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r ENVIRONMENTAL HEALTH DEPARTMENT <br /> u�N SAN JOAQUIN COUNTY <br /> UnrtSupervisors <br /> Donna K. Horan,R.E.H.S. <br /> Director 304 East Weber Avenue, Third Floor Carl Dorgman,R.E.H.S. <br /> At Olsen,R.E.H.S. StocktonCalifornia 95202-2708 Mike Huggins,R.E.H.S.,R,D1 <br /> , <br /> • r '""p • Program Manager Douglas W.Wilson,R.E_H.S. <br /> Q�iFsRN� <br /> Laurie A.Cotulla,R.E.H.S. g <br /> Telephone: (209) 468-3420 Margaret La orio,R.E.H.S. <br /> Cl ,R.E.H.S. <br /> Manager Fax: (209) 464-0138 Robert Mccllon <br /> Mark Barcellos,R.E.H.S. <br /> DAVID ATWATER RECEIVED jUL 1 ,4 2005 <br /> FUEL STOPS LAND & DEVELOPMENT LLC J U l 15 2005 <br /> P O BOX 1207 <br /> STOCKTON CA 95201 <br /> RE: Lathrop Gas&Food Mart SITE CODE: 1507 <br /> 14800 Highway 99 RO: 0199 <br /> Manteca, CA 95336 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Subsurface <br /> Investigation Report dated March 31, 2005, and prepared by Advanced GeoEnvironmental, Inc. <br /> (AGE) on your behalf. In this report AGE presents a summary of the site history that began in <br /> 1988 when petroleum hydrocarbon contamination was discovered as the result of the leaking, <br /> underground storage tank (UST) system. In December 1998, after site remediation, a no further <br /> action letter was issued by EHD. At that time residual mass balance calculations indicated that <br /> 0.068 pounds methyl tertiary-butyl ether (MTBE), 0.032 pounds 1,2-dichloroethane (1,2-DCA),, <br /> and 0.56 pounds total petroleum hydrocarbons as diesel (TPH-d) remained in groundwater, and <br /> 0.01 pounds 1,2-DCA remained in soil at this site. <br /> In January 2003, during excavation and upgrade of the UST dispenser and piping system, <br /> petroleum hydrocarbon contamination was discovered in two soil samples collected near <br /> dispensers D1 and D4. As a result, in August 2004, three soil borings were advanced to <br /> investigate current petroleum hydrocarbon contamination; boring B1 was advanced to a total <br /> depth of 40 feet below surface grade (bsg), and borings B2 and B3 were advanced to total depths <br /> of 35 feet bsg. Soil results at 15 feet bsg showed that total petroleum hydrocarbons as gasoline <br /> (TPH-g) and. TPH-d were detected in B1 at concentrations of 250 milligrams per kilogram <br /> (mg/kg) and 190 mg/kg, respectively; and TPH-g and TPH-d were detected in groundwater from <br /> B I at concentrations of 2,100 micrograms per liter (gg/L) and 7,200 µg/L, respectively. MTBE <br /> and 1,2-DCA were also detected in groundwater from B1 at concentrations of 18 4g/L and 2.7 <br /> pg/L, respectively. Soil samples collected at five-foot intervals revealed sail consisting of silt; <br /> sand, sandy silt and silty sand from surface grade to total depth with a clay layer at approximately <br /> 25 feet bsg. <br /> Based on the following findings, interpretations, and conclusions, AGE recommends <br /> consideration of case closure for this site: <br /> • Soil and groundwater contamination in the dispenser area is defined to the west by boring <br /> B2. <br /> • VerticaI extent of hydrocarbon-impacted soil is defined by boring B1 since no <br /> contamination was detected in soil samples collected at 25 and 35 feet bsg in B1. <br />