ARCHIVED REPORTS XR0000212 - Laserfiche WebLink

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4 0 SUMMARY AND CONCLUSIONS ' o December 3, 1998 groundwater elevation data indicates the groundwater flow direction beneath the site is towards the east, with an average hydraulic gradient of 0 0027 meter per meter (0 0027 foot per foot) ' o Groundwater elevations have nsen an average of 0 18 meters (0 61 feet) from the previous average elevations measured for the Third Quarter 1998 monitoring event o TPH-G concentrations were detected in two of the seven groundwater samplesN M-1 [1,000], and VM-2 [4,200 pg/11) The concentrations have significantly decreased since ' the previous quarterly sampling event MTBE was not detected in any of the monitoring wells sampled this quarter and ' analyzed by EPA Method 8260 Benzene concentrations were detected in six of seven groundwater wells sampled (MW-12 [2 0 pg/1], MW-14 [0 9 pg/l], MW-24 [0 9 pg/1], MW-25 [18 pgll], VM-1 [82 pg/1], VM-2 [510 pg/11 The concentrations have generally decreased since the previous quarterly sampling event BTEX concentrations in Wells VM-1 and VM-2 have significantly decreased since the previous quarterly sampling event The oxygenates TBA, DIPE, ETBE, and TAME were not detected in any groundwater ' samples this quarter Gasoline related volatile organic compounds were reported in the EPA Method 8260 analysis o The chlorinated solvent 1,2-Dichloroethane (1 ,2-DCA) was detected in VM-1 (15 pg/1), VM-2 (230 ug/1) and MW-14 (1 0 ug/1) All the reported concentrations exceed the MCL (0 5 ug/1) ' a Four monitoring wells sampled this quarter at the site had benzene concentrations above the State of California Primary Drinking Water Standards (PDWS) for benzene ' 5 0 RECOMMENDATIONS As benzene concentrations in four monitoring wells and 1,2-DCA concentrations in three monitoring wells exceeded the MCL, PSI recommends that quarterly sampling continue at the site 4 P NTS.SPER\pROdrMCALTI 7 71017 :--,P1O\t'4,HFIN DOC