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1 1 <br /> 05 April 1996 <br /> AGE-NC Project No 95-0111 <br /> Page 5 of 6 <br />' 5.0. CONCLUSIONS AND RECOMMENDATIONS <br />' 51 HYDROCARBON-IMPACTED SOIL <br /> Petroleum hydrocarbons have been detected in soil samples collected from the site between depths <br />' of 5 and 15 feet bsg However, because of the relatively shallow ground water depth at the site <br /> (approximately 7 to 8 feet bsg), most of the impacted soil is present in the capillary fringe or saturated <br /> zones The vertical distribution of hydrocarbons in the capillary fringe or saturated zones may be the <br />' result of fluctuating ground water elevations creating an extensive"smear zone" at the site' , <br /> Remediation of impacted soil at the site, if necessary, should be performed in conjunction with <br />' mitigation of hydrocarbon-impacted ground water <br />' 5 2 HYDROCARBON-DvIPACTED GROUND WATER <br /> Free product has been encountered at the site Therefore, according to California Underground <br /> Storage Tank Regulations, Article 5, Section 2655, a free product removal system must be <br /> implemented at the site We recommend monthly measurements of free product thickness in wells <br />' MW-4 and MW-5 If present, free product will be removed by hand bailing Results of free product <br /> removal procedures will be reported in regular Quarterly Reports <br />' Free product removal should minimize migration of the impacted ground water However, if <br /> analytical results of ground water samples indicate that the free product or dissolved hydrocarbon <br /> plume is nvgrating, initiation of interim remedial action may be required Based upon the lithology <br />' and extent of impacted ground water encountered in Grant Line Road (City of Tracy - Right of Way), <br /> a"pump and treat" system, in the vicinity of MW-4 and MW-5, may be necessary to prevent further <br /> migration of contaminants I <br />' Since free product has been encountered in wells MW-4 and MW-5, installation of one additional <br /> ground water monitoring well, east (down-gradient) of MW-4 may be required to determine the <br /> lateral extent of hydrocarbon-impacted ground water The proposed monitoring well location is <br /> illustrated on Figure 2 Installation of a ground water extraction well and/or rte-situ air spargmg (IAS) <br /> wells should also be considered to perform remediation feasibility testing <br /> We recommend schedulingthe next quarterly monitoring at the site for June 1996 If additional <br /> q Y g <br /> monitoring wells, extraction wells or IAS wells are required, installation procedures should be <br /> performed prior to June 1996 <br />