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r rSite Background Information-Guardmo and Crawford i Page 2 of 6 i A letter from the San Joaquin County Environmental Health Department (EHD), dated 07 March r 1996, indicated that father investigation related to the former UST would be required before site closure could be issued ' SITE ASSESSMENT ACTIVITIES A total of eight soil probe borings (P 1 through P8)were advanced at the site,under the observation of a representative of the EHD On 19 September 1995,probe boring P 1 was advanced north of the former UST area,probe boring P2 was advanced near the center of the former UST excavation,and rprobe boring P3 was advanced near the former dispenser location Each of these borings were advanced to a depth of 25 feet bsg On 21 April 1997, soil boring P4 was advanced in the City of Stockton nght-of-way in Fremont Street Four additional soil probe borings(P5 through P8)were advanced on the site in the vicinity r the former UST,mcluding probe boring P7,which was advanced under the building on the site Each of these borings were advanced to a vertical depth of 15 feet bsg ' • • Total petroleum hydrocarbons quantified as gasoline(TPH-g)was detected in soil samples from probe borings P2,P3, and P7 at concentrations as high as 230 mg/kg(P3-I0) Volatile aromatic compounds benzene, toluene, ethylbenzene, and total xylenes (BTEX) were ' detected in soil samples collected from P3 at concentrations ranging from 0 010 mg/kg (ethylbenzene, P3-25) to 19 mg/kg (xylenes, P3-10) Petroleum hydrocarbons were not detected in soil samples analyzed from any other probe borings advanced during this rinvestigation • Analytical results of soil samples submitted for physicochemical analysis and ' microbiological enumeration indicated that there is microbial activity at the site,however it is segregated from the area of the hydrocarbon release The lack of biodegrading bacteria in the area of the dispenser maybe due to the presence of biotoxic compounds in the subsurface r at the site, such as metals or pesticides However, adequate concentrations of necessary nutrients for microbe growth and sustenance were present in the soil at the site • TPH-g was detected in four of six grab ground water samples collected from the site at concentrations ranging from 510 micrograms per liter (4g/1) to 94,000 µg/1 BTEX compounds were detected in five of six samples analyzed at concentrations ranging from r 13 µg/1 benzene in boring P1 to 19,000 µg/1 toluene in boring P6 MTBE was detected at concentrations as high as 290 µg/1. No petroleum hydrocarbons were detected in the grab ground water sample collected from the City of Stockton right-of-way in Fremont Street, ' located in the apparent up-gradient direction from the former UST area On IS and 16 June 1999,AGE advanced four pilot soil borings for the construction of ground water r Advanced GeoEnvironmenw,Inc r