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r <br /> 1 <br /> May 2001 Quarterly Ground Water Monitoring <br /> 1645 Cherokee Lane,Stockton,CA <br />' Hydro Environmental Technologies,Inc. <br /> 3.0 CONCLUSI®NS AND REC®IVIMENDATI®NS <br /> 3.1 Conclusions <br /> Residual TPH as diesel remain in soil and ground water on the subject property Diesel concentrations <br />' have decreased from the initial sampling event where TPH as diesel was detected at 100 parts per billion <br /> (ppb) in MW-1 and MW-3 and at 87 ppb in MW-2 For the first quarter sampling event, TPH as diesel <br /> was detected at 60 ppb in MW-1 and at 89 ppb in MW-3, no detectable concentrations of TPH as diesel <br />' was found in MW-2 No detectable concentrations of TPH as gasoline, BTEX, the five fuel oxygenates, <br /> 1,2-DCA and EDB were found in the ground water samples submitted for analysis <br />' 3.2 Recommendations <br /> Ground water monitoring will continue for three additional quarters HETI recommends that no- or non- <br /> purge ground water sampling methods be instituted at this site According to an American Petroleum <br /> Institute (2000) study, no purge ground water sampling has been successfully used for routine ground <br /> water monitoring at fuel hydrocarbon sites where monitoring wells are <br /> (1) not impacted by non-aqueous phase liquids, <br />' (2) are in unconfined aquifers and are screened through the aquifer, <br /> (3)have prior monitoring data from conventional sampling <br /> No purge sampling has also been endorsed by the Santa Ana Regional Water Quality Control Board <br />' (1997) and by the Los Angeles Regional Water Quality Control Board (1997) <br /> Because no TPH as gasoline has been detected in the initial and first quarter ground water monitoring <br />' event, HETI recommends that the five fuel oxygenates be removed from the subsequent ground water <br /> monitoring rounds <br />' References cited are in Appendix C Limitations to this report are in Appendix D <br /> 4 <br />