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Mr.Mike Oliphant—CEMC Soil and Groundwater Investigation Report March 29,2013 Ahern Road—Vernalis Page 3 of 6 APN 255-180-15. Borings SB-7 through SB-9 were advanced to depths ranging from 40 to 42.5 feet bgs. There were no indications of hydrocarbons in these borings. The boring locations are shown on Figure 2. The boring logs, which describe Unified Soil Classification System descriptions, PID readings, and observations of hydrocarbon- affected soil and/or groundwater, are provided as Attachment C. SAIC collected soil samples from less than 10 feet bgs and just above first-encountered groundwater for analytical sampling. An additional soil sample was collected from borings SB-1 through SB-6 between 10 feet bgs and first-encountered groundwater. Due to the presence of SPO in borings SB-1 through SB-3, grab groundwater samples from first-encountered groundwater were not collected from these borings. A depth-discrete groundwater sample was collected from SB-2 from at 84 feet bgs. A representative of the SJCEHD was on site during borehole abandonment activities. ANALYTICAL METHODS AND SCREENING LEVELS SAIC submitted the soil and groundwater samples to Eurofins Lancaster Laboratories, LLC, for the following analyses: • Total petroleum hydrocarbons (TPH)quantified as crude oil (TPHc; carbon range C 10 to C36) using United States Environmental Protection Agency(EPA) Method 8015B Modified (this analysis performed on soil only); • TPH quantified as diesel (TPHd; carbon range CIO to C25) using EPA Method 8015B Modified with and without silica-gel cleanup if detected, and solely without silica-gel cleanup if not detected(this analysis performed on groundwater only); • Benzene,toluene, ethylbenzene, and total xylenes (BTEX) using EPA Method 8260B (groundwater by 25-milliliter purge); and • Polynuclear aromatic hydrocarbons (PAHs)using EPA Method 8270C (soil by selective ion monitoring and groundwater by large-volume injection). Groundwater analytical results were compared to the lowest,most conservative San Francisco Bay RWQCB Environmental Screening Levels?(ESLs) and interpreted narrative water quality objective (WQO) values for delineation purposes. Under the California Water Code, WQOs are numerical or narrative limits for constituents or characteristics of water designed to protect beneficial uses of a body of groundwater or surface water. EPA Regional Screening Levels9 (RSLs) and ESLs are used to evaluate soil laboratory analytical data. 7. San Francisco Bay RWQCB,2008. Screening for Environmental Concerns at Sites with Contaminated Soil and Groundwater(Interim Final). May. 8. Central Valley RWQCB,2007. Water Quality Control Plan(Basin Plan)for the Sacramento River Basin and San Joaquin River Basin(Fourth Edition). October. 9. EPA,2008. Regional Screening Levels(RSL)for Chemical Contaminants at Superfund Sites. September.