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29 January 1998 <br /> AGE-NC Project'No 95-0184 <br />' Page 4 of 4 f <br />' • Ground water is currently within the screened interval in four vapor wells The data collected <br /> from these wells should be representative of shallow ground water conditions <br /> • The data is suggestive of two plumes of impacted ground water, one plume centered near <br />' Tank A and the second plume centered near former Tanks B and C The area of well MW-7 <br /> may be in an area of co-mingling of the plumes , <br />' • Petroleum hydrocarbons were detected in soil samples collected from each boring advanced <br /> at the site The lateral extent'of hydrocarbon-impacted soil at the site has not been defined <br /> The San Joaquin County PHS/EHD is anticipated to require additional assessment to <br /> determine the extent of impacted soil <br /> I5.0 RECOMMENDATIONS <br /> Based upon data collected from the site, AGE recommends the following <br /> • Additional monitoring wells should be installed to define the horizontal extent of <br /> hydrocarbon-impacted ground water We recommend the installation of monitoring wells in <br /> the sidewalk approximately 80 feet east of MW-4, southeast of MW-4 across Miner Avenue <br /> and inside the building at 825 Miner Avenue, approximately 80 feet north of MW-4 These <br /> wells will help delineate the eastern, down-gradient margin of the ground water plume(s) <br /> • A soil vapor extraction/in-situ air sparging pilot test should be conducted to evaluate these <br /> remediation options for this site Findings of the vapor extraction/air sparging test can be <br /> Iused to determine the spacings of potential additional vapor and sparging wells <br /> • Additional soil sampling should be performed to define the lateral extent of the hydrocarbon- <br /> impacted soil plume to determine the number of additional vapor and sparging wells required <br /> for effective remediation <br /> I • The next ground water monitoring event is scheduled for 30 January 1998 <br /> 60. LIMITATIONS <br /> Our 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 /> 11 analytical results provided by an independent laboratory Evaluations of the geologic/hydrogeologic <br /> conditions at the site for the purpose of this investigation were made from a limited number of <br /> 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 /> Advanced CeoEn,iron mental,Inc <br /> I <br />