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r <br /> yW,4#10 OPNml9ll.cullLLSNfi!� <br /> Mr. Michael Collins, REHS September 15, 1993 <br /> San Joaquin County Public Health Services Page 2 <br /> Quarterly Groundwater Sampling Results SummaU <br /> Table 1 summarizes analytical results for groundwater samples collected from the site since <br /> January 1987. All quarterly groundwater sampling results since December 1991, as well as <br /> initial groundwater sampling in 1987, have consistently shown non-detectable results for both <br /> total petroleum hydrocarbons as gasoline (TPH-G) and benzene, toluene, ethylbenzene and <br /> xylenes (BTEX). <br /> TABLE I <br /> Historical TPH-G and BTEX Concentrations in Groundwater Summary (;.g/L) <br /> San Joaquin County Mosquito and Vector Control District <br /> Beckman Road Site <br /> Well ID Sample Date <br /> January 1987 December 1991 August 1992 November 1992 January 1993 <br /> MW-1 ND NDS ND —z -- <br /> MW-2 ND -- -- -- <br /> MW-3 ND -- -- -- -- <br /> MW-4 NI NI3 ND ND ND <br /> 1. ND = not detected above laboratory detection limit <br /> 2. Monitor well not sampled due to the well being dry <br /> 3. NI = monitor well not yet installed <br /> This site has been under investigation and/or monitoring for approximately six years. The <br /> District has shown responsiveness and due diligence in their efforts to respond to EHD's <br /> requests and all groundwater sampling results indicate that groundwater on this site has not been <br /> impacted by TPH-G or BTEX compounds. Hence, WESTON recommends no additional <br /> quarterly groundwater monitoring on the site. <br /> Should you have any questions regarding this information and recommendation, please do not <br /> hesitate to contact me in the Stockton office or John Stroh of the District. <br /> Sincerely, <br /> ROY F. WESTON, I C. <br /> Robert M. Sengebush, R.G. <br /> Project Manager <br /> RMS/cmc <br /> cc: John R. Stroh, SJCMVCD <br /> Christopher K. Eley, Attorney at Law <br /> Diane Hinson, San Joaquin County EHD <br /> MXWMSICOLL[NS.WPI <br />