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r <br /> i <br /> 4.0 INTERPRETATION OF RESULTS <br /> HY <br /> 4.1 fringe zone in <br /> As shown in Table 1, toluene was found in'�soil samples <br /> W�afrom ylene wathe s foundinMW-4, <br /> Mont well borings MW-4, MW-5, M <br /> = presence of these gasoline constituents in the capillary fringe <br /> Mont and MW-7. The p resent in groundwater when the water level was <br /> zone suggests that hydrocarbons were p <br /> higher in the soil column. Borings MW4�SMOf{hEMour affeed locations. <br /> rgroundw ter <br /> downgradient from the former tank loca with 37 uglKg and 3.5 <br /> in MW-4 has the highest concentrations of toluene and xylene <br /> ug/Kg, respectively. <br /> Analyses for total Wad revealed a range of glK lead ll MW-4o Alliofthe heseil from a low Of <br /> valu s may be <br /> Y <br /> 7 mg/Kg in well MW-5 to a high of 16.5 m9 g <br /> interpreted as background levels, based a d statistical studies <br /> in he Stockton, <br /> Survey (Connor and Shacklette, 1975) <br /> California area. <br /> However, the minimal residues found in the soil appears to be a negligible issue. and As <br /> Howe MW-5, MW-6 and <br /> discussed in the next section, groundwater samples from wells MW-4,ng that the residual <br /> MW_7 all showed an absence <br /> {hecso if at this anime le yarecnotop esenns 'tlyt�impacting the local <br /> compounds present <br /> groundwater quality to any detectable extent. <br /> r i t <br /> 4.2 i tri ti <br /> t alaral and VeCY4�1� <br /> sults of groundwater sampling from all seven monitoring`s well contaells on i}nedi1600fcate <br /> ugIL <br /> The re g resent only in well MW <br /> that hydrocarbon residues are p !L TPH-G. No floating product (gasoline) was <br /> benzene, 500 ug/L xylene and 16 mg compound <br /> presence can be interpreted <br /> observed during sampling. The lateral extent of comp p ring wells. Because the other <br /> based on the absence of the hydrocarbons <br /> yd oca be ns in the eioundwater, a boundary representing <br /> wells contain no detectable by <br /> 9 <br /> ' oundwater impact. This area is depicted In Fl;;-,.,e 7. <br /> non-detectable concentrations ma; be drawn between MW-1 and each of the ober wells <br /> servatively chosen to be one he <br /> to define a maximum likely area of gr <br /> Non-detectable concentration points ther wells he downgrad ent directions. Although <br /> distance between <br /> well MW-1 and was extended in the <br /> the hydrocarbon source location is still uncertain, the boundaryhad <br /> ch <br /> u radient direction to include the former undres ihatergoundione of the tantank kstwas hel <br /> pgsource <br /> shown BTEX residue in soil samples. This assum <br /> of the gasoline compounds. <br /> - 13 - <br />