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<br /> TAIt4 1 - CHECKLIST OF REQUIREDUTA
<br /> . FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: California Highway Patrol, 385 Grant Line Road, Tracy, San Joaquin County
<br /> 1. Distance to production wells for municipal, domestic, agriculture, One municipal supply,2 domestic and 2 irrigation
<br /> industry and other uses within 2000 feet of the site; wells are'located within 2000 feet of the site. One
<br /> domestic well is 300 feet NW of the site. i
<br /> Y 2. Site maps, to scale, of area impacted showing locations of former and existing tank One 12,000-gallon gasoline UST
<br /> systems, excavation contours and sample locations, boring and monitoring well elevation was removed 5/00.
<br /> contours, gradients, and nearby surface waters, buildings, streets, and subsurface
<br /> utilities;
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<br /> 3. Figures depicting lithology(cross section), treatment system diagrams; Site lithology consists of sand,silt and clay.
<br /> The total depth investigated was 36 feet.
<br /> QThe fate of the 118 cubic yards of excavated soil is unknown. `
<br /> 4. Stockpiled soil disposed off-site(quantity); Y f
<br /> 0 5. Monitoring wells remaining on-site, fate; Four monitoring wells(MW-1 through MW-4)installed for this investigation
<br /> will be abandoned.
<br /> S. Tabulated results of all groundwater elevations and depths to water,* The depth to water varied from 3 to 7 feet.
<br /> -�•}-^'_ ��-�- - ----Greundwater.flow,direction varied from-north to --
<br /> northwest at a gradient of 0.005ft/ft.
<br /> 0 7.Tabulated results of all sampling and In 6/00, maximum soil results from MW-1 installation were: TPHg
<br /> analyses: (1.1 mglkg),xylenes(0.088 mg/kg), and MtSE(0.25 mg/kg). No soil
<br /> ®Y samples were taken after installation of monitoring wells. Maximum
<br /> Detection limits for confirmation sampling groundwater results(MW-1)in 6/00 were TPHg(2,000 ug/1),benzene
<br /> Lead analyses (20 ug/l), toluene(8.2 ug/l), ethylbenzene(19 ug/l),xylenes(275 ug/1),
<br /> TAME(2.9 pg/1), and MtBE(660 ug/I). In 1/05, maximum groundwater
<br /> results(MW-1) were MtBE(1.7 ug/l).
<br /> 0 8. Concentration contours of contaminants found and those remaining in soil
<br /> and groundwater, both on-site and off-site: The extent of contamination is defined by
<br /> Lateral and Vertical extent of soil contamination soil borings and monitoring wells.
<br /> Lateral and Vertical extent of groundwater contamination
<br /> 0 9. Zone of influence calculated and assumptions used for subsurface An engineering remediation was not
<br /> remediation system and the zone of capture attained for the soil and required.
<br /> groundwater remedia tion s stem;
<br /> 0 10.Reports/information LJ Unauthorized Release Form Y❑ 7 QMRs(6/00 to 105)
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<br /> ElBoringlogs El PAR N� J FRP Y❑ Other.,Sensitive Receptor Survey, Closure Report
<br /> Y❑ 11.Best Available Technology(BAT) used or an explanation for not using BAT Remove USTs and natural attenuation.
<br /> 12.Reasons why background wasps Minor soil and groundwater contamination remains on-site.
<br /> unattainable using BAT;
<br /> 13.Mass balance calculation of substance The remaining mass ba`iarlce was`riof cafculatcd.:-
<br /> treated versus that remaining;
<br /> 0 14. Assumptions, parameters, calculations and model
<br /> used in risk assessments, and fate and transport A risk assessment was not required. The remaining soil
<br /> modeling;and concentration(1.1 mg/kg) exceeded Region 2 ESLs for TPHg
<br /> Y (0.1 mg/kg).
<br /> 15. Rationale why conditions remaining at site will not Soil contamination is limited in extent, and based on 7 quarters of
<br /> adversely impact water quality, health, or other:, groundwater monitoring with declining concentrations,
<br /> beneficial uses. contamination is not continuing to leach into groundwater. .
<br /> By: Comments: One 12,000-gallon gasoline UST was removed 5/00 from the subject site. In 6/00, maximum soil results from
<br /> Y,B MW-1 installation were: TPHg(1.1 mg/kg), xylenes(0.088 mg/kg), and MtBE(0.25 mg/kg). No soil samples were taken
<br /> after installation of monitoring wells. Maximum groundwater results(MW-1)in 6/00 were TPHg(2,000 pgfl),`benzene(20
<br /> Date: psi►), toluene (8.2 pgR), ethylbenzene (19 pg/l),xylenes(275 pg1l), TAME(2.9 pgR), and MtBE(660 Ng/1). M4105,
<br /> maximum groundwater results(MW-1) were MTBE(1.7 pg4).. Based on the limited mass of remaining soil and
<br /> 916/05 groundwater contamination, and decreasing contaminant concentrations in groundwater, Regional Board staff concur with
<br /> San Joaquin County's Closure Recommendation.
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