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40 Monitoring Well Installation Report - Chevron Station 49-5775, Lodi, CA Apri17, 2000 were collected from each of the wells Purge water generated during development and sampling procedures was transported by Integrated Wastestream Management (IWM) to McKittrtck for disposal Well development procedures are included in Appendix A Copies of the well development forms are included in Appendix D Monitoring data are summarized in Table 2 Wellhead Surve Following installation of the wells, the elevations were surveyed by Virgil Chavez Land Surveying of Vallejo, CA (Iicense #6323) Top of casing and vault box elevations were measured relative to MSL, and the horizontal locations of the wells measured The surveyor's report is included in Appendix E Well elevations are summarized in Table 2 RESULTS OF THE SUBSURFACE INVESTIGATION Soil encountered during this investigation consisted of interbedded silts, clays and sands to the total depth explored, which is similar to previous investigations at and in the vicinity of the site Groundwater was encountered and stabilized at depths between 54 and 56 feet bgs Detailed descriptions of the soil encountered during drilling are presented on the boring logs in Appendix C The subsurface stratigraphy of the site is depicted on cross sections A -A', B -B', and C -C' (Figures 5 though 7) Cross section lines are shown on Figure 3 Based on the groundwater monitoring data collected on March 1, 2000, shallow groundwater beneath the site appears to flow to the southeast at a gradient of 0 005 ft/ft (Figure 4) CHEMICAL ANALYTICAL RESULTS A total of forty six soil samples from the well and soil borings, four composite soil samples from the stockpiled drill cuttings, and eight groundwater samples were submitted under cham- of -cu stody for chemical analysis Analyses were performed by Sequoia Analytical (FLAP #127I and 41624) Copies of the laboratory reports and chain -of -custody forms are included in Appendix F Soil and groundwater chemical analytical data are summarized in Tables I and 2, respectively Chemical Analytical Procedures All soil samples from the borings were analyzed for TPHg, BTEX and MtBE by DHS LUFT Method with selected MtBE detections confirmed by EPA Method 8260 Groundwater samples were analyzed for TPHg, BTEX, and MtBE by DHS LUFT Method and oxygenates TBA, MtBE, DIPS, ETRE, and TAME by EPA Method 8260A As required by the disposal facility, the stockpiled drill cutting samples were analyzed for TPHg and BTEX by DHS LUFT Method and total lead by EPA 6000/7000 Series Methods or EPA Method 6010A except for sample SP -3 (A -D), which was analyzed only for volatile organic compounds (VOCs) by EPA Method 8021B Sail Analytical Results TPHg, BTEX, or MtBE were not detected in any of the soil samples from off-site well borings MW -7 through MW -9 TPHg were not detected in well boring MW -5, but benzene and MtBE were detected at concentrations up to 0 019 and 2 0 ppm, respectively, with the highest concentrations from a sample at 46 • feet bgs 34640806-1 4