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FIRST QUARTER, 1997 GROUNDWATER MONITORING REPORT ' FORMER DIAMOND LUMBER - MANTECA APRIL, 1997 ' 2.2 Monitoring Well Purging Each sampled well was purged using a submersible pump until at least three equivalent well ' volumes of water had been removed and pH, temperature and conductivity measurements had stabilized. All purging and sampling equipment was washed in a trisodium phosphate solution and rinsed in distilled water prior to each usage to reduce the potential for cross contamination between wells. The pH, temperature and conductivity measurements were recorded on field data sheets, which are kept in a permanent project file. The wells were allowed to stand for a period of ' time to equilibrate prior to sampling. Groundwater purged from the wells was placed into DOT approved 55-gallon drums. The purge water will be disposed of by pumping into a vacuum truck and sending it to a recycling facility. ' 2.3 Groundwater Sampling ' Proper sample collection and handling are essential to assure quality data obtained from a sample. Each groundwater sample, therefore, was collected using a new disposable bailer for each well and placed in the appropriate laboratory prepared containers, using proper protocol. The samples were labeled with the date, time, identifying well number, placed into a cooler at 4° C, and transported to the laboratory under continuous chain-of-custody (COC) documentation. The laboratory reports and COC documentation are included in Appendix B. 2.4 Groundwater Analyses ' Analyses of the sampled groundwater was performed by Sierra Laboratories,Inc. (Sierra), a California certified laboratory. Samples were analyzed in accordance with state guidelines and EPA protocols. ' 3.0 SUMMARY AND CONCLUSIONS 3.1 Results of Groundwater Laboratory Analyses ' TPH G was reported in four of the eight sampled wells. TPH G was reported at concentrations ranging from non-detect in SRK-MW1, SPK-MW3, MW-7-P, and MW-S-P to 22,000 ' micrograms per liter 0.cg/l) in BEI-MW3. Benzene was reported in all wells sampled this quarter at concentrations ranging from 1.0 Ag/l in SRK-MW3 to 2,500 ,ugA in BEI-MW3. Both off-site wells were non-detect (ND) for TPH, and low to ND for BTEX constituents. The laboratory ' results for this sampling event are presented on Figure 3, and in Table 2.