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GSI Job No.: 14� G S 1T Issued: 15 November 2017 ENVIRONMENTAL 1.0 INTRODUCTION This Site Investigation Work Plan (Work Plan) has been prepared by GSI Environmental Inc. (GSI) on behalf of Sims-Grupe Management Corporation, Inc. (SGM) in response to the Central Valley Regional Water Quality Control Board's (Water Board) Monitoring and Reporting Order 85-2017- 0835 issued under Water Code Section 13267 dated 13 September 2017 (Order). The Order was issued to potentially responsible parties (PRPs) for the "Parkwoods Shopping Center" and "Parkwoods Cleaners." SGM refers to the center and cleaners as "Park Woods" though the spelling "Parkwoods" is used in the Order and both spellings have been identified in historical records. For consistency "Park Woods" is used in this Work Plan. The Park Woods Shopping Center is located on West Hammer Lane between Brentwood Drive and Alexandria Place in Stockton, California (herein referred to as the "Site" and shown on Figure 1). The Order requires potentially responsible parties, including SGM, to provide current and historical operating information and investigate the potential presence of dry cleaning solvents in soil gas and groundwater. The Water Board issued the Order based on detections of tetrachlorethene (PCE; a common dry cleaning solvent) in groundwater samples collected from domestic wells located in the downgradient direction of groundwater flow from the Site. The domestic well groundwater samples were collected in August 2017. Dry cleaning operations were historically performed at the Site in tenant spaces 1744 West Hammer Lane (currently a pizza restaurant) and 1762 West Hammer Lane (current location of Park Wood Cleaners, which has operated as a drop-off facility since on-Site dry cleaning ceased in January 1995). SGM retained E2C Remediation (E2C) and GSI to assist in responding to the Order. An initial project meeting was held at the Water Board's office on 6 October 2017 where historical dry cleaning tenancy at the Site and an overview of the domestic well sampling data were discussed. Based on the historical on-Site dry cleaning operations and geographic location with respect to groundwater flow and detections of PCE in domestic well samples, Site investigation to assess whether releases of PCE have occurred is required. 2.0 INVESTIGATION OBJECTIVES The objective of the investigation activities is to assess whether PCE was released to the subsurface from historical dry cleaning operations. Soil and soil gas sampling are described in this Work Plan. Based on the results of this investigation, a groundwater sampling program will be designed and submitted to the Water Board for approval, if warranted. This phased approach is recommended based on concerns for potential cross-contaminating (down slough or between sample depths) of soils and/or shallow groundwater that may be impacted with PCE. It is essential to assess the presence, if any, of PCE in shallow soil before proceeding with deeper sampling activities due to likely lateral and vertical variability of the Iithology (i.e. interbedded and/or alternating fine and coarse-grained layers from the ground surface to saturated sediments at approximately 30 to 40 feet below ground surface [bgs]) observed in the vicinity of the Site and anticipated to be present at the Site (further discussed in Section 3.2). 3.0 SITE BACKGROUND, SETTING, AND DOMESTIC WELL SAMPLING A summary of Site background information, Site and Site vicinity information, geology and hydrogeology, and results of recent domestic well sampling are included in the following subsections. Site Investigation Work Plan Park Woods Cleaners