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Sampling and Analysis Plan for Phase II Environmental Site Assessment 125 North Stockton Street, Lodi,CA 95240 2.0 DATA QUALITY OBJECTIVES 2.1 Conceptual Site Model The foundation for site-related decisions in conducting a Phase II ESA that are both correct and optimized (from a cost-benefit standpoint) is the 'Conceptual Site Model' (CSM; Crumbling, 2004). A CSM uses available historical and current information to help determine or predict: • The types of contaminants most likely to be present at concentrations that exceed regulatory limits, or which could impact redevelopment. • The locations where contamination is most likely to be present. • The mechanisms through which contamination was likely or potentially released and the associated zones or depth intervals that are most likely to have been impacted. • The characteristics of geologic materials underlying the property (and in particular, the permeability of geologic materials). • The depth to the water table and flow direction for shallow groundwater. • The known or potential presence of natural or man-made subsurface features that could affect contaminant migration pathways or impede sample collection. • Future plans for use of the property, and particularly if redevelopment activities will be performed. 2.1.1 Basis for Conceptual Site Model The current CSM is based on information presented in the previous environmental study summarized in Section 1.5: • Portions of the western edge of the Property were historically developed with an MGP in the late 1800s to the early 20th century. According to historical Sanborn Maps, a fuel- containing UST was located in the northwestern portion of the Property.The site inspection identified a combined gasoline/diesel AST present in the northern portion of the Property, and oil staining within the equipment repair building. Based on the current and historical uses of this Site, there is a possibility that shallow soils on the Property may have been contaminated with COPCs. • Findings from Stantec's Phase I ESA identified that groundwater beneath portions of the downtown area of the City of Lodi is known to be impacted by chlorinated solvents and related VOCs.The Property is located on the northeastern periphery of the Northern Plume area.The documented regional PCE impacts to groundwater in the vicinity of the Property presents the risk that volatile constituents may volatilize from groundwater and accumulate beneath or within proposed structures, which represents a potential vapor intrusion risk to future occupants and site users. (� Stantec 5