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ults <br /> Ms Margaret Lagono Page 8 <br /> San Joaquin County Environmental Health Department <br /> June 27, 2003 <br /> These levels do not threaten the beneficial use of groundwater as shown by the continuing downward <br /> i trend of contannation identified in groundwater In addition, the contamination does not represent a <br /> threat to human health since the contamination does not occur near the ground surface and the levels <br /> identified are low and will continue to degrade naturally over time <br /> GROUNDWATER IMPACTS SUMMARY <br /> Historical groundwater investigations delineated the extent of groundwater impacts at the site Recent <br /> groundwater sampling occurring from January 2000 to June 2003 show that concentrations of fuel- <br /> related compounds have naturally attenuated to levels that no longer threaten the beneficial use of <br /> groundwater The highest concentrations in groundwater were reported in 2000 and low concentrations <br /> of contaminants detected during 2003 are restricted to wells W-2 and W-2A <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Based on a review of historical soil and groundwater investigations, Arco Station 434 is considered "low <br /> risk" as set forth in State of California standards for USTs Therefore, this site is recommended for <br /> closure and no further investigation or remediation should be warranted at this site The source of the <br /> contamination has been removed from the site, and additional excavation of impacted soil occurred <br /> during the 1999 tank upgrade activities The levels of soil contamination existing at the site are <br /> extremely low and therefore do not represent a threat to human health and do not threaten the beneficial <br /> use of the groundwater Current contaminants in groundwater are restricted to two on-site wells and will <br /> continue to decrease in those wells to levels that are below method reporting limits <br /> Other than the municipal well Iocated approximately 240 feet south-southeast of the site, there are no <br /> sensitive receptors within 2,000 feet of the site (Attachment 1) Based on the declining groundwater <br /> sample results and the limned extent of contamination, this off-site receptor is not threatened by site <br /> contamination <br /> This document is based on data, site conditions, and other information that are generally applicable as of <br /> the date of the document, and the conclusions and recommendations herein are therefore applicable only <br /> ' to that time frame <br /> • <br /> K 1WprocessV5 6P ARCO\004341Closure Requestlstabon 434 Closure Doc doc <br />