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Ms Lori Duncan January31, 2003 Page 2 DISCUSSION (ARCO): On December 17, 2002, SECOR International Inc (SECOR) conducted groundwater monitoring and sampling for the 4`" quarter 2002 ARCO station 2133, in conjunction with Gettler-Ryan (G-R) performing groundwater monitoring and sampling for Chevron service station 9-4275 Nine ARCO wells were sampled during this event Groundwater samples were analyzed for total petroleum hydrocarbons quantified as gasoline (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX), and the fuel oxygenate methyl-tertiary-butyl-ether (MtBE) TPHg were reported in 3 of the 9 wells sampled this quarter at concentrations ranging from 72 gg/L (BHP-1) to 12,000 µg/L (E-10) Benzene was reported in 1 of the 9 wells at a concentration of 620 pg/L (E-10) Methyl tert-butyl ether (MtBE) was reported in 3 of the 9 wells at concentrations ranging from 2 5 pg/L (E-9) to 8,500 jag/L (E-10) Groundwater elevations across the site increased by an average of 1 66 ft DISCUSSION (CHEVRON): Nine Chevron wells were sampled during this event Groundwater samples were analyzed for TPHg, BTEX, and the fuel oxygenates MtBE, ethyl-tertiary- butyl-ether (EtBE), di-isopropyl ether (DIPE), ternary-amyl-methyl-ether (TAME), tertiary-butanol/tertiary- butyl-alcohol (TBA), 1,2 drehloroethane (1,2 DCA) and 1,2 dibromoethane (EDB) Benzene, toluene, TBA, DIPE, ETBE, 1,2-DCA, and EDB were not detected in samples from any of the wells TPHg was detected in two wells at concentrations of 130 micrograms per liter (µg/L) in the sample collected from MW-1 and 140 µg/L in the sample collected from MW-2 MtBE was detected in five wells at concentrations ranging from 4 µg/L in the sample collected from MW-4 to 3,300 µg/l- in the sample collected from MW-1 Ethylbenzene was detected in two wells at concentrations of 0 9 lug/I in the sample collected from MW-5 and 3 µg/I in the sampled collected from MW-2 Xylenes were detected in one well at a concentration of 51xg/I in the sample collected in MW-2 TAME was detected in two wells at concentrations of 3 jag/l- in the sample collected from MW-3 and 34 ug/L in the sample collected from MW-1 Groundwater flow across both sites was to the north at an approximately gradient of 0 009 foot per feet (ft/ft), which is generally consistent with historical data ARCO's groundwater elevation and analytical data are summarized in Table 1 Chevron's groundwater elevation and analytical data are summarized in Tables 2 and 3 Table 4 presents historical groundwater gradient data A groundwater elevation contour map of the two sites is presented as Figure 2 Groundwater concentrations for both sites are summarized for TPHg, benzene, and MtBE in Figure 3 Attachment 1 contains ARCO's historical SVE and recent AS system operational data Attachment 2 contains field and laboratory procedures Attachment 3 contains ARCO laboratory analytical results, chain of custody documentation, and field data sheets Attachment 4 tl contains Chevron laboratory analytical results, chain of custody documentation, and field data sheets This report presents our understanding of existing conditions at the subject site The conclusions contained herein are based on the analytical results, and professional judgment in accordance with current standards of professional practice, no other warranty is expressed or implied SECOR assumes no responsibility for exploratory borings or data reported by other consultants or contractors i