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r- iN Monitonng Well installation Report—Former Unocal Station#0123,Tracy,CA January 17 2001 Wellhead Survey Following installation of the wells, the elevations were surveyed by Virgil Chavez Land Surveying of Vallejo, CA (license #6323) Top of casing and vault box elevations were measured relative to mean sea level (MSL), and the horizontal locations of the wells were 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 silty gravel (fill/roadbase) and clay to approximately 3 feet bgs, then interbedded silty and sandy horizons to the total depth explored, with minor amounts of clay in well U-8 between approximately 8 and 18 feet bgs Minor amounts of gravel were present in both wells below approximately 18 feet bgs This is similar to previous investigations at the site Groundwater was encountered at approximately 10 feet bgs in well boring U-7 and at approximately 20 feet bgs in well boring U-8, and stabilized at depths between 9 and I 1 feet bgs in both wells Detailed descriptions of the soil encountered during drilling are presented on the boring logs in Appendix C Based on the groundwater monitoring data collected on December 6, 2000, shallow groundwater beneath the site appears to flow in a northerly direction at a gradient of 0 003 (Figure 2) This is consistent with historical monitoring data . CHEMICAL ANALYTICAL RESULTS A total of six soil samples from the well borings, one composite soil sample from the drill cuttings, and two groundwater samples from the newly installed wells were submitted under chain-of-custody for chemical analysts Analyses were performed by Sequoia Analytical (ELAP #1271, #1624, and #2374) Copies of the laboratory reports and cham-of-custody forms are included in Appendix F Soil and groundwater chemical analytical data are summarized in Tables 1 and 2, respectively Chemical Analytical Procedures The soil and groundwater samples were analyzed for TPHg, TPHd, BTEX, and MtBE by DHS LUFT Method, ethanol, tert-butyl alcohol (TBA), MtBE, di-isopropyl ether (DIPS), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), 1,2-dichloroethane (1,2-DCA), and ethylene dibromide (EDB) by EPA Method 8260, methanol by EPA Method 8015M, and total lead by EPA Method 6010A The drill cuttings composite sample was analyzed for TPHg, BTEX, and MtBE by DHS LUFT Method, and total lead by EPA Method 6010A Soil Analytical Results TPHg, TPHd, BTEX, oxygenates except methanol, 1,2-DCA, EDB, or lead were not reported in any soil samples Methanol was reported in well boring U-8 at 21 feet bgs at a concentration of 1 95 ppm Groundwater Analytical Results TPHg, BTEX, oxygenates, 1,2-DCA, EDB, or lead were not reported in groundwater samples from the newly installed wells Diesel range hydrocarbons were reported in wells U-7 and U-8 at concentrations of 24007305-1 4