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I"'W97 ; rmn R F=L These concentrations are below the DL's of 100 mg/Kg, 620 mg/Kg and }� 1400 mg/Kg for Toluene, Xylene and Ethylbenzene respectively. is Total Petroleum Hydrocarbons (TPH) were also detected in sample NB at a concentration of 105 mg/Kg. Since no established criteria exists for the allowable concentrations of TPH, WESTON utilized Table 2.1 of the LUFT Manual for the evaluation of an allowable F..d concentration. The LUFT manual Table 2.1 was utilized to estimate A)o the concentrations of BTX&E and TPH that can be safely left in k place without threatening water quality based on leaching 5-d potential. This Table provides a leaching potential analysis based ". on Ecosy::tem Modeling Results and the best professional judgement �a :.; of experienLz California Regional Water Quality Control Board Staff. _. As part of the analysis requires data on depth to groundwater, WESTON utilized both a client supplied well installation report and the San Joaquin County Flood Control and Water Conservation District, Lines of Equal Depth to Water in Wells, Fall 1988 map to determine the depth to first groundwater at the site. The depth was found to be greater than 100' . This depth to first ground- water, coupled with the lack of subsurface fractures, an average aP� annual precipitation of approximately 14 inches, no presence of mar. 1 made vertical co;iduits and no unique site features provide a cumulative score from Table 2-1 of 49 points. For this score, the P[ LUFT manual recommends. a maximum allowable TPH level for gasoline' o rPof 1000 mg/Kg and maximum BTX&E levels of 1/50/50/50 .mg/Kg. respectively. Both the Luft manual Table 2-1 and the well installation report are presented in Appendix C. Based on these considerations, there does not appear to be any need k , for additional site investigation o-- remediation for this area of ` the site. 3.2 Soil stockpiles Samples #1 through #7 were taken from the stockpiled soils removed from Pit A. Sample #8 was taken from the stockpiled soils removed from Pit B. A review of the data presented in Table 1 indicates that TPH, BTX&E, EDB and total lead were detected within these stockpiles at very low concentrations. The concentrations detected are well below the levels which would designate the stockpile as hazardous waste. — ------ -- - -- —. 4.0 -conclusions and Recommendations The analytical results for samples taken from Pit A indicate,that no concentrations of hydrocarbon related compounds_remain in-' the excavation. Therefore, it is recommended that this area be closed. - 4 - f .