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i San Joaquin County, Local Oversight Program March 19, 2001 # Page 2 + 2.0 MONITORING WELL PURGING AND SAMPLING The monitoring wells were purged using an ES-60 submersible pump marketed for monitoring well purging by Enviro-Tech Services Co. of Martinez, California. Field measured water quality parameters were measured using a Cambridge Scientific Industries HydacTM Conductivity Temperature pH.Tester. The appropriate information.was logged onto the fieldsampling.farms. Well purging activities and the field measured water quality parameters are documented in Attachment A. The specific conductance and the total.groundwater volumes purged are " summarized in Table 3. Following completion of well purging and field parameter determination the pump discharge was reduced to less than I L/min. Groundwater samples were collected into five 40-mL.glass vials ± with TeflonTM septum lids. Following sample collection, each sample bottle was labeled with the r 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. The ice was not allowed to completely melt before it was replaced. The sample number, date, and time was entered onto chain-of-custody form(s) that included the request for analysis by U.S. EPA Method 8015M/8020 for total petroleum hydrocarbons in the gasoline range(TPH-gasoline or TPHG)and for volatile aromatic hydrocarbon compounds (benzene, toluene, ethylbenzene, and total xylene isomers) and by U.S. EPA Method 8260 for the Fuel Oxygenates: tertiary-Butyl alcohol(TBA); Methyl tertiary-butyl ether MtBE • Di- isopropyl Ether(DIPE);Ethyl tertiary-butyl ether(ETBE); and tertiary-Amyl methyl ether (TAME) and ethylene dibromide and 1,2-Dichloroethane. Samples and chain-of-custody documentation were then delivered to STL San Francisco (formerly STL Chromalab, Inc.) (retained certification number is 1094) of Pleasanton, California. Copies of the monitoring well groundwater sample laboratory reports and the chain- of-custody hain- ofcustody forms are included in Attachment B. 3.0 GROUNDWATER ANALYTICAL RESULTS I Groundwater samples were submitted to STL San Francisco for analysis using EPA Method 8015M/8020 and Method 8260 on February 25, 2002. Copies of the laboratory report and chain- of-custody documentation are contained in Attachment B. The analytical results are summarized in Table 3. Total petroleum hydrocarbons in the gasoline range(TPHG)were not detected in any of the eight wells. The detection Iimit for the sample from MW-5 was elevated due to the presence of 290 :g/L MtBE in the sample. See Table 3 and Figure 3. H2 A GROUNDWATER CONSULTANCY