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MR [ C 0 R Additional Site Assessment and Site Conceptual Model 7-11 Store#14117 September 30, 2005 Page 8 supervision of a California registered geologist Each soil sample was screened for hydrocarbon vapors with a portable photoionization detector (PID) Sall samples retained for analysis were sealed with Teflon® sheets and plastic caps, then labeled and placed on Ice in an Insulated container for delivery to Klff Analytical located in Davis, California under chain-of-custody documentation Selected soil samples were analyzed for TPHg, BTEX, MtBE, tert-butyl alcohol (TBA), and 1,2-dichloroethane (1,2 DCA) by Environmental Protection Agency (EPA) Method 8260B Copies of field notes documenting boring activities and are in Attachment C 4.4 Current Soil Data Summary MtBE was not detected in soil samples collected during this phase of site assessment Tert- butanol (TBA) was reported In soil samples collected from CPT-1 at concentrations of 00094 mg/kg (CPT-1-80') and 0 029 mg/kg (CPT-1-105') (Table 3) TBA was not detected in samples collected from shallow borings GP-1 and GP-2 TPHg was reported in samples collected from CPT-1 at concentrations from 2 6 mg/kg (CPT-1-60') to 7 2 mg/kg (CPT-1- 70') The certified laboratory analytical report and chain-of-custody documentation are presented as Attachment F Based on the data described above, the vertical limits of hydrocarbon contamination in deep portions of soil onsite have not been defined (Figures 3 and 4) However, the lateral extent of shallow contamination in soil has been defined to the north, west and southwest of the site Due to the presence of an active gas station with a previous fuel release, the eastern extent of soil Impacts are not defined Definition of the southern limit of soil Impact is pending installation of proposed groundwater monitoring well MW-10 on the south side of Country Club Boulevard 4 5 Estimated Mass of Petroleum Hydrocarbons Remaining In Soil Not enough data are available to calculate the estimated mass of petroleum hydrocarbons present in soil 4.6 Groundwater Monitoring and Sampling Groundwater at this site has been monitored since the third quarter 1999 DTW has ranged from 6 69 feet to 10 15 feet in MW-1, and groundwater flows primarily to the southeast and northwest with an average gradient of 0 017 (Table 1 and Figure 5) During the most recent groundwater monitoring event (.lune 27, 2005) groundwater flow direction is northeast with a gradient of 0 010 feet per foot (Figure 6) I 17-Elevenl7-11 stores1141171Reports114117 SCM and Additional Assessment doc Page 8