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QABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT'UNDERGROUND TANK SITES
<br /> If �
<br /> Site Name and Location: Thrifty Oil Company#171,'1250 N. Wilson Way,Stockton, San Joaquin County(RB#390187)
<br /> Y 1. Distance to production wells for municipal, domestic, A 2008'sensitive receptor survey reported no active
<br /> agriculture, industry and other uses within 2000 feet of the site. supply,,wells within 2,000'of the site.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of in 10194, two 5,000-gallon gasoline, one 8,000-gallon
<br /> any fomlerand existing tank systems, excavation contours and gasoline, and'two 12,000-gallon gasoline USTs and
<br /> sample locations, boring and monitoring well elevation associated dispensers and piping were removed.
<br />' contours, gradients, and nearby surface waters, buildings,
<br />}_ streets, and subsurface utilities; i
<br /> Y 3. Figures depicting lifhology(cross section), treatment system
<br /> Site lithology consists of clay, silt and sand to 122, the
<br /> diagrams; total depth in pestigated.
<br /> Y 4. Stockpiled soil remaining on-site or off-site disposal (quantity); Approximately 718 tons of excavated soil was returned
<br /> < immediatel ,Ito the USTs pit
<br /> Y 5. Monitoring wells remaining on-site, fate; Twenty one(21)monitoring wells fEW--5S, EW-5D, MW-2, MW-3R, MW-4,
<br /> MW-5, MW-6, TB-1, TB-3, TB-4, TB-6, TB-7, TB-8, TB-9[nested double
<br /> casing], TB-10, TB-11[nested double casing],and TB-12[nested triple
<br /> casing]) will be properly abandoned.
<br /> Depth to groundwater varied from 39'bgs to 52'bgs. Groundwater
<br /> 6. Tabulated results of all groundwater gradient varied from 0.'001 ft/ft to 0.003 ft/ft. Groundwater flow direction, .
<br /> elevations and depths to water,' varied clockwise from northeast to east.
<br /> 7. Tabulated results of all sampling. All data adequately tabularized in various reports, including closure report.
<br /> and analyses:
<br /> Detection limits for confirmation li
<br /> it
<br /> sampling
<br /> 0 Lead analyses i
<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: i contamination is described M the
<br /> available reports.
<br /> 0 Lateral and Y❑Vertical extent of soil contamination If
<br />' Ey lLateral and FY Vertical extent of groundwater contamination it
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation 11 SVE and groundwater pump and
<br /> system and the zone of capture attained for the soil and groundwater remediation ;l treatment(GIVE) were the engineered
<br /> system; 1. remediation.
<br /> 10.Reports I information Unauthorized Release Form QMRs 11/92 to 6/11
<br />$
<br /> FY] Well and boring logs 0 PAR
<br /> 10 FRP �y Other ;Soil Vapor Reports(6111 & 9111), Closure Report
<br /> 2111
<br /> YJ 11.Best Available Technology(BAT) used or an explanation for not using USTs removal, SVE, GWE,and natural
<br /> BAT, attenuation. DPE was pilot tested.
<br /> 12. Reasons why background wasfis unattainable Minor residual soil and groundwater contamination remains on-site., .
<br /> BAT;
<br /> i
<br /> 7Y 13.Mass balance calculation of substance treated Consultant estimates TPR;removed as approximately 171,237 lbs by
<br /> versus that remaining; SVE, 31 lbs. by DPE, and 601bs by GWE. Residual mass was not
<br /> calculated. i
<br /> Y 14. Assumptions, parameters, calculations and Soil vapor did exceed Region 2 Environmental Screening Levels
<br /> 7
<br /> model used in risk assessments, and fate and (ESLs)for TPHg, but passed a TIER 2 evaluation. Soil ESLs were
<br /> transport modeling; exceeded for benzene(direct exposure, 35'bgs)and for gross
<br /> contamination and direct contact for TPHg(5'bgs)and xylenes
<br /> (20'bgs). There is a kiosk for the station cashier. The consultant
<br /> states no significant risk exists.
<br /> Y 15. Rationale why conditions remaining at site will Soil and groundwater contamination reportedly are limited in extent.
<br /> not adversely impact water quality, health, or other Land use(commercial)is not expected to change in the foreseeable
<br /> beneficial uses;and future. TPN is estimated to reach WQGs in 2019. f
<br /> By: JL Comments:In 10194, two 5,000-gallon gasoline, one 8,000�4allon'gasoline,and two 12,000-gallon gasoline
<br /> US Ts and associated dispensers and piping were removed.at the;subject site. Minor residual soil and
<br /> Date: groundwater contamination remains on-site. Based upon the limited extent of contamination reported in soil
<br /> 1 11/28/2011 and groundwater,a stable groundwater plume with declining concentrations,no foreseeable changes in
<br /> future land use(commercial),and minimal risks from soil,.jsoil vapor,and groundwater, Regional Board staff
<br /> concur with San Joaquin County's Closure Recommendation.
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