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1 <br />1 <br />1 <br />i <br />1 <br />1 <br />1 <br />1 <br />1 <br />I, <br />I <br />..nom.. � v c n�n� z —u aa�--_-_�_ -..T�c �st-r o --Sr xuc>aua,al�wuuacfixfnz4i•1'»�,-�..`.�'31� <br />I 4 <br />1 I , <br />I � � <br />y I I 1 1 <br />Page 2 <br />Ms Margaret Lagono <br />I <br />March 23, 19951110:' <br />f <br />samples ranged from non-detected to 2,000 pg/L Phase -separated hydrocarbon <br />product has not been detected in any of the wells. <br />The extent of any remaining residual gasoline -impacted soil is limited Only one <br />soil sample collected dunng the groundwater monitoring well installation <br />investigation contained petroleum hydrocarbons That one impacted sample was <br />collected at a depth dust below the groundwater table, and was likely <br />contaminated by the gasoline -impacted groundwater at that location <br />Hazardous Substance Characteristics <br />As described in the October 18, 1989 Cahforma Leakrng Underground Fuel Tank <br />Manual, gasoline is a mixture of over 200 petroleum-denved chemicals plus a few <br />synthetic products that are added to improve fuel performance The majority of <br />gasoline components range from C4 to C 12 hydrocarbons Analysis of gasoline <br />components is usually limited to detection of benzene, toluene, ethylbenzene, and <br />xylenes (BTEX) because they are readily measurable to gas chromatographic <br />detection, they pose a threat to human health (benzene is known as a carcinogen), <br />and they have the potential to migrate through soil and impact groundwater <br />Physical properties of the BTEX compounds are tabulated below <br />Compound <br />Wt. Percent <br />in Gasoline <br />Vapor <br />Pressure <br />Water <br />Solubility <br />Henry's Law <br />Constant <br />Benzene <br />0 12-3 50 <br />76 <br />1,780 <br />230 <br />Toluene, <br />273-21 80 <br />22 <br />515 <br />217 <br />Eth lbenzene <br />0 36-2 86_+ <br />7 <br />152 <br />359 <br />Xylenes <br />068-3 87 <br />5-6 5 <br />175-198 <br />266 <br />I I <br />Vapor pressure in millimeters of mercury at 20 degrees centigrade <br />Water solubility equal to milligrams per liter at 20 degrees centigrade <br />Henry's Law Constant equal to atmospheres <br />' Hydrogeology <br />I I <br />Shallow groundwater at the facility, which is under confined or semi -confined <br />conditions, flows northeasterly at approximately 0 23 ft/d. The groundwater <br />surface gradient is 2 5 x 10-3 ft/ft In March 1994, this shallow groundwater <br />was approximately 55 feet BGS, but has been observed closer to the surface <br />prior to the recent drought <br />I <br />11 , <br />