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41BLE 1 -CHECKLIST OF REQUIRED DATA •
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> rSite
<br /> Location: ARCO Service Station 4932, 16 E. Harding Way, Stockton, San Joaquin County(RB 11390322)
<br /> e to production wells for municipal, domestic, A 2012 sensitive receptorsurvey reported thirteen water
<br /> re, industry and other uses within 2000 feet of supply wells within 2,000'of the Site. The closest well is
<br /> 1,200'to the north.None of the wells are threatened by the
<br /> etroleum hydrocarbons release.
<br /> in to scale, of area impacted showing In 5/99, three 12,000-gallon gasoline USTs were removed.
<br /> of any former and existing tank systems, Site maps andfigures showing tank locations, excavations,
<br /> excavation contours and sample locations, boring and buildings and residual pollutants were provided in
<br /> monitoring well elevation contours, gradients, and investigation reports.
<br /> nearby surface waters, buildings,streets,and
<br /> subsurface utilities;
<br /> YJ 3. Figures depicting lithology (cross Site lithology consists of clay,silt, and sand to 120', the total depth investigated.
<br /> section),treatment system diagrams; Active remediation included groundwater extraction(GWE, 2000-2008),soil
<br /> vapor extraction(SVE, 2002-2008)and ozone injection(01, 2005-2008).All
<br /> figures were provided in the remediation reports.
<br /> Y 4. Stockpiled soil remaining on-site Approximately 781 tons of soil was excavated and transported to BFINasco
<br /> or off-site disposal (quantity); Road Landfill, Livermore. Approximately 373 lbs. (56 gal.)of TPH were removed
<br /> b over-excavation.
<br /> Y 5. Monitoring wells remaining on-site, I All 20 monitoring wells(DMW-1 through DMW-10, MW-1 through,MW 10)and 15
<br /> ate; remediation wells(EW-1 through EW-7, SVE-1, SVE-2, S-1 through S-6)will be
<br /> ro a destro ed rior to closure.
<br /> 6. Tabulated results of all groundwater Tabulated data was provided in reports indicating depth to groundwater ranged
<br /> elevations and depths to water; from 24'bgs to 40'bgs. Groundwater flow was from northeast to north-
<br /> northeast. Groundwater gradient varied from 0.001 ft/ft to 0.004 ft/ft.
<br /> 7.Tabulated results of all sampling All data was adequately tabulated in various reports.
<br /> and analyses:
<br /> ❑Y Detection limits for
<br /> confirmation sampling
<br /> FY Lead analyses
<br /> 8. Concentration contours of contaminants found and those remaining in The horizontal extent of the petroleum
<br /> soil and groundwater,and both on-site and off-site: pollution extends from the site to
<br /> ElLateral and ❑Y approximately 200'to the northeast under
<br /> Vertical extent of soil contamination Harding Way from MW-4 to MW-6. Deep
<br /> Lateral and Vertical extent of roundwater contamination ""ells (DMW)are ND.
<br /> 9. Zone of influence calculated and assumptions used for subsurface GWE, SVE, and OI treatment systems were
<br /> remediation system and the zone of capture attained for the soil and installed. The calculated zone of capture
<br /> roundwater remediation s stem; varied from 46'to 89'.
<br /> 10.Reports/informationUnauthorized Release Form QY QMRs (52)9-00 to 8-13
<br /> ❑Y Welland boring logs PAR EY FRP 0 Other Case Closure Request, 11-13
<br /> Y 11.Best Available Technology(BAT) used or Leak was stopped by removing tanks and piping. Over-excavation,
<br /> an explanation for not using BAT; GWE, SVE,and O/were implemented as the BAT.
<br /> y 12. Reasons why background was/is not Contaminant concentrations are declining naturally and background is
<br /> inable using BAT; redicted to be restored in a reasonable time frame.
<br /> Y 13.Mass balance calculation of substance Consultant estimated GWE and SVE removed 26,322.8 lbs. (3,988 gal.)
<br /> treated versus that remaining; of TPH. Residual TPH mass is estimated as 4,285 lbs. (649 gal.)in soil
<br /> and 9.9 lbs. 1.3 al. in groundwater
<br /> I, 14. Assumptions, parameters, calculations Site is an active service station. The LTCP provides an exemption for
<br /> and model used in risk assessments,and fate evaluating potential vapor intrusion at active service stations assuming
<br /> and transport modeling; ambient air quality is impacted by operations. Consultant states site
<br /> does not represent a significant environmental or health risk.
<br /> I, 15. Rationale why conditions remaining at Groundwater pollution is reportedly confined to 200'from the property
<br /> site will not adversely impact water quality, 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 2035.
<br /> Groundwater plume is stable and slowly decreasing in concentration.
<br /> By: JLB Comments: Multiple USTs were removed at the subject site.Soil pollution presents a minimal threatto human
<br /> health and groundwater pollution is predicted to be restored in 21 years. Based on the stable and declining
<br /> Date: concentrations in groundwater,no foreseeable changes in future land use(commercial),and minimal risks
<br /> 2/28/2014 from soil vapor and soil,Regional Board staff concur with San Joaquin County's Closure Recommendation.
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