ARCHIVED REPORTS_XR0008315 - Laserfiche WebLink

Home Browse Search

� rtr � Chemical analysis } z HEALTH • The groundwater samples collected were analyzed f tal Petroleum Hydrocarbons as Gasoline (TPHG) ; Benzene, Tolu � CjEtIO)Vnfne and Xylene (BTEX) and Methyl-tert-butyl ether (MTBE) . he groundwater samples were analyzed for TPHG by EPA Method 8015 modified with purge and trap preparation 5030 (GC/FID) with detection limits of 50ug/l. EPA Method 602 was utilized for BTEX with a detection limit of 0. 5ug/l as required by the SJCEHD. The results of the analysis of the groundwater samples in parts per bl-llion (ppb) are shown in Table 3 . The laboratory data sheets with detection limits and COC documentation are contained in Appendix B. TABLE 3 June 10, 1996 Groundwater Sample Analysis Results in ppb. Sample TPHG MTBE B T E X MW-1 73 ND ND ND ND ND MW-2 5, 300 38 1,600 34 36 22 HAW-3 ND ND 2. 8 ND ND ND ND = Not. De ecUe-a • The concentrations of TPHG and BTEX in the groundwater collected from MW-2 are high. Quarterly sampling should be continued. SUMMARY, CONCLUSIONS AND RECOMMENDATIONS The groundwater samples from wells MW-2 and MW-3 had actionable levels of Benzene and from well MW-2 actionable levels of TPHG. The calculated gradient is to the southeast at approximately 0. 05 ft;ft. The calculated gradient in the prior quarterly measurement had shifted from a southwesterly to a southeasterly direction with a slight slope. The calculated gradient has a much greater slope i . e. 0. 05 ft/ft. The field had been irrigated a short time before the water depth was measured. The local groundwater recharge conditions irrigation and slough depths are most likely the main influences on the gradient. The concentrations of TPHG and BTEX in the groundwater are less than the values initially reported in the prior 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 6