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1989 is still in use (see preceding paragraph) Nine additional wells were identified in the survey, <br /> these wells are located over 1,500 feet from the site <br /> 7.0 Conclusions <br /> Soil sample data indicates petroleum hydrocarbon impacted soil is present between 4 feet <br /> (Pipeline sample PBPL-2[2']) and 12 feet bsg (excavation sample PBTP-1[12']) in the vicinity of <br /> the former UST The remaining petroleum hydrocarbons have low volatility and are relatively <br /> immobile Laboratory analytical data indicates the remaining hydrocarbons are non-hazardous in <br /> concentration Based on the depth and the low mobility of the remaining petroleum <br /> hydrocarbons, the soil plume is not likely to affect potential and existing beneficial uses of <br /> groundwater <br /> Based on the findings of this report, this site can be categorized as a low-risk site The majority of <br />' impacted soil has been removed,with only minor concentrations of impacted soil present adjacent to <br /> the former UST system Results of the analysis of groundwater samples collected in the vicinity of <br /> the UST system indicate the TPH-D-Impacted groundwater has not migrated The site presents no <br /> significant risk to human health or the environment Natural degradation will likely remediate the <br /> • remaining petroleum hydrocarbon soil plume No further action is recommended <br />' Case closure is recommended, along with proper destruction of the associated monitoring wells <br /> upon permission from the S]CEHD <br /> 8.0 References <br />' Central Valley Regional Water Quality Control Board (RWQCB, 1994),Appendix B Tri- <br /> Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of <br /> Underground Storage Tank Sites, No Further Action Requests, March 1, 1994, Draft Revision <br /> October 1996 <br /> Central Valley Regional Water Quality Control Board(RWQCB, 1998), The Water Quality <br />' Control Plan (Basin Plan)for the California Regional Water Quality Control Board Central <br /> Valley Region, Fourth Edition-1998, September 1998 <br />' Department of Water Resources (DWR, 2003), California's Groundwater Bulletin 118, San <br /> Joaquin River Hydrologic Region, Tracy Groundwater Basin, September 1, 2003 <br />' CNCDISHAR.EIUSTN04.0001 doe 6 <br /> 1 <br />