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f QUARTERLY MONITORING REPORT FORMER DIAMOND LUMBER - MANTECA OCTOBER, 1995 ' 2.2 Monitoring Well Purging Due to the various well diameters present on-site, a double diaphragm pump was used to purge all of the sampled wells Each sampled well was purged until at least three equivalent well volumes of water had been removed and pH, temperature and conductivity measurements had stabilized within 10 percent of the previous reading All purging and sampling equipment was washed in a tri-sodium phosphate solution and rinsed in potable water prior to each usage to reduce the potential for cross contamination between the 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 senthng it to a recycling facility 2.3 Groundwater Sampling IProper sample collection and handling are essential to assure quality data obtained from a sample Therefore, each groundwater sample was collected using a new disposable bailer for each well and placed into the appropriate laboratory prepared containers, using proper protocol The samples were labeled with the date, time and identifying well number, then placed into a cooler at 4° degrees Celsius, and then transported to a California state certified laboratory under chain-of- custody (COC) The laboratory reports and COC documentation are included in Appendix A 2.4 Groundwater Analyses Analyses of the sampled groundwater were performed by Sierra Laboratories, Inc and Anlab Analytical Laboratories, both California certified laboratories, in accordance with state guidelines ' and EPA protocols The samples were analyzed for total petroleum hydrocarbons in the gasoline range (TPH G, EPA Method 8015 Modified), benzene,toluene, ethylbenzene and xylenes (BTEX, EPA Method 602) Anlab completed the Pb analyses,with in-laboratory filtering of the groundwater samples, using Method 239 2 3.0 SUMMARY AND CONCLUSIONS 3.1 Results of Groundwater Laboratory Analyses {BEI-MW-1, BEI-MW-2, BEI-MW-3, and detected in four of the six wells sampled TPH G was P SRK-MW-2), and reported at concentrations of 1,000,4,500, 44,000, and 4,400 parts per billion (ppb or pg/1), respectively Benzene concentrations were 60, 310, 7,000 and 230 ppb (µg/1), respectively Total lead was only detected in BEI-MW-3 at a concentration of 3 ppb (Jig/1), with ' a detection limit of 2 ppb (µg/1) The laboratory results are summarized for all sampling events performed by Park and others in Table 2 2