Laserfiche WebLink
. FROM = CURLJCCB TEL: 916 255 3015 >: OCT. 9.1998 12:14 PM P 4 <br /> 113336 Ent Highway 88 <br /> 1 <br /> LOCkeford,San Joaquin County October 1488 <br /> r., <br /> FAFT <br /> concentrations of TPHg and BTEX constituents to the to depth of the soil borings. The soil samples <br /> contained contaminants at concentrations up to 3200 rng/Kg'i(ppm) for TPHg, and 6.7 mg/Kg for <br /> berjzerte. <br /> F <br /> On 29 December 1997, SJCHM sent a "Case Closmre Summar"and tete chronology to the RegionalHerd,for the site. Regional Board staff did not concur with theNFAR decision by SJCEHD,and in the <br /> 13 February 199$letter.Ms.Anderson requcsmd that the Vertical.extent of contamination be determined <br /> below the gasoline UST excavation, and that a groundwater„sample be collected to determine if <br /> petrdlemm contamination had impacted groundwater. <br /> Jn order to determine the vertical extent of soil contaminatiori,;and to .evaluxte if site activities have <br /> impactod groundwater, one soil boring was advanced 100 feet lags between 26 June and I July 1998. <br /> SIMM soil samples and one grab groundwater sample wer6 Submitted to a State certified laboratory and <br /> analyzed for TPHg, BTEX and the fuel oxygenates. Tine 'analytical results of the soil samples indicate <br /> that soil contamination, in the area of the UST excavation, extends to approximately 45 feet Ings for <br /> TPHS and to 60 feet bgs for benzene. The highest concentations of TPHg and benzene detected at the <br /> site to date, 3,300 mg/Kg, and 13 mg/K. respectively, wer+ delec ed i4 this boring at apprd ately 40 <br /> fret bgs. Samples were analyzed by Toxicity Characteristic <xchingPmcedure <br /> (TCLP) with the <br /> I' <br /> highest leachable benzene concentration of 460 ftM dete"eted iA the sample collected from <br /> approximately 39 to 40 feet bgs. The single groundwater s 'ample;bras analyzed and is reported to contain <br /> 210 pg/L(ppb)TPHS.4.3µg/1,.benzene and 16.0}tgll.,tolu`crte. <br /> lite 13 July 1998 report, Excavation For Orbe Soil Boring, prTared by UeoSoly, included a map <br /> patenting the regional groundwater gradient 'and flow direction and one boring log depicting the <br /> geology underlying the site. I'rhe calculated hydraulic gradient;and groundwater flow direction are <br /> &rived from Department of Water Resources DWR, well r+ecords!for three doffostictsupply wells located <br /> 300*feet or more east of the site. The information provided is not valid, because the depth to water <br /> maasnrroments for each well are from three different years (December 1970. November 1975. and <br /> November 1986). This information is not acceptable to determine the groundwater gradient and flow <br /> direction.The boring log,however,is useful,by providing data for"[she geology. <br /> r <br /> The highest concentrations of soil contamination: are present in�cIayey sand and silty sand, between <br /> 22 and 42 feet bgs.Between 42 and 60 feet bgs, sandy silt a nd til!me present, with silty sand and clayey <br /> sand logged between 60 feet and approximately 87 feet bgs. First groundwater was encountered in the <br /> baring.B7 in sandy silt,at 96.4 feet bgs on 1 July 1998. <br /> Soil contamination is adequately defined in the vicinity of the former waste oil tank,with the bulk of the <br /> contamination remaining in the soil between 7.5 and 9 feet bgs beneath the former UST. Some leaching <br /> of contaminants has occurred, wish low concentrations of etbylbal"nzene and xylenes adsorbed to soil at <br /> 16 foot bgs. <br /> Soil contamination is defined laterally to approximately 24 feet bgs in the vicinity of rhe former gasoline <br /> USTs. Below til feet bgs, the lateral extent of soil coa6minaition is not defined. The soil sample <br /> collected between 25 and 26 feet bgs from luring B1 contmined TPHg and BTEX contamination. The <br /> total depth of S1 is 30 feet bgs, however, no sonl sample was sub'rinittecl for analysis below 26 feet bgs, <br />