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Date: January 31,2005 Quarter- 4a'Quarter,2004 f • • The result for 1,2-dichlorethane (1,2-DCA) in sample VW-12 should be considered estimated The result exceeded the calibration range of the instrument • The reported results for ethylbenzene in samples VW-1 and VW-11, 1,2-DCA in samples VW-5 and VW-7,benzene in samples VW-8 and VW-11, and all EPA Method 8260E analytes in sample VW-10 should be considered estimated, the samples were initially analyzed within holding time but required dilution The dilution was performed out of holding time The results from the reanalysis are summarized in this report • The EPA Method 8260B results for sample VW-12 were flagged by the laboratory because the initial calibration requirements were not met Recoveries were acceptable for all target compounds The data are not impacted • The elevated reporting limits in the EPA Method 8015B analysis of samples VW-2 and VW-5 were due to instrument insensitivity in these samples • The elevated reporting lirruts were the result of dilutions performed by the laboratory in order to quantitate a target analyte DISCUSSION: GRO, benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tert-butyl ether (MtBE), and 1,2-DCA were detected above laboratory reporting limits in groundwater samples collected from site wells this quarter GRO and benzene concentrations in the monitoring wells (MW) were generally consistent with previous quarters MtBE was detected above laboratory reporting limits in the following MWs this quarter MW-2 at 0 60 micrograms per liter (µg1L),MW-3 at 2 2 pg(L,and MW-4 at 18 gg/L This is the first detection of MtBE in MW-4 since December 1998 . and the only concentration of MtBE over the secondary maximum contarrunant level (MCL) of 5 pg(L reported in the MWs since December 2003 (MW-6) GRO, benzene, and MtBE concentrations in the vapor extraction wells (VW)were generally consistent with historical data with a few exceptions In VW-7,MtBE concentrations increased from 12 tig/L, reported during third quarter 2004, to 13 /Cg/L this quarter The increase in MtBE concentration is generally consistent with an increase in concentration reported from third quarter 2003 (<0 5 µg/L)to fourth quarter 2003 (9 1 µg/L) In VW-8, GRO concentrations decreased from 51,000 yg/L,a historic high concentration reported in this well during third quarter, to 15,000 pg/L and benzene concentrations decreased from 2,400 tig/L, reported during third quarter, to 1,200 pg/L this quarter (estimated concentration per previous section) In VW-10, GRO concentrations increased from 640 pgfL during third quarter to 34,000 pg/L this quarter This is a historic high GRO concentration detected in VW-10 Additionally in VW-10, the BTEX compounds increased significantly relative to the previous quarter but, as discussed in the previous section, these results should be considered estimated and are generally consistent with increased concentrations reported during the fourth quarter of 2003 with the exception of toluene GRO and benzene concentrations in VW-11 were reported at the highest concentrations historically(1,000 1ig/L,and 48 pg/L,respectively)but are also considered estimated per the previous section Depth to water at the site was approximately 45 feet bgs during this quarter Groundwater elevations increased approximately three feet relative to the previous sampling event The inferred direction of groundwater flow across the site ranged from the southeast to southwest with an average hydraulic gradient of 0 01 ft/ft I K%Wp�mV5 BP ARC0W130\Quanv1y1200444 QTR 0412130 GWMR 4Q04 dm Page 2