ARCHIVED REPORTS XR0000817 - Laserfiche WebLink

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Date. January 24,2005 Quarter 4`"Quarter,2004 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-1B is due to a discrete peak in the quantitation range(probably methyl tert-butyl ether[MtBE]) • The elevated reporting limits in the methanol analysis of samples MW-4, MW-6, VW-1B, and VW-3B were due to the presence of matrix interference in these samples • 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), and 1,2- dichloroethane (1,2-DCA) 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-I increased relative to the previous quarter but remain significantly below historic high concentrations MtBE concentrations increased in VW-IB but are consistent with first quarter 2004 In VW-2B, GRO, benzene, toluene, total xylenes, 1,2-DCA, and TBA were reported at the highest concentrations since sampling began in March 2001 and MtBE concentrations increased but remain within historic ranges In VW-3B, MtBE and total xylenes concentrations increased relative to the previous quarter 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 Dow direction across the site was toward the southeast at an average hydraulic gradient of 0 03 ft/ft The SVE system began operations on August 30,2004 Approximately 30 4 lbs of GRO and 0 48 lbs of MtBE were removed during the fourth quarter 2004 No benzene was removed due to non-detect influent concentrations The SVE system operated in compliance with the San Joaquin Valley Air Pollution Control District (SJVAPCD) Initial sampling and flow data was submitted to SJVAPCD on September 28, 2004 The system was shutdown on September 7,2004,due to excessive noise The system was restarted on November 30,2004, after a sound enclosure was installed A performance evaluation of the remedial systems between October 1, 2004,and December 28, 2004, are presented as Appendix A K\WP-cessV5 BP ARC0102]86\Quwn JyVW414 QTR 04\2186 GWMR 4QC4 dor Page 2