GAS INVESTIGATIONS <br />CSM organizes and communicates information about the site characteristics and <br />provides all interested parties with an understanding of the potential for exposure to <br />chemicals of potential concern (COPCs) at a site. Resources regarding CSMs include: <br />(1) SWRCB, 2012; (2) DTSC, 2011; (3) ITRC, 2007; (4) DTSC, 1994; (5) USEPA, 1994; <br />(6) USEPA, 1989; and (7) USEPA, 1988. <br />The basic components of a CSM are: <br />Type of contaminants, including VOCs, currently or previously stored or <br />handled at the site, to develop a site-specific target analyte list; <br />Known concentrations of COPCs in media such as soil gas, soil and <br />groundwater; <br />Identification of the primary and secondary sources of COPCs; <br />Location, depth, and phase(s) of COPCs; <br />Primary release mechanism; <br />Exposure media such as surface soil, drinking water and air; <br />Potential human and ecological receptors and groundwater; and <br />Unique site features. <br />The CSM is a dynamic and iterative tool, and is updated as new information becomes <br />available. Therefore, it should be reviewed after each stage of investigation and revised <br />as appropriate. <br />The following information should be considered to identify contaminant sources, <br />potential release mechanism(s) and pathway(s) for vapor migration: <br />Soil types; <br />Subsurface geology; <br />Hydrogeology (local and regional), including depth to groundwater and <br />groundwater flow direction; <br />Subsurface heterogeneity; <br />Preferential pathways, such as fractures, sand lenses, and utility corridors; <br />Groundwater quality data; <br />Contamination plume extent; <br />Well records; <br />Boring logs; <br />Building construction details; and <br />Surficial features of the area, such as ground cover and surface water bodies. <br />A CSM should be supported by contaminant plume maps and geological cross sections. <br />The narrative description should clearly describe known site conditions and state what <br />assumptions were made to generate the CSM. <br />2.3.3 Sampling and Analysis Plan <br />The SAP should specify all procedures and techniques used for soil gas sample <br />collection, shipment, analytical procedures and chain of custody documentation. Field <br />personnel should follow the SAP while collecting and analyzing soil gas samples. <br />July 2015 5