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WORK PLAN FOR GROUNDWATER INVESTIGATION Chevron Service Station # 94054 Stockton, CA October 26, 2016 1.0 Introduction On behalf of Chevron Environmental Management Company (Chevron), Stantec Consulting Services Inc. (Stantec) has prepared this Work Plan for Installation of Monitoring Wells for further delineation of A and B zones (Work Plan). Chevron Facility #94054 located at 2103 Country Club Boulevard Stockton, California (the "Site"). This Work Plan will address the project objectives directed by the Central Valley Regional Water Board (CVRWQCB) in their August 15, 2016 letter (Appendix A) following review of Stantec's Semi-Annual Groundwater Monitoring Report dated April 28, 2016. These objectives include the following: Provide further plume delineation in areas including: the 'A' water bearing zone to the east of MW-6 the 'B' water bearing zone to the west of MW-10 and north of MW-11 This following Work Plan includes a brief description of the Site, basis for the proposed scope of work, detailed description of the proposed scope of work, reporting requirements, and an implementation schedule. Upon regulatory approval of this Work Plan, the scope of work and associated budget will be submitted to the State of California Underground Storage Tank (UST) Fund for their pre-approval prior to initiating any work. 2.0 Background 2.1 SITE DESCRIPTION AND LOCATION The Site is located in a mixed commercial and residential area at the intersection of Country Club Boulevard and Franklin Avenue in Stockton, California. The site address is 2103 Country Club Boulevard (Figure 1). The former service station was in operation from 1962 to 1986 and was razed in late 1988 (Terra Vac Corporation, 1998). The site is currently an unpaved vacant lot owned by Mr. Mark Springs. A detailed site plan is included as Figure 2. 2.2 SUMMARY OF RECENT ENVIRONMENTAL ACTIVITIES The recent monitoring and sampling events show groundwater concentrations above water quality objectives (WQ0s) for total petroleum hydrocarbons as gasoline (TPHg) and benzene in downgradient B zone monitoring well MW-12B and for TPHg in cross-gradient A zone well MW-6. Results from the third quarter 2016 sampling event reported TPHg concentrations of 580 micrograms per liter (pg/L), and 340 pg/L, in wells MW-12B, and MW-6, respectively. The same sampling event reported concentrations of benzene at 160 pg/L, and <0.5 pg/L, in wells MW-12B, and MW-6, respectively (Table 1). These most recent results are a decrease from other recent Stan tee 2