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Ms. Vera Fischer, P.G., RWQCB April 24, 2017 Work Plan for Additional Site Assessment Project No. 2154-1817-01 1817 South Fresno Avenue, Stockton, CA Page 4 In March 2015, Stratus prepared and submitted a Remedial Action Work Plan for the Site, which proposed using CH remediation at the Site, and the work scope was subsequently approved by the SJCEHD. After obtaining a Waste Discharge Requirement (WDR) permit from the RWQCB, ()I remediation was initiated in April 2016. Since remediation was implemented, maximum benzene concentrations in groundwater have declined from approximately 4,400 micrograms per liter (i.tg/L) to 1,700 pg/L. The RWQCB has directed that OI be performed until benzene concentrations are remediated to less than 1,000 tg/L, due to the agencies belief that a benzene plume length of less than 250 feet cannot be adequately demonstrated at this time. SCOPE OF WORK The objectives of the proposed scope of work are to: . Further assess the vertical and lateral extent of petroleum hydrocarbon impact to 05 groundwater. Additionally characterize geologic conditions (subsurface strata) at the Site, in particular below approximately 35 feet bgs. I Evaluate c9nc-911trations of fuel contaJniIants in shallow soil gas. \O 'I accomplish these objectives, Stratus is prop mg the following work activities: Advance two (2) cone penetrometer test borings (CPT-1 and CPT-2) to approximately 90 feet bgs for profiling of soil lithologies. Collect depth discrete groundwater samples from separate borings immediately adjacent to the CPT profiling boreholes. Drill and install two (2) offsite groundwater monitoring wells (MW-12 and MW- 13) to approximately 30 to 35 feet bgs using hollow stem augers. Collect soil samples in 5-foot intervals during the advancement of well borings MW-12 and MW-13 for lithologic comparison. Develop and sample wells MW-12 and MW-13. Install three (3) soil gas monitoring probe wells (SG-1 through SG-3) to approximately 5 feet bgs using hand tools. Collect soil gas samples from SG-1 through SG-3. The proposed scope of work has been subdivided into four tasks, as outlined below. All work will be conducted under the direct supervision of a State of California Professional Geologist or Professional Engineer, and will be conducted in accordance with standards established by the Tr-Regional Board Staff Recommendations of Preliminary Investigation and Evaluation of Underground Tank Sites (RWQCB, April 2004). KAI:lames Trucking\Work Plans \barnes trucking work plan 2017.doc STRATUS