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Chevron Products Company • 3 Chevron Service Station 20-0764 4747 West Lane Stockton Califomia April 5 2002 The hydraulic conductivity ranged from 1.3 x 10-3 to 9.8 x 10-3 centimeters per second • (cm/sec)with a calculated geometric mean of 3.4 x 10-3 cm/sec (approximately 10 feet/day). These values of hydraulic conductivity are consistent with those for poorly- graded sands that are present at the site as described in the boring logs for the tested wells. The transmissivity was 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 420 to 3,100 gallons per day per foot(gpd/ft)with a calculated geometric mean of 1,100 gpd/ft. Slug test results are summarized in Table 2. Attachment E contains the data plots and analyses for each test. CPT Investigation On January 9 through 15, 2002, SECOR supervised Precision Sampling Incorporated of Richmond, California, as they advanced cone penetration test (CPT) and direct-push borings at six onsite locations (CPT-1 through CPT-6) along the 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, approximately 90 feet below ground surface(bgs) at each location. 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 silty sand and sand comprising the stratigraphy to an approximate depth of approximately 90 feet bgs at borings. Groundwater was generally encountered at approximately 60 feet bgs at each boring location. CPT 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 from the CPT investigation 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.