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r <br /> No soil. contamination was detected in any samples collected <br /> from the unsaturated zone. Gray discoloration and xylene <br /> odors were noted in soils within the capillary fringe and <br /> saturated zone in boring MW3, however, indicating that some <br /> groundwater contamination is present at the site. <br /> Groundwater was encountered at approximately 16 feet below <br /> grade and subsequently rose to 12-14 feet below grade, <br /> suggesting that groundwater exists under semi-confined <br /> conditions. The wells were monitored again on May 17, 1991 to <br /> verify monitoring data. Based upon the May 17, 1991 <br /> monitoring data (Table 3) static groundwater is approximately <br /> 14-15 feet below grade and flows to the southeast under a <br /> gradient of 0.017 ft/ft or 90 feet per mile. A groundwatar <br /> gradient map is presented on Figure 6. <br /> Laboratory analyses of groundwater samples collected from <br /> downgradient well MW3 detected xylene at levels below State <br /> Maximum Contamination Levels (MCL's) for drinking water <br /> standards, as established by the California Department of <br /> Health Services (DHS) . Also, ethylbenzene was detected at 1600 <br /> ppb, a level above the MCL of 680 ppb (Table 2) . <br /> 4.0 CONCLUSIONS/RECOMMENDATIONS <br /> 4.1 soil Contamination <br /> Approximately 750 cubic yards of contaminated soil associated <br /> with the former xylene tank were excavated. soils were <br /> + excavated vertically down to the water table. Soils within <br /> the saturated zone were not removed. Contaminated soils were <br /> removed laterally until field evidence (i.e. odor, <br /> discoloration, PILE readings) suggested all affected soils had <br /> been excavated. Verification soil sampling and analysis <br /> confirmed clean soils existed in siCe walls on the north, <br /> northeast, and south walls of the excavation. The excavation <br /> was limited on the west side by the warehouse and acce,3s rp:np. <br /> A verification sample collected from the west wall of the <br /> excavation contained xylene at 2.3 ppm, indicating that a <br /> small volume of contaminated soil remains beneath the building <br /> foundation. Although it is impractical to remove any <br /> remaining soil, the excavation area will be capped wit-31 <br /> asphalt, thereby mitigating the potential for contaminants <br /> leaching into the groundwater. It is anticipated that the <br /> residual xylene and associated contaminants in the soil will <br /> LC50510.wp <br />