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Extended Site Characterization Report: 7500 West Eleventh Street, Tracy, CA. Page 35 j- been located there. However, no such feature has been discovered at that location (Dietz 1998). 7.3.2 Prima Plume of Diesel and Gasoline ,J SJC developed its interpretation of the primary plume of fuel hydrocarbons emanating from the 7500 West Eleventh Street in stages as information became available from the progressive phases of subsurface investigation. That process is described below. 7.3.2.1 Primary Plume Directly Beneath Subject Property -� Examination of the results of analyses of groundwater(as presented in Table 4) recovered in April and May 2000 from Exploratory Boring PP-3 and Monitoring Well MW-3 4 (which, as shown on Figure 2, are located near the West Eleventh Street frontage of the :.. former fueling station, a short distance down-gradient from the location of the dispenser islands), reveals moderate- to-high concentrations of petroleum hydrocarbons, the molecular chains of which are in both the diesel and gasoline range. Those concentrations amount to 14,000 µg/L and 2,800 µg/L of diesel-range product in groundwater recovered :1 from PP-3 and MW-3, respectively. The corresponding concentrations of gasoline-range product were 1,600 pg/L and 11,000 pg/L, respectively. To the west of PP-3 and MW-3, the concentration of diesel-range hydrocarbons in groundwater recovered from PP-2 in April 2000 was only 190 pg/L, and the corresponding value for gasoline-range hydrocarbons was only 300 µg/L. Further to the -`� west, there were no detectable concentrations of either diesel or gasoline in the sample of groundwater recovered from groundwater recovered on May 11, 2000 from MW-2, which is located near the western boundary of the subject property, although the sample from that well did contain 7.7 pg/L of benzene, 0.86 pg/L of ethyl benzene, 1.1 pg/L of total xylene isomers and 4.6 gg/L of MTBE. a Directly to the east of PP-3 and MW-3, the concentrations of diesel- and gasoline-range hydrocarbons in groundwater recovered from PP-4 and MW-4 in April and May 2000 were significantly reduced, compared to those in locations close to the area where the fuel dispensing pumps had been located. The concentrations of diesel-range fuel in groundwater recovered from PP-4 and MW-4 in April and May 2000 were 400 gg/L and 300 pg/L, respectively. The corresponding concentrations of gasoline in the groundwater at those locations were 880 pg/L and 52 pg/L, respectively. (Note: A similar relationship exists between the concentrations of MTBE in samples of groundwater recovered from MW-2, MW-3 and MW-4: MTBE was present in MW-3 at a concentration of 10,000 } L but less than 1 000 IL in MW-4 and as noted above there was only 4.6 p� � pg � Y pg/L of that oxygenate in the groundwater sample recovered from MW-2.) By examining the results of analysis of samples of soil recovered from PP-2, PP-3 and PP-4 and MW-2, MW-3 and MW-4 that are presented in Table 3, it can be seen that the jdistribution of fuel hydrocarbons in the soil reflects their distribution in groundwater. f 1 --` sic - s