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3 Chevron Products Company A ri15 2002 Chevron Service Station 20 8718 3355 E. imer Lane Stockton CA calculated by multiplying the hydraulic conductivity by the effective thickness of the saturated interval in each well as evaluated from the geologic logs and depth to groundwater level measurements. The transmissivity ranged from 1,200 to 4,200 gallons per day per foot (gpd/ft) with a calculated geometric mean of 2,600 gpd/ft. Slug test results are presented in Table 2. Data plots and analyses for each test are included in Attachment E. CPT Investigation On January 2 through January 8, 2002, SECOR supervised Precision Sampling, Incorporated of Richmond, California, as they advanced cone penetration test(CPT) and direct-push borings at eleven onsite locations (CPT-1 through CPT-11) along the eastern and southern property boundary to assess soil stratigraphy and to collect discrete groundwater samples (Figure 2). CPT borings advanced at each location were monitored continuously for soil behavior and pore pressure to their respective total depth. The CPT borings were advanced to depths ranging from approximately 81 to 90 feet below ground surface (bgs). Based on pore pressure and on lithologic information collected from the CPT logs, one to two depth-discrete groundwater samples were collected from an additional direct push boring advanced adjacent to each CPT boring. The findings of this assessment are summarized below: • Subsurface Conditions. Review of the CPT profiles suggests clay mixtures with silt and/or very stiff fine grained material,with small layers of sand and sand mixtures comprising the stratigraphy to an approximate depth of approximately 90 feet bgs at borings CPT-1 through CPT-11. Groundwater was generally encountered between approximately 62 to 72 feet bgs at each boring location. Cone penetration test data logs are included in Attachment F. • Groundwater Analytical Results. Groundwater samples were collected from each boring from an identified water-bearing zone, or at a depth interval showing distinct pore pressure, and submitted for chemical analysis. TPHg, BTEX and MtBE were not detected in any of the groundwater samples collected. A copy of the laboratory analytical reports and chain-of- custody documentation are presented in Attachment G. DISCUSSION OF FINDINGS Based on the results of this assessment, this site does not appear to present an MtBE threat to the nearby municipal drinking water supply well, as only low levels of petroleum hydrocarbons (toluene, ethylbenzene, and xylenes)were detected in soil or groundwater samples analyzed and ambient groundwater flow appears to be away from the nearby production well. Additionally, SECOR proposes to destroy the monitoring wells according to the procedures described below. The groundwater monitoring wells will be destroyed in accordance with the California Well Standards, Bulletin 74-90. The wells will be pressure grouted from the bottom up using tremie pipe, the top five feet of the wells will then be drilled out, the well boxes removed, and the wells completed to the surface with concrete. Appropriate permits will be secured from SIMS prior to the work being performed and appropriate agency notification will be made before the work is to be performed. SECOR and Chevron look forward to receiving the SJPHS's approval to properly destroy the groundwater monitoring wells. If there are any questions regarding the contents of this report,please I:1Chevron1208118\Reports1208118 site assessment 200kloc