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'bdABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: 7-Eleven#2243-20632,4627 Da Vinci Dr., Stockton, San Joaquin County(RB#390977)
<br /> 7Y 1. Distance to production wells for municipal, domestic, A 1999 sensitive receptor survey reported one water
<br /> agriculture, industry and other uses within 2000 feet of the supply well(500'north)within 2,000'of the site. The
<br /> well is not threatened by the release.
<br /> site.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of /n 10/98, three 10,000-gallon gasoline USTs were
<br /> any former and existing tank systems, excavation contours removed.
<br /> and sample locations,boring and monitoring well elevation
<br /> contours,gradients, and nearby surface waters, buildings,
<br /> streets,and subsurface utilities;
<br /> Site lithology consists of clay,silt,sand,and gravel to 30', the total depth
<br /> Y 3. Figures depicting lithology(cross
<br /> section), treatment sstem diagrams investigated.
<br /> y 4. Stockpiled soil remaining on-site Approximately 967 tons of excavated soil and 92,000 gallons of water pumped
<br /> or offsite disposal(quantity); from the excavation were transported to Berkshire Environmental in Lake
<br /> Forest, CA.
<br /> y 5. Monitoring wells remaining on-site, Seven(7)monitoring(MW-1 through MW-3, MW-4R, and MW-5 through MW-7)
<br /> ate; and two(2)remediation wells(SPV-1 and SPV-2)will be properly destroyed prior
<br /> to closure.
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 3'bgs to 8'bgs. Groundwater flow direction
<br /> elevations and depths to water, varied from southeast to southwest. Groundwater gradient varied from
<br /> 0.001 ft/ft to 0.005 ft/ft.
<br /> 7. Tabulated results of all sampling All data adequately tabularized in various reports.
<br /> and analyses:
<br /> Y❑ Detection limits for
<br /> confirmation sampling
<br /> �Y Lead analyses
<br /> LyJ 8. Concentration contours of contaminants found and those remaining in The extent of the identified contamination
<br /> soil and groundwater,and both on-site and off-site: is described in the available reports.
<br /> Y❑Lateral and �Vertical extent of soil contamination
<br /> Lateral and Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface The engineered remediation was over-
<br /> remediation system and the zone of capture attained for the soil and excavation and dewatering.Soil vapor
<br /> groundwater remediation system; extraction(SVE)was pilot tested but not
<br /> effective.
<br /> 10.Reports/information QY Unauthorized Release Form 1Y QMRs(55)10-97 to 1-13
<br /> ❑Y Well and boring logs�y PAR FRP ❑Y Other No Further Action Report, 5-13
<br /> Y11.Best Available Technology(BAT)used or an Over-excavation and dewatering, SVE(pilot study only),
<br /> explanation for not using BAT and natural attenuation.
<br /> UY 12. Reasons why background was/is -/t was not cost effective to implement additional active-remediation and
<br /> ttainable using BAT, residual soil and groundwater pollution will degrade naturally.
<br /> :Y::] 13.Mass balance calculation of substance Consultant estimated residual TPH mass as 323 lbs in soil.
<br /> treated versus that remaining;
<br /> Y 14. Assumptions,parameters, calculations Site passed LTCP except for vertical definition in groundwater,
<br /> and model used in risk assessments,and fate however, County stated in LTCP checklist site is ready for closure.
<br /> and transport modeling; Consultant states site does not represent a significant risk.
<br /> Y 15. Rationale why conditions remaining at Soil and groundwater contamination reportedly are limited in extent.
<br /> site will not adversely impact water quality, Land use(commercial)is not expected to change in the foreseeable
<br /> health, or other beneficial uses;and future. Consultant estimated time to reach WQGs as 2016. Groundwater
<br /> plume is stable and pollutant concentrations are declining.
<br /> By: JLB Comments:In 10/98, three 10,000-gallon gasoline USTs were removed at the subject site.Residual soil and
<br /> groundwater contamination remains. Based upon the limited extent of contamination reported in soil and
<br /> Date: groundwater,a stable and declining concentration plume,no foreseeable changes in future land use
<br /> 6/6/2013 (commercial),and minimal risks from groundwater,soil vapor and soil,Regional Board staff concur with
<br /> San Joaquin County's Closure Recommendation.
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