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�.7
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<br /> Date May 13,2004
<br /> Quarter 151 Quarter,2004
<br /> Based on the review of the analytical and hardcopy data (chain-of-custody records,blanks, dilutions, holding times,
<br /> LCS/LCSD results,MS/MSD results, and surrogate recoveries),the data are acceptable as reported by the laboratory
<br /> with the following limitations
<br /> • The results for tetrachloroethene (PCE) in samples MW-6 and MW-7 should be considered estimated,
<br /> the results were above the calibration range The PGE result reported for sample MS-1A may be the
<br /> result of carryover
<br /> • The reported results for methanol in sample VW-1 may be biased low as demonstrated by a low
<br /> surrogate recovery due to matrix interference
<br /> • The reported results for gasoline range organics (GRO) in samples MW-6 and MW-7 are due to a
<br /> discrete peak at 7 5 minutes(probably PCE)
<br /> • The reported results for trichloroethene (TCE), benzene, 1,2-dichloroethane(1,2-DCA), ethylbenzene,
<br /> methyl tert-butyl ether(MtBE),and total xylenes in samples VW-1, VW-3, and VW-11 may be biased
<br /> high as demonstrated by a high surrogate recovery due to matrix interference
<br /> • The reported results for total xylenes in sample MW-1 may be biased low due to a low average percent
<br /> recovery reported in the associated MS/MSD analysis
<br /> • The elevated reporting limits reported in the methanol analysis of samples VW-1, VW-3, VW-8, and
<br /> VW-11 were due to the presence of coeluting organic compounds in these samples
<br /> • The elevated reporting limits were the result of dilutions performed by the laboratory in order to
<br /> quantitate a target analyte(s)
<br /> . DISCUSSION:
<br /> GRO, benzene, toluene,ethylbenzene,total xylenes(BTEX),methyl tert-butyl ether(MtBE), and 1,2-dichloroethane
<br /> were reported above method detection limits in groundwater samples collected from site wells this quarter Analyte
<br /> concentrations were generally consistent with historic data with the following exceptions in MW-5, GRO was
<br /> reported at the highest concentration since December 1994,benzene and ethylbenzene were reported at the highest
<br /> concentrations since September 1996, and total xylenes was reported as below method detection limits for the first
<br /> time since March 2002 In MW-6,GRO concentrations decreased,MtBE and tert-butyl alcohol(TBA) were reported
<br /> as below method detection limits, and 1,2-DCA decreased from 140 micrograms per liter (pglL) last quarter to 2 1
<br /> gg/L this quarter A low-level concentration of GRO was reported above method detection limits in MW-7 for the
<br /> first time since March 1994 and 1,2-DCA was reported above method detection limits for the first time at 2 0µg/L
<br /> GRO increased to the highest concentrations historically in VW-3, VW-11, MS-2A, MS-213, and MS-3A this
<br /> quarter In VW-1, GRO concentrations increased and TBA was reported as below method detection limits GRO
<br /> and 1,2-DCA concentrations decreased in VW-2 In VW-4, GRO, benzene, and ethylbenzene concentrations were
<br /> reported at the highest levels historically and total xylenes and 1,2-DCA were reported as below method detection
<br /> limits this quarter GRO and 1,2-DCA concentrations in VW-5 and VW-7 decreased this quarter GRO,benzene and
<br /> ethylbenzene concentrations in VW-8 increased relative to the previous quarter but are generally consistent with
<br /> concentrations reported during third quarter 2003 In VW-10, GRO,benzene,and ethylbenzene were reported at the
<br /> lowest concentrations historically and toluene, total xylenes,and 1,2-DCA were reported as below method detection
<br /> limits this quarter TBA was reported as below method detection limits in VW-1 I In VW-12,GRO and MtBE were
<br /> reported as below method detection limits and 1,2-DCA decreased from 150 jigfL last quarter to 2 9 ug/L this
<br /> quarter In MS-lA and MS-113, benzene concentrations decreased, toluene, ethylbenzene, and total xylenes were
<br /> reported as below method detection limits, and MtBE was reported at the highest concentrations relative to historic
<br /> data In MS-2A and MS-2B, benzene and ethylbenzene concentrations increased, toluene and total xylenes were
<br /> reported as below method detection limits, and MtBE was reported at the highest concentrations relative to historic
<br /> sampling events In MS-3A and MS-313, benzene concentrations increased, toluene concentrations decreased to dust
<br /> • above method detection limits, and total xylenes were reported as below method detection limits relative to the
<br /> previous quarter
<br /> K1Wpr0cessli5 SP ARC0\021301Quamcr1yN1 QTR 04\2130 GWMR IQ04doc Page 2
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