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S E C O R <br /> Mr Jim Barton <br /> February 23, 2006 <br /> Page 5 <br /> Detected constituents in groundwater are summarized below <br /> Number of Detections Minimum Reported Maximum Reported <br /> Constituents Above the MDL Concentration in pg/L Concentration in pg/L <br /> Total Samples Collected=13 (Well ID) (Well ID) <br /> TPHg"' 0 <200 <200 <br /> PCE" 12 <0 8(GEW-022B) 14,000(MW-3) <br /> TCE" 12 <1 (GEW-005A) 28(MW-3) <br /> Benzene 0 <0 5 <5 <br /> MtBE 1 <0 5 220 (GEW-007A) <br /> EXPLANATION <br /> MDL=Method detection limit <br /> pg/L=Micrograms per liter <br /> TPHg=Total petroleum hydrocarbons as gasoline <br /> PCE=Tetrachloroethene <br /> TCE=Tnchloroethene <br /> MtBE=Methyl tert-butyl ether <br /> `=TPHg by GC-FID(Water)—Method SW-846 8015E modified <br /> Analyzed using EPA Method 8260 <br /> iCONCLUSIONS <br /> An evaluation of previous site sampling chromatograms using gas chromatography by <br /> mass spectrometry (GC-MS) was preformed A library search performed by Lancaster <br /> Laboratories Inc (LLI), EMC's contracted laboratory, Indicates reported detections of TPHg <br /> were PCE, and no TPHg components existed in groundwater beneath the site This <br /> observation has been confirmed by the results of the GC-FID analyses, and by analyzing <br /> groundwater samples for PCE using EPA Method 8260 GC-FID analyses performed on <br /> groundwater samples collected from wells MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, MW- <br /> 11 D, GEW-005A, GEW-006A, GEW-007A, GEW-008A, GEW-02213, and GEW-0238 <br /> Indicated no petroleum-hydrocarbon compounds, Including TPHg and diesel fuel, were <br /> detected In these samples at or above their respective MDLs This observation Is <br /> consistent with the low sporadic detections of TPHg in soil samples collected during <br /> previous monitoring well installations and soil boring activities <br /> No BTEX components were reported in groundwater samples collected during 4Q2005 <br /> monitoring event Although MtBE was detected In well GEW-007A at a concentration of <br /> 220 pglL it appears that the source of MtBE detected in well GEW-007A is not located <br /> beneath the site This assumption is based on the observation MtBE was not detected In <br /> nearby, upgradient and crossgradient wells MW-7 or MW-11 D screened through similar <br /> depth Intervals No other constituents were detected In groundwater samples collected <br /> during the 402005 monitoring event <br /> N 1Flfes4ProlectslChevronV4etarA#9-617I Penodic Mondonng12005140MR1402005QMR doc <br />