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San Joaquin County, Local Oversight Program December 10, 2001 • Page 2 2 0 MONITORING WELL PURGING AND SAMPLING The monitoring wells were purged using a Grundfos 2-inch submersible pump or 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 field sampling forms 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 1 L/min. Groundwater samples were collected into five 40-mL glass vials with TeflonTM septum lads. 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 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 (RIPE),Ethyl tertiary-butyl ether(ETBE), and tertiary-Amyl methyl ether (TAME) and ethylene dibromnde and 1,2-Dichloroethane Samples and chain-of-custody documentation were then delivered to STL Chromalab, Inc (certification number is 1094) of Pleasanton, California. Copies of the monitoring well groundwater sample laboratory reports and the chain-of-custody forms are included in Attachment B. 3 0 GROUNDWATER ANALYTICAL RESULTS Groundwater samples were submitted to STL Chroma.lab for analysis using EPA Method 8015M/8020 and Method 8260 on November 19, 2001 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 limit for the sample from MW-5 was elevated due to the presence of 210 µg/L MtBE in the sample See Table 3 and Figure 3 H2OGEOL A GROUNDWATER CONSULTANCY