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TABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location-7[Shell-Branded Service Station, 620 W. Charter Way, Stockton, San Joaquin County(RB#390396)
<br /> :Y::] 1. Distance to production wells for municipal,domestic, A 2004 sensitive receptor survey reported no water supply
<br /> agriculture, industry and other uses within 2000 feet of wells within 2,000'of the Site.
<br /> the site.
<br /> Y 2.Site maps,to scale,of area impacted showing In 6/87, one 550-gallon waste oil UST was removed. In
<br /> locations of any former and existing tank systems, 11/89,one 8,000-gallon, two 10,000-gallon gasoline and one
<br /> excavation contours and sample locations,boring and 550-gallon waste oil USTs were removed. Site maps and
<br /> monitoring well elevation contours,gradients,and figures showing tank locations, excavations,building and
<br /> nearby surface waters,buildings,streets,and residual pollutants were provided in investigation reports.
<br /> subsurface utilities;
<br /> Y 3.Figures depicting lithology(cross Site lithology consists of clay,silt,and sand to 100, the total depth investigated
<br /> section), treatment system diagrams; Active remediation included free product skimmer(1990),and soil vapor
<br /> extraction 1992-1996.All figures were provided in the remediation reports.
<br /> Y 1 4.Stockpiled soil remaining on-site Approximately 1,058 cubic yards of soil was excavated and transported to an
<br /> or off-site disposal(quantity); unknown location. Mass estimate for excavated soil was not reported by the
<br /> consultant.
<br /> S.Monitoring wells remaining on-site, Twenty(20)monitoring wells(MW-1 through MW-11,MW-13-50,MW-13-77, MW-
<br /> ate; 14-50,MW-14-77,MW-15-77,MW-16-50, MW-16-77,MW-16-90 and MW-17-50)will
<br /> be properly destroyed prior to closure.
<br /> 6. Tabulated results of all groundwater Tabulated data was provided in reports indicating depth to groundwater from
<br /> elevations and depths to water; 14'bgs to 39'bgs. Groundwater flow direction was from east to northwest.
<br /> Groundwater gradient varied from 0.002 ft/ft to 0.006 ft/ft.
<br /> LYJ 7. Tabulated results of all sampling All data was adequately tabulated in various reports, including waste oil analyses.
<br /> and analyses:
<br /> Y❑ Detection limits for
<br /> confirmation sampling
<br /> Lead analyses
<br /> 8. Concentration contours of contaminants found and those remaining in The horizontal and vertical extent of the
<br /> soil and groundwater,and both on-site and off-site: petroleum pollution extends from the site
<br /> to approximately 80'to the east under the
<br /> Y❑Lateral and Y❑Vertical extent of soil contamination neighboring motel at MW-14-77. Shallower
<br /> Lateral and Vertical extent of groundwater contamination adjacent MW-14-50 is non-detect.
<br /> 9.Zone of influence calculated and assumptions used for subsurface A free product skimmer and a soil vapor
<br /> remediation system and the zone of capture attained for the soil and extraction treatment system were installed.
<br /> groundwater remediation system;
<br /> 10.Reports/information FY Unauthorized Release Form ❑Y QMRs(86) 12-89 to 10-12
<br /> ❑Y Well and boring logs 0 PAR EY FRP ❑Y Other Case Closure Request, 10-13
<br /> Y 11.Best Available Technology(BAT)used or Leak was stopped by removing tanks and piping. Over-excavation,free
<br /> an explanation for not using BAT; product skimming,and SVE were chosen as the BAT.
<br /> Y 12. Reasons why background was/is-not Soil pollution presents a minimal threat to human health and
<br /> finable using BAT; groundwater pollution is predicted to be restored in 33 years.
<br /> Y 13.Mass balance calculation of substance Consultant estimated gasoline release of 23,361 lbs. (3,805 gal.).
<br /> treated versus that remaining; Skimmer removed 1,188 lbs.(180 gal.)of free product, SVE removed
<br /> 17,628 lbs. (2,670 gal.)of TPH in soil.Residual TPH mass is estimated
<br /> as 4,285 lbs. 649 al. in soil and 10.3 lbs. 1.37 al. in groundwater.
<br /> Y 14. Assumptions, parameters, calculations Site is an active service station and passed the LTCP. Consultant states
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<br /> and model used in risk assessments,and fate site does not represent a significant environmental or health risk.Fund
<br /> and transport modeling; recommended case for closure.
<br /> Y 15. Rationale why conditions remaining at Soil and groundwater pollution is reportedly confined to 80'from the
<br /> site will not adversely impact water quality, property limits.Land use(commercial)is not expected to change in the
<br /> health,or other beneficial uses;and foreseeable future. WQOs are predicted to be reached by 2047.
<br /> Groundwater plume is stable and slowly decreasing in concentration.
<br /> By: JLB Comments:Multiple USTs were removed at the subject site.Based on the stable and declining
<br /> concentrations in groundwater,no foreseeable changes in future land use(commercial),and minimal risks
<br /> Date: from soil vapor and soil,Regional Board staff concur with San Joaquin County's Closure Recommendation.
<br /> 2/4/2014
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