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Chevron Products Company Page 4 Chevron Station 9-1452 334 East Main Street Ripon,California June 11 2002 Slug test results are summarized in Table 3. Attachment H contains the data plots and analyses for each test. %.01 WORK PLAN FOR FURTHER SITE ASSESSMENT Based on the results of this investigation, the MtBE concentrations in the newly installed wells MW-5S and MW-6S, and the low MtBE concentrations at depth in MW-5D and MW-6D warrant further investigation. SECOR recommends the advancement of two cone penetration test borings in the vicinity of MW-5S and MW-6S for vertical definition and the installation of one shallow 6-inch monitoring well to facilitate an aquifer pump test. The specific scope of work is discussed below: • CPT Borings. Two CPT borings will be advanced in the general locations shown in Figure 5. The borings will be advanced to a maximum depth of 120 feet bgs or until rig refusal is met to assess soil stratigraphy at depth and aid in the possible construction of a deep well (greater that 60 feet deep). • Groundwater Sampling. Immediately adjacent to each CPT borehole, a second direct-push borehole will be advanced to specifically collect discrete groundwater samples. Depths of the discrete groundwater samples will be determined from the CPT logs in the field. Groundwater samples submitted for chemical analysis will be analyzed for TPHg, BTEX, MtBE, TBA, DIPE, EtBE, TAME, EDB, 1,2-DCA, methanol, and ethanol. • Groundwater Monitoring Well. One soil boring will be advanced near MW-6S using 12-inch diameter hollow-stem augers to approximately 40 feet bgs (Figure 5). Groundwater is expected to be encountered at 25 feet bgs. No soil samples will be collected due to the well's close proximity to MW-6S. Upon completion of drilling, a 6-inch diameter groundwater monitoring well will be installed in the borehole and screened from approximately 5 feet above to 10 feet below first encountered groundwater. • Monitoring Well Development and Sampling. Following installation, the monitoring well will be developed using a Smeal rig. After well development, groundwater samples will be collected and sent under standard chain-of-custody procedures to a California certified laboratory. The groundwater samples will be analyzed for TPHg and methanol using modified EPA Method 8015, BTEX and fuel oxygenates (MtBE, TBA, DIPE, EtBE, TAME, EDB, 1,2-DCA, and ethanol)by EPA Method 8260. • Well Surveying and Groundwater Gradient Interpretation. A state-licensed surveyor will survey the CPT borings and newly installed well. Depth to groundwater measurements will be collected during sampling activities and utilized for interpretation of groundwater flow and gradient beneath the site. 1AChevron1914521REP0RTS19-1452 2002 MW SA.doc