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FOURTH QUARTER 1995 GROUNDWATER MONITORING REPORT ' FORMER DIAMOND LUMBER-MANTECA FEBRUARY, 1996 ' 2.2 Monitoring Well Purging Each sampled well was purged using a bailer 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 tri-sodium 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 a field data sheet, 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 Samples N collected for dissolved total lead analysis were field filtered prior to being acidified The samples were labeled with the date, time and identifying well number, then placed into a cooler at 4°C, and then transported to the laboratories under continuous chain-of-custody (COC) documentation The laboratory reports and CDCs are included in Appendix B 2.4 Groundwater Analyses ' Analyses of the sampled groundwater were performed by Sierra Laboratories, Inc and Anlab Analytical Laboratories, California, which are both California certified laboratories Samples were ' analyzed in accordance with state guidelines and EPA protocols Sierra performed the analyses for TPH G and BTEX using EPA Methods 8015 Modified and 602,respectively Anlab completed the TPb analyses using Method 239 2 1 3.0 SUMMARY AND CONCLUSIONS 3.1 Results of Groundwater Laboratory Analyses TPH G was detected in three of the six wells sampled (BEI-MW1, BEI-MW2, and BEI-MW3), and reported at concentrations of 7,000, 3,400, and 25,000 micrograms per liter(µg/1 or ppb), ' respectively Benzene concentrations were 190, 110 and 3,800 µg/1,respectively Total lead was only detected in BEI-MW3 at a concentration of 18 µg/1, with a detection limit of 1 µg/l The laboratory results are summarized for all sampling events performed by Park and others in Table ' 2 ' 5023-03 2