ARCHIVED REPORTS XR0000816 - Laserfiche WebLink

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Date: April 28,2005 Quarter 1st Quarter,2005 ANALYTICAL DATA REVIEW: Based on the review of the analytical and hardcopy data (chain-of-custody records,blanks, dilutions, holding times, LCS/LCSD results,MSIMSD results,and surrogate recoveries),the data are acceptable as reported by the laboratory with the following limitations • The reported result for gasoline range organics (GRO) in sample VW-213 is due to a discrete peak in the quantitation range(probably methyl tert-butyl ether[MtBE]) • The reported result for ethanol in MW-3 may be biased low due to a low average percent recovery reported in the associated MS/MSD analysis • The reported results for ethanol in samples MW-2 and MW-3 were confirmed on reanalysis, the results from the initial analysis are summarized in this report • The elevated reporting limits were the result of dilutions performed by the laboratory in order to quantitate a target analyte DISCUSSION: GRO, benzene, toluene, ethylbenzene, total xylenes (BTEX), MtBE, tert-butyl alcohol (TBA), 1,2-dichloroethane (1,2-DCA), and ethanol were detected above laboratory reporting limits in groundwater samples collected from site wells this quarter GRO, benzene, ethylbenzene, total xylenes, and MtBE concentrations in MW-1 increased relative to the previous quarter but remain significantly below historic high ranges Ethanol was detected above laboratory reporting limits in monitoring wells MW-2 (320 micrograms per liter[µgIL])and MW-3 (280 pg/L)for the first time historically In MW-4, GRO was not detected and MtBE concentrations decreased to the lowest concentration • reported since June 1999 A low-level concentration of total xylenes was detected in MW-8 this quarter In VW-1B, GRO was not detected and MtBE concentrations were reported at the lowest concentration historically In VW-213, GRO and MtBE concentrations decreased and benzene,toluene,total xylenes,TBA,and 1,2-DCA were not detected above laboratory reporting limits (two dilution factor) In VW-3B, GRO and total xylenes were not detected and MtBE concentrations decreased to the lowest level reported since March 2001 Other analyte concentrations were generally consistent with historic data Groundwater elevations in wells across the site increased relative to the previous quarter The inferred groundwater flow direction across the site was toward the southeast at an average hydraulic gradient of 0 04 ft/ft The SVE system began operations on August 30, 2004 Approximately 369 6 lbs of GRO, 0 09 lbs of benzene and 2 94 lbs of MtBE were removed during the first quarter 2005 The SVE system operated in compliance with the San Joaquin Valley Air Pollution Control District (SIVAPCD) Initial sampling and flow data was submitted to SJVAPCD on September 28,2004 A performance evaluation of the remedial systems between January 1,2005, and March 31,2005,are presented as Appendix A K 1WP-ccss1E5 BP ARC01021861Q--nert)'s200511 QTR 0512186 GWMR 1Q05 dw Page 2