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February 28, 2018 Project No. 2154-1817-01 Ms. Vera Fischer, P.G., RWQCB Work Plan for Additional Site Assessment 1817 South Fresno Avenue, Stockton, CA Page 3 Health Department, [SJCEHD]) approved the RAP; however, the remedial work outlined in that document was never implemented. After assuming consulting duties in March 2012, and meeting with SJCEHD personnel to discuss the Site, Stratus prepared and submitted a Modified Remedial Action Plan and Feasibility Study (RAP/FS). The document originally proposed to perform dual phase extraction (DPE) for a period of approximately 6 to 12 weeks; however, during the 2012/2013 UST Cleanup Fund fiscal year, insufficient funds were available to implement DPE for this length of time. Instead, Stratus attempted to evaluate DPE during a shorter period of time (5 days) between April 29 and May 3, 2013. This proved to be an insufficiently short period of time to evaluate DPE as a remedial technology for the Site. Between November 20 and December 31, 2013, a longer duration DPE event was performed, with the equipment operating approximately 579 hours (24 days), using four wells (MW-5B, IW-2, IW-7, and either IW-6 or IW-8) for extraction. During this time, an estimated mass of approximately 83 pounds of GRO was removed from the subsurface in the vapor phase. At the time of test termination, approximately 4 pounds per day of GRO was being removed from the subsurface in the vapor phase. Groundwater was extracted during the test at an average rate of approximately 3.6 gallons per minute (gpm). Stratus previously concluded, based on the results of this pilot test, that a full-scale DPE system capable of remediating the Site for several years would likely be needed in order to manage the Site's environmental case to closure, but that this course of action was not likely to be the most cost-effective approach for achieving case closure. In March 2015, Stratus prepared and submitted a Remedial Action Work Plan for the Site, which proposed using OI remediation at the Site, and the work scope was subsequently approved by the SJCEHD. After obtaining a Notice of Applicability (NOA) permit from the RWQCB, OI remediation was initiated in April 2016. During the recent JET meeting, Stratus was directed to terminate CH remediation and CH was subsequently discontinued in January 2018. The NOA permit was cancelled after CH was discontinued. In November 2017, Stratus implemented a subsurface investigation that included an onsite soil gas survey, advancement of two direct push borings to 60 feet bgs, and installation of two monitoring wells (MW-12 and MW-13) behind a City of Stockton fire station building at 1818 South Fresno Avenue. The investigation indicated that petroleum hydrocarbon impact to the subsurface extended to over 60 feet bgs onsite and offsite, and that GRO impact to shallow groundwater extended to at least the MW-12 area, indicating a plume length of over 250 feet. KABames Trucking\Work Planammes trucking cpt work plan 2018.doc STRATUS