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k' ■ KLEINFELDER ' Kleinfelder referenced the San Joaquin County Flood Control and Water Conservation District (SJCFC/WCD) "Lines of Equal Depth to Groundwater, Spring 1999" Map. It is Kleinfelder's understanding that more recent depth to groundwater maps have not been generated through SJCFC/WCD since 1999. According to this map, depth to groundwater is estimated at ' approximately 40 feet bsg in the general proximity to the subject site. No fractures or conduits were noted in the assessment area (excavation) and the soil was noted as a black silty clay to clay. Please note this leaching potential assessment is general in nature. Additional site specific details such as percolation rates, soil leaching analytical results, etc was not conducted by Kleinfelder for the purpose of a more detailed and thorough leaching potential assessment. ' The 1 eaching p otential w orksheet s core (Attachment D) w as a in iddle r p ang e 4 4 oints, w hich correlates with the following allowable concentrations in soil according to the county worksheet: ' 1,000 mg/kg TPH-D, 100 TPH-G, 300 µg/kg benzene, 300 µg/kg toluene, 1,000 µg/kg xylenes and 1,000 µg/kg ethylbenzene. Based on this evaluation TPH-G, TPH-D and BTEX ' concentrations did not exceed these allowable concentrations. Although TPH-MO concentrations are not directly addressed in the attached worksheet, TPH- ' MO was detected at the site at concentations ranging from 40 to 280 mg/kg. TPH-MO is a heavier extractable compound than diesel and generally does not leach as readily as TPH-D constituents. Therefore it is Klemfelder's opinion that these values of TPH-MO would not be ' more inclined to present a leaching potential threat to groundwater then the TPH-D at similar concentrations. A dditionally t his a rea i s p roposed t o b e h ardscaped b y the c ontractor, w hich would additionally decrease leaching potential of said contaminants. ' CONCLUSIONS ANDS RECOMMENDATIONS ' Based on Kleinfelder's experience with similar projects and based on the data presented in this report, it is Kleinfelder's opinion that the petroleum constituent concentrations detected at the site would not generally trigger additional sampling or enforcement actions by regulatory ' enforcement agencies. Kleinfelder however recommends submitting this report to San Joaquin County Public Health ' Services Department Environmental Health Division (PHS/EHD) for their review and comment. This report, and the conclusions and recommendations presented in this report are subject to the ' "Limitations" presented below. Any other party (other than SJRTD or regulatory agencies having enforcement jurisdiction for this site) who would like to use this report shall notify Kleinfelder, Inc. of such intended use in writing for permission. 51726/ST05R157/DH:ly Page 5 of 7 ' °2005,Kleinfelder,Inc. February 8,2005