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r <br /> CHAPTER 5 <br /> SUMMARY AND SUGGESTED REMEDIAL ACTIOV <br /> Total fuel hydrocarbons, benzene, toluene, and xylene (BTX) , and <br /> total lead concentrations in the soil were below California Regional <br /> Dater Quality Control Board, Central Valley Region (Regional Board) , <br /> designated levels. Dissolved fuel hydrocarbons and BTX <br /> concentrations above California Department of Health Services <br /> action levels were identified in the {DHS) <br /> bon <br /> film exists as free product on the groundwater. <br /> Ainh wells W-2 rand <br /> W-3, and possibly in Well tV-1. This section identifies possible <br /> remedial action alternatives. It is unknown at this time whether <br /> municipal wells other than Well 12 are threatened. No threats to <br /> nearby buildings or utilities were identified. <br /> 3 Soil <br /> r <br /> The soil at the locations of wells W-1, W-2, and W-3 does not <br /> appear to contain significant levels of hydrocarbons. Therefore, <br /> rA excavation on--site soil aeration, <br /> landfilling are probably off-site soil treatment, and <br /> { � unnecessary. If subsequent soil <br /> ..x problems <br /> are encountered, soil venting would be the <br /> preferred option. <br /> qi Groundwater <br /> Benzene concentrations in each groundwater sample exceeded the <br /> DHS . action level of 0.7 microgramser liter <br /> xylene concentrations exceeded DHS action levels(ug/1) <br /> lmonitoringnwells <br /> W-2 . and W-3. The 'highest concentrations of dissolved fuel <br /> 2 pw <br /> hydrocarbons and BTX were identified in monitoring well W-3. <br /> Groundwater extraction and treatment by air strip <br /> inossibly <br /> in conjunction with carbon filtration, would meet the main,objectiive <br /> of removing dissolved hydrocarbons from the <br /> i• site. Recovering the groundwater b groundwater beneath the <br /> Y pumping would be possible if: <br /> {l) Well 12 is kept out of service during clean up to avoid <br /> overpowering the low pumping rate of the recovery well 6y the <br /> stronger .pumping rate of well 12, or (2) by injecting water between <br /> the plume and Well 12 creating a reverse gradient in the direction of <br /> ARCO Service Station 434, The extent of the plume <br /> to be identified, would first have <br /> s <br /> T The feasibility of biodegradation T- <br /> Physical containment and chemical neutralizare <br /> is unknown at this time. <br /> impractical at this site, tion ajudged to ..be <br /> Details of an agreed-upon remedial plan will be discussed in a <br /> separate report. <br />