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LTH <br /> PUBLIC '11EA SER� �CE S <br /> SAN JOAQUIN COUNTY T <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 9520 <br /> ciFoa <br /> 209/468-3420 <br /> ADADU YEMANE MAR 2 4 997 <br /> UNOCAL CORPORATION <br /> 2000 CROW CANYON PLACE STE 400 <br /> SAN RAMON CA 94583 <br /> RE: UNOCAL STATION#5886 SITE CODE: 1176 <br /> 2701 MARCH LANE <br /> STOCKTON CA <br /> As a result of reviewing historical and relatively recent site specific data which indicates the potential <br /> existence of new discharges of petroleum products to the subsurface environment at the above referenced <br /> site, San Joaquin County Public Health Services Environmental Health Division (PHS/EHD)provides the <br /> following comments and directives. <br /> Data received from ground water monitoring events at the above referenced site in September and <br /> December of 1996 were reviewed by PHS/EHD which indicated significant increases in MTBE <br /> concentrations in monitoring well number two (MW 2). As a result of this increase in MTBE <br /> concentration PHS/EHD staff performed an inspection on March 7, 1997 of the facility Underground <br /> Storage Tank (UST) system. The inspection revealed the presence of free phase fuel hydrocarbons in the <br /> piping sumps(west ends) of the diesel and regular tanks with strong petroleum and ether odors from these <br /> tanks including the premium fuel tank(odor,no visible product at the time of inspection). <br /> In addition all monitoring wells on site were sampled by staff from MPDS services on March 7, 1997. <br /> Strong ether odors were noted in groundwater samples from MW 2 when the sample was agitated. The <br /> following tabulated data has been recreated from analytical reports submitted to PHS/EHD which includes <br /> the most recent ground water data. This data further supports the possibility that a potentially new and <br /> significant unauthorized release is occuring at the above referenced site. <br /> TPH as TPH asEthyl- <br /> W611# Date Diesel Gasoline Benzene Toluene Benzene Xylenes MTBE <br /> MW 1 9/9/96 61 <50 <0.5 <0.5 <0.5 <0.5 230 <br /> 12/6/96 74 <50 <0.5 <0.5 <0.5 <0.5 90 <br /> 3/7/97 ND <50 <0.5 <0.5 <0.5 <0.5 110 <br /> MW 2 9/9/96 54 <50 <0.5 <0.5 <0.5 <0.5 1800_ <br /> 12/6/96 64 <50 <0.5 <0.5 <0.5 6.0 6100 ,; r <br /> 3/7/97 ND <50 <0.5 <0.5 <0.5 <0.5 6700: <br /> MW 3 9/9/96 130 <50 <0.5 <0.5 <0.5 <0.5 "*10&_,`�; <br /> 12/6/96 68 <50 <0.5 <0.5 <0.5 <0.5 660 <br /> 3/7/97 ND <50 <0.5 <0.5 <0.5 <0.5 20000"° <br /> All tabulated data reported as ug/l. <br /> * Confirmed by GC/MS. <br /> A Division of San Joaquin County Health Care Services <br />