ARCHIVED REPORTS_XR0008315 - Laserfiche WebLink

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Chemical analysis The groundwater samples collected were analyzed for Total Petroleum Hydrocarbons as Gasoline (TPHG) ; Benzene, Toluene, Ethylbenzene an Xylene (BTEX) and Methyl--tert-butyl ether (MTBE) . The gro dwater samples were analyzed for TPHG by EPA Method 8015 modeed with purge and trap preparation 5030 (GC/FID) with detec on limits of 50ug/l . EPA Method 602 was utilized for BTEX with XB. limit of 0. 5ug/1 as required by the SJCEHD. The re analysis of the groundwater samples in parts per billie shown in Table 3 . The laboratory data sheets with limits and COC documentation are contained in AppenTABLE 3 96 roundwater Sample Analysis Results in ppb. Sample TPHG MTBE B T E X MW-1 73 ND ND ND ND ND MW- 1 5 , 300 38 1, 600 34 36 22 MW-3 ND ND 2 . 8 ND ND ND ND = Nat Detecte The concentrations of TPHG and BTEX in the groundwater collected from MW-2 are high. Quarterl s ing should be continued. SUMMARY CONCLUSIONS AND RECOMMENDA US The groundwater samples from wells MWnd MW-3 had actionable levels of Benzene and from well MW-2 a ion e levels of TPHG. The calculated gradient is to the\�Southea approximately 0 05 ft/ft. The calculated gradient in the priorerly measurement had shifted from a southwesterly to a, southeaCte direction with a slight slope . The calculated gradient hasuc g eater slope i . e. 0 . 05 ft/ft. The field had been irrigated a sho time before the water depth was measured. The ocal groun at r recharge conditions irrigation and slough depths are most 1 y the in influences on the gradient. The concentrations of TPHG and BTEX in the, groundwate`k are less than the values initially reported in the� pri.or environmental investigation at this site. Continued quarterly monitoring readings obtained over a longer period of time should indicate a consistent gradient or provide a reason \for the gradient I 6 l