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'q- ABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Shell.#204-7884-0901,3725 Tracy Blvd., Tracy,San Joaquin County (Lustis Case 390142)
<br /> y 1. Distance to production wells for municipal, domestic,. A 1999 well survey showed 10 public and domestic wells
<br /> agriculture, industry and other uses within 2000 feet of the site. exist within 2000 feet of the site.The nearest
<br /> downgradient well, 100 feet to the north at the Chevron
<br /> (RB case. 390795),was not found although a supply well
<br /> at the site was found,tested ND,and abandoned 2103.
<br /> Remaining wells are over 700 feet from site.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of One 8,000-gallon(11185), one 10,000-gallon(11185), three
<br /> any former and existing tank systems, excavation contours and 10,000-gallon(5190)gasoline,and one unknown volume
<br /> sample locations, boring and-monitoring well elevation ..waste oil(4185) USTs were removed, and
<br /> contours, gradients, and nearby surface waters,buildings,' piping/dispensers upgraded 3104.
<br /> streets, and subsurface utilities; -
<br /> 7Y 3. Figures depicting lithology(cross section), treatment system Site lithology consists,of clay,'silt and sand to
<br /> diagrams; 141 feet, the total depth investigated.
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<br /> Y1 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 400 yards of aver-excavated soil was
<br /> removed and transported to Forward Landfill 4190
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<br /> 5. Monitoring wells remaining on-site,-fate;
<br /> Three monitoring wells(MW-IA through MW-3A)remaining on-site will be
<br /> properly abandoned. ,
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 8 to 10 feet below ground surface
<br /> elevations and depths to water,.. (bgs). The groundwater gradient varied from 0.001 to 0.005 ft/ft,and the
<br /> down radient direction varied from northeast to southeast.
<br /> 7. Tabulated results of all sampling - In 8189, maximum confirmation sample soil concentrations were TPHg, 140 mg/kg;
<br /> and analyses: benzene, 0.01 mg/kg;toluene;0.04 mg/kg;ethylbenzene,.0.02 mglkg;xylenes,
<br /> 0.04 mg/kg;and MtBE, 1.7 mg/kg;and TPHd, 3,000 mg/kg(3104) . Maximum
<br /> Detection limits for confirmation, groundwater concentrations in 8196 were TPHg, 2,700 ug/L; TPHd, 81 ug/L;
<br /> sampling benzene, 4.5 ug/L;toluene,2.1 ug/L;ethylbenzene, 22 ug/L;xylenes,34 ug/L;and
<br /> MtBE; 771rg/L: In 4107, maximum groundwater concentrations were TPHd, 51 uglL
<br /> Lead analyses and MtBE;6.1 ug/L.
<br /> 8. Concentration contours of contaminants found and-those remaining in.soil and The extent of'the identified
<br /> groundwater, and both on-site and off-site: contamination shown.in applicable
<br /> reports.
<br /> ElLateral and Vertical extent of soil contamination
<br /> FYI Lateral and MY Vertical extent of grouii dwatercontamination
<br /> NI 9. Zone of influence calculated and assumptions used for subsurface remediation An engineered remediation was not
<br /> system and the zone of capture attained for the soil and groundwater remediation required by the lead agency.
<br /> system;
<br /> 10.Reports 1 information ❑Y Unauthorized R61ease.Foun ❑Y QMRs(76 from 9189 to 4107)
<br /> Well and boring logs QY PAR F FRP Y Other;.Dispenser/Piping Report, 8104, Closure.Report, 6107
<br /> Y 11.Best Available Technology(BAT) used or an explanation for not usingRemoval of US Ts periodic groundwater
<br /> BA T; batch extraction(2/00 to 9103) and natural
<br /> x 'attenuation.
<br /> Y 12. Reasons why background wars unaftainable Limited soil contamination and groundwater pollution remain on-site. E
<br /> BAT,. v
<br /> _ 13.Mass balance calculation of substance treated' Periodic batch extractions removed 5.45 lbs. of TPHg,
<br /> versus that remaining; 0.1 lbs of benzene,and 51.5 lbs of MtBE. In 4107, the residual
<br /> contamination was estimated in soil as TPHd,
<br /> 12 gal.;MtBE, 0.02 gal.;and TBA, 0A4 gal.;and in groundwater, MtBE,
<br /> 0.0002 lbs.
<br /> Y 14. Assumptions, parameters, calculations and, Although TPHd soil ESLs were exceeded for gross contamination and
<br /> model used in risk assessments, and fate and direct contact in a limited area around the active dispensers, County
<br /> transport modeling; staff have determined the minimal amount of impacted soil not to be a
<br /> threaten to human health or water quality.;,Further,site will remain-an
<br /> active service station for the foreseeable future.
<br /> Y 15. Rationale why conditions remaining at site will Soil contamination is limited in extent. Results of 76 quarters of
<br /> not adversely impact water quality, health, or other , groundwater monitoring show a decreasing trend in concentrations.
<br /> beneficial uses;and TPHd in soil limited in extent.
<br /> By: JLB Comments:Based upon 76 quarters of declining groundwater concentrations, and the limited extent of
<br /> contamination present in soil and.groundwater, Regional Board staff concur with San Joaquin County's
<br /> Date: Closure Recommendation'.
<br /> 1/22/2008
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