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Treadwell&Rollo 5.3. 2. 1 Shallow Zone Grab Groundwater Shallow groundwater samples were collected between 36 and 36 feet bgs. TPH-g was detected in three "1 out of five shallow groundwat tr samples. Concentrations ranged between 94 micrograms per liter (pg/L) - � in SB-5 to 4, 100 Ng/L in SB-4. TPH-g was not detected above laboratory reporting limits in SB-6 and SB-7. -� With the exception of SB-5, TPH-k was detected in all shallow groundwater samples. TPH-k concentrations ranged between 58 pg/L from SB-6 to 11500 pg/L from SB-4. However concentrations were generally of lesser magnitude than TPH-g with the exception of SB-6 and SB-7 (Table. In addition, the lab report indicated that in all samples TPH-k chromatograms did not resemble the -J chromatogram for the TPH-k laboratory standard. BTEX was detected in groundwater samples from SB4 and SB-3. Benzene was detected at 4.0 and 13 pg/L in SB4 and SB-3 respectively./ Toluene and ethylbenzene were only detected in SB-4 at 0.84 and 3. 3 pg/L respectively. % . � The remaining fuel oxygenates and VOCs including TBA, DIPE, MTBE, ETBE,, TAME, 1,2-DCA, EDB, ethanol and methanol were not detected above laboratory reporting limits. l N 1h7-8 k1¢s �fOur� 5.3. 2. 2 Shallow Zone Monitoring Wells ar-357 Four shallow screene monitoring wells (MWI through MW4) have been monitored ten times since July 2002. MW-4 has historically been below laboratory reporting limits for all analyses indicating it is outside of the zone of contamination. Table presents all analytical results reported for these monitoring wells. TPH as gasoline and as kerosene has been detected in MW-1. MW-2, and MW-3. Concentrations of TPH have historically been greatest in MW-3 (located near the former pump station and distribution lines). i The concentration of TPH-g in MW-3 as of December 2004 was 32,000 pg/L. In December 2004, MW-2 J ' j also had a concentration of TPWg of 32,000 pg/L and MW- 1 had a concentration of 8,700 pg/L. Figure 4 >n 1S3yi provides plots of TPH-gasoline concentrations over time. Figure 4 illustrates that natural attenuation , processes have significantly decreased TPH-gasoline concentrations across the site. r�Pu r6 ,J Concentrations of benzene, ethylbenzene, and xylenes have been detected in wells MW-1, MW-2, andel MW-3 . During the December 2004 monitoring, benzene was detected at concentrations of 220, 3„600, vtok 9 38 � 25971201. DGD 6 February 2008