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F i <br /> SS No. 6348 , Tracy <br /> PIER, 1/33/92 <br /> + 4 <br /> BACKGROUND <br /> The business at- the-site is- a Unocal -service station <br /> which has been in operation since 1972 and is scheduled for <br /> closure atrthe end-of-March;1992 . The`facrlitres-. The -of-a <br /> metal and stone building- containing .-an, office - area and three <br /> service bays; as - well as -two pump islands and- associated <br /> canopy, underground product tanks , an enclosure containing <br /> waste--oil storage drums , an above-ground propane tank, and <br /> -- -- - -- stor-age---buildings.- -Major--site --features -and -the locations- -of- <br /> all <br /> ocations- -of-.all monitoring wells and borings are shown on Figure 2 . <br /> On June 18 , 1990 a 550-gallon underground waste-oil <br /> storage tank was removed. According to San Joaquin County <br /> Public Health Service records and a report by Kaprealian <br /> Engineering, (9/24/90) , the steel tank was found to have holes v <br /> and to .have leaked . Following tank removal , an excavation <br /> that measured '91 wide, - 12 ' long, and 14 .5' deep was' made to <br /> remove oil-contaminated soil. Not all oil-contaminated soil <br /> was removed, ,due to the proximity of the fuel storage tanks:. <br /> The excavation was backfilled with pea gravel. <br /> Laboratory analysis of soil samples taken from the <br /> base of the over-excavated tank pit indicated 3 .7 ppm TEPH at <br /> the 14 foot depth, with BTEX not detected. Three sidewall <br /> ..samples,.co1lected_6-to_12L' abov_e—the-obser_v_ed-wate_r_level- had <br /> Total Extractable Hydrocarbon concentrations of 210 ppm (north <br /> _ 95.-ppm- .(north-s ide�of-the,-east-wall)_,`and.270-ppm_._.(south _ <br /> side of the east wall) . The four samples }were also analyzed <br /> - ---=for --ha-J:ogenatedL volati-le organic= --substances- -and- -for <br /> - <br /> semivolatile organic substances . Kaprelian Engineering <br /> reported that none of these was detected. The samples were <br /> also analyzed for heavy met-ars,—With-out-any-unusual-results . <br /> A Phase I investigation of records pertaining to the r <br /> site and an inspection of the physical property were conducted <br /> by PHR Environmental Consultants , - Inc. in June of 1991. PHR <br /> identified areas of potential contamination as follows: pit of <br /> the former underground waste-oil tank; storage tanks, piping, <br /> and pumps of the gasoline supply ; observed spillage at <br /> above-ground waste-oil storage drums; floor-drain/clarifier <br /> system within the service bays ; and off-site` sources of <br /> contamination. <br /> -2- <br />