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i <br /> I27 July 1998 <br /> . AGE-NC Project No 95-0104 <br /> Page 4 of 4 <br /> • A plot of TPH-g and benzene concentrations over time versus ground water elevation over <br />' time (Appendix C) suggests a negative correlation at well MW-5, that is, as one increases, <br /> the other decreases <br /> • Concentrations of benzene detected in samples collected from wells MW-1 and VW-1 were <br /> above the State of California Maximum Contaminant Level (MCL) for drinking water of 10 <br /> ppb <br /> • Concentrations of toluene were above the MCL of 150 ppb in well VW-I <br /> • Utilizing EPA Method 8020, concentrations of MTBE were not detected above the <br /> laboratory reporting limits, however, utilizing EPA Method 8260B, MTBE was detected in <br /> samples collected from wells MW-1 and VW-1 at concentrations as high as 1 5 ppb <br /> • Utilizing EPA Method 8260B, TBA was detected from wells MW-6 and VW-1 at <br /> concentrations as high as 6 9 ppb <br /> • The elevated concentrations of petroleum hydrocarbons detected in samples collected from <br /> well VW-1 indicates that this well is within or near the "core area"of the plume of dissolved <br /> petroleum hydrocarbons <br /> I• <br /> 5.0. RECOMMENDATIONS <br /> IBased upon the results esults of this investigation, AGE recommends the following <br /> • Initiation of a soil vapor extraction/air sparging pilot test upon preapproval by the UST <br /> Cleanup Fund <br /> I • Continued quarterly monitoring and sampling of selected ground water monitoring wells, <br /> currently scheduled for September 1998 <br /> 6.0. LIMITATIONS <br /> IOur professional services were performed using that degree of care and skill ordinarily exercised by <br /> environmental consultants practicing in this or similar localities The findings were based upon <br />' analytical results provided by an independent laboratory Evaluations of the geologic/hydrogeologic <br /> conditions at the site for the purpose of this investigation are made from a limited number of <br /> I available data points (i a monitoring wells) and subsurface conditions may vary away from these <br /> data points No other warranty, expressed or implied, is made as to the professional <br /> recommendations contained in this report <br /> I <br /> Advanced GeoEnvironmental,Inc <br /> I <br />