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Bank of Stockton Page 3 Autumn 1996 Quarterly Monitoring Report Project No 102 2 December 27, 1996 ' Extreme care was exercised while collecting samples to prevent agitation of the water contained in the bailer Water samples were transferred from the bailer into 40 ml VOA ' vials preserved with hydrochloric acid and 1 liter capacity amber glass bottles (provided by the analytical laboratory) All samples were checked for head space bubbles, labeled, inserted into foam holders and placed in an ice chest cooled to 4°C for transport to the ' laboratory A chain of custody document, listing all samples collected and their intended analyses, ' accompanied the samples from field to the laboratory, thereby providing a means to track their movement and insure their integrity ' 1.4 Laboratory Analyses The groundwater samples obtained December 12, 1996 were delivered to Sherwood Lab ' (Department of Health Services Certification No 1400), of Hilmar, California, for analyses These samples were stored overnight in a secure Del Tech refrigerator and relinquished to the Sherwood courier the following day, December 13, 1996 I The samples were analyzed using the following methods • method 8020 - benzene toluene eth lbenzene total x BTEX), > Y � lens (Y • method LUFT/8015m/- total petroleum hydrocarbons as gasoline (TPH-Gasoline), • method 3510/8015m- total extractable petroleum hydrocarbons as diesel (TEPH-D), ' The detection limits for the above analyses are listed in Table 2 of Appendix B 2.0 FINDINGS AND DISCUSSION ' The followingsummary of findings is based on field and laboratory data collected to date �'Y g ' MW-1 In monitoring well MW-1, the BTEX compounds detected from the sample of December ' 12, 1996 were benzene (0 8 ppb), toluene (ND), ethylbenzene (ND) and xylene (ND) The total detectable TPH as gasoline and as diesel was found to be non-detectable These levels compare to 74 TPH-G in the September sampling event and 2 0 ppb of benzene, ' 0 6 ppb of toluene, and 0 9 ppb of total xylene These sample results are consistent with the generally decreasing contaminant levels at the site In the last monitoring event of September of 1996, abnormally high levels of 1 2937 Veneman Ave ,#B240 Phase One Environmental Inc Phone (209) 569-0293 Modesto, CA 95356 Fax (209) 569-0295