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1992 Quarterly Groundwater Monitoring Report `tel Western Stone Products, Tracy, California }r� Page 3 summarized in Table 3. Laboratory data sheets and chain-of-custody documentation are included in Attachment 2. Excavated soil was stockpiled on site, underlain and covered by visqueen. The location of the stockpiled soil, the estimated volume in each pile, and the soil pile sampling locations are depicted on Figure 3. Two soil samples were collected from each 50 cubic yards of soil, composited by the laboratory and analyzed for TPHD and BTEX. Analytical results of the soil pile sampling is presented on Table 4. Analytical data and chain-of-custody documentation are presented in Attachment 2. A disposal plan, based on the soil pile sample analyses, will be prepared in the near future. Groundwater which recharged to the pit was pumped into Baker tanks. A total volume of 20,600 gallons of water was pumped from the excavation during and after soil removal as water recharged to the pit. The influence of pumping from the pit was observed in the site monitoring wells. Water levels dropped 0.76, 0.30, and 0.34 feet in wells MW1, MW2, and MW3, respectively from October 7, 1992 to October 9, 1992. A water sample was collected from the Baker tank, and from the excavation after the pit was allowed to recharge. The water samples collected from the tank and pit were analyzed for BTEX and TPHD. Total petroleum hydrocarbons as diesel (TPHD) were present at 1900 ttgle and xylenes were present at 11 tZglf in the Baker tank water sample and TPHD was present at 330 tcglf and ethylbenzene and xylenes were detected in the pit water at concentrations of 4.8 ttg/f and 3.4 yglf, respectively. Analytical results are presented in Table 2. Analytical data sheets and chain-of-custody documentation are presented in Attachment 2. The water in the Baker tank will be remediated by enhanced bioremediation. The stored water will be periodically sampled and analyzed for TPHD and BTEX to gauge the progress of remediation. If samples confirm that the water is clean, San Joaquin County PHSIEHD will be notified requesting permission to discharge directly to the surface or to the facility septic system. Based on the limited volume of petroleum hydrocarbon impacted soil remaining in place beneath the storage shed, the fact that the soil is overlain with concrete, and the lack of historical groundwater contamination RESNA recommends two quarters of groundwater sampling. If petroleum hydrocarbon concentrations in the groundwater are found to be below MCLs RESNA ' will recommend case closure. QR102592.FNL