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<br /> ;V ABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FUR7*R ACTION REQUESTS AT UNDERGROUNDLK SITES
<br /> Site Name and Location: Shelf Service Station, 2375 Grant Line Road, Tracy, San Joaquin County(RB#391145)
<br /> Y 1. Distance to production wells for municipal,domestic, A 2004 sensitive receptor survey identified eight
<br /> agriculture, industry and other uses within 2000 feet of the site. domestic and one unknown wells located within 2000'of
<br /> the site, with the nearest well 1400'to the south.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of In March 2003, an unauthorized release from the USTs
<br /> any former and existing tank systems, excavation contours and system was discovered after four monitoring wells were
<br /> sample locations, boring and monitoring well elevation installed and sampled onsite.In November 2004,soil
<br /> contours, gradients, and nearby surface waters,buildings, contamination was discovered when the dispensers and
<br /> streets, and subsurface utilities; piping were upgraded.
<br /> Y 3. Figures depicting lithology(cross section), treatment system Site lithology consists of clay,silt, and sand to e
<br /> diagrams; total depth investigated.
<br /> N 4. Stockpiled soil remaining on-site or off-site disposal(quantity); The available documents state "There is no stockpiled
<br /> p g p soil remaining on slte".
<br /> Nine monitoring wells( - roug -9, and MW-1
<br /> y NiMW1 through MW-7,MW 0 5. Monitoring wells remaining on-site, fate; )will be
<br /> ro erly abandoned.
<br /> 6. Tabulated results of all groundwater Depth'to groundwater varied from 9'to 13'bgs. Groundwater flow
<br /> elevations and depths to water; direction varied from north to northwest Groundwater gradient varied
<br /> from 0.005 to 0.020 ft/ft.
<br /> '7."Tabu aft wire-silts ofal-sampling- X171 diff a ed guately tab hin-zed in various reports;rncludifigclbsure report.
<br /> and analyses:
<br /> Detection limits for confirmation `
<br /> sampling
<br /> N Lead analyses,
<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: contamination shown in applicable
<br /> reports.
<br /> Y❑Lateral and Y❑Vertical extent of soil contamination
<br /> MY Lateral and FYI.Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation Periodic batch extraction of
<br /> system and the zone of capture attained for the soil and groundwater remediation groundwater from select monitoring
<br /> system" wells was the approved remediation.
<br /> 10.Reports/information ❑Y Unauthorized Release Form 0 QMRs 210306110
<br /> ❑Y Well and boring logs ❑y PAR �y FRP Ry Other Closure Report(8-09), Closure Response(2-10)
<br /> :YD-1 1.Best Available Technology(BAT)used or an explanation for not USTs piping and dispensers trench soil removal,
<br /> using BAT; batch groundwater extraction, and natural
<br /> attenuation.
<br /> UY 12. Reasons why background waers Minor residual soil and groundwater contamination remains on-site.
<br /> ttainable using BAT;
<br />-- 1.3-Mass�balance-calculation-of•substance-treated--Batch-groundw.ater_extraction.r-emov_eeL01.85_lbs..of.JP-H_and-MTBE. —_
<br /> versus that remaining;Y ,y The consultant estimates 0.31 lbs. of MTBE remain in groundwater.
<br /> Y 14. Assumptions, parameters, calculations and The regulatory agency did not require a soil vapor survey,due to the
<br /> model used in risk assessments, and fate and location of residual soil and groundwater contaminants(mainly MTBE
<br /> transport modeling; in fuel island),limited threats from unsaturated zone vapor intrusion
<br /> due to small vadose zone(less than 10'depth),distance to building
<br /> (-30'), and no change in site use(service station). The residual soil
<br /> passed the Region 2 ESLs-
<br /> Y1 15. Rationale why conditions remaining at site Soil and groundwater contamination reportedly is limited in extent.
<br /> will not adversely impact water quality, health, or Land use(commercial)is not expected to change in the foreseeable
<br /> other beneficial uses;and future. Vapor intrusion risk has been addressed. Water quality goals
<br /> will be reached in.10 years.
<br /> By., JL Comments: In March 2003, an unauthorized release from the USTs system was discovered after four
<br /> kz monitoring wells were installed and sampled onsite.In November 2004, soil contamination was discovered
<br /> Date: when the dispensers and piping were upgraded at the subject Site. Based upon groundwater monitoring,
<br /> 9/14/2010 showing a stable plume with declining concentrations, the limited extent of contamination remaining in soil
<br /> and groundwater,no foreseeable changes in land use, and limited threats from groundwater, soil and soil
<br /> vapor intrusion, Regional Board staff concur with San Joaquin County's Closure Recommendation.
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