SITE INFORMATION AND CORRESPONDENCE

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TABLE 1 -CHECKLIST OF REQUIRED DAA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: New Jerusalem School,31400 Koster Road,Tracy,San Joaquin County 1. Distance to production wells for municipal, domestic, agriculture,industry Two wells,one irrigation and one domestic,are and other uses within 2000 feet of the site; located approximately 30'and 100'north and northeast of the site,respectively. 2. Site maps, to scale, of area impacted showing iocatlons of former and existing tank systems, In July 1989,two USTs,one excavation co.Ontours and sample locations,boring and monitoring well elevation contours, were removed-gallon and one 350-:gallon, were ed from the site. gradients, and nearby surface wafers, buildings, streets, and subsurface utilities; Y❑ 3. Figures depicting lithology(cross section), treatment system diagrams; No treatment system was used. Site lithology consists of clays to 20 feet bgs and sands below 20 feet 4. Stockpiled soil remaining on-site or off-site disposal(quantify); There is no indication that soil was stockpiled on site. NA 5_ Monitoring wells remaining on-site, fate; Three monitoring wells were installed. San Joaquin County has proposed decommissioning these wells pending the Regional Board's concurrence with the closure recommendation. Lit 6. Tabulated results of all groundwater elevations and depths to water;. _Groundwater elevation is estimated between 5 and 10 feet bgs,whh-a northeasterly flaw-direction. FTI 7.Tabulated results of all sampling and analyses: BTEX at 0.68 mg/kg and TPHg at 0.037 mg/kg were detected in the excavation soil samples. Three soil borings were advanced in 1996. One sample from Iq Defection limits for confirmation sampling under the 350-gallon tank showed BTEX as high as 62 mg/kg and TPHg at Lead analyses 930 mg/kg. A grab groundwater sample revealed BTEX as high as 4.7 mg/1 and low TPHg concentrations. Three monitoring wells were installed in 1998. Contaminants were not detected above detectable limits in the water samples. ❑ Y 8. Concentration contours of contaminants found and those remaining in soil d groundwater, and bot -site and off-site: 1=J Latera!and II Vertical extent of soil contamination y� 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, FE 10.Reports/information 0 Unauthorized Release Form '-- 6MRs(Dates)December 1998 El Welland boring logs aPAR NA IsFRP rq Other(report name)July 22, 1999 Closure Report 11.Best Available Technology(BAT)used or an explanation for not using BAT,• The leak sources were removed from the site. 12.Reasons why background wasrs unattainable using BAT, Remaining hydrocarbons require Sate to naturally attenuate. 13.Mass balance calculation of substance treated versus that remaining; An estimated 0.42 pounds of TPHg remain in groundwater and 1.3 pounds of TPHg remain in soil. 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 The remaining hydrocarbons should naturally degrade over impact water quality,health, or other beneficial uses,and time. No oxygenated compounds were detected in samples from the site. 16.WET or TCLP results By. �7 Comments: In 1996,soil boring and ground water samples showed contamination limited to the subsurface area beneath the former 350-gallon UST. Three monitoring wells were installed at the site. No contaminants above laboratory detection limits were found in Date: the water samples. The consultant estimates minor contamination remains in soil and groundwater. These remaining carbon-based compounds should naturally attenuate in the subsurface environment.An irrigation well and a domestic well are located within 2,000 feet of the site. Water from the irrigation well was analyzed for TPHg,BTEX,and MISE;none were detected. The upper screen on ' the domestic well is separated from the upper aquifer by two,20-foot thick clay layers, which should prevent it from being impacted. Based on the low mobility of the remaining contaminants,the absence of MtBE, the lack of contaminants in the downgradient well samples,and the retarding subsurface soil matrix,staff concurs with San Joaquin County closure recommendation.