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Chevron Products Company Page 3 Chevron station 9-1452,334 Fast Main Street Ripon,California .Tune 11 2002 from MW-6S. TPHg was detected in two groundwater samples at concentrations of r 450 pg/l in the sample from MW-5S and 720 µg/1 in the sample from MW-6S. TAME was detected in three groundwater samples at concentrations ranging from 9 µg/1 in the sample from MW-4 to 630 µg/1 in the sample from MW-6S. Toluene was detected in one groundwater sample at a concentration of 0.7 µg/1 in the sample from MW-6D. No other target analytes were detected above their respective method detection limits. • Resampling of Wells MW-51) and MW-61). Due to the MtBE detections in wells MW-5D and MW-6D, a SECOR representative purged and resampled those wells on March 27, 2002 to confirm the MtBE detections. The laboratory reported detections of MtBE at concentrations of 7 µg/1 in the sample from MW-5D and 5 [ig/l in the sample from MW-6D. Toluene was also detected in the samples from MW-5D and MW-6D at concentrations of 2 µg/1 and 3 pg/l, respectively. Analytical results of the resampling are summarized in Table 2. A copy of the laboratory analytical report and chain of custody documentation are included in Attachment E. Copies of the field data sheets are included in Attachment G. • Monitoring Well Survey and Groundwater Gradient Interpretation. The newly installed wells were surveyed along with the four previously installed wells to 0.01- foot accuracy relative to mean sea level (MSL). Based on GR's depth to water measurements taken during the first quarter 2002, groundwater flow was to the south at a gradient of 0.0002 foot per foot (ft/ft). Groundwater flow direction and gradient are shown graphically in Figure 4. • Slug Tests. On November 1, 2001, slug tests were performed in wells MW-2, MW- 3, and MW-4. Slug insertion and removal tests were conducted in the wells by creating a near instantaneous change in water level by inserting or removing a"slug" in the well. The hydraulic response was recorded using an automated pressure transducer, containing an internal data logger(Troll') until the water elevation equilibrated to its pre-test level or until sufficient data was obtained for analysis. Responses from slug tests conducted in MW-2 were extremely rapid. Because of this, field data could not be collected at intervals small enough to illustrate groundwater displacement and recovery from the slug test. As such, field data collected from the slug tests at MW-2 were not analyzed. The estimated hydraulic conductivity ranged from 1799 to 27.30 feet per day(ft/day) with a calculated geometric mean of 22.65 ft/day based on the slug tests performed on wells MW-3 and MW-4. These values of hydraulic conductivity are consistent with those for unconsolidated silty sands that are present at the site. 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 116.58 to 209.83 gallons per day per foot (gpd/ft) with a calculated geometric mean of 169.29 gpd/ft. LlChevron1914521REP0RTSI9-1452 2002 MW SA.doe