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i'I . ii
<br /> BLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURII wrR ACTION.REQUESTS AT UNDERGROUND K SITES
<br /> I 10)
<br /> Site Name and Location: San Joaquin Co Courthouse,222 E.Weber Ave.,Stockton,San Joaquin County(Case 3906
<br /> Distance to production wells for municipal, domestic, A 2002 well survey reported no supply or domestic wells
<br /> Y culture, industry and other use
<br /> within 2000 feet of.the site. within 2000'of the site.
<br /> Y 2. Site maps, to scale, of area impacted showing locations One 10,000-gallon gasoline UST and associated piping were
<br /> of any farmer and existing tank systems, excavation removed 8196. TPHg,benzene, toluene, ethylbenzene,
<br /> contours and sample locations, boring and monitoring well xylenes,and,MTBE were detected in soil beneath the UST.
<br /> l elevation contours, gradients, and nearby surface waters, No new USTs were installed:
<br /> buildin s, streets, and subsurface utilities, consists of clay,sift, and sand to
<br /> Y 3. Figures depicting lithology(cross section), treatment Site lithology
<br /> 39 feet, the total depth investigated.
<br /> system diagrams; F.
<br /> f The fate of the excavated soil is not discussed in the
<br /> Y 4. Stockpiled soil remaining on=site or off-site disposal(quantity); T or
<br /> Y 5. Monitoring wells remaining on-site, fate; Three monitoring wells(MW-1 through MW-3)remaining on-site will be
<br /> pro erly abandoned. i 1.
<br /> s 1 6. Tabulated results of all groundwater Depth to groundwater varied from 11 to 29 feet below ground surface(bgs). The groundwater,gradient varied from 0.006 to 0.01 ft/ft, with the
<br /> +' elevations and depths to water, down radient direction towards the northeast.
<br /> 7. Tabelated results of all sampling Maximum confirmation soil concentrations(8/96)were TPHg, 1,600 mg/kg;�_�
<br /> w " and analyses: benzene;0:8'mg/kg;toluene,42 mg/kg;ethylbenzene, 26 mglkg;xylenes;
<br /> 140 mg/kg;and MTBE,0.2 mglkg.'.r to 2101,soil boring after results were TPHg,
<br /> PDetection limits for confirmation 400 mg/kg;benzene, 0.3 mglkg;toluene,15.9 mg/kg;ethylbenzene, 11 mg/kg;
<br /> sampling xylenes,43 mg/kg;and MTBE, 0.6,65 mg%kg. Maximum grab groundwater
<br /> concentrations(2101) were TPHg,'136,000�ug/L;benzene, 1,700 ug/L;toluene,
<br /> nY Lead analyses 4,600 ug/L;ethylbenzene, 1,400 ug/L;xylenes , 5,900 ug/L;and MTBE;25 pg/L.
<br /> In 12/07, maximum groundwater concentrations were TPHg, 112 ug/L;benzene,
<br /> 7.9 ug/L;ethylbenzene, 1.6 u /L;x lenes, 8.9 ug/L;and MTBE, 0.8 ug/L.
<br /> 8. Concentration contours of contaminants found and those remaining in soil and I The extent of the identified
<br /> groundwater, and both on-site and off-site: contamination shown in applicable
<br /> reports.
<br /> 0 Lateral and 0 Vertical extent of soil contamination
<br /> FY]Lateral and Vertical extent of groundwatercontamination�
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation The regulatory agency did not require an
<br /> system and the zone of capture attained for the soil and groundwater remediation ;7 engineered remediation.
<br /> system; ;l
<br /> 10.Reports/information Unauthorized Release Form QMRs(22 from,2102 to 2108)
<br /> E Well and boring logs PAR FRP 0 Other,-Site Conceptual Model,8104;Additional Site
<br /> 1
<br /> Investigation, 2/07;Soil Vapor Sampling and Human Health Risk Assessment,4108 •. it
<br /> Y 11,Best Available Technology(BAT) used or an explanation for not using Removal of US Ts and natural attenuation.
<br /> BAT;
<br /> Y 12. Reasons why background wasfis unattainable Limited soil contamination 'remains on-site.
<br /> .BA_ �s373 13.Mass balance calculation of substance treated The consultant estimated approximately 294 pounds-of TPHg
<br /> contamination remain in soil.
<br /> versus that remaining,
<br /> Y 14. Assumptions, parameters, calculations and No soil vapor ESLs were exceeded during the soil vapor analyses.
<br /> 7
<br /> model used in risk assessments, and fate and
<br /> '
<br /> transport modeling, '? i
<br /> Y 15. Rationale why conditions remaining of site will Soil contamination is limited in extent and not leaching to
<br /> not adversely impact water quality, health, or other groundwater. Results of 23 quarters of groundwater monitoring show l
<br /> beneficial uses;and a decreasing trend!n concentrations.
<br /> By: JLB Comments:One 10,000-gallon gasoline UST and associated piping were removed 8196 at the subject site.
<br /> Maximum confirmation soil concentrations(8196)were TPHg,,
<br /> 1,600 i ig/kg;benzene, 0.8 mg/kg;toluene,
<br /> Date: 42 mg/kg;ethylbenzene, 26 mglkg;xylenes, 140 mg/kg;and MTBE, 0.2 mg/kg. in 2101, soil boring after results
<br /> 8121/2008 were TPHg,400 mg/kg;benzene, 0.3 mg/kg;toluene, 5.9 mg/kg;ethylbenzene, 11 mg/kg;xylenes, 43 mg/kg; j
<br /> and MTBE, 0.065 mg/kg. Maximum grab groundwater conceritratioris(2/01)were TPHg, 36,000 ug/L;benzene,
<br /> 1,700 ug/L;toluene,4,600 ug/L;ethylbenzene, 1,400 ug/L;xylenes,5,900 ug/L;and MTBE;25,ug/L. In 12/07,
<br /> maximum groundwater concentrations were TPHg, 112 ug/L;ibenzehe, 7.9 ug/L;ethylbenzene, 1.6 ug/L;
<br /> xylenes, 8.9 ug/L;and MTBE, 0.8 ug/L. Based upon 23 quarters of declining groundwater concentrations,no
<br /> reported threat from vapor intrusion, no anticipated threats to sensitive receptors, and the limited extent of
<br /> ` contamination present in soil, Regional Board staff concur with Sari Joaquin County's Closure
<br /> Recommendation. ;',
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