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1 � r <br /> Geological Technics Inc Page 6 <br /> 1 Ripon Milling Inc <br /> Report-Groundwater Investigation <br /> �) Project No 253 2 <br /> July 31, 1995 <br /> 1 <br />' 2.0 CONCLUSIONS AND RECOMMENDATIONS <br /> From the data generated during this assessment and the previous tank excavation <br />' work, the following conclusions are drawn <br /> • The excavation work performed after the tank was removed was successful in <br />' removing the soil impacted by the release of diesel from these tanks This is <br /> evidenced by both the confirmation soil samples collected at the bottom of the <br /> excavation and the soil samples from borehole MW-1 were non detect for the <br />' hydrocarbon compounds tested for (TPH-gasoline, TEPH-diesel, and BTEX) <br /> • The relatively low levels of benzene, toluene and xylene (BTX) detected in both <br />' rounds of groundwater samples suggest that the groundwater may have been <br /> impacted by a release of petroleum hydrocarbons The source of these BTX <br /> compounds is not clear at this time <br /> • The fact that onlyBTX compounds have been detected com p c ed n the groundwater <br /> during these two monitoring events, that the compounds were present at <br /> rapproximately the same concentrations in both monitoring events, and that no <br /> diesel was detected in the groundwater, indicates that the diesel contained in the <br /> storage tanks at this site was not the source of the BTX compounds discovered in <br /> the groundwater <br /> • The Nestle facility adjacent to the east of Ripon Milling is presently undergoing a <br /> groundwater investigation and it is possible that the chemical compounds <br /> detected in MW-1 are sourced from this site and have migrated onto the Ripon <br /> site by the flow of groundwater or by diffusion Further investigation (starting <br /> with a review of the Nestle file at SJCPHSEHD) would be required to evaluate <br /> the probability of this <br /> Geological Technics Inc recommends that the significance of these relatively low <br /> levels of aromatic range petroleum hydrocarbons be evaluated by the following <br /> I • a reviewof the Nestle file at SJCPHSEHD be performed, <br /> • hold a meeting with SJCPHSEHD personnel to discuss these results, and <br /> • perform additional monitoring to determine if the BTX concentrations change <br /> I <br />