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FIRST QUARTER,1998 , GROUNDWATER MONITORING REPORT USA STATION#65-LODI FEBRUARY,1998 ' Monitoring well S-2 could not be located during this sampling event It appears that the well may have been covered during station retrofit activities This well will be found and either abandoned , in accordance with County regulations or repaired Groundwater elevation data are summarized in Table 1, and field data sheets are included in Appendix A 4.2 MonitoringPurging Well ' The monutonng-wells_were purged-using-a-2-inch diameter submersible Grundfos groundwater pump or disposable bailer, until a minimum of three equivalent well volumes of water were removed from each well To reduce the potential for cross-contamination between wells, all ' purging and sampling equipment was washed in a tnsodium phosphate solution and rinsed in potable water prior to each use Groundwater purged from the wells was placed into Department of Transportation (DOT) approved 55-gallon drums and stored on-site prior to disposal by USA , During the groundwater purging operations, physical parameters such as pH and conductivity were monitored and recorded on field data sheets Groundwater purging was discontinued when ' the physical parameters indicated above stabilized in the purged groundwater 4.3 Groundwater Sampling Prior to sampling, the wells were allowed to recharge to a minimum of 80 percent of their initial - 4 static water levels Groundwater samples were then collected from each well using a new ' disposable bailer The samples were placed into the appropriate laboratory prepared containers, using proper sample handling and chain-of-custody(COC) protocol established under applicable SW-846 procedures issued by the USEPA The samples were labeled with the date,time, ' identifying well number, stored in a cooler at 4° Centigrade or less, and transported to a state certified laboratory under completed COC documentation 4.4 Groundwater Analyses ' Groundwater samples were analyzed for TPH G, BTEX and MTBE using EPA Methods 8015 ' Modified and 8020, respectively The analyses were conducted by Sierra Laboratories, Inc (Sierra), a California State certified laboratory in accordance with state guidelines and EPA ' protocol 5.0 SUMMARY AND CONCLUSIONS , The following sections discuss findings from the groundwater gauging and sampling activities ' conducted on January 16, 1998 4