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San Joaquin County, Local Oversight Program . Apn115,2003 Page 2 2.0 MONITORING WELL PURGING AND SAMPLING Monitoring wells MW-1 through MW-7 were purged using an ES-60 submersible pump marketed for monitoring well purging by Enviro-Tech Services Co of Martinez, California Monitoring well MW-8 was purged using a Grundfos RediFlo2 submersible electric pump due to its higher purge volume Field measured water quality parameters were measured using a Cambridge Scientific Industries HydacTm Conductivity Temperature pH Tester. The appropriate information was logged onto the field sampling forms. Well purging activities and the field measured water quality parameters are documented in Attachment A. Following completion of well purging and field parameter determination the pump discharge was reduced to less than 1 L/min. Groundwater samples were collected into four 40-mL glass vials with Teflon septum lids. Following sample collection, each sample bottle was labeled with the sample designation, date and time, and the initials of the sampler. The sample bottles were then placed directly into a divided plastic box located in an ice chest maintained at the temperature available from its also containing and bed of crushed ice placed there at the start of the sampling day Th ece ii was not allowed to completely melt before it was replaced. The sample number, date, and time were entered onto a chain-of-custody form that included the request for analysis by U.S EPA Method 8260FAB for total petroleum hydrocarbons in the gasoline range(TPH-gasoline or TPHG), for the volatile aromatic hydrocarbon compounds (benzene, toluene, ethylbenzene, and total xylene isomers), and for the Fuel Oxygenates: tertiary- Butyl alcohol(TBA);Methyl tertiary-butyl ether(MtBE);Di-isopropyl Ether(RIPE);Ethyl tertiary-butyl ether(EtBE),and tertiary-Amyl methyl ether(TAME). Samples and chain-of-custody documentation were then delivered to STL San Francisco (CA DHS ELAP#2496)of Pleasanton, Cahforma Copies of the monitoring well groundwater sample laboratory reports and the chain-of-custody form are included in Attachment B. 3,0 GROUNDWATER ANALYTICAL RESULTS Groundwater samples were submitted to STL San Francisco for analysis using EPA Method 8260FAB on February 18, 2003. Copies of the laboratory report and chain of custody documentation are contained in Attachment B The analytical results are summarized in Table 3. 'jm `lI2zld3 Total petroleum hydrocarbons in the gasoline range (TPHG)were pe detected in two of the eight wells(MW4 at 150 µg/L and MW-5 at 68 µg/L. Theotj�her six wells were reported as "N D at X50 gg/L. See Table 3 and Figure 3. 1� Benzene was detectable in five of the eight monitoring wells at concentrations ranging from 14 to 7.0 gg/L. See Table 3 and Figure 3 The other aromatic hydrocarbon compounds;toluene, ethylbenzene, and total xylene isomers, were as reported in Table 3. H20GEOL AGRWWWATER TANCY