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boring is unexpected, since it has never been detected during <br /> tank removal, operations or the placement of the three monitoring <br /> wells. The source of that substance is inknown, since the UST' s <br /> never contained gasoline. <br /> The soil boring recently placed encountered water at about 811 <br /> below grade, but was not collected for analysis . The report does <br /> not detail the grouting of the hole, but verbal conversations <br /> with Lush Geosciences confirm that it was done as directed by the <br /> San Joaquin County EHD. <br /> while we agree in general with the conclusions presented in the <br /> attached report, we wish to add the following observations : <br /> 1. Water analyses from MW-1 taken during 11 sampling events over <br /> a 2 1/2 year period revealed only minor amounts of benzene (3 <br /> events, ) and xylene (1 event; ) toluene, ethylbenzene and were ND <br /> in all samplings . TPHg was ND during the first two samplings in <br /> all three wells, and has not been tested since May, 1992 . TPHd <br /> was analysed in all 11 sampling events in MW-1, but detected in <br /> only 4 - 9/92, 6/93, 1/94, & 11/94 . <br /> 2 . During the latest work, benzene & toluene were ND in all 13 <br /> soil samples analyzed; ethylbenzene was detected in 4, and xylene <br /> in 9 . TPH as gasoline was measured iji all but 2 of the soil <br /> samples, at concentrations ranging from 40 .9 to 800 mg/kg. The <br /> lack of lighter compounds indicates that the TPHg has degraded <br /> considerably over time. <br /> 3 . TPH as diesel was measured at 25, 200 mg/kg in the soil sample <br /> at 36 ' bgl from SB-1, whereas the soil sample from MW-1, less <br /> than 40 feet away, measured only 140 mg/kg. The soil sample in <br /> SB-1 at 46 , recorded 6, 300 mg/kg; it was 66 mg/kg in MW-1 . The <br /> soil sample at 661 in SB-1 measured 3,480 mg/kg; it was 21 mg/kg <br /> at .68 .5 ' in MW-1 . The sample at 711 bgl in SB-1 recorded 18, 000 <br /> mg/kg; this is the approximate top of the potentiometric surface <br /> based on recorded data. TPHd was measured at 2 .9 mg/kg in the <br /> soil sample at 771 bgl from MW-1. Water samples taken from MW-1 <br /> never measured TPHd higher than 3 .0 mg/L. This supports our <br /> prior conclusions that soil permeabilities are extremely low, <br /> preventing significant horizontal movement . <br /> RECOMMENDATIONS: <br /> None of the three existing monitoring wells have been sampled <br /> since November, 1994 . Monitoring was discontinued at that time <br /> per agreement with the County EHD, since only low levels of TPHd <br /> had been measured in MW-1; MW-2 & 3 had never recorded any <br /> 2 <br />