SITE INFORMATION AND CORRESPONDENCE

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STABLE 1 -CHECKLIST OFREQUIRED DATj, FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SiTES Site Name and Location: City of Stockton Fire Station#1,1701 West Was ington Street,Stockton,San Joaquin County 1_ Distance to production wells for municipal, domestic, agriculture,i dustry San iCounty indicates that no water and other uses within 2000 feet of the site; suppllyy wweellss are affected. I Y 2. Site maps, to scale, of area impacted showing locations of farmer nd existing tank systems, In December 1992,one 500- excavation co.Ontours and sample locations, boring and monitoring well elevation contours, gallon diesel tank and P 9 g associated piping were removed gradients, and nearby surface waters, buildings, streets, and subsurface utilities; from the site. Y� 3. Figures depicting Ethology(cross section), treatment system diagrams, No treatment system was used. Lif consists of sand 0 to 3.5 feet bgs ann Lithology clay clay 3.5 to 20 feet bgs. 0 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Stockpiled soil was returned to the fanner tank pit. NA 5. Monitoring wells remaining on-site, fate; No monitoring wells wej a installed at the site. 6. Tabulated results of all groundwater elevations and depths to water, Groundwater elevation is estimated between 10 and 15 feet bgs. MY In 1992, TPHd was detected in soil at 1,200 mg/kg after the tank was removed. 7. Tabulated results of all sampling and analyses: During 1999 soil borings, TPHd was detected in two of four soil borings at 19 Detection limits for confirmation sampling 12 mg/kg and 50 mg/kg. TPHd was also found in the grab water sample at 210 Lead analyses 11gli. BTEX and MOE was not defected in any samples Eq8. Concentration contours of contaminants found and those remaining in soil and groundwater, and both on-site and off-site: ElLateral and rq Vertical extent of soil contamination Lateral and 0 Vertical extent of groundwater contamination NA 9. Zone of influence calculated and assumptions used for subsurface No subsurface remediation system was used at remediation system and the zone of capture attained for the soil and this site. groundwater remediation system; 10.Reports/information El Unauthorized Release Form NA Rs(Dates) El Well and boring logs 19PAR FRP rfl O her(report name)July 12, 1999 Closure Report 11.Best Available Technology(BAT) used or an explanation for not u ing BAT,- The leak sources,(UST and piping)were removed from the site. 12.Reasons why background wass unattainable using BAT, Remaining contaminants require time to naturally attenuate. lJ 13_Mass balance calculation of substance treated versus that remain h An estimated f pounds of diesel fuel remains in the g' soil under the former Tank. 0 14.Assumptions,parameters, calculations and model used in risk assessments, and fate and transport modeling, 15.Rationale why conditions remaining at site will not adversely ite.ng diesel should not further degrade wafer quality at a s impact water quality, health, or other beneficial uses,and a site. 16.WET or TCLP results By. !40! Comments: TPHd was the only constituent detected during the 1996 subsurface investigation. Four soil borings were advanced in L' the vicinity of the former underground storage tank(UST). TP d at 12 mg/kg and 50 mg/kg was found in two of the four borings. TPHd at 210 ug/J was also found in a grab water sample from the site. BTEX and MtBE were not found above detectable limits in Date. any samples during the investigation. A clay Ions exists in the subsurface from 3.5 to 20 feet bgs. The lens should retard migration of the diesel constituents. Based on this information and site conditions,staff concurs with San Joaquin County's closure recommendation.