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1 <br /> ' A letter from the San Joaquin County Environmental Health Department (EHD), dated 07 March <br /> 1996, indicated that further investigation related to the former UST would be required before site <br /> closure could be issued <br /> ' SITE ASSESSMENT ACTIVITIES <br /> A total of eight soil probe borings (P 1 through P8)were advanced at the site,under the observation <br /> of a representative of the EHD On 19 September 1995, probe boring P1 was advanced north of the <br /> former UST area,probe boring P2 was advanced near the center of the former UST excavation,and <br /> ' probe bonng P3 was advanced near the former dispenser location Each of these borings were <br /> advanced to a depth of 25 feet bsg <br /> On 21 April 1997, soil boring P4 was advanced in the City of Stockton right-of-way in Fremont <br /> Street Four additional soil probe borings (P5 through P8)were advanced on the site in the vicinity <br /> the former UST,including probe boring P7,which was advanced under the building on the site Each <br /> of these borings were advanced to a vertical depth of 15 feet bsg <br /> • Total petroleum hydrocarbons quantified as gasoline (TPH-g) was detected in soil samples <br /> from probe borings P2,P3, and P7 at concentrations as high as 230 mg/kg(P3-10) Volatile <br /> aromatic compounds benzene, toluene, ethylbenzene, and total xylenes (BTEX) were <br /> detected in soil samples collected from P3 at concentrations ranging from 0 010 mg/kg <br /> ' . (ethylbenzene, P3-25) to 19 mg/kg (xylenes, P3-10) Petroleum hydrocarbons were not <br /> detected in soil samples analyzed from any other probe borings advanced during this <br /> investigation <br />' a Analytical results of soil samples submitted for physicochemical analysis and <br /> microbiological enumeration indicated that there is microbial activity at the site,however it <br />' is segregated from the area of the hydrocarbon release The lack of biodegrading bacteria in <br /> the area of the dispenser maybe due to the presence of biotoxic compounds in the subsurface <br /> at the site, such as metals or pesticides However, adequate concentrations of necessary <br />' nutrients for microbe growth and sustenance were present in the soil at the site <br /> • TPH-g was detected in four of six grab ground water samples collected from the site at <br />' concentrations ranging from 510 micrograms per liter (µg/1) to 94,000 µg/1 BTEX <br /> compounds were detected in five of six samples analyzed at concentrations ranging from <br /> 13 4g/1 benzene in boring P1 to 19,000 µg11 toluene in boring P6 MTBE was detected at <br />' concentrations as high as 290 µg/1 No petroleum hydrocarbons were detected in the grab <br /> ground water sample collected from the City of Stockton nght-of way in Fremont Street, <br /> located in the apparent up-gradient direction from the former UST area <br />' On 15 and 16 June 1999 AGE advanced four pilot soil borings for the construction of ground water <br />' monitoring wells and collected and procured laboratory analysis of soil samples The four soil <br /> borings(MW-1 through MW-4)were advanced utilizing hollow-stem auger drilling techniques and <br /> . were subsequently completed as monitoring wells of the same designations <br /> Advanced GeoEnvtronmental,Inc <br />