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Geosyntec consultants 1. INTRODUCTION On behalf of the Lincoln Center Environmental Remediation Trust (the Trust), Geosyntec Consultants, Inc. (Geosyntec) has prepared this Soil Vapor Investigation Work Plan (Work Plan) to evaluate the extent of residual subsurface impacts of chlorinated solvents from former dry-cleaning operations in a localized remediated area at the Lincoln Village Shopping Center in Stockton, California(Lincoln Center, or the Site) (Figure 1). In April 2020, Geosyntec submitted a Vapor Intrusion Pilot Study Work Plan (Pilot Study Work Plan)to assess vapor intrusion(VI)at the Site. The Central Valley Regional Water Quality Control Board (CVRWQCB) approved the Pilot Study Work Plan (CVRWQCB, 2020) and the initial phase of field work occurred between August and September 2020 which included the installation and sampling of a soil gas probe, SG-100, in the northern portion of the Site that had already been remediated as part of the on-Site soil cleanup action (Figure 2). Tetrachloroethene (PCE) was reported in the shallow sample collected at SG-100 at a concentration of 22,000 micrograms per cubic meter (µg/m3), which is above the cleanup level used during the cleanup. This Work Plan proposes investigation activities to collect the data needed to evaluate the extent of elevated chlorinated volatile organic compounds(VOCs)(primarily tetrachloroethene [PCE])concentrations in shallow soil vapor in the vicinity of SG-100. 1.1 Work Plan Objectives The primary objectives of this Work Plan are to describe the proposed investigation activities to evaluate the extent of Site-related chlorinated VOC impacts in soil vapor in the area of sample location SG-100. The primary chemicals of concern (COCs) are PCE, trichloroethylene (TCE), cis-1,2-dichloroethlyene (cis-1,2-DCE) and vinyl chloride (VC). The proposed activities will be conducted in accordance with the DTSC 2015 Active Soil Gas Advisory (DTSC, 2015). The data collected will be used to obtain a better understanding of the extent of chlorinated VOCs in soil vapor near this sample point,to evaluate the potential for VI in surrounding buildings and to assess the need for further remedial action. 1.2 Document Organization Following this introduction, this report is organized as follows: • Section 2 "Vapor Intrusion Conceptual Site Model" • Section 3 "Investigation Objectives" • Section 4 "Scope of Work" • Section 5 "Reporting and Schedule" • Section 6 "References" lists the published reports and correspondence cited herein. 202012 Lincoln Center Soil Vapor Assessment Work Plan I December 2020